Characteristics of Methane Hydrate Formation in Artificial and Natural Media

Directory of Open Access Journals (Sweden)

Qingbai Wu

2013-03-01

Full Text Available The formation of methane hydrate in two significantly different media was investigated, using silica gel as an artificial medium and loess as a natural medium. The methane hydrate formation was observed through the depletion of water in the matrix, measured via the matrix potential and the relationship between the matrix potential and the water content was determined using established equations. The velocity of methane hydrate nucleation slowed over the course of the reaction, as it relied on water transfer to the hydrate surfaces with lower Gibbs free energy after nucleation. Significant differences in the reactions in the two types of media arose from differences in the water retention capacity and lithology of media due to the internal surface area and pore size distributions. Compared with methane hydrate formation in silica gel, the reaction in loess was much slower and formed far less methane hydrate. The results of this study will advance the understanding of how the properties of the environment affect the formation of gas hydrates in nature.

Controls on Gas Hydrate Formation and Dissociation

Energy Technology Data Exchange (ETDEWEB)

Miriam Kastner; Ian MacDonald

2006-03-03

The main objectives of the project were to monitor, characterize, and quantify in situ the rates of formation and dissociation of methane hydrates at and near the seafloor in the northern Gulf of Mexico, with a focus on the Bush Hill seafloor hydrate mound; to record the linkages between physical and chemical parameters of the deposits over the course of one year, by emphasizing the response of the hydrate mound to temperature and chemical perturbations; and to document the seafloor and water column environmental impacts of hydrate formation and dissociation. For these, monitoring the dynamics of gas hydrate formation and dissociation was required. The objectives were achieved by an integrated field and laboratory scientific study, particularly by monitoring in situ formation and dissociation of the outcropping gas hydrate mound and of the associated gas-rich sediments. In addition to monitoring with the MOSQUITOs, fluid flow rates and temperature, continuously sampling in situ pore fluids for the chemistry, and imaging the hydrate mound, pore fluids from cores, peepers and gas hydrate samples from the mound were as well sampled and analyzed for chemical and isotopic compositions. In order to determine the impact of gas hydrate dissociation and/or methane venting across the seafloor on the ocean and atmosphere, the overlying seawater was sampled and thoroughly analyzed chemically and for methane C isotope ratios. At Bush hill the pore fluid chemistry varies significantly over short distances as well as within some of the specific sites monitored for 440 days, and gas venting is primarily focused. The pore fluid chemistry in the tub-warm and mussel shell fields clearly documented active gas hydrate and authigenic carbonate formation during the monitoring period. The advecting fluid is depleted in sulfate, Ca Mg, and Sr and is rich in methane; at the main vent sites the fluid is methane supersaturated, thus bubble plumes form. The subsurface hydrology exhibits both

A unified approach for description of gas hydrate formation kinetics in the presence of kinetic promoters in gas hydrate converters

International Nuclear Information System (INIS)

ZareNezhad, Bahman; Varaminian, Farshad

2013-01-01

Highlights: • A unified kinetic model for description of promoted and non-promoted gas hydrate formation processes is presented. • Effects of impeller speed, promoter concentration and different kinetic promoters are investigated. • A unique region of gas hydrate formation is identified regarding gas hydrate formation processes. • The proposed model is useful for understanding the behavior of gas hydrate formation processes and design of GTH converters. - Abstract: The kinetic promoters have found wide applications in enhancing the rate of energy conversion and storage via gas hydrate formation processes. Effects of different kinetic promoters such as anionic surfactants sodium dodecyl sulfate (SDS), dodecylbenzene sulfonic acid (DBSA), and sodium dodecyl benzene sulfonate (SDBS); cationic surfactants, Cetyl trimethyl ammonium bromide (CTAB), dodecyl trimethyl ammonium bromide (DTAB) and non-ionic surfactants, alkylpolyglucoside (APG), dodecyl polysaccharide glycoside (DPG), TritonX-100 (TX100) on methane (CH 4 ), ethane (C 2 H 6 ) and propane (C 3 H 8 ) gas hydrate formation processes are investigated in this work. A macroscopic kinetic model based on the time variations of reaction chemical potential is also presented for global description of gas hydrate formation processes. Experimental gas hydrate formation data are employed to validate the proposed kinetic model. Effects of promoter’s concentrations and agitation intensities on the gas consumption profiles are also investigated. A universal correlation and a unified kinetic map have been proposed for macroscopic description of gas hydrate formation kinetics in the presence or absence of kinetic promoters. According to the presented unified kinetic map, a unique region of gas hydrate formation is identified for the first time. For negligible amounts of kinetic promoters, the presented region disappears and approaches to a unique path at high agitation intensities. The presented unified approach is

Hydrate bearing clayey sediments: Formation and gas production concepts

KAUST Repository

Jang, Jaewon; Santamarina, Carlos

2016-01-01

Hydro-thermo-chemo and mechanically coupled processes determine hydrate morphology and control gas production from hydrate-bearing sediments. Force balance, together with mass and energy conservation analyses anchored in published data provide robust asymptotic solutions that reflect governing processes in hydrate systems. Results demonstrate that hydrate segregation in clayey sediments results in a two-material system whereby hydrate lenses are surrounded by hydrate-free water-saturated clay. Hydrate saturation can reach ≈2% by concentrating the excess dissolved gas in the pore water and ≈20% from metabolizable carbon. Higher hydrate saturations are often found in natural sediments and imply methane transport by advection or diffusion processes. Hydrate dissociation is a strongly endothermic event; the available latent heat in a reservoir can sustain significant hydrate dissociation without triggering ice formation during depressurization. The volume of hydrate expands 2-to-4 times upon dissociation or CO2single bondCH4 replacement. Volume expansion can be controlled to maintain lenses open and to create new open mode discontinuities that favor gas recovery. Pore size is the most critical sediment parameter for hydrate formation and gas recovery and is controlled by the smallest grains in a sediment. Therefore any characterization must carefully consider the amount of fines and their associated mineralogy.

Hydrate bearing clayey sediments: Formation and gas production concepts

KAUST Repository

Jang, Jaewon

2016-06-20

Hydro-thermo-chemo and mechanically coupled processes determine hydrate morphology and control gas production from hydrate-bearing sediments. Force balance, together with mass and energy conservation analyses anchored in published data provide robust asymptotic solutions that reflect governing processes in hydrate systems. Results demonstrate that hydrate segregation in clayey sediments results in a two-material system whereby hydrate lenses are surrounded by hydrate-free water-saturated clay. Hydrate saturation can reach ≈2% by concentrating the excess dissolved gas in the pore water and ≈20% from metabolizable carbon. Higher hydrate saturations are often found in natural sediments and imply methane transport by advection or diffusion processes. Hydrate dissociation is a strongly endothermic event; the available latent heat in a reservoir can sustain significant hydrate dissociation without triggering ice formation during depressurization. The volume of hydrate expands 2-to-4 times upon dissociation or CO2single bondCH4 replacement. Volume expansion can be controlled to maintain lenses open and to create new open mode discontinuities that favor gas recovery. Pore size is the most critical sediment parameter for hydrate formation and gas recovery and is controlled by the smallest grains in a sediment. Therefore any characterization must carefully consider the amount of fines and their associated mineralogy.

CLATHRATE HYDRATES FORMATION IN SHORT-PERIOD COMETS

International Nuclear Information System (INIS)

Marboeuf, Ulysse; Mousis, Olivier; Petit, Jean-Marc; Schmitt, Bernard

2010-01-01

The initial composition of current models of cometary nuclei is only based on two forms of ice: crystalline ice for long-period comets and amorphous ice for short-period comets. A third form of ice, i.e., clathrate hydrate, could exist within the short-period cometary nuclei, but the area of formation of this crystalline structure in these objects has never been studied. Here, we show that the thermodynamic conditions in the interior of short-period comets allow the existence of clathrate hydrates in Halley-type comets. We show that their existence is viable in the Jupiter family comets only when the equilibrium pressure of CO clathrate hydrate is at least 1 order of magnitude lower than the usually assumed theoretical value. We calculate that the amount of volatiles that could be trapped in the clathrate hydrate layer may be orders of magnitude greater than the daily amount of gas released at the surface of the nucleus at perihelion. The formation and the destruction of the clathrate hydrate cages could then explain the diversity of composition of volatiles observed in comets, as well as some pre-perihelion outbursts. We finally show that the potential clathrate hydrate layer in comet 67P/Churyumov-Gerasimenko would, unfortunately, be deep inside the nucleus, out of reach of the Rosetta lander. However, such a clathrate hydrate layer would show up by the gas composition of the coma.

Numerical analysis of wellbore instability in gas hydrate formation during deep-water drilling

Science.gov (United States)

Zhang, Huaiwen; Cheng, Yuanfang; Li, Qingchao; Yan, Chuanliang; Han, Xiuting

2018-02-01

Gas hydrate formation may be encountered during deep-water drilling because of the large amount and wide distribution of gas hydrates under the shallow seabed of the South China Sea. Hydrates are extremely sensitive to temperature and pressure changes, and drilling through gas hydrate formation may cause dissociation of hydrates, accompanied by changes in wellbore temperatures, pore pressures, and stress states, thereby leading to wellbore plastic yield and wellbore instability. Considering the coupling effect of seepage of drilling fluid into gas hydrate formation, heat conduction between drilling fluid and formation, hydrate dissociation, and transformation of the formation framework, this study established a multi-field coupling mathematical model of the wellbore in the hydrate formation. Furthermore, the influences of drilling fluid temperatures, densities, and soaking time on the instability of hydrate formation were calculated and analyzed. Results show that the greater the temperature difference between the drilling fluid and hydrate formation is, the faster the hydrate dissociates, the wider the plastic dissociation range is, and the greater the failure width becomes. When the temperature difference is greater than 7°C, the maximum rate of plastic deformation around the wellbore is more than 10%, which is along the direction of the minimum horizontal in-situ stress and associated with instability and damage on the surrounding rock. The hydrate dissociation is insensitive to the variation of drilling fluid density, thereby implying that the change of the density of drilling fluids has a minimal effect on the hydrate dissociation. Drilling fluids that are absorbed into the hydrate formation result in fast dissociation at the initial stage. As time elapses, the hydrate dissociation slows down, but the risk of wellbore instability is aggravated due to the prolonged submersion in drilling fluids. For the sake of the stability of the wellbore in deep

Thermodynamic simulations of hydrate formation from gas mixtures in batch operations

International Nuclear Information System (INIS)

Kobayashi, Takehito; Mori, Yasuhiko H.

2007-01-01

This paper deals with the hydrate formation from mixed hydrate-forming gases such as natural gas to be converted to hydrates for the purpose of its storage and biogases from which carbon dioxide is to be separated by hydrate formation. When a batch operation is selected for processing such a gas mixture in a closed reactor, we need to predict the evolution of the thermodynamic and compositional states inside the reactor during the operation. We have contrived a simulation scheme that allows us to estimate the simultaneous changes in the composition of the residual gas, the structure of the hydrate formed and the guest composition in the hydrate, in addition to the change in the system pressure, with the progress of hydrate formation during each operation. This scheme assumes the transient hydrate forming process in a reactor during each operation to be a series of numerous equilibrium states, each slightly deviating from the preceding state. That is, a thermodynamic system composed of the contents of the reactor is assumed to be subjected to a quasi-static, irreversible change in state, instantaneously keeping itself in thermodynamic equilibrium. The paper demonstrates a simulation of a process of hydrate formation from a methane + propane mixture and compares its results to relevant experimental results reported by Uchida et al. [Uchida T, Morikawa M, Takeya S, Ikeda IY, Ohmura R, Nagao J, et al. Two-step formation of methane-propane mixed gas hydrates in a batch-type reactor. AIChE J 2004;50(2):518-23

Influence of surfactants on gas-hydrate formation' kinetics in water-oil emulsion

Science.gov (United States)

Zemenkov, Yu D.; Shirshova, A. V.; Arinstein, E. A.; Shuvaev, A. N.

2018-05-01

The kinetics of gas hydrate formation of propane in a water-oil emulsion is experimentally studied when three types of surfactants (SAA (surface acting agent)) - anionic type emulsifiers - are added to the aqueous phase. It is shown that all three types of surfactants decelerate the growth of the gas-hydrate in the emulsion and can be considered as anti-agglutinating and kinetic low-dose inhibitors. The most effective inhibitor of hydrate formation in water-oil emulsion of SV-102 surfactant was revealed. For comparison, experimental studies of gas-hydrate formation under the same conditions for bulk water have been carried out. It is shown that in bulk water, all the surfactants investigated act as promoters (accelerators) of hydrate formation. A qualitative explanation of the action mechanisms of emulsifiers in the process of gas-hydrate formation in water-oil emulsion is given.

Formation of nitric acid hydrates - A chemical equilibrium approach

Science.gov (United States)

Smith, Roland H.

1990-01-01

Published data are used to calculate equilibrium constants for reactions of the formation of nitric acid hydrates over the temperature range 190 to 205 K. Standard enthalpies of formation and standard entropies are calculated for the tri- and mono-hydrates. These are shown to be in reasonable agreement with earlier calorimetric measurements. The formation of nitric acid trihydrate in the polar stratosphere is discussed in terms of these equilibrium constants.

Experimental determination of methane hydrate formation in the presence of ammonia

Energy Technology Data Exchange (ETDEWEB)

Dong, T.B.; Wang, L.Y.; Liu, A.X.; Guo, X.Q.; Chen, G.J.; Ma, Q.L.; Li, G.W. [China Univ. of Petroleum, Beijng (China). State Key Laboratory of Heavy Oil Processing

2008-07-01

Gas hydrates are non-stoichiometric inclusion compounds that are created by a lattice of water molecules. The host molecule has a strong hydrogen bond and encages low molecular weight gases or volatile liquids. The guest molecules favor hydrate formation. Historically, gas hydrates have been thought to be problematic during natural gas transportation because the formed solid hydrate can block pipelines and cause tubing and casing collapse. However, the discovery of huge deposits of gas hydrates in deep-sea sediments and in permafrost has renewed interest in gas hydrates as a new energy resource. This paper discussed a study that is a part of an ongoing experimental and computational program dealing with the thermodynamics of gas hydrate formation in ammonia-water systems. The purpose of the study was to develop a new method to separate and recycle the vent gas of ammonia synthesis by forming or dissociating hydrate. The hydrate-forming conditions of methane in ammonia and water system were studied and reported in this paper with reference to the experimental apparatus and procedure. The materials and preparation of samples were also explained. The experimental results showed that the ammonia had an inhibitive effect on the hydrate formation. 26 refs., 2 tabs., 3 figs.

Modeling of Hydrate Formation Mode in Raw Natural Gas Air Coolers

Science.gov (United States)

Scherbinin, S. V.; Prakhova, M. Yu; Krasnov, A. N.; Khoroshavina, E. A.

2018-05-01

Air cooling units (ACU) are used at all the gas fields for cooling natural gas after compressing. When using ACUs on raw (wet) gas in a low temperature condition, there is a danger of hydrate plug formation in the heat exchanging tubes of the ACU. To predict possible hydrate formation, a mathematical model of the air cooler thermal behavior used in the control system shall adequately calculate not only gas temperature at the cooler's outlet, but also a dew point value, a temperature at which condensation, as well as the gas hydrate formation point, onsets. This paper proposes a mathematical model allowing one to determine the pressure in the air cooler which makes hydrate formation for a given gas composition possible.

Determining the mechanism and parameters of hydrate formation and loss in glucose.

Science.gov (United States)

Scholl, Sarah K; Schmidt, Shelly J

2014-11-01

Water-solid interactions are known to play a major role in the chemical and physical stability of food materials. Despite its extensive use throughout the food industry, the mechanism and parameters of hydrate formation and loss in glucose are not well characterized. Hydrate formation in alpha-anhydrous glucose (α-AG) and hydrate loss in glucose monohydrate (GM) were studied under equilibrium conditions at various relative humidity (RH) values using saturated salt slurries for 1 y. The mechanism of hydrate formation and hydrate loss were determined through mathematical modeling of Dynamic Vapor Sorption data and Raman spectroscopy was used to confirm the mechanisms. The critical temperature for hydrate loss in GM was determined using thermogravimetric analysis (TGA). The moisture sorption profiles of α-AG and GM were also studied under dynamic conditions using an AquaSorp Isotherm Generator. Hydrate formation was observed at and above 68% RH at 25 °C and the conversion of α-AG to GM can best be described as following a nucleation mechanism, however, diffusion and/or geometric contraction mechanisms were also observed by Raman spectroscopy subsequent to the coalescence of initial nucleation sites. Hydrate loss was observed to occur at and below 11% RH at 25 °C during RH storage and at 70 °C during TGA. The conversion of GM to α-AG follows nucleation and diffusion mechanisms. Hydrate formation was evident under dynamic conditions in α-AG and GM prior to deliquescence. This research is the first to report hydrate formation and loss parameters for crystalline α-AG and GM during extended storage at 25 ˚C. © 2014 Institute of Food Technologists®

Characteristics of Methane Hydrate Formation in Artificial and Natural Media

OpenAIRE

Peng Zhang; Qingbai Wu; Yuzhong Yang

2013-01-01

The formation of methane hydrate in two significantly different media was investigated, using silica gel as an artificial medium and loess as a natural medium. The methane hydrate formation was observed through the depletion of water in the matrix, measured via the matrix potential and the relationship between the matrix potential and the water content was determined using established equations. The velocity of methane hydrate nucleation slowed over the course of the reaction, as it relied on...

Hydraulic and Mechanical Effects from Gas Hydrate Conversion and Secondary Gas Hydrate Formation during Injection of CO2 into CH4-Hydrate-Bearing Sediments

Science.gov (United States)

Bigalke, N.; Deusner, C.; Kossel, E.; Schicks, J. M.; Spangenberg, E.; Priegnitz, M.; Heeschen, K. U.; Abendroth, S.; Thaler, J.; Haeckel, M.

2014-12-01

The injection of CO2 into CH4-hydrate-bearing sediments has the potential to drive natural gas production and simultaneously sequester CO2 by hydrate conversion. The process aims at maintaining the in situ hydrate saturation and structure and causing limited impact on soil hydraulic properties and geomechanical stability. However, to increase hydrate conversion yields and rates it must potentially be assisted by thermal stimulation or depressurization. Further, secondary formation of CO2-rich hydrates from pore water and injected CO2 enhances hydrate conversion and CH4 production yields [1]. Technical stimulation and secondary hydrate formation add significant complexity to the bulk conversion process resulting in spatial and temporal effects on hydraulic and geomechanical properties that cannot be predicted by current reservoir simulation codes. In a combined experimental and numerical approach, it is our objective to elucidate both hydraulic and mechanical effects of CO2 injection and CH4-CO2-hydrate conversion in CH4-hydrate bearing soils. For the experimental approach we used various high-pressure flow-through systems equipped with different online and in situ monitoring tools (e.g. Raman microscopy, MRI and ERT). One particular focus was the design of triaxial cell experimental systems, which enable us to study sample behavior even during large deformations and particle flow. We present results from various flow-through high-pressure experimental studies on different scales, which indicate that hydraulic and geomechanical properties of hydrate-bearing sediments are drastically altered during and after injection of CO2. We discuss the results in light of the competing processes of hydrate dissociation, hydrate conversion and secondary hydrate formation. Our results will also contribute to the understanding of effects of temperature and pressure changes leading to dissociation of gas hydrates in ocean and permafrost systems. [1] Deusner C, Bigalke N, Kossel E

Hydrate formation in drilling fluids: prevention and countering; Formacao de hidratos em fluidos de perfuracao: prevencao e controle

Energy Technology Data Exchange (ETDEWEB)

Villas Boas, Mario Barbosa [PETROBRAS, Macae, RJ (Brazil). Distrito de Perfuracao do Sudeste. Setor de Fluidos de Perfuracao

1988-12-31

The possibility of hydrates forming during deep water well drilling is analyzed under conditions typical of the state of Rio de Janeiro`s coastal ocean bed. Relying on an extensive review of technical literature, an effort has been made to ascertain the conditions which favor the occurrence of such hydrates in gas-contaminated water-based drilling muds. Based on this study, methods are proposed for preventing and countering this problem. (author) 58 refs., 10 figs.

Application of gas hydrate formation in separation processes: A review of experimental studies

International Nuclear Information System (INIS)

Eslamimanesh, Ali; Mohammadi, Amir H.; Richon, Dominique; Naidoo, Paramespri; Ramjugernath, Deresh

2012-01-01

Highlights: ► Review of gas hydrate technology applied to separation processes. ► Gas hydrates have potential to be a future sustainable separation technology. ► More theoretical, simulation, and economic studies needed. - Abstract: There has been a dramatic increase in gas hydrate research over the last decade. Interestingly, the research has not focussed on only the inhibition of gas hydrate formation, which is of particular relevance to the petroleum industry, but has evolved into investigations on the promotion of hydrate formation as a potential novel separation technology. Gas hydrate formation as a separation technology shows tremendous potential, both from a physical feasibility (in terms of effecting difficult separations) as well as an envisaged lower energy utilization criterion. It is therefore a technology that should be considered as a future sustainable technology and will find wide application, possibly replacing a number of current commercial separation processes. In this article, we focus on presenting a brief description of the positive applications of clathrate hydrates and a comprehensive survey of experimental studies performed on separation processes using gas hydrate formation technology. Although many investigations have been undertaken on the positive application of gas hydrates to date, there is a need to perform more theoretical, experimental, and economic studies to clarify various aspects of separation processes using clathrate/semi-clathrate hydrate formation phenomena, and to conclusively prove its sustainability.

Water Transfer Characteristics during Methane Hydrate Formation Processes in Layered Media

Directory of Open Access Journals (Sweden)

Yousheng Deng

2011-08-01

Full Text Available Gas hydrate formation processes in porous media are always accompanied by water transfer. To study the transfer characteristics comprehensively, two kinds of layered media consisting of coarse sand and loess were used to form methane hydrate in them. An apparatus with three PF-meter sensors detecting water content and temperature changes in media during the formation processes was applied to study the water transfer characteristics. It was experimentally observed that the hydrate formation configurations in different layered media were similar; however, the water transfer characteristics and water conversion ratios were different.

Methane hydrate synthesis from ice: Influence of pressurization and ethanol on optimizing formation rates and hydrate yield

Science.gov (United States)

Chen, Po-Chun.; Huang, Wuu-Liang; Stern, Laura A.

2010-01-01

Polycrystalline methane gas hydrate (MGH) was synthesized using an ice-seeding method to investigate the influence of pressurization and ethanol on the hydrate formation rate and gas yield of the resulting samples. When the reactor is pressurized with CH4 gas without external heating, methane hydrate can be formed from ice grains with yields up to 25% under otherwise static conditions. The rapid temperature rise caused by pressurization partially melts the granular ice, which reacts with methane to form hydrate rinds around the ice grains. The heat generated by the exothermic reaction of methane hydrate formation buffers the sample temperature near the melting point of ice for enough time to allow for continuous hydrate growth at high rates. Surprisingly, faster rates and higher yields of methane hydrate were found in runs with lower initial temperatures, slower rates of pressurization, higher porosity of the granular ice samples, or mixtures with sediments. The addition of ethanol also dramatically enhanced the formation of polycrystalline MGH. This study demonstrates that polycrystalline MGH with varied physical properties suitable for different laboratory tests can be manufactured by controlling synthesis procedures or parameters. Subsequent dissociation experiments using a gas collection apparatus and flowmeter confirmed high methane saturation (CH 4·2O, with n = 5.82 ± 0.03) in the MGH. Dissociation rates of the various samples synthesized at diverse conditions may be fitted to different rate laws, including zero and first order.

The combined effect of thermodynamic promoters tetrahydrofuran and cyclopentane on the kinetics of flue gas hydrate formation

DEFF Research Database (Denmark)

Daraboina, Nagu; von Solms, Nicolas

2015-01-01

) hydrate formation using a rocking cell apparatus. Hydrate formation and decomposition kinetics were investigated by constant cooling (hydrate nucleation temperature) and isothermal (hydrate nucleation time) methods. Improved (synergistic) hydrate formation kinetics (hydrate nucleation and growth) were...... of these two promoters is favorable both thermodynamically and kinetically for hydrate formation from flue gas....

Methane Hydrate Formation and Dissociation in the Presence of Silica Sand and Bentonite Clay

Directory of Open Access Journals (Sweden)

Kumar Saw V.

2015-11-01

Full Text Available The formation and dissociation of methane hydrates in a porous media containing silica sand of different sizes and bentonite clay were studied in the presence of synthetic seawater with 3.55 wt% salinity. The phase equilibrium of methane hydrate under different experimental conditions was investigated. The effects of the particle size of silica sand as well as a mixture of bentonite clay and silica sand on methane hydrate formation and its dissociation were studied. The kinetics of hydrate formation was studied under different subcooling conditions to observe its effects on the induction time of hydrate formation. The amount of methane gas encapsulated in hydrate was computed using a real gas equation. The Clausius-Clapeyron equation is used to estimate the enthalpy of hydrate dissociation with measured phase equilibrium data.

Energy consumption estimation for greenhouse gas separation processes by clathrate hydrate formation

International Nuclear Information System (INIS)

Tajima, Hideo; Yamasaki, Akihiro; Kiyono, Fumio

2004-01-01

The process energy consumption was estimated for gas separation processes by the formation of clathrate hydrates. The separation process is based on the equilibrium partition of the components between the gaseous phase and the hydrate phase. The separation and capturing processes of greenhouse gases were examined in this study. The target components were hydrofluorocarbon (HFC-134a) from air, sulfur hexafluoride (SF 6 ) from nitrogen, and CO 2 from flue gas. Since these greenhouse gases would form hydrates under much lower pressure and higher temperature conditions than the accompanying components, the effective capturing of the greenhouse gases could be achieved by using hydrate formation. A model separation process for each gaseous mixture was designed from the basis of thermodynamics, and the process energy consumption was estimated. The obtained results were then compared with those for conventional separation processes such as liquefaction separation processes. For the recovery of SF 6 , the hydrate process is preferable to liquefaction process in terms of energy consumption. On the other hand, the liquefaction process consumes less energy than the hydrate process for the recovery of HFC-134a. The capturing of CO 2 by the hydrate process from a flue gas will consume a considerable amount of energy; mainly due to the extremely high pressure conditions required for hydrate formation. The influences of the operation conditions on the heat of hydrate formation were elucidated by sensitivity analysis. The hydrate processes for separating these greenhouse gases were evaluated in terms of reduction of global warming potential (GWP)

Detection of Occupancy Differences in Methane Gas Hydrates by Raman Spectroscopy

DEFF Research Database (Denmark)

Hansen, Susanne Brunsgaard; Berg, Rolf W.; Stenby, Erling Halfdan

2004-01-01

of reservoir fluids due to plugging. Methods to prevent hydrate formation are in use, e.g. by injection of inhibitors. From environmental and security points of view an easy way to detect hydrate formation is of interest. We have tried to detect methane hydrate formation by use of Raman spectroscopy....

Experimental and modeling investigation on structure H hydrate formation kinetics

International Nuclear Information System (INIS)

Mazraeno, M. Seyfi; Varaminian, F.; Vafaie sefti, M.

2013-01-01

Highlights: • Applying affinity model for the formation kinetics of sH hydrate and two stage kinetics. • Performing the experiments of hydrate formation of sH with MCP. • A unique path for the SH hydrate formation. - Abstract: In this work, the kinetics of crystal H hydrate and two stage kinetics formation is modeled by using the chemical affinity model for the first time. The basic idea is that there is a unique path for each experiment by which the crystallization process decays the affinity. The experiments were performed at constant temperatures of 274.15, 275.15, 275.65, 276.15 and 277.15 K. The initial pressure of each experiment is up to 25 bar above equilibrium pressure of sI. Methylcyclohexane (MCH), methylcyclopentane (MCP) and tert-butyl methyl ether (TBME) are used as sH former and methane is used as a help gas. The parameters of the affinity model (A r and t k ) are determined and the results show that the parameter of (A r )/(RT) has not a constant value when temperature changes in each group of experiments. The results indicate that this model can predict experimental data very well at several conditions

Hydration for the prevention of contrast medium-induced nephropathy. An update

International Nuclear Information System (INIS)

Heinrich, M.; Uder, M.

2006-01-01

Contrast medium-induced nephropathy (CIN) continues to be one of the most common causes of hospital-acquired acute renal failure. Since most of the clinical studies on the prophylactic use of different drugs to prevent CIN produced disappointing results, hydration remains the mainstay of prophylaxis. A number of recent prospective randomized trials provided further evidence of the effectiveness of hydration and relevant information regarding the optimization of hydration protocols. It was shown that a bolus hydration solely during examination is not sufficient to prevent CIN. In addition, isotonic 0.9% saline was superior to the commonly used halfisotonic 0.45% saline in another trial. An outpatient hydration protocol including oral hydration before the examination followed by forced intravenous hydration over 6 hrs. beginning 30 to 60 min. prior to examination seems to be comparable to the usual hydration over 24 hrs. Another hydration protocol, which could also be very attractive especially for outpatients, included the infusion of sodium bicarbonate. In a recent trial, hydration with sodium bicarbonate, given as a bolus for 1 hr. prior to examination followed by an infusion for 6 hrs. after examination, was more effective than hydration with sodium chloride for the prophylaxis of CIN. However, there is still a lack of large-scale, multi-center trials comparing different hydration protocols and investigating their influence on clinically relevant endpoints such as mortality or the need for dialysis. (orig.)

How Sodium Chloride Salt Inhibits the Formation of CO2 Gas Hydrates.

Science.gov (United States)

Holzammer, Christine; Finckenstein, Agnes; Will, Stefan; Braeuer, Andreas S

2016-03-10

We present an experimental Raman study on how the addition of sodium chloride to CO2-hydrate-forming systems inhibits the hydrate formation thermodynamically. For this purpose, the molar enthalpy of reaction and the molar entropy of reaction for the reaction of weakly hydrogen-bonded water molecules to strongly hydrogen bonded water molecules are determined for different salinities from the Raman spectrum of the water-stretching vibration. Simultaneously, the influence of the salinity on the solubility of CO2 in the liquid water-rich phase right before the start of hydrate formation is analyzed. The results demonstrate that various mechanisms contribute to the inhibition of gas hydrate formation. For the highest salt concentration of 20 wt % investigated, the temperature of gas hydrate formation is lowered by 12 K. For this concentration the molar enthalpy and entropy of reaction become smaller by 50 and 20%, respectively. Concurrently, the solubility of carbon dioxide is reduced by 70%. These results are compared with data in literature for systems of sodium chloride in water (without carbon dioxide).

Clathrate hydrates - the energy of the future an overview and a postulated formation mechanism

International Nuclear Information System (INIS)

Pratt, R.M.

2000-01-01

Clathrate hydrates are non-stoichiometric compounds that form when water and certain low molecular weight hydrocarbons coexist at high pressures and low temperatures. The majority of the earth hydrocarbons are in the hydrate phase and are primarily located along the ocean bottoms and to a lesser degree in the permafrost regions. In addition, hydrate formation is induced in undersea gas transmission lines and causes costly pipeline plugs and requires expensive inhibition measures to be taken. Therefore, both a stick and a carrot motivate hydrate research. They are a costly and dangerous nuisance to the oil and gas industry and represent a tremendous, untapped energy resource of the future. The formation mechanism of clathrate hydrate formation has always been shrouded in mystery, and an ongoing debate has ensued as to whether their formation is a bulk or surface phenomenon. Molecular dynamics simulation and fractal modeling suggest that this may be an irrelevant issue and that two independent factors contribute to the symmetrical ordered structure of clathrate hydrates: hydrophobic hydration of hydrocarbon molecules in water and formation of linked cavities as these small clusters aggregate. (Author)

Experimental hydrate formation and gas production scenarios based on CO{sub 2} sequestration

Energy Technology Data Exchange (ETDEWEB)

Stevens, J.C.; Howard, J.J. [ConocoPhillips, Bartlesville, OK (United States). Reservoir Laboratories; Baldwin, B.A. [Green Country Petrophysics LLC, Dewey, OK (United States); Ersland, G.; Husebo, J.; Graue, A. [Bergen Univ., Bergen (Norway). Dept. of Physics and Technology

2008-07-01

Gas hydrate production strategies have focused on depressurization or thermal stimulation of the reservoir, which in turn leads to hydrate dissociation. In order to evaluate potential production scenarios, the recovery efficiency of the natural gas from hydrate must be known along with the corresponding amounts of produced water. This study focused on the exchange of carbon dioxide (CO{sub 2}) with the natural gas hydrate and the subsequent release of free methane (CH{sub 4}). Laboratory experiments that investigated the rates and mechanisms of hydrate formation in coarse-grained porous media have shown the significance of initial water saturation and salinity on forming methane hydrates. Many of the experiments were performed in a sample holder fitted with an MRI instrument for monitoring hydrate formation. Hydrate-saturated samples were subjected to different procedures to release methane. The rates and efficiency of the exchange process were reproducible over a series of initial conditions. The exchange process was rapid and efficient in that no free water was observed in the core with MRI measurements. Injection of CO{sub 2} into the whole-core hydrate-saturated pore system resulted in methane production at the outlet end. Permeability measurements on these hydrate saturated cores during hydrate formation decreased to low values, but enough for gas transport. The lower permeability values remained constant during the methane-carbon dioxide exchange process in the hydrate structure. 12 refs., 9 figs.

Development of an offshore gas field - investigation of hydrate and paraffin formation potential with regard to flow assurance; Entwicklung eines Offshore-Gasfeldes: Hydrat- und Paraffinuntersuchungen zur Sicherstellung der kontinuierlichen Produktion

Energy Technology Data Exchange (ETDEWEB)

Zettlitzer, M.; Busch, M. [RWE Dea AG, Wietze (Germany)

2005-11-01

During the production of offshore gas fields, raw gas from a number of production wells is usually led to a platform or - for reservoirs located close to shore - even transported as wet gas to an onshore gas treatment plant. The pipelines are located at the sea bottom, resulting in significant cooling of the raw gas with subsequent potential for the formation of hydrates and/or precipitation of paraffin on the pipeline walls. In order to safeguard continuous production, additional installations and/or dosage of chemicals would possibly be required. On the basis of gas and condensate samples from production tests, the formation potential for paraffins was experimentally investigated while the hydrate formation potential was assessed by simulations. The very small volume of condensate available (2-3 ml of each sample) formed a special challenge and limited the number of possible analytical investigations. Nevertheless, wax appearance temperature of five condensates under investigation could successfully be determined by a combination of gas-chromatographic and rheological measurements. Two of the three gas-bearing layers turned out to produce dry gas so that paraffin problems can be excluded. However, according to the simulations, hydrate formation at temperatures {<=}+20 C has to be expected under the formation pressure of about 200 bars. The third layer contains a gas condensate, causing paraffin precipitation at {<=}0 C and forming hydrate in a temperature range similar to that of the other two sands. Hence, precautions have to taken to prevent hydrate formation in all field lines containing wet gas. Furthermore, the paraffin precipitation potential has to be taken into account in the subsequent low-temperature gas-treatment plant. (orig.)

Gas Hydrate Formation Probability Distributions: The Effect of Shear and Comparisons with Nucleation Theory.

Science.gov (United States)

May, Eric F; Lim, Vincent W; Metaxas, Peter J; Du, Jianwei; Stanwix, Paul L; Rowland, Darren; Johns, Michael L; Haandrikman, Gert; Crosby, Daniel; Aman, Zachary M

2018-03-13

Gas hydrate formation is a stochastic phenomenon of considerable significance for any risk-based approach to flow assurance in the oil and gas industry. In principle, well-established results from nucleation theory offer the prospect of predictive models for hydrate formation probability in industrial production systems. In practice, however, heuristics are relied on when estimating formation risk for a given flowline subcooling or when quantifying kinetic hydrate inhibitor (KHI) performance. Here, we present statistically significant measurements of formation probability distributions for natural gas hydrate systems under shear, which are quantitatively compared with theoretical predictions. Distributions with over 100 points were generated using low-mass, Peltier-cooled pressure cells, cycled in temperature between 40 and -5 °C at up to 2 K·min -1 and analyzed with robust algorithms that automatically identify hydrate formation and initial growth rates from dynamic pressure data. The application of shear had a significant influence on the measured distributions: at 700 rpm mass-transfer limitations were minimal, as demonstrated by the kinetic growth rates observed. The formation probability distributions measured at this shear rate had mean subcoolings consistent with theoretical predictions and steel-hydrate-water contact angles of 14-26°. However, the experimental distributions were substantially wider than predicted, suggesting that phenomena acting on macroscopic length scales are responsible for much of the observed stochastic formation. Performance tests of a KHI provided new insights into how such chemicals can reduce the risk of hydrate blockage in flowlines. Our data demonstrate that the KHI not only reduces the probability of formation (by both shifting and sharpening the distribution) but also reduces hydrate growth rates by a factor of 2.

Investigation of Methane Hydrate Formation in a Recirculating Flow Loop: Modeling of the Kinetics and Tests of Efficiency of Chemical Additives on Hydrate Inhibition Étude de la formation de l'hydrate de méthane dans une conduite de recirculation : modélisation de la cinétique et tests d'efficacité d'additifs chimiques inhibiteurs d'hydrates de gaz

Directory of Open Access Journals (Sweden)

Peytavy J. L.

2006-12-01

Full Text Available Gas hydrates can be formed when light gases, such as the components of natural gas, come into contact with water under particular conditions of temperature and pressure. These solid compounds give rise to problems in natural gas and oil industry because they can plug pipelines and process equipment. To prevent hydrate formation methanol and glycols are commonly and extensively used as inhibitors. Today, the thermodynamic equilibria of hydrate formation are well known, but the kinetics of gas hydrate formation and growth has to be studied in order to find means of controlling these processes and to explore the mechanisms for hydrate formation that follows non equilibrium laws. The present work deals with the kinetics of methane hydrate formation studied in a laboratory loop where the liquid blend saturated with methane is circulated up to a pressure of 75 bar. Pressure is maintained at a constant value during experimental runs by means of methane gas make-up. First the effects of pressure (35-75 bar, liquid velocity (0. 5-3 m/s, liquid cooling temperature ramp (2-15°C/h, and liquid hydrocarbon amount (0-96%, on hydrate formation kinetics are investigated. Then a new method is proposed to predict firstly the thermodynamic conditions (pressure and temperature at the maximum values of the growth rate of methane hydrate and secondly the methane hydrate growth rate. A good agreement is found between calculated and experimental data. Finally the evaluation of the efficiency of some kinetic additives and some surfactants developed to avoid either nucleation or crystal growth and agglomeration of methane hydrates is tested based on the proposed experimental procedure. Les hydrates de gaz des composés légers du gaz naturel se forment lorsque ceux-ci entrent en contact avec l'eau dans certaines conditions de température et de pression. Ces composés solides sont nuisibles pour les industries gazière et pétrolière car des bouchons solides peuvent

Study of formation and stability conditions of gas hydrates in drilling fluids; Etude des conditions de formation et de stabilite des hydrates de gaz dans les fluides de forage

Energy Technology Data Exchange (ETDEWEB)

Kharrat, M.

2004-10-15

Drilling fluids are complex media, in which solid particles are in suspension in a water-in-oil emulsion. The formation of gas hydrates in these fluids during off shore drilling operations has been suspected to be the cause of serious accidents. The purpose of this thesis is the study of the formation conditions as well as the stability of gas hydrates in complex fluids containing water-in-oil emulsions. The technique of high-pressure differential scanning calorimetry was used to characterise the conditions of hydrates formation and dissociation. Special attention has first been given to the validation of thermodynamic measurements in homogeneous solutions, in the pressure range 4 to 12 Mpa; the results were found to be in good agreement with literature data, as well as with modelling results. The method was then applied to water-in-oil emulsion, used as a model for real drilling fluids. It was proven that thermodynamics of hydrate stability are not significantly influenced by the state of dispersion of the water phase. On the other hand, the kinetics of formation and the amount of hydrates formed are highly increased by the dispersion. Applying the technique to real drilling fluids confirmed the results obtained in emulsions. Results interpretation allowed giving a representation of the process of hydrate formation in emulsion. Empirical modelling was developed to compute the stability limits of methane hydrate in the presence of various inhibitors, at pressures ranging from ambient to 70 MPa. Isobaric phase diagrams were constructed, that allow predicting the inhibiting efficiency of sodium chloride and calcium chloride at constant pressure, from 0,25 to 70 MPa. (author)

Sodium bicarbonate-based hydration prevents contrast-induced nephropathy: a meta-analysis

Directory of Open Access Journals (Sweden)

Tamhane Umesh

2009-05-01

Full Text Available Abstract Background Contrast-induced nephropathy is the leading cause of in-hospital acute renal failure. This side effect of contrast agents leads to increased morbidity, mortality, and health costs. Ensuring adequate hydration prior to contrast exposure is highly effective at preventing this complication, although the optimal hydration strategy to prevent contrast-induced nephropathy still remains an unresolved issue. Former meta-analyses and several recent studies have shown conflicting results regarding the protective effect of sodium bicarbonate. The objective of this study was to assess the effectiveness of normal saline versus sodium bicarbonate for prevention of contrast-induced nephropathy. Methods The study searched MEDLINE, EMBASE, Cochrane databases, International Pharmaceutical Abstracts database, ISI Web of Science (until 15 December 2008, and conference proceedings for randomized controlled trials that compared normal saline with sodium bicarbonate-based hydration regimen regarding contrast-induced nephropathy. Random-effects models were used to calculate summary odds ratios. Results A total of 17 trials including 2,633 subjects were pooled. Pre-procedural hydration with sodium bicarbonate was associated with a significant decrease in the rate of contrast-induced nephropathy (odds ratios 0.52; 95% confidence interval 0.34–0.80, P = 0.003. Number needed to treat to prevent one case of contrast-induced nephropathy was 16 (95% confidence interval 10–34. No significant differences in the rates of post-procedure hemodialysis (P = 0.20 or death (P = 0.53 was observed. Conclusion Sodium bicarbonate-based hydration was found to be superior to normal saline in prevention of contrast-induced nephropathy in this updated meta-analysis.

Formation and Transformation Behavior of Sodium Dehydroacetate Hydrates

Directory of Open Access Journals (Sweden)

Xia Zhang

2016-04-01

Full Text Available The effect of various controlling factors on the polymorphic outcome of sodium dehydroacetate crystallization was investigated in this study. Cooling crystallization experiments of sodium dehydroacetate in water were conducted at different concentrations. The results revealed that the rate of supersaturation generation played a key role in the formation of the hydrates. At a high supersaturation generation rate, a new sodium dehydroacetate dihydrate needle form was obtained; on the contrary, a sodium dehydroacetate plate monohydrate was formed at a low supersaturation generation rate. Furthermore, the characterization and transformation behavior of these two hydrated forms were investigated with the combined use of microscopy, powder X-ray diffraction (PXRD, Raman spectroscopy, Fourier transform infrared (FTIR, thermal gravimetric analysis (TGA, scanning electron microscopy (SEM and dynamic vapor sorption (DVS. It was found that the new needle crystals were dihydrated and hollow, and they eventually transformed into sodium dehydroacetate monohydrate. In addition, the mechanism of formation of sodium dehydroacetate hydrates was discussed, and a process growth model of hollow crystals in cooling crystallization was proposed.

Investigation on the effect of THF on Nitrogen Hydrate formation under isobaric condition

Science.gov (United States)

Jamil, N.; Husin, H.; Aman, Z.; Hassan, Z.

2018-03-01

In this paper, we studied nitrogen (N2) hydrate formation in the presence of tetrahydrofuran (THF) under 3 different conditions; different concentration of THF (0, 3 and 30 %(v/v), different temperature setting (room temperature and induced temperature) and different water content (15, 35 and 55 mL) in an isobaric condition. We found that in the presence of THF which acting as an enhancer, hydrate formation kinetic is highly influenced by these parameters. We observed a striking contrast in hydrate formation behaviour observed at room temperature (RT) and induced temperature (IT) with and without the presence of THF under similar operating conditions. At the presence of 30 %(v/v) of THF in 15 mL water, it can be seen that, hydrate tend to form faster than other samples. Visual observation of N2hydrates are also conducted at 30 %(v/v) of THF in 15 mL water.

Ultrasonic experiment on hydrate formation of a synthesis gas

Energy Technology Data Exchange (ETDEWEB)

Sun, Shicai; Fan, Shuanshi; Liang, Deqing; Zhang, Junshe; Feng, Ziping

2005-07-01

The effect of ultrasonic on the induction time and formation rate of natural gas hydrates was investigated in a stainless steel cell in this study. The results show that the induction time with ultrasonic was about 1/6 of that without ultrasonic and only about 1/10 if rehydration after decomposition in water-gas system. In sodium dodecyl sulfate (SDS) solution-gas system, the critical micellar concentration (CMC) was not identified with ultrasonic. The formation rate and storage capacity of hydrate increased with increasing SDS concentration at a range of 0 to 800ppm. However, the increase was insignificant as the SDS concentration increased from 600 to 800ppm, (Author)

Complex formation constant and hydration number change of aqua-rare earth ions

International Nuclear Information System (INIS)

Kanno, H.

1998-01-01

Full text: It is now well established that the inner-sphere hydration number of aqua-rare earth ions changes from nine to eight in the middle of the rare earth series. This hydration number change greatly affects the complex formation of rare earth ions as we observe irregular variations in most series behaviours of the complex formation constant (K) in aqueous solution systems when K being plotted against 1/r or r (r is ionic radius of rare earth ion). Furthermore, it shows very anomalous concentration dependence in the sense that nona-aqua Ln 3+ ion increases in number with increase in salt concentration in aqueous rare earth salt solution (salt chloride, perchlorate). In this report, a theoretical derivation of the formation constant (K) for the inner-sphere complex formation of rare earth ions with a monodentate ligand was made by taking account of both the hydration number change in the middle of the series and its anomalous salt concentration dependence. The series behaviour of the formation constant against 1/r (or r) is successfully explained with using the empirical finding that K varies almost linearly with 1/r (or r) in the region where only one hydration number dominates. This success is also taken as evidence that the anomalous salt concentration dependence of the hydration number change is caused by the outer-sphere complex formation of rare earth ions with the condition that nona-aqua rare earth ions form outer-sphere complexes more easily than octa-aqua ions

Investigation of the Methane Hydrate Formation by Cavitation Jet

Science.gov (United States)

Morita, H.; Nagao, J.

2015-12-01

Methane hydrate (hereafter called "MH") is crystalline solid compound consisting of hydrogen-bonded water molecules forming cages and methane gas molecules enclosed in the cage. When using MH as an energy resource, MH is dissociated to methane gas and water and collect only the methane gas. The optimum MH production method was the "depressurization method". Here, the production of MH means dissociating MH in the geologic layers and collecting the resultant methane gas by production systems. In the production of MH by depressurization method, MH regeneration was consider to important problem for the flow assurance of MH production system. Therefore, it is necessary to clarify the effect of flow phenomena in the pipeline on hydrate regeneration. Cavitation is one of the flow phenomena which was considered a cause of MH regeneration. Large quantity of microbubbles are produced by cavitation in a moment, therefore, it is considered to promote MH formation. In order to verify the possible of MH regeneration by cavitation, it is necessary to detailed understanding the condition of MH formation by cavitation. As a part of a Japanese National hydrate research program (MH21, funded by METI), we performed a study on MH formation using by cavitation. The primary objective of this study is to demonstrate the formation MH by using cavitation in the various temperature and pressure condition, and to clarify the condition of MH formation by using observation results.

Natural gas hydrate formation and inhibition in gas/crude oil/aqueous systems

DEFF Research Database (Denmark)

Daraboina, Nagu; Pachitsas, Stylianos; von Solms, Nicolas

2015-01-01

Gas hydrate formation in multi phase mixtures containing an aqueous phase (with dissolved salts), reservoir fluid (crude oil) and natural gas phase was investigated by using a standard rocking cell (RC-5) apparatus. The hydrate formation temperature was reduced in the presence of crude oils...... can contribute to the safe operation of sub sea pipelines in the oil and gas industry....

Formation and dissociation of CO{sub 2} and CO{sub 2}-THF hydrates compared to CH{sub 4} and CH{sub 4}-THF hydrates

Energy Technology Data Exchange (ETDEWEB)

Giavarini, C.; Maccioni, F.; Broggi, A. [Roma Univ. La Sapienza, Roma (Italy). Dept. of Chemical Engineering; Politi, M. [ENEL-RICERCHE, Brindisi (Italy)

2008-07-01

Carbon sequestration involves the removal of greenhouse gases from industrial or utility plant streams and their long term storage so that they cannot interact with the climate system. Different methods for selective carbon dioxide (CO{sub 2}) removal are in commercial use and are based on, gas absorption, membrane process, and cryogenic fractionation. In addition, disposal of captured CO{sub 2} in the ocean and in geological reservoirs has been proposed by researchers. Another challenge is to take advantage of the properties of CO{sub 2} hydrates for carbon sequestration since it could have a number of uses such as chemical production. As such, it is important to understand the hydrate decomposition kinetics during storage, transportation, and disposal. This paper presented a project that involved the separation of carbon dioxide from the flue gases of powers plants, in the form of hydrate. The project also involved the storage, use, and disposal of the hydrate. The purpose of the study was to evaluate the decomposition kinetics of CO{sub 2} hydrate containing different quantities of ice, at low pressures and temperatures between -3 and 0 degrees Celsius. In addition, in order to evaluate the tetrahydrofuran (THF) stabilization effect, the study examined the influence of THF on the formation and decomposition kinetics of mixed THF-methane (CH{sub 4}) and THF-CO{sub 2} hydrates. Preservation tests were conducted to determine the best pressure and temperature conditions for the mixed-hydrates conservation, with reference to the simple hydrates. The paper described the apparatus for the formation and dissociation tests which consisted of a jacketed stainless steel reactor, equipped with stirrer. The paper also described the hydrate formation procedure as well as hydrate characterization. Last, the paper discussed the hydrate dissociation tests that were conducted immediately after hydrate formation in the reactor. It was concluded that the hydrophilic and hydrophobic

Experimental investigation of methane release from hydrate formation in sandstone through both hydrate dissociation and CO{sub 2} sequestration

Energy Technology Data Exchange (ETDEWEB)

Husebo, J.; Graue, A.; Kvamme, B. [Bergen Univ., Bergen (Norway). Dept. of Physics and Technology; Stevens, J.; Howard, J.J. [ConocoPhillips, Ponca City, OK (United States); Baldwin, B.A. [Green Country Petrophysics LLC, Dewey, OK (United States)

2008-07-01

Large amounts of natural gas trapped in hydrate reservoirs are found in Arctic regions and in deep offshore locations around the world. Natural gas production from hydrate deposits offer significant potential for future energy needs. However, research is needed in order to propose potential production schemes for natural gas hydrates. Natural gas molecules can be freed from hydrate structured cages by depressurization, by heating and by exposing the hydrate to a substance that will form a thermodynamically more stable hydrate structure. This paper provided a comparison of two approaches for releasing methane from methane hydrate in porous sandstone. The study scope covered the dissociation rate of methane hydrate in porous media through depressurization, and also referred to previous work done on producing methane from hydrates in sandstone while sequestering carbon dioxide (CO{sub 2}). The study was conducted in a laboratory setting. The paper discussed the experimental design which included the placing of a pressure- and temperature-controlled sample holder inside the bore of a magnetic resonance imager. The experimental procedures were then outlined, with reference to hydrate formation; carbon dioxide sequestration; hydrate dissociation experiments with constant volume; and hydrate dissociation experiments at constant pressure. The constant volume experiments demonstrated that in order to dissociate a large amount of hydrate, the initial depressurization had to be significantly lower than the hydrate stability pressure. 9 refs., 9 figs.

Gas hydrate formation process for pre-combustion capture of carbon dioxide

International Nuclear Information System (INIS)

Lee, Hyun Ju; Lee, Ju Dong; Linga, Praveen; Englezos, Peter; Kim, Young Seok; Lee, Man Sig; Kim, Yang Do

2010-01-01

In this study, gas hydrate from CO 2 /H 2 gas mixtures with the addition of tetrahydrofuran (THF) was formed in a semi-batch stirred vessel at various pressures and temperatures to investigate the CO 2 separation/recovery properties. This mixture is of interest to CO 2 separation and recovery from Integrated Gasification Combine Cycle (IGCC) power plants. During hydrate formation the gas uptake was determined and composition changes in the gas phase were obtained by gas chromatography. The impact of THF on hydrate formation from the CO 2 /H 2 was observed. The addition of THF significantly reduced the equilibrium formation conditions. 1.0 mol% THF was found to be the optimum concentration for CO 2 capture based on kinetic experiments. The present study illustrates the concept and provides thermodynamic and kinetic data for the separation/recovery of CO 2 (pre-combustion capture) from a fuel gas (CO 2 /H 2 ) mixture.

Study on the Promotion Effect of Ionic Liquid on CH4 Hydrate Formation

International Nuclear Information System (INIS)

Shin, Ju-Young; Mun, Sungyong; Kang, Seong-Pil; Kim, Kisub

2013-01-01

In this study, we investigated the kinetics of gas hydrate formation in the presence of ionic liquid (IL). Hydroxyethyl-methyl-morpholinium chloride (HEMM-Cl) was chosen as a material for the promotion effect test. Phase equilibrium curve for CH 4 hydrate with aqueous IL solution was obtained and its induction time and consumed amount of CH 4 gas were also measured. Aqueous solutions containing 20-20,000 ppm of HEMM-Cl was prepared and studied at 70 bar and 274.15 K. To compare the measured results to those of the conventional promoter, sodium dodecyl sulfate was also tested at the same condition. Result showed that the hydrate equilibrium curve was shifted toward higher pressure and lower temperature region. In addition, the induction time on CH 4 hydrate formation in the presence of IL was not shown. The amount of consumed CH 4 was increased with the whole range of tested concentration of IL and the highest consumption of CH 4 happened at 1,000 ppm of HEMM-Cl. HEMM-Cl induced and enhanced the CH 4 hydrate formation with a small amount of addition. Obtained result is expected to be applied for the development of technologies such as gas storage and transport using gas hydrates

Topological modeling of methane hydrate crystallization from low to high water cut emulsion systems

OpenAIRE

Melchuna , Aline; Cameirão , Ana; Herri , Jean-Michel; Glénat , Philippe

2016-01-01

International audience; Hydrate formation and remediation in oil flowlines facilities represent a major concern for oil industry in respect of capital and operational costs. It is necessary to have a better understanding on the hydrate formation process to be more efficient in hydrate prevention, especially in respect to additive dosage. This work is a contribution to enhance the knowledge of hydrate formation at high water cuts, by introducing new techniques of analysis in the Archimede flow...

Tetrafluoroethane (R134a) hydrate formation within variable volume reactor accompanied by evaporation and condensation

Energy Technology Data Exchange (ETDEWEB)

Jeong, K.; Choo, Y. S.; Hong, H. J.; Yoon, Y. S.; Song, M. H., E-mail: songm@dgu.edu [Department of Mechanical, Robotics, and Energy Engineering, Dongguk University, Seoul 100-715 (Korea, Republic of)

2015-03-15

Vast size hydrate formation reactors with fast conversion rate are required for the economic implementation of seawater desalination utilizing gas hydrate technology. The commercial target production rate is order of thousand tons of potable water per day per train. Various heat and mass transfer enhancement schemes including agitation, spraying, and bubbling have been examined to maximize the production capacities in scaled up design of hydrate formation reactors. The present experimental study focused on acquiring basic knowledge needed to design variable volume reactors to produce tetrafluoroethane hydrate slurry. Test vessel was composed of main cavity with fixed volume of 140 ml and auxiliary cavity with variable volume of 0 ∼ 64 ml. Temperatures at multiple locations within vessel and pressure were monitored while visual access was made through front window. Alternating evaporation and condensation induced by cyclic volume change provided agitation due to density differences among water and vapor, liquid and hydrate R134a as well as extended interface area, which improved hydrate formation kinetics coupled with latent heat release and absorption. Influences of coolant temperature, piston stroke/speed, and volume change period on hydrate formation kinetics were investigated. Suggestions of reactor design improvement for future experimental study are also made.

Tetrafluoroethane (R134a) hydrate formation within variable volume reactor accompanied by evaporation and condensation

International Nuclear Information System (INIS)

Jeong, K.; Choo, Y. S.; Hong, H. J.; Yoon, Y. S.; Song, M. H.

2015-01-01

Vast size hydrate formation reactors with fast conversion rate are required for the economic implementation of seawater desalination utilizing gas hydrate technology. The commercial target production rate is order of thousand tons of potable water per day per train. Various heat and mass transfer enhancement schemes including agitation, spraying, and bubbling have been examined to maximize the production capacities in scaled up design of hydrate formation reactors. The present experimental study focused on acquiring basic knowledge needed to design variable volume reactors to produce tetrafluoroethane hydrate slurry. Test vessel was composed of main cavity with fixed volume of 140 ml and auxiliary cavity with variable volume of 0 ∼ 64 ml. Temperatures at multiple locations within vessel and pressure were monitored while visual access was made through front window. Alternating evaporation and condensation induced by cyclic volume change provided agitation due to density differences among water and vapor, liquid and hydrate R134a as well as extended interface area, which improved hydrate formation kinetics coupled with latent heat release and absorption. Influences of coolant temperature, piston stroke/speed, and volume change period on hydrate formation kinetics were investigated. Suggestions of reactor design improvement for future experimental study are also made

First Study of Poly(3-Methylene-2-Pyrrolidone) as a Kinetic Hydrate Inhibitor

DEFF Research Database (Denmark)

Abrahamsen, Eirin; Heyns, Ingrid Marié; von Solms, Nicolas

2017-01-01

Formation of gas hydrates is a problem in the petroleum industry where the gas hydrates can cause blockage of the flowlines. Kinetic hydrate inhibitors (KHIs) are water-soluble polymers, sometimes used in combination synergistically or with non-polymeric synergists, that are used to prevent gas h...... are preferable in KHI polymers as long as they are water-soluble at hydrate-forming temperatures.......Formation of gas hydrates is a problem in the petroleum industry where the gas hydrates can cause blockage of the flowlines. Kinetic hydrate inhibitors (KHIs) are water-soluble polymers, sometimes used in combination synergistically or with non-polymeric synergists, that are used to prevent gas...... hydrate blockages. They have been used in the field successfully since 1995. In this paper, we present the first KHI results for the polymer, poly(3-methylene-2-pyrrolidone) (P(3M2P)), which is structurally similar to poly(N-vinylpyrrolidone) (PVP), one of the first KHIs to be discovered. 3M2P polymers...

Surface Assisted Formation of methane Hydrates on Ice and Na Montmorillonite Clay

Energy Technology Data Exchange (ETDEWEB)

Gordon, Margaret Ellen [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Teich-McGoldrick, Stephanie [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Cygan, Randall Timothy [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Meserole, Stephen P. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Rodriguez, Mark A. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

2015-07-01

Methane hydrates are extremely important naturally-occurring crystalline materials that impact climate change, energy resources, geological hazards, and other major environmental issues. Whereas significant experimental effort has been completed to understanding the bulk thermodynamics of methane hydrate assemblies, little is understood on heterogeneous nucleation and growth of methane hydrates in clay-rich environments. Controlled synthesis experiments were completed at 265-285 K and 6.89 MPa to examine the impact of montmorillonite surfaces in clay-ice mixtures to nucleate and form methane hydrate. The results suggest that the hydrophilic and methane adsorbing properties of Namontmorillonite reduce the nucleation period of methane hydrate formation in pure ice systems.

Synergistic kinetic inhibition of natural gas hydrate formation

DEFF Research Database (Denmark)

Daraboina, Nagu; Malmos, Christine; von Solms, Nicolas

2013-01-01

Rocking cells were used to investigate the natural gas hydrate formation and decomposition in the presence of kinetic inhibitor, Luvicap. In addition, the influence of poly ethylene oxide (PEO) and NaCl on the performance of Luvicap was investigated using temperature ramping and isothermal...

Modelling a deep water oil/gas spill under conditions of gas hydrate formation and decomposition

International Nuclear Information System (INIS)

Zheng, L.; Yapa, P.D.

2000-01-01

A model for the behavior of oil and gas spills at deepwater locations was presented. Such spills are subjected to pressures and temperatures that can convert gases to gas hydrates which are lighter than water. Knowing the state of gases as they rise with the plume is important in predicting the fate of an oil or gas plume released in deepwater. The objective of this paper was to develop a comprehensive jet/plume model which includes computational modules that simulate the gas hydrate formation/decomposition of gas bubbles. This newly developed model is based on the kinetics of hydrate formation and decomposition coupled with mass and heat transfer phenomena. The numerical model was successfully tested using results of experimental data from the Gulf of Mexico. Hydrate formation and decomposition are integrated with an earlier model by Yapa and Zheng for underwater oil or gas jets and plumes. The effects of hydrate on the behavior of an oil or gas plume was simulated to demonstrate the models capabilities. The model results indicate that in addition to thermodynamics, the kinetics of hydrate formation/decomposition should be considered when studying the behavior of oil and gas spills. It was shown that plume behavior changes significantly depending on whether or not the local conditions force the gases to form hydrates. 25 refs., 4 tabs., 12 figs

Report: Fourth International Conference on Gas Hydrates, held at Yokohama, Japan, 19-23 May 2002

Digital Repository Service at National Institute of Oceanography (India)

Karisiddaiah, S.M.

formations, while Dr. L. Stern presented ne insights into the phenomena of anomalous or self- preservation of gas hydrates. JOUR.GEOL.SOC.INDIA, VOL.61, JAN. 2001 Posters on hydrate formation and prevention in pipelines and hydrate based...-1 REPORT ON THE 4TH INTERNATIONAL CONFERENCE ON GAS HYDRATES The fourth International Conference on Gas Hydrates was recently held at Yokohama, Japan, between 19-23 May 2002 following the earlier conferences held in USA (1993...

The role of hydrophobic interactions for the formation of gas hydrates

Energy Technology Data Exchange (ETDEWEB)

Yoon, R.H.; Wang, J.; Eriksson, J.C. [Virginia Polytech Inst. and State Univ., Blacksburg, VA (United States). Center for Advanced Separation Technologies; Sum, A.K. [Colorado School of Mines, Golden, CO (United States). Dept. of Chemical Engineering

2008-07-01

The process of hydrate formation remains largely unexplained due to a lack of evidence for the water molecules around the hydrophobic solute such as methane, and the nucleation process leading to the clustering that induces hydrate growth. However, the water structure is known to play a major role in the mechanism for hydrate nucleation. This paper presented evidence that hydrophobic solutes promote the structuring of water. Water molecules at room temperature tend to form ice structures around the hydrocarbon chains of surfactant molecules dissolved in water. An atomic force microscope (AFM) was used in this study to measure the surface forces between thiolated gold surfaces. The purpose was to better understand the structure of the thin films of water between hydrophobic surfaces. The water molecules tended to reorganize themselves to form ordered structures, which may be related to the nucleation of hydrates. The entropy reduction associated with the ice structure can be considered as the net driving force for self-assembly. Recent studies have revealed that long-range attractive forces exist between hydrophobic surfaces, which are likely to result from structuring of the water molecules in the vicinity of the hydrophobic surfaces. Similarly, the hydrophobic nature of most gas hydrate formers may induce ordering of water molecules in the vicinity of dissolved solutes. It was concluded that the results of this study may be used to develop a new mechanism for the formation of gas hydrates, including methane. 20 refs., 2 figs.

A sample cell to study hydrate formation with x-ray scattering

International Nuclear Information System (INIS)

Conrad, Heiko; Lehmkuehler, Felix; Sternemann, Christian; Feroughi, Omid; Tolan, Metin; Simonelli, Laura; Huotari, Simo

2009-01-01

We present a new sample cell for measuring nonresonant inelastic x-ray scattering spectra of a tetrahydrofuran (THF)-water liquid mixture and THF hydrate. The hydrate is formed inside the cell after nucleation seeds have been offered by a special magnetic stirring mechanism. Hydrate formation was verified by wide angle x-ray scattering and nonresonant x-ray Raman scattering spectra at the oxygen K-edge. A broad range of scattering angles can be studied with this cell which is necessary for momentum transfer dependent inelastic x-ray scattering. This cell is ideal to examine other liquid hydrate formers or other liquid samples, which have to be mixed in situ during the measurements.

Hydrate formation during wet granulation studied by spectroscopic methods and multivariate analysis

DEFF Research Database (Denmark)

Jørgensen, Anna; Rantanen, Jukka; Karjalainen, Milja

2002-01-01

PURPOSE: The aim was to follow hydrate formation of two structurally related drugs, theophylline and caffeine, during wet granulation using fast and nondestructive spectroscopic methods. METHODS: Anhydrous theophylline and caffeine were granulated with purified water. Charge-coupled device (CCD......) Raman spectroscopy was compared with near-infrared spectroscopy (NIR) in following hydrate formation of drugs during wet granulation (off-line). To perform an at-line process analysis, the effect of water addition was monitored by NIR spectroscopy and principal components analysis (PCA). The changes...

The inhibition of methane hydrate formation by water alignment underneath surface adsorption of surfactants

Energy Technology Data Exchange (ETDEWEB)

Nguyen, Ngoc N.; Nguyen, Anh V.; Dang, Liem X.

2017-06-01

Sodium dodecyl sulfate (SDS) has been widely shown to strongly promote the formation of methane hydrate. Here we show that SDS displays an extraordinary inhibition effect on methane hydrate formation when the surfactant is used in sub-millimolar concentration (around 0.3 mM). We have also employed Sum Frequency Generation vibrational spectroscopy (SFG) and molecular dynamics simulation (MDS) to elucidate the molecular mechanism of this inhibition. The SFG and MDS results revealed a strong alignment of water molecules underneath surface adsorption of SDS in its sub-millimolar solution. Interestingly, both the alignment of water and the inhibition effect (in 0.3 mM SDS solution) went vanishing when an oppositely-charged surfactant (tetra-n-butylammonium bromide, TBAB) was suitably added to produce a mixed solution of 0.3 mM SDS and 3.6 mM TBAB. Combining structural and kinetic results, we pointed out that the alignment of water underneath surface adsorption of dodecyl sulfate (DS-) anions gave rise to the unexpected inhibition of methane hydration formation in sub-millimolar solution of SDS. The adoption of TBAB mitigated the SDS-induced electrostatic field at the solution’s surface and, therefore, weakened the alignment of interfacial water which, in turn, erased the inhibition effect. We discussed this finding using the concept of activation energy of the interfacial formation of gas hydrate. The main finding of this work is to reveal the interplay of interfacial water in governing gas hydrate formation which sheds light on a universal molecular-scale understanding of the influence of surfactants on gas hydrate formation. This work was supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences, and Biosciences. The calculations were carried out using computer resources provided by the Office of Basic Energy Sciences.

Methane hydrate distribution from prolonged and repeated formation in natural and compacted sand samples: X-ray CT observations

Energy Technology Data Exchange (ETDEWEB)

Rees, E.V.L.; Kneafsey, T.J.; Seol, Y.

2010-07-01

To study physical properties of methane gas hydrate-bearing sediments, it is necessary to synthesize laboratory samples due to the limited availability of cores from natural deposits. X-ray computed tomography (CT) and other observations have shown gas hydrate to occur in a number of morphologies over a variety of sediment types. To aid in understanding formation and growth patterns of hydrate in sediments, methane hydrate was repeatedly formed in laboratory-packed sand samples and in a natural sediment core from the Mount Elbert Stratigraphic Test Well. CT scanning was performed during hydrate formation and decomposition steps, and periodically while the hydrate samples remained under stable conditions for up to 60 days. The investigation revealed the impact of water saturation on location and morphology of hydrate in both laboratory and natural sediments during repeated hydrate formations. Significant redistribution of hydrate and water in the samples was observed over both the short and long term.

Examination of Hydrate Formation Methods: Trying to Create Representative Samples

Energy Technology Data Exchange (ETDEWEB)

Kneafsey, T.J.; Rees, E.V.L.; Nakagawa, S.; Kwon, T.-H.

2011-04-01

Forming representative gas hydrate-bearing laboratory samples is important so that the properties of these materials may be measured, while controlling the composition and other variables. Natural samples are rare, and have often experienced pressure and temperature changes that may affect the property to be measured [Waite et al., 2008]. Forming methane hydrate samples in the laboratory has been done a number of ways, each having advantages and disadvantages. The ice-to-hydrate method [Stern et al., 1996], contacts melting ice with methane at the appropriate pressure to form hydrate. The hydrate can then be crushed and mixed with mineral grains under controlled conditions, and then compacted to create laboratory samples of methane hydrate in a mineral medium. The hydrate in these samples will be part of the load-bearing frame of the medium. In the excess gas method [Handa and Stupin, 1992], water is distributed throughout a mineral medium (e.g. packed moist sand, drained sand, moistened silica gel, other porous media) and the mixture is brought to hydrate-stable conditions (chilled and pressurized with gas), allowing hydrate to form. This method typically produces grain-cementing hydrate from pendular water in sand [Waite et al., 2004]. In the dissolved gas method [Tohidi et al., 2002], water with sufficient dissolved guest molecules is brought to hydrate-stable conditions where hydrate forms. In the laboratory, this is can be done by pre-dissolving the gas of interest in water and then introducing it to the sample under the appropriate conditions. With this method, it is easier to form hydrate from more soluble gases such as carbon dioxide. It is thought that this method more closely simulates the way most natural gas hydrate has formed. Laboratory implementation, however, is difficult, and sample formation is prohibitively time consuming [Minagawa et al., 2005; Spangenberg and Kulenkampff, 2005]. In another version of this technique, a specified quantity of gas

The formation of gas hydrates and the effect of inhibitiors on their ...

African Journals Online (AJOL)

Natural gas hydrate is a solid crystalline compound produced by combining water and gas and it is considered as the clathrates. Guest gas molecules are stuck insider the pores of water networks produced by hydrogen bonds between molecules of water. There are different ways to analyze the hydrate formation operating ...

Gas hydrate formation and accumulation potential in the Qiangtang Basin, northern Tibet, China

International Nuclear Information System (INIS)

Fu, Xiugen; Wang, Jian; Tan, Fuwen; Feng, Xinglei; Wang, Dong; He, Jianglin

2013-01-01

Highlights: • Qiangtang Basin is the biggest residual petroleum-bearing basin in Tibet Plateau. • The Late Triassic Tumen Gela Formation is the most important gas source rock. • Seventy-one potential anticline structural traps have been found. • A favorable geothermal condition for gas hydrate formation. • A large number of mud volcanoes were discovered in the basin. - Abstract: The Qiangtang Basin is the biggest residual petroleum-bearing basin in the Qinghai–Tibet Plateau, and is also an area of continuous permafrost in southwest China with strong similarities to other known gas-hydrate-bearing regions. Permafrost thickness is typically 60–180 m; average surface temperature ranges from −0.2 to −4.0 °C, and the geothermal gradient is about 2.64 °C/100 m. In the basin, the Late Triassic Tumen Gela Formation is the most important gas source rock for gas, and there are 34.3 × 10 8 t of gas resources in the Tumen Gela Formation hydrocarbon system. Seventy-one potential anticline structural traps have been found nowadays covering an area of more than 30 km 2 for each individual one, five of them are connected with the gas source by faults. Recently, a large number of mud volcanoes were discovered in the central Qiangtang Basin, which could be indicative of the formation of potential gas hydrate. The North Qiangtang depression should be delineated as the main targets for the purpose of gas hydrate exploration

Adsorption of water and carbon dioxide on hematite and consequences for possible hydrate formation.

Science.gov (United States)

Kvamme, Bjørn; Kuznetsova, Tatiana; Kivelae, Pilvi-Helina

2012-04-07

The interest in carbon dioxide for enhanced oil recovery is increasing proportional to the decline in naturally driven oil production and also due to the increasing demand for reduced emission of carbon dioxide into the atmosphere. Transport of carbon dioxide in offshore pipelines involves high pressure and low temperatures, conditions which may lead to formation of hydrates from residual water dissolved in carbon dioxide and carbon dioxide. The critical question is whether the water at certain temperatures and pressures will drop out as liquid droplets first, and then form hydrates, or alternatively, adsorb on the pipeline surfaces, and subsequently form hydrates heterogeneously. In this work, we used several different basis sets of density functional theory in ab initio calculations to estimate the charge distribution of hematite (the dominating component of rust) crystals. These rust particles were embedded in water and chemical potential for adsorbed water molecules was estimated through thermodynamic integration and compared to similar estimates for water clusters of the same size. While the generated charges were not unique, the use of high order approximations and different basis sets provides a range of likely charge distributions. Values obtained for the chemical potential of water in different surroundings indicated that it would be thermodynamically favorable for water to adsorb on hematite, and that evaluation of potential carbon dioxide hydrate formation conditions and kinetics should be based on this formation mechanism. Depending on the basis set and approximations, the estimated gain for water to adsorb on the hematite surface rather than condense as droplets varied between -1.7 kJ mole(-1) and -3.4 kJ mole(-1). The partial charge distribution on the hematite surface is incompatible with the hydrate structure, and thus hydrates will be unable to attach to the surface. The behavior of water outside the immediate vicinity of hematite (beyond 3

A rigorous mechanistic model for predicting gas hydrate formation kinetics: The case of CO2 recovery and sequestration

International Nuclear Information System (INIS)

ZareNezhad, Bahman; Mottahedin, Mona

2012-01-01

Highlights: ► A mechanistic model for predicting gas hydrate formation kinetics is presented. ► A secondary nucleation rate model is proposed for the first time. ► Crystal–crystal collisions and crystal–impeller collisions are distinguished. ► Simultaneous determination of nucleation and growth kinetics are established. ► Important for design of gas hydrate based energy storage and CO 2 recovery systems. - Abstract: A rigorous mechanistic model for predicting gas hydrate formation crystallization kinetics is presented and the special case of CO 2 gas hydrate formation regarding CO 2 recovery and sequestration processes has been investigated by using the proposed model. A physical model for prediction of secondary nucleation rate is proposed for the first time and the formation rates of secondary nuclei by crystal–crystal collisions and crystal–impeller collisions are formulated. The objective functions for simultaneous determination of nucleation and growth kinetics are presented and a theoretical framework for predicting the dynamic behavior of gas hydrate formation is presented. Predicted time variations of CO 2 content, total number and surface area of produced hydrate crystals are in good agreement with the available experimental data. The proposed approach can have considerable application for design of gas hydrate converters regarding energy storage and CO 2 recovery processes.

An Examination of the Prediction of Hydrate Formation Conditions in the Presence of Thermodynamic Inhibitors

Directory of Open Access Journals (Sweden)

Carollina de M. Molinari O. Antunes

Full Text Available Abstract Gas hydrates are crystalline compounds, solid structures where water traps small guest molecules, typically light gases, in cages formed by hydrogen bonds. They are notorious for causing problems in oil and gas production, transportation and processing. Gas hydrates may form at pressures and temperatures commonly found in natural gas and oil production pipelines, thus causing partial or complete pipe blockages. In order to inhibit hydrate formation, chemicals such as alcohols (e.g., ethanol, methanol, mono-ethylene glycol and salts (sodium, magnesium or potassium chloride are injected into the produced stream. The purpose of this work is to briefly review the literature on hydrate formation in mixtures containing light gases (hydrocarbons and carbon dioxide and water in the presence of thermodynamic inhibitors. Four calculation methods to predict hydrate formation in those systems were examined and compared. Three commercial packages (Multiflash®, PVTSim® and CSMGem and a hydrate prediction routine in Fortran90 using the van der Waals and Platteeuw theory and the Peng-Robinson equation of state were tested. Predictions given by the four methods were compared to independent experimental data from the literature. In general, the four methods were found to be reasonably accurate. CSMGem and Multiflash® showed the best results.

Methane recovery from coal mine gas using hydrate formation in water-in-oil emulsions

International Nuclear Information System (INIS)

Zhong, Dong-Liang; Ding, Kun; Lu, Yi-Yu; Yan, Jin; Zhao, Wei-Long

2016-01-01

Highlights: • A water-in-oil emulsion was developed for CH_4 separation from coal mine methane gas. • Stable W/O emulsions were obtained with water cut in the range of (10–70%). • Gas hydrates nucleated faster with the reduction of water–oil volume ratio. • Gas uptake increased with the decrease of water–oil volume ratio. • CH_4 recovery was greatly enhanced by hydrate formation in W/O emulsions. - Abstract: In this work, a water-in-oil (W/O) emulsion was developed using liquid water, mineral oil, Sorbitan monooleate (Span 80), and cyclopentane. It was employed to enhance gas hydrate formation for CH_4 separation from a simulated coal mine methane (CMM) gas (30 mol% CH_4, 60 mol% N_2, and 10 mol% O_2). The stability test at atmospheric pressure and at a high pressure of 3.5 MPa showed that stable W/O emulsions were obtained when the water–oil volume ratio (WOR) was below 80%. The emulsified droplets size was measured with WOR ranging from 10% to 70%. Then kinetic experiments of CH_4 separation by hydrate formation in W/O emulsions were carried out at 273.6 K and (3.5–5.0) MPa in batch operation. The results indicated that water–oil volume ratio is a key factor that affects the kinetics of gas hydrate formation from the CMM gas mixture. Hydrate nucleation was observed to occur faster while WOR was decreased, and gas uptake increased significantly with the decrease of WOR. CH_4 concentration in the recovered gas mixture was increased to 52 mol% as compared to 30 mol% in the original gas mixture through one-stage hydrate formation in the W/O emulsions. It was found that the experimental conditions of 273.6 K, 3.5 MPa and WOR = 30% were favorable for CH_4 recovery from the CMM gas. The CH_4 recovery obtained under these conditions was 43%. It was higher than those obtained at WOR = 10% and 70%, and was greatly increased as compared with those obtained in the same reactor with the presence of TBAB (26%) and CP (33%).

Synthesis, formation mechanism and sensing properties of WO3 hydrate nanowire netted-spheres

International Nuclear Information System (INIS)

Yan, Aihua; Xie, Changsheng; Zeng, Dawen; Cai, Shuizhou; Hu, Mulin

2010-01-01

Tungsten oxide hydrate nanowire netted-spheres were successfully synthesized in the glycol solution using a facile solvothermal approach. The nanowires with uniform diameter of 4-6 nm are actually a kind of tungsten oxide hydrate/surfactant hybrid materials. The influence of surfactant, solvent, time and temperature on tailoring morphology was investigated in detail. The possible formation process of WO 3 hydrate nanowire netted-sphere was proposed. Sensing properties of such WO 3 hydrate sensor show that the desirable sensing characteristics towards 100 ppm ammonia gas at 320 o C were obtained, such as rapid response (18.3 s), high sensitivity, good reproducibility and stability.

New generation LDHI with an improved environmental profile[Low dosage hydrate inhibitors

Energy Technology Data Exchange (ETDEWEB)

Fu, Bob; Houston, Christopher; Spratt, Tony

2005-07-01

A new generation of low dosage hydrate inhibitors has been developed. These inhibitors are specially designed and synthesized in the laboratory in order to achieve a high level of performance as hydrate inhibitors and to improve their environmental profiles. These new inhibitors have been extensively evaluated in the laboratory using high pressure rocking cells. They function like anti-agglomerants by preventing the formation of large hydrate crystals or agglomerates. The resulting hydrate crystals are extremely tiny and finely dispersed in the hydrocarbon stream. In addition to controlling the hydrate crystal growth, these novel molecules demonstrate the ability to extend the induction time to onset of hydrate formation. When compared to the previous generations, the improved performance as well as the favorable environmental characteristics further expand the window for LDHI applications in the fields. (Author)

The potential for methane hydrate formation in deep repositories of spent nuclear fuel in granitic rocks

International Nuclear Information System (INIS)

Tohidi, Bahman; Chapoy, Antonin; Smellie, John; Puigdomenech, Ignasi

2010-12-01

The main aim of this work was to establish whether the pertaining pressure and temperature conditions and dissolved gas concentration in groundwater is conducive to gas hydrate formation using a modelling approach. The hydrate stability pressure-temperature zone of dissolved methane in the presence of salt has been obtained through calculations which show that a decrease in the system pressure and/or an increase in salt concentration favours hydrate formation, as both factors reduce equilibrium gas solubility in the aqueous phase. This behaviour is unlike that of the system including a gas phase, where the water phase is always saturated with methane, and hence the methane solubility in water is not a limiting factor. The main conclusion is that hydrate formation is not possible at the reported methane concentrations and water salinities for the Forsmark and Laxemar sites in Sweden and Olkiluoto in Finland. At the highest salinities and methane concentrations encountered, namely ∼0.00073 mole fraction methane and ∼10 mass % NaCl at a depth of 1,000 m in Olkiluoto, Finland, hydrates could form if the system temperatures and pressures are below 2.5 deg C and 60 bar, respectively, i.e. values that are much lower than those prevailing at that depth (∼20 deg C and ∼100 bar, respectively). Furthermore, the calculated results provide the necessary data to estimate the effect of increase in dissolved methane concentration on potential hydrate formation, as well as two phase flow. The available depth dependency of methane concentration at the sites studied in Sweden and Finland was used in another study to estimate the diffusive flow of methane in the rock volumes. These diffusion rates, which are highest at Olkiluoto, indicate that even if the conditions were to become favourable to methane hydrate formation, then it would take several millions of years before a thin layer of hydrates could be formed, a condition which is outside the required period of satisfactory

The potential for methane hydrate formation in deep repositories of spent nuclear fuel in granitic rocks

Energy Technology Data Exchange (ETDEWEB)

Tohidi, Bahman; Chapoy, Antonin (Hydrafact Ltd, Inst. of Petroleum Engineering, Heriot-Watt Univ., Edinburgh (United Kingdom)); Smellie, John (Conterra AB, Uppsala (Sweden)); Puigdomenech, Ignasi (Swedish Nuclear Fuel and Waste Management Co., Stockholm (Sweden))

2010-12-15

The main aim of this work was to establish whether the pertaining pressure and temperature conditions and dissolved gas concentration in groundwater is conducive to gas hydrate formation using a modelling approach. The hydrate stability pressure-temperature zone of dissolved methane in the presence of salt has been obtained through calculations which show that a decrease in the system pressure and/or an increase in salt concentration favours hydrate formation, as both factors reduce equilibrium gas solubility in the aqueous phase. This behaviour is unlike that of the system including a gas phase, where the water phase is always saturated with methane, and hence the methane solubility in water is not a limiting factor. The main conclusion is that hydrate formation is not possible at the reported methane concentrations and water salinities for the Forsmark and Laxemar sites in Sweden and Olkiluoto in Finland. At the highest salinities and methane concentrations encountered, namely approx0.00073 mole fraction methane and approx10 mass % NaCl at a depth of 1,000 m in Olkiluoto, Finland, hydrates could form if the system temperatures and pressures are below 2.5 deg C and 60 bar, respectively, i.e. values that are much lower than those prevailing at that depth (approx20 deg C and approx100 bar, respectively). Furthermore, the calculated results provide the necessary data to estimate the effect of increase in dissolved methane concentration on potential hydrate formation, as well as two phase flow. The available depth dependency of methane concentration at the sites studied in Sweden and Finland was used in another study to estimate the diffusive flow of methane in the rock volumes. These diffusion rates, which are highest at Olkiluoto, indicate that even if the conditions were to become favourable to methane hydrate formation, then it would take several millions of years before a thin layer of hydrates could be formed, a condition which is outside the required period of

Equivalent formation strength as a proxy tool for exploring the existence and distribution of gas hydrates

Science.gov (United States)

Hamada, Y.; Yamada, Y.; Sanada, Y.; Nakamura, Y.; Kido, Y. N.; Moe, K.

2017-12-01

Gas hydrates bearing layer can be normally identified by a basement simulating reflector (BSR) or well logging because of their high acoustic- and electric impedance compared to the surrounding formation. These characteristics of the gas hydrate can also represent contrast of in-situ formation strength. We here attempt to describe gas hydrate bearing layers based on the equivalent strength (EST). The Indian National Gas Hydrate Program (NGHP) Expedition 02 was executed 2015 off the eastern margin of the Indian Peninsula to investigate distribution and occurrence of gas hydrates. From 25 drill sites, downhole logging data, cored samples, and drilling performance data were collected. Recorded drilling performance data was converted to the EST, which is a developed mechanical strength calculated only by drilling parameters (top drive torque, rotation per minute , rate of penetration , and drill bit diameter). At a representative site, site 23, the EST shows constant trend of 5 to 10 MPa, with some positive peaks at 0 - 270 mbsf interval, and sudden increase up to 50 MPa above BSR depth (270 - 290 mbsf). Below the BSR, the EST stays at 5-10 MPa down to the bottom of the hole (378 mbsf). Comparison of the EST with logging data and core sample description suggests that the depth profiles of the EST reflect formation lithology and gas hydrate content: the EST increase in the sand-rich layer and the gas hydrate bearing zone. Especially in the gas hydrate zone, the EST curve indicates approximately the same trend with that of P-wave velocity and resistivity measured by downhole logging. Cross plot of the increment of the EST and resistivity revealed the relation between them is roughly logarithmic, indicating the increase and decrease of the EST strongly depend on the saturation factor of gas hydrate. These results suggest that the EST, proxy of in-situ formation strength, can be an indicator of existence and amount of the gas-hydrate layer. Although the EST was calculated

Towards an understanding of the propensity for crystalline hydrate formation by molecular compounds

Directory of Open Access Journals (Sweden)

Alankriti Bajpai

2016-11-01

Full Text Available Hydrates are technologically important and ubiquitous yet they remain a poorly understood and understudied class of molecular crystals. In this work, we attempt to rationalize propensity towards hydrate formation through crystallization studies of molecules that lack strong hydrogen-bond donor groups. A Cambridge Structural Database (CSD survey indicates that the statistical occurrence of hydrates in 124 molecules that contain five- and six-membered N-heterocyclic aromatic moieties is 18.5%. However, hydrate screening experiments on a library of 11 N-heterocyclic aromatic compounds with at least two acceptor moieties and no competing hydrogen-bond donors or acceptors reveals that over 70% of this group form hydrates, suggesting that extrapolation from CSD statistics might, at least in some cases, be deceiving. Slurrying in water and exposure to humidity were found to be the most effective discovery methods. Electrostatic potential maps and/or analysis of the crystal packing in anhydrate structures was used to rationalize why certain molecules did not readily form hydrates.

Communication: Quantitative Fourier-transform infrared data for competitive loading of small cages during all-vapor instantaneous formation of gas-hydrate aerosols

Science.gov (United States)

Uras-Aytemiz, Nevin; Abrrey Monreal, I.; Devlin, J. Paul

2011-10-01

A simple method has been developed for the measurement of high quality FTIR spectra of aerosols of gas-hydrate nanoparticles. The application of this method enables quantitative observation of gas hydrates that form on subsecond timescales using our all-vapor approach that includes an ether catalyst rather than high pressures to promote hydrate formation. The sampling method is versatile allowing routine studies at temperatures ranging from 120 to 210 K of either a single gas or the competitive uptake of different gas molecules in small cages of the hydrates. The present study emphasizes hydrate aerosols formed by pulsing vapor mixtures into a cold chamber held at 160 or 180 K. We emphasize aerosol spectra from 6 scans recorded an average of 8 s after "instantaneous" hydrate formation as well as of the gas hydrates as they evolve with time. Quantitative aerosol data are reported and analyzed for single small-cage guests and for mixed hydrates of CO2, CH4, C2H2, N2O, N2, and air. The approach, combined with the instant formation of gas hydrates from vapors only, offers promise with respect to optimization of methods for the formation and control of gas hydrates.

Molecular dynamics study of methane hydrate formation at a water/methane interface.

Science.gov (United States)

Zhang, Junfang; Hawtin, R W; Yang, Ye; Nakagava, Edson; Rivero, M; Choi, S K; Rodger, P M

2008-08-28

We present molecular dynamics simulation results of a liquid water/methane interface, with and without an oligomer of poly(methylaminoethylmethacrylate), PMAEMA. PMAEMA is an active component of a commercial low dosage hydrate inhibitor (LDHI). Simulations were performed in the constant NPT ensemble at temperatures of 220, 235, 240, 245, and 250 K and a pressure of 300 bar. The simulations show the onset of methane hydrate growth within 30 ns for temperatures below 245 K in the methane/water systems; at 240 K there is an induction period of ca. 20 ns, but at lower temperatures growth commences immediately. The simulations were analyzed to calculate hydrate content, the propensity for hydrogen bond formation, and how these were affected by both temperature and the presence of the LDHI. As expected, both the hydrogen bond number and hydrate content decreased with increasing temperature, though little difference was observed between the lowest two temperatures considered. In the presence of PMAEMA, the temperature below which sustained hydrate growth occurred was observed to decrease. Some of the implications for the role of PMAEMA in LDHIs are discussed.

Impact of left ventricular end diastolic pressure guided hydration on prevention of contrast induced nephropathy post cardiac catheterization

Directory of Open Access Journals (Sweden)

Sherif Wagdy Ayad

2015-12-01

Conclusions: LVEDP-guided hydration is superior to standard hydration in prevention of CIN. Hydration can be done based on LVFP in patients with pre-procedure normal LVF and in patients with pre-procedure elevated LVFP but not in those patients with inconclusive LVFP in which hydration should be guided by the invasively measured LVEDP.

The investigation of lithium formate hydrate, sodium dithionate and N-methyl taurine as clinical EPR dosimeters

International Nuclear Information System (INIS)

Lelie, S.; Hole, E.O.; Duchateau, M.; Schroeyers, W.; Schreurs, S.; Verellen, D.

2013-01-01

Introduction: EPR-dosimetry using L-α-alanine is an established method for measuring high doses of ionizing radiation. However, since a minimum dose of approximately 4 Gy is required to achieve sufficient low uncertainties (1–2%) for clinical application, alternative dosimeter materials are being inquired. Lithium formate (LiFo) monohydrate has been studied by several groups and has revealed several promising properties in the low dose region (<4 Gy). The fading properties, however, are somewhat unpredictable, and depend on properties not yet fully uncovered. This paper reports the results from a study of lithium formate hydrate and N-methyl taurine as potential low dose EPR dosimeters. Methods and materials: Pellet shaped dosimeters of lithium formate monohydrate, lithium formate hydrate, sodium dithionate and N-methyl taurine were produced using a manual Weber press, L-α-alanine was obtained from Harwell dosimeters and irradiated using 60 kV and 6 MV X-ray beams, and Co-60 gamma-rays to a dose of 30 Gy and dose ranges of 0.5–100 Gy and 2–20 Gy respectively. The dosimeters were measured using an Electron Paramagnetic Resonance (EPR)-spectrometer. The detector responses for 6 MV and Co-60 radiation beams, the fading behaviors and signal shape in time were investigated. Results: Lithium formate monohydrate and lithium formate hydrate are apparently associated with near identical EPR-spectra (mainly one broad line), and the same spectrum arises for all radiation energies investigated. The shape of the EPR resonance remains constant with time, but the intensities decreases, and the fading is more prominent for the monohydrate than for the hydrate. The EPR resonance associated with N-methyl taurine is more complex than the resonance associated with LiFo and it changes with time, implying radical transitions and growth. Conclusions: The study showed that lithium formate hydrate is a strong candidate for EPR dosimetry with slightly better fading characteristics

Observation of ice sheet formation on methane and ethane gas hydrates using a scanning confocal microscopy

Energy Technology Data Exchange (ETDEWEB)

Nagao, J.; Shimomura, N.; Ebinuma, T.; Narita, H. [National Inst. of Advanced Industrial Science and Technology, Toyohira, Sapporo (Japan). Methane Hydrate Research Lab.

2008-07-01

Interest in gas hydrates has increased in recent years due to the discovery of large deposits under the ocean floor and in permafrost regions. Natural gas hydrates, including methane, is expected to become a new energy source and a medium for energy storage and transportation. Gas hydrates consist of an open network of water molecules that are hydrogen-bonded in a similar manner to ice. Gas molecules are interstitially engaged under high pressures and low temperatures. Although the dissociation temperature of methane hydrate under atmospheric pressure is about 193 K, studies have shown that methane hydrate can be stored at atmospheric pressure and 267 K for 2 years. Because of this phenomenon, known as self-preservation, transportation and storage of methane hydrate can occur at temperature conditions milder than those for liquefied methane gas at atmospheric pressure. This study examined the surface changes of methane and ethane hydrates during dissociation using an optical microscope and confocal scanning microscope (CSM). This paper reported on the results when the atmospheric gas pressure was decreased. Ice sheets formed on the surfaces of methane and ethane gas hydrates due to depressurizing dissociation of methane and ethane hydrates when the methane and ethane gas pressures were decreased at designated temperatures. The dissociation of methane gas hydrate below below 237 K resulted in the generation of small ice particles on the hydrate surface. A transparent ice sheet formed on the hydrate surface above 242 K. The thickness of the ice sheet on the methane hydrate surface showed the maximum of ca. 30 {mu}m at 253 K. In the case of ethane hydrates, ice particles and ice sheets formed below 262 and 267 respectively. Since the ice particles and ice sheets were formed by water molecules generated during the gas hydrate dissociation, the mechanism of ice sheet formation depends on the dissociation rate of hydrate, ice particle sintering rate, and water molecule

Gas hydrates in gas storage caverns; Gashydrate bei der Gaskavernenspeicherung

Energy Technology Data Exchange (ETDEWEB)

Groenefeld, P. [Kavernen Bau- und Betriebs-GmbH, Hannover (Germany)

1997-12-31

Given appropriate pressure and temperature conditions the storage of natural gas in salt caverns can lead to the formation of gas hydrates in the producing well or aboveground operating facilities. This is attributable to the stored gas becoming more or less saturated with water vapour. The present contribution describes the humidity, pressure, and temperature conditions conducive to gas hydrate formation. It also deals with the reduction of the gas removal capacity resulting from gas hydrate formation, and possible measures for preventing hydrate formation such as injection of glycol, the reduction of water vapour absorption from the cavern sump, and dewatering of the cavern sump. (MSK) [Deutsch] Bei der Speicherung von Erdgas in Salzkavernen kann es unter entsprechenden Druck- und Temperaturverhaeltnissen zur Gashydratbildung in den Foerdersonden oder obertaegigen Betriebseinrichtungen kommen, weil sich das eingelagerte Gas mehr oder weniger mit Wasserdampf aufsaettigt. Im Folgenden werden die Feuchtigkeits-, Druck- und Temperaturbedingungen, die zur Hydratbildung fuehren erlaeutert. Ebenso werden die Verringerung der Auslagerungskapazitaet durch die Hydratbildung, Massnahmen zur Verhinderung der Hydratbildung wie die Injektion von Glykol, die Verringerung der Wasserdampfaufnahme aus dem Kavernensumpf und die Entwaesserung der Kavernensumpfs selbst beschrieben.

Methane Recycling During Burial of Methane Hydrate-Bearing Sediments

Science.gov (United States)

You, K.; Flemings, P. B.

2017-12-01

We quantitatively investigate the integral processes of methane hydrate formation from local microbial methane generation, burial of methane hydrate with sedimentation, and methane recycling at the base of the hydrate stability zone (BHSZ) with a multiphase multicomponent numerical model. Methane recycling happens in cycles, and there is not a steady state. Each cycle starts with free gas accumulation from hydrate dissociation below the BHSZ. This free gas flows upward under buoyancy, elevates the hydrate saturation and capillary entry pressure at the BHSZ, and this prevents more free gas flowing in. Later as this layer with elevated hydrate saturation is buried and dissociated, the large amount of free gas newly released and accumulated below rapidly intrudes into the hydrate stability zone, drives rapid hydrate formation and creates three-phase (gas, liquid and hydrate) equilibrium above the BHSZ. The gas front retreats to below the BHSZ until all the free gas is depleted. The shallowest depth that the free gas reaches in one cycle moves toward seafloor as more and more methane is accumulated to the BHSZ with time. More methane is stored above the BHSZ in the form of concentrated hydrate in sediments with relatively uniform pore throat, and/or with greater compressibility. It is more difficult to initiate methane recycling in passive continental margins where the sedimentation rate is low, and in sediments with low organic matter content and/or methanogenesis reaction rate. The presence of a permeable layer can store methane for significant periods of time without recycling. In a 2D system where the seafloor dips rapidly, the updip gas flow along the BHSZ transports more methane toward topographic highs where methane gas and elevated hydrate saturation intrude deeper into the hydrate stability zone within one cycle. This could lead to intermittent gas venting at seafloor at the topographic highs. This study provides insights on many phenomenon associated with

Measurements of relevant parameters in the formation of clathrate hydrates by a novel experimental apparatus

Energy Technology Data Exchange (ETDEWEB)

Arca, S.; Di Profio, P.; Germani, R.; Savelli, G. [Perugia Univ., CEMIN, Perugia (Italy). Dept. of Chemistry

2008-07-01

There is a growing interest in understanding the thermodynamics and kinetics of clathrate hydrate formation. This paper presented a study that involved the design, construction, calibration, and testing of a new apparatus that could obtain as many parameters as possible in a single formation batch and that could measure unexplored clathrate hydrate parameters. The apparatus was capable of measuring equilibrium phases involving gaseous components. The paper described the conceptual design as well as the chamber, pressure line, temperature control, liquid addition line, and conductometric probe. The paper also discussed data acquisition, stirring, measurement examples, and internal illumination and video monitoring. It was concluded that refining measurements, particularly those concerning kinetic characterizations, is important in order to clarify several uncertain kinetic behaviors of clathrate hydrates. 6 refs., 16 figs.

Unexpected inhibition of CO₂ gas hydrate formation in dilute TBAB solutions and the critical role of interfacial water structure

Energy Technology Data Exchange (ETDEWEB)

Nguyen, Ngoc N.; Nguyen, Anh V.; Nguyen, Khoi T.; Rintoul, Llew; Dang, Liem X.

2016-12-01

Gas hydrates formed under moderated conditions open up novel approaches to tackling issues related to energy supply, gas separation, and CO₂ sequestration. Several additives like tetra-n-butylammonium bromide (TBAB) have been empirically developed and used to promote gas hydrate formation. Here we report unexpected experimental results which show that TBAB inhibits CO₂ gas hydrate formation when used at minuscule concentration. We also used spectroscopic techniques and molecular dynamics simulation to gain further insights and explain the experimental results. They have revealed the critical role of water alignment at the gas-water interface induced by surface adsorption of tetra-n-butylammonium cation (TBA⁺) which gives rise to the unexpected inhibition of dilute TBAB solution. The water perturbation by TBA⁺ in the bulk is attributed to the promotion effect of high TBAB concentration on gas hydrate formation. We explain our finding using the concept of activation energy of gas hydrate formation. Our results provide a step toward to mastering the control of gas hydrate formation.

Experimental study and thermodynamic modeling of CO2 gas hydrate formation in presence of zinc oxide nanoparticles

International Nuclear Information System (INIS)

Mohammadi, Mohsen; Haghtalab, Ali; Fakhroueian, Zahra

2016-01-01

Highlights: • Nanofluids enhance heat and mass transfer and affect on kinetic and thermodynamics. • The ZnO nanoparticles in liquid affect on kinetics and P-T curve of CO 2 hydrate. • ZnO nanoparticles enhance the growth rate and gas storage in CO 2 hydrate. • A thermodynamic modeling of CO 2 hydrate proposed in the presence of nanoparticles. • Water activity in ZnO + nanofluid was affected by enhancement of the CO 2 solubility. - Abstract: The effect of synthesized zinc oxide (ZnO) nanoparticles was investigated on the kinetic and thermodynamic equilibrium conditions of CO 2 hydrate formation. The amount of the gas consumption was measured and compared for the four sample fluids: pure water, aqueous solution of sodium dodecyl sulfate (SDS), water-based ZnO-nanofluid and water-based ZnO-nanofluid in the presence of SDS (0.001 mass fraction). The time of hydrate growth decreased and the amount of the storage gas enhanced in the presence of nanoparticles. Moreover, the nanoparticles size effect besides the CO 2 solubility enhancement in ZnO-nanofluid led to the reduction of water activity, so that the equilibrium curve of hydrate formation was shifted to higher pressures. A new correlation for Henry’s law constant was obtained using CO 2 -solubility data in ZnO-nanofluid. Finally using this correlation, the water activity was calculated through the Chen–Guo approach to propose a thermodynamic method for prediction of the equilibrium hydrate formation conditions in the presence of the nanoparticles.

Modeling the methane hydrate formation in an aqueous film submitted to steady cooling

Energy Technology Data Exchange (ETDEWEB)

Avendano-Gomez, J.R. [ESIQIE, Laboratorio de Ingenieria Quimica Ambiental, Mexico (Mexico). Inst. Politecnico Nacional; Garcia-Sanchez, F. [Laboratorio de Termodinamica, Mexico (Mexico). Inst. Mexicano del Petroleo; Gurrola, D.V. [UPIBI, Laboratorio de Diseno de Plantas, Mexico (Mexico). Inst. Politecnico Nacional

2008-07-01

Gas hydrates, or clathrate hydrates, are ice-like compounds that results from the kinetic process of crystallization of an aqueous solution supersaturated with a dissolved gas. This paper presented a model that took into account two factors involved in the hydrate crystallization, notably the stochastic nature of crystallization that causes sub-cooling and the heat resulting from the exothermic enthalpy of hydrate formation. The purpose of this study was to model the thermal evolution inside a hydrate forming system which was submitted to an imposed steady cooling. The study system was a cylindrical thin film of aqueous solution at 19 Mpa. The study involved using methane as the hydrate forming molecule. It was assumed that methane was homogeneously dissolved in the aqueous phase. Ethane hydrate was formed through a kinetic process of nucleation and crystallization. In order to predict the onset time of nucleation, the induction time needed to be considered. This paper discussed the probability of nucleation as well as the estimation of the rate of nucleation. It also presented the mathematical model and boundary conditions. These included assumptions and derivation of the model; boundary conditions; initial conditions; and numerical solution of the model equation. It was concluded that the heat source must be considered when investigating crystallization effects. 34 refs., 2 tabs., 2 figs.

A polyether glycol derived from cashew nutshell as a kinetic inhibitor for methane hydrate formation

Energy Technology Data Exchange (ETDEWEB)

Ferreira, Jorge Cesar; Esteves, Pierre M., E-mail: pesteves@iq.ufrj.br [Instituto de Quimica, Universidade Federal do Rio de Janeiro, Rio de Janeiro, RJ (Brazil); Teixeira, Adriana [Centro de Pesquisa e Desenvolvimento Leopoldo Americo Miguez de Mello, PETROBRAS, Rio de Janeiro, RJ (Brazil)

2012-07-01

The polyether glycol derived from cashew nutshell liquid inhibited the formation of methane hydrate. The polymer proved to be more efficient than the polyvinyl pyrrolidone-poly(N-vinyl) caprolactam (PVP-PVCap) co-polymer under tested conditions (CH{sub 4}, 1470 psi and 4 degree C), being the latter one of the best commercially available hydrate inhibitors. (author)

A study on dehydration of rare earth chloride hydrate

International Nuclear Information System (INIS)

Cho, Yong Zun; Eun, Hee Chul; Son, Sung Mo; Lee, Tae Kyo; Hwang, Taek Sung

2012-01-01

The dehydration schemes of rare earth (La, Ce, Nd, Pr, Sm. Eu, Gd, Y) chloride hydrates was investigated by using a dehydration apparatus. To prevent the formation of the rare earth oxychlorides, the operation temperature was changed step by step (80→150→230 degree C) based on the TGA (thermo-gravimetric analysis) results of the rare earth chloride hydrates. A vacuum pump and preheated Ar gas were used to effectively remove the evaporated moisture and maintain an inert condition in the dehydration apparatus. The dehydration temperature of the rare earth chloride hydrate was increased when the atomic number of the rare earth nuclide was increased. The content of the moisture in the rare earth chloride hydrate was decreased below 10% in the dehydration apparatus.

Towards understanding the role of amines in the SO2 hydration and the contribution of the hydrated product to new particle formation in the Earth's atmosphere.

Science.gov (United States)

Lv, Guochun; Nadykto, Alexey B; Sun, Xiaomin; Zhang, Chenxi; Xu, Yisheng

2018-08-01

By theoretical calculations, the gas-phase SO 2 hydration reaction assisted by methylamine (MA) and dimethylamine (DMA) was investigated, and the potential contribution of the hydrated product to new particle formation (NPF) also was evaluated. The results show that the energy barrier for aliphatic amines (MA and DMA) assisted SO 2 hydration reaction is lower than the corresponding that of water and ammonia assisted SO 2 hydration. In these hydration reactions, nearly barrierless reaction (only a barrier of 0.1 kcal mol -1 ) can be found in the case of SO 2  + 2H 2 O + DMA. These lead us to conclude that the SO 2 hydration reaction assisted by MA and DMA is energetically facile. The temporal evolution for hydrated products (CH 3 NH 3 + -HSO 3 - -H 2 O or (CH 3 ) 2 NH 2 + -HSO 3 - -H 2 O) in molecular dynamics simulations indicates that these complexes can self-aggregate into bigger clusters and can absorb water and amine molecules, which means that these hydrated products formed by the hydration reaction may serve as a condensation nucleus to initiate the NPF. Copyright © 2018 Elsevier Ltd. All rights reserved.

Zirconium molybdate hydrate precipitates in spent nuclear fuel reprocessing

International Nuclear Information System (INIS)

Magnaldo, A.; Noire, M.H.; Esbelin, E.; Dancausse, J.P.; Picart, S.

2004-01-01

This paper presents through 2 posters a general overview studies realised by CEA teams on deposits observed in the La Hague plant dissolution facilities. Their main constituents are metallic debris bound together with zirconium molybdate hydrate. A comprehensive study of zirconium molybdate hydrate formation included nucleation and growth kinetics was developed. Fouling mechanisms were consequently explained as influenced by the operation conditions. Pu insertion was also overviewed. Its behaviour is important when curative and preventive chemical treatments are considered. (authors)

Effects of C3H8 on hydrate formation and dissociation for integrated CO2 capture and desalination technology

International Nuclear Information System (INIS)

Yang, Mingjun; Zheng, Jianan; Liu, Weiguo; Liu, Yu; Song, Yongchen

2015-01-01

Hydrate-based technology has been developing for decades to meet the demands in industrial applications. With the global demands for reduced carbon dioxide (CO 2 ) emissions and more fresh water, CHBD (CO 2 hydrate-based desalination) was proposed and has developed rapidly. In this study, to provide basic data for the improvement of CHBD, the thermodynamic and kinetic characteristics of CO 2 and propane (C 3 H 8 ) mixed-gas hydrates in salt solution were experimentally investigated in which C 3 H 8 was chosen as the hydrate formation promoter. We studied nine experimental cases (54 cycles) with different C 3 H 8 proportions (ranging from 0 to 13%) and different initial solution saturations (30%, 40% and 50%). The hydrate phase equilibrium data were generated using the isochoric method, and the hydrate formation saturations were calculated using the relative gas uptake equation. The results indicated that the increase in the C 3 H 8 proportion significantly decreases the gas mixture hydrate equilibrium pressure. Additionally, the relative gas uptake was reduced as the C 3 H 8 proportion increased. A lower relative gas uptake was obtained at a lower gas pressure for the same gas mixture. The initial solution saturation exhibited an insignificant effect on the hydrate phase equilibrium conditions. When the initial solution saturations increased from 30% to 50%, the relative gas uptake decreased. - Highlights: • C 3 H 8 improves the thermodynamics and kinetics of CO 2 hydrates formation. • Hydrates equilibrium pressure decreases with the increase of C 3 H 8 proportion. • Higher C 3 H 8 proportion and/or solution saturation decrease relative gas uptake. • Initial pressure and solution saturation has interactive effect on gas uptake.

Separation of water through gas hydrate formation

DEFF Research Database (Denmark)

Boch Andersen, Torben; Thomsen, Kaj

2009-01-01

Gas hydrate is normally recognized as a troublemaker in the oil and gas industry. However, gas hydrate has some interesting possibilities when used in connection with separation of water. Nordic Sugar has investigated the possibility of using gas hydrates for concentration of sugar juice. The goal...... of the project was to formulate an alternative separation concept, which can replace the traditional water evaporation process in the sugar production. Work with the separation concept showed that gas hydrates can be used for water separation. The process is not suitable for sugar production because of large...... volumes and the needs for high pressure. The process could be interesting for concentration of heat sensitive, high value products...

Pore Effect on the Occurrence and Formation of Gas Hydrate in Permafrost of Qilian Mountain, Qinghai-Tibet Plateau, China

Science.gov (United States)

Gao, H.; Lu, H.; Lu, Z.

2014-12-01

Gas hydrates were found in the permafrost of Qilian Mountain, Qinghai- Tibet Plateau, China in 2008. It has been found that gas hydrates occur in Jurassic sedimentary rocks, and the hydrated gases are mainly thermogenic. Different from the gas hydrates existing in loose sands in Mallik, Mackenzie Delta, Canada and North Slope, Alaska, USA, the gas hydrates in Qilian Mountain occurred in hard rocks. For understanding the occurrence and formation mechanism of gas hydrate in hard rcok, extensive experimental investigations have been conducted to study the pore features and hydrate formation in the rocks recovered from the hydrate layers in Qilian Mountain. The structures of sedimentary rock were observed by high-resolution X-ray CT, and pore size distribution of a rock specimen was measured with the mercury-injection method. Methane hydrate was synthesized in water-saturated rocks, and the saturations of hydrate in sedimentary rocks of various types were estimated from the amount of gas released from certain volume of rock. X-ray CT observation revealed that fractures were developed in the rocks associated with faults, while those away from faults were generally with massive structure. The mercury-injection analysis of pore features found that the porosities of the hydrate-existing rocks were generally less than 3%, and the pore sizes were generally smaller than 100 nm. The synthesizing experiments found that the saturation of methane hydrate were generally lower than 6% of pore space in rocks, but up to 16% when fractures developed. The low hydrate saturation in Qilian sedimentary rocks has been found mainly due to the small pore size of rock. The low hydrate saturation in the rocks might be the reason for the failure of regional seismic and logging detections of gas hydrates in Qilian Mountain.

Role of excipients in hydrate formation kinetics of theophylline in wet masses studied by near-infrared spectroscopy

DEFF Research Database (Denmark)

Jørgensen, Anna C; Airaksinen, Sari; Karjalainen, Milja

2004-01-01

. Anhydrous theophylline was chosen as the hydrate-forming model drug compound and two excipients, silicified microcrystalline cellulose (SMCC) and alpha-lactose monohydrate, with different water absorbing properties, were used in formulation. An early stage of wet massing was studied with anhydrous...... theophylline and its 1:1 (w/w) mixtures with alpha-lactose monohydrate and SMCC with 0.1g/g of purified water. The changes in the state of water were monitored using near-infrared spectroscopy, and the conversion of the crystal structure was verified using X-ray powder diffraction (XRPD). SMCC decreased...... the hydrate formation rate by absorbing water, but did not inhibit it. The results suggest that alpha-lactose monohydrate slightly increased the hydrate formation rate in comparison with a mass comprising only anhydrous theophylline....

Effect of conditioners upon the thermodynamics and kinetics of methane hydrate formation. A preliminary structure-properties relationship study

Energy Technology Data Exchange (ETDEWEB)

Di Profio, Pietro; Arca, Simone; Germani, Raimondo; Savelli, Gianfranco

2005-07-01

The synthesis and stability of gas hydrates was found to be heavily affected by the presence of small quantities of additives, or conditioners, particularly surfactants. In a recent work, we showed that the enhancement of hydrate formation, both from previously described and newly synthesized surfactants, is probably due to surfactant monomers, rather than micelles, and that the features of hydrate induction time should not be used as a measure of critical micelle concentration. In the present paper, we discuss the results of a structure-properties relationship study in which a preliminary attempt to relate the structural features of several amphiphilic additives to some kinetic and thermodynamic parameters of methane hydrate formation - e.g., induction times, rate of formation, occupancy, etc. - is conducted. According to the present study, it is found that, for a particular conditioner, a reduction of induction time does not correlate to an increase of the formation rate and occupancy, and vice versa. This may be related to the nature of chemical moieties forming a particular amphiphile (e.g., the hydrophobic tail, head group, counterion, etc.). The understanding of the mechanisms by which those moieties play their differential role may be the key tool to the design and synthesis of tailored conditioners. (Author)

Le problème des hydrates dans le contexte de la production et du transport polyphasiques des pétroles bruts et des gaz naturels. Première partie : physico-chimie de la formation et de la dissociation des hydrates Hydrates Problem Within the Framework of Multiphase Production and Transport of Crude Oils and Natural Gases. Part One: Physical-Chemistry of Hydrates Formation and Dissociation

Directory of Open Access Journals (Sweden)

Behar E.

2006-11-01

Full Text Available L'exploitation en mer des gisements de combustibles fossiles fluides a amplifié le besoin d'accroître nos connaissances sur les hydrates qui sont susceptibles de boucher les installations de production, de traitement et de transport. Dans cette publication, la structure moléculaire des hydrates I, II et H est rappelée, ensuite l'analyse physico-chimique de leur formation est succinctement décrite tant sur les plans thermodynamique que cinétique. Enfin, les remèdes possibles aux problèmes rencontrés par les compagnies opératrices sont indiqués, essentiellement les inhibiteurs thermodynamiques classiques tels que les alcools ou les sels qui diminuent la température de formation des hydrates, et les additifs dispersants qui évitent la croissance et/ou l'agglomération des cristaux. Pour terminer, une boucle pilote de circulation originale est présentée, ses caractéristiques qui permettent la validation des additifs dispersants dans des conditions hydrodynamiques et physico-chimiques représentatives étant soulignées. Offshore exploitation of fossil fluid fuels has emphasized the need of improving our knowledge on hydrates which can plug production, treatment and transport facilities. In this paper, the molecular structure of I, II and H hydrates is recalled, then the physical-chemistry of their formation is briefly reviewed from both the thermodynamic and the kinetic points of view. Finally, the possible remedies to the problems met by operating companies are described, mainly classical thermodynamic inhibitors such as alcohols or salts which decrease the hydrates formation temperature, and dispersant additives which avoid crystals growth and/or agglomeration. At last an original circulation loop at pilot scale is presented, its characteristics which allow the testing of dispersant additives under representative hydrodynamic and physico-chemical conditions being outlined.

Effects of cyclopentane on CO2 hydrate formation and dissociation as a co-guest molecule for desalination

International Nuclear Information System (INIS)

Zheng, Jia-nan; Yang, Ming-jun; Liu, Yu; Wang, Da-yong; Song, Yong-chen

2017-01-01

Highlights: • CP decreases CO 2 hydrate phase equilibrium pressure by forming CO 2 -CP hydrates. • The increase of CP can’t decrease hydrates phase equilibrium pressure unlimitedly. • Higher CP concentration lowers CO 2 hydrate gas uptake. • The optimal CP molar ratio is 0.01 based on hydrate phase equilibrium and gas uptake. - Abstract: Cyclopentane (CP) is considered to be a potential co-guest molecule in carbon dioxide (CO 2 ) hydrate-based desalination. The experimental thermodynamic data of CO 2 -CP hydrates were measured for a salt solution, where CP was chosen as a hydrate promoter. Seven experimental cases (62 cycles) were studied with different molar ratios of CP/water (0, 0.0025, 0.005, 0.0075, 0.01, 0.02, and 0.03). Hydrate phase equilibrium data were generated using an isochoric method, and the hydrate saturations were calculated based on gas uptake. The results indicated that the increase in CP concentration significantly decreased the CO 2 hydrate equilibrium pressure to a certain limit; the hydrate saturation also decreased during this process. Also, it was determined that CP encouraged the formation of s-II double CO 2 -CP hydrates, which are different from s-I simple CO 2 hydrate. The CO 2 -CP guest provides a strengthened stability and moderate hydrate phase equilibrium conditions for hydrate-based desalination. The recommended optimal molar ratio of CP is 0.01 when the increase in equilibrium was more than 10 K, and the decrease in hydrate saturation was less than 2%.

Gas hydrate nucleation

Energy Technology Data Exchange (ETDEWEB)

NONE

1997-12-31

The overall aim of the project was to gain more knowledge about the kinetics of gas hydrate formation especially the early growth phase. Knowledge of kinetics of gas hydrate formation is important and measurements of gas hydrate particle size and concentration can contribute to improve this knowledge. An experimental setup for carrying out experimental studies of the nucleation and growth of gas hydrates has been constructed and tested. Multi wavelength extinction (MWE) was the experimental technique selected for obtaining particle diameter and concentration. The principle behind MWE is described as well as turbidity spectrum analysis that in an initial stage of the project was considered as an alternative experimental technique. Details of the experimental setup and its operation are outlined. The measuring cell consists of a 1 litre horizontal tube sustaining pressures up to 200 bar. Laser light for particle size determination can be applied through sapphire windows. A description of the various auxiliary equipment and of another gas hydrate cell used in the study are given. A computer program for simulation and analysis of gas hydrate experiments is based on the gas hydrate kinetics model proposed by Skovborg and Rasmussen (1993). Initial measurements showed that knowledge of the refractive index of gas hydrates was important in order to use MWE. An experimental determination of the refractive index of methane and natural gas hydrate is described. The test experiments performed with MWE on collectives of gas hydrate particles and experiments with ethane, methane and natural gas hydrate are discussed. Gas hydrate particles initially seem to grow mainly in size and at latter stages in number. (EG) EFP-94; 41 refs.

Gas hydrate nucleation

Energy Technology Data Exchange (ETDEWEB)

NONE

1998-12-31

The overall aim of the project was to gain more knowledge about the kinetics of gas hydrate formation especially the early growth phase. Knowledge of kinetics of gas hydrate formation is important and measurements of gas hydrate particle size and concentration can contribute to improve this knowledge. An experimental setup for carrying out experimental studies of the nucleation and growth of gas hydrates has been constructed and tested. Multi wavelength extinction (MWE) was the experimental technique selected for obtaining particle diameter and concentration. The principle behind MWE is described as well as turbidity spectrum analysis that in an initial stage of the project was considered as an alternative experimental technique. Details of the experimental setup and its operation are outlined. The measuring cell consists of a 1 litre horizontal tube sustaining pressures up to 200 bar. Laser light for particle size determination can be applied through sapphire windows. A description of the various auxiliary equipment and of another gas hydrate cell used in the study are given. A computer program for simulation and analysis of gas hydrate experiments is based on the gas hydrate kinetics model proposed by Skovborg and Rasmussen (1993). Initial measurements showed that knowledge of the refractive index of gas hydrates was important in order to use MWE. An experimental determination of the refractive index of methane and natural gas hydrate is described. The test experiments performed with MWE on collectives of gas hydrate particles and experiments with ethane, methane and natural gas hydrate are discussed. Gas hydrate particles initially seem to grow mainly in size and at latter stages in number. (EG) EFP-94; 41 refs.

Alcohol cosurfactants in hydrate antiagglomeration.

Science.gov (United States)

York, J Dalton; Firoozabadi, Abbas

2008-08-28

Because of availability, as well as economical and environmental considerations, natural gas is projected to be the premium fuel of the 21st century. Natural gas production involves risk of the shut down of onshore and offshore operations because of blockage from hydrates formed from coproduced water and hydrate-forming species in natural gas. Industry practice has been usage of thermodynamic inhibitors such as alcohols often in significant amounts, which have undesirable environmental and safety impacts. Thermodynamic inhibitors affect bulk-phase properties and inhibit hydrate formation. An alternative is changing surface properties through usage of polymers and surfactants, effective at 0.5 to 3 weight % of coproduced water. One group of low dosage hydrate inhibitors (LDHI) are kinetic inhibitors, which affect nucleation rate and growth. A second group of LDHI are antiagglomerants, which prevent agglomeration of small hydrate crystallites. Despite great potential, work on hydrate antiagglomeration is very limited. This work centers on the effect of small amounts of alcohol cosurfactant in mixtures of two vastly different antiagglomerants. We use a model oil, water, and tetrahydrofuran as a hydrate-forming species. Results show that alcohol cosurfactants may help with antiagglomeration when traditional antiagglomerants alone are ineffective. Specifically, as low as 0.5 wt. % methanol cosurfactant used in this study is shown to be effective in antiagglomeration. Without the cosurfactant there will be agglomeration independent of the AA concentration. To our knowledge, this is the first report of alcohol cosurfactants in hydrate antiagglomerants. It is also shown that a rhamnolipid biosurfactant is effective down to only 0.5 wt. % in such mixtures, yet a quaternary ammonium chloride salt, i. e., quat, results in hydrate slurries down to 0.01 wt. %. However, biochemical surfactants are less toxic and biodegradable, and thus their use may prove beneficial even if at

Thermodynamics of Uranyl Minerals: Enthalpies of Formation of Uranyl Oxide Hydrates

International Nuclear Information System (INIS)

Kubatko, K.; Helean, K.; Navrotsky, A.; Burns, P.C.

2005-01-01

The enthalpies of formation of seven uranyl oxide hydrate phases and one uranate have been determined using high-temperature oxide melt solution calorimetry: [(UO 2 ) 4 O(OH) 6 ](H 2 O) 5 , metaschoepite; β-UO 2 (OH) 2 ; CaUO 4 ; Ca(UO 2 ) 6 O 4 (OH) 6 (H 2 O) 8 , becquerelite; Ca(UO 2 ) 4 O 3 (OH) 4 (H 2 O) 2 ; Na(UO 2 )O(OH), clarkeite; Na 2 (UO 2 ) 6 O 4 (OH) 6 (H 2 O) 7 , the sodium analogue of compreignacite and Pb 3 (UO 2 ) 8 O 8 (OH) 6 (H 2 O) 2 , curite. The enthalpy of formation from the binary oxides, ΔH f-ox , at 298 K was calculated for each compound from the respective drop solution enthalpy, ΔH ds . The standard enthalpies of formation from the elements, ΔH f o , at 298 K are -1791.0 ± 3.2, -1536.2 ± 2.8, -2002.0 ± 3.2, -11389.2 ± 13.5, -6653.1 ± 13.8, -1724.7 ± 5.1, -10936.4 ± 14.5 and -13163.2 ± 34.4 kJ mol -1 , respectively. These values are useful in exploring the stability of uranyl oxide hydrates in auxiliary chemical systems, such as those expected in U-contaminated environments

Ductile flow of methane hydrate

Science.gov (United States)

Durham, W.B.; Stern, L.A.; Kirby, S.H.

2003-01-01

Compressional creep tests (i.e., constant applied stress) conducted on pure, polycrystalline methane hydrate over the temperature range 260-287 K and confining pressures of 50-100 MPa show this material to be extraordinarily strong compared to other icy compounds. The contrast with hexagonal water ice, sometimes used as a proxy for gas hydrate properties, is impressive: over the thermal range where both are solid, methane hydrate is as much as 40 times stronger than ice at a given strain rate. The specific mechanical response of naturally occurring methane hydrate in sediments to environmental changes is expected to be dependent on the distribution of the hydrate phase within the formation - whether arranged structurally between and (or) cementing sediments grains versus passively in pore space within a sediment framework. If hydrate is in the former mode, the very high strength of methane hydrate implies a significantly greater strain-energy release upon decomposition and subsequent failure of hydrate-cemented formations than previously expected.

FY1995 molecular control technology for mining of methane-gas-hydrate; 1995 nendo methane hydrate no bunshi seigyo mining

Energy Technology Data Exchange (ETDEWEB)

NONE

1997-03-01

The objectives of the investigation are as follows: 1) developing a method to control formation/dissociation of methane-gas-hydrate, 2) developing a technology to displace methane gas by CO{sub 2} in methane-gas-hydrate deposit, 3) developing a technology to produce methane gas from the deposit efficiently. The final purpose of the project is to create new mining industry that solves both the problems of energy and global environment. 1) Clustering of water molecules is found to play the key role in the methane gas hydrate formation. 2) Equilibrium properties and kinetics of gas hydrates formation and dissociation in bulk-scale gas-hydrate are clarified in the practical environmental conditions. 3) Particle size of hydrate deposit influences the formation and dissociation of bulk-scale gas-hydrate crystal. 4) Mass transfer between gas and liquid phase in turbulent bubbly flow is a function of bubble diameter. The mass transfer depends on interfacial dynamics. (NEDO)

Modeling hydrate formation conditions in the presence of electrolytes and polar inhibitor solutions

International Nuclear Information System (INIS)

Osfouri, Shahriar; Azin, Reza; Gholami, Reza; Izadpanah, Amir Abbas

2015-01-01

Highlights: • A new predictive model is proposed for prediction of hydrate formation pressures. • A new local composition model was used to evaluate water activity in the presence of electrolyte. • MEG, DEG and TEG were used to test ability of the proposed model in the presence of polar inhibitors. • Cage occupancies by methane for the small cage were higher than carbon dioxide for gas mixtures. • The proposed model gives better match with experimental data in mixed electrolyte solutions. - Abstract: In this paper, a new predictive model is proposed for prediction of gas hydrate formation conditions in the presence of single and mixed electrolytes and solutions containing both electrolyte and a polar inhibitor such as monoethylene glycol (MEG), diethylene glycol (DEG) and triethylene glycol (TEG). The proposed model is based on the γ–φ approach, which uses modified Patel–Teja equation of state (VPT EOS) for characterizing the vapor phase, the solid solution theory by van der Waals and Platteeuw for modeling the hydrate phase, the non-electrolyte NRTL-NRF local composition model and Pitzer–Debye–Huckel equation as short-range and long-range contributions to calculate water activity in single electrolyte solutions. Also, the Margules equation was used to determine the activity of water in solutions containing polar inhibitor (glycols). The model predictions are in acceptable agreement with experimental data. For single electrolyte solutions, the model predictions are similar to available models, while for mixtures of electrolytes and mixtures of electrolytes and inhibitors, the proposed model gives significantly better predictions. In addition, the absolute average deviation of hydrate formation pressures (AADP) for 144 experimental data in solutions containing single electrolyte is 5.86% and for 190 experimental data in mixed electrolytes solutions is 5.23%. Furthermore, the proposed model has an AADP of 14.13%, 5.82% and 5.28% in solutions

Comparing effectiveness of rhamnolipid biosurfactant with a quaternary ammonium salt surfactant for hydrate anti-agglomeration.

Science.gov (United States)

York, J Dalton; Firoozabadi, Abbas

2008-01-24

Natural gas is projected to be the premium fuel of the 21st century because of availability, as well as economical and environmental considerations. Natural gas is coproduced with water from the subsurface forming gas hydrates. Hydrate formation may result in shutdown of onshore and offshore operations. Industry practice has been usage of alcohols--which have undesirable environmental impacts--to affect bulk-phase properties and inhibit hydrate formation. An alternative to alcohols is changing the surface properties through usage of polymers and surfactants, effective at 0.5-3 wt % of coproduced water. One group of low-dosage hydrate inhibitors (LDHI) are kinetic inhibitors, which affect nucleation rate and growth. A second group of LDHI are anti-agglomerants, which prevent agglomeration of small hydrate crystallites. Despite great potential, reported work on hydrate anti-agglomeration is very limited. In this paper, our focus is on the use of two vastly different surfactants as anti-agglomerants. We use a model oil, water, and tetrahydrofuran as a hydrate-forming species. We examine the effectiveness of a quaternary ammonium salt (i.e., quat). Visual observation measurements show that a small concentration of the quat (0.01%) can prevent agglomeration. However, a quat is not a green chemical and therefore may be undesirable. We show that a rhamnolipid biosurfactant can be effective to a concentration of 0.05 wt %. One difference between the two surfactants is the stability of the water-in-oil emulsions created. The biosurfactant forms a less stable emulsion, which makes it very desirable for hydrate application.

Thermodynamic analysis of hydrates formation in drilling activities; Analise termodinamica da formacao de hidratos em atividades de perfuracao

Energy Technology Data Exchange (ETDEWEB)

Baptista, Joao Marcelo Mussi; Rossi, Luciano Fernando dos Santos; Morales, Rigoberto E.M. [Universidade Tecnologica Federal do Parana (UTFPR), Curitiba, PR (Brazil)], e-mail: joaommussi@yahoo.com.br, e-mail: lfrossi@cefetpr.br, e-mail: rmorales@cefetpr.br

2006-07-01

The present work has for objective to present an analysis of hydrates formation in drilling activities. This analysis presents a study of the state conditions for gas hydrates formation in inhibitors containing systems (salts and alcohols, separately). To describe the nonidealities of liquid phase in electrolytic solutions, the activity coefficient model of Debye-Hueckel is used, as [4], and to describe the influence of alcohols in the activity of water, the UNQUAC model is used, as Parrish and Prausnitz. The hydrate phase is described by thermodynamic statistic model of van der Waals and Platteeuw, and the gaseous phase fugacities are modeled by the Peng-Robinson Equation of State. Some results are presented for saline inhibitors, and for methanol and ethyleneglycol. (author)

Experimental flowloop study on methane hydrate formation and agglomeration in high water cut emulsion systems

OpenAIRE

Pham , Trung-Kien; Cameirao , Ana ,; Herri , Jean-Michel

2016-01-01

Thème de cette communication: International Conference on Integrated Petroleum Engineering (IPE); International audience; hydrate risk also increases. Especially in the offshore systems, operating at low temperature and high pressure, conditions are favourable to the formation of gas hydrate, from the combination of liquid water and gas molecules, under the form of a solid phase. It is a serious issue in the flow assurance; it may cause many troubles, up to plugging.This work brings new under...

Influence of polymeric excipient properties on crystal hydrate formation kinetics of caffeine in aqueous slurries.

Science.gov (United States)

Gift, Alan D; Southard, Leslie A; Riesberg, Amanda L

2012-05-01

The influence of polymeric excipients on the hydrate transformation of caffeine (CAF) was studied. Anhydrous CAF was added to aqueous solutions containing different additives and the transformation to the hydrate form was monitored using in-line Raman spectroscopy. Various properties of two known inhibitors of CAF hydrate formation, polyacrylic acid (PAA) and polyvinyl alcohol (PVA), were investigated. For inhibition by PAA, a pH dependence was observed: at low pH, the inhibition was greatest, whereas no inhibitory effects were observed at pH above 6.5. For PVA, grades with high percent hydrolysis were the most effective at inhibiting the transformation. In addition, PVA with higher molecular weight showed slightly more inhibition than the shorter chain PVA polymers. A variety of other hydroxyl containing compounds were examined but none inhibited the CAF anhydrate-to-hydrate transformation. The observed inhibitory effects of PAA and PVA are attributed to the large number of closely spaced hydrogen bond donating groups of the polymer molecule, which can interact with the CAF hydrate crystal. Copyright © 2012 Wiley Periodicals, Inc.

A study of the methane hydrate formation by in situ turbidimetry

Energy Technology Data Exchange (ETDEWEB)

Herri, J M

1996-02-02

The study of the Particle Size Distribution (PSD) during the processes of crystallization is a subject of considerable interest, notably in the offshore exploitation of liquid fuels where the gas hydrate crystallization can plug production, treatment and transport facilities. The classical remedy to this problem is mainly thermodynamic additives such as alcohols or salts, but a new way of research is the use of dispersant additives which avoid crystals formation. In this paper, we show an original apparatus that is able to measure in situ the polychromatic UV-Visible turbidity spectrum in a pressurised reactor. We apply this technology to the calculation of the PSD during the crystallization of methane hydrate particles in a stirred semi-batch tank reactor. We discuss the mathematics treatment of the turbidity spectrum in order to determine the PSD and especially the method of matrix inversion with constraint. Moreover, we give a method to calculate theoretically the refractive index of the hydrate particles and we validate it experimentally with the methane hydrate particles. We apply this technology to the study of the crystallization of methane hydrate from pure liquid water and methane gas into the range of temperature [0-2 deg. C], into the range of pressure [30-100 bars] and into the range of stirring rate [0-600 rpm]. We produce a set of experiments concerning these parameters. Then we realize a model of the crystallization taking into account the processes of nucleation, of growth, of agglomeration and flotation. We compare this model with the experimental results concerning the complex influence of stirring rate at 1 deg. C and 30 bars. Then, we investigate the influence of additives such as Fontainebleau Sand, Potassium Chloride and a surfactant such as Poly-Vinyl-Pyrrolydone. (authors). 133 refs., 210 figs., 54 tabs.

Characterization of methane-hydrate formation inferred from insitu Vp-density relationship for hydrate-bearing sediment cores obtained off the eastern coast of India

Science.gov (United States)

Kinoshita, M.; Hamada, Y.; Hirose, T.; Yamada, Y.

2017-12-01

In 2015, the Indian National Gas Hydrate Program (NGHP) Drilling Expedition 02 was carried out off the eastern margin of the Indian Peninsula in order to investigate distribution and occurrence of gas hydrates. From 25 drill sites, downhole logging data, cored samples, and drilling performance data were collected. One of the target areas (area B) is located on the axial and flank of an anticline, where the BSR is identified 100 m beneath the summit of anticline. 3 sites were drilled in the crest. The lower potential hydrate zone II was suggested by downhole logging (LWD) at 270-290 m below seafloor across the top of anticline. Core samples from this interval is characterized by a higher natural gamma radiation, gamma-ray-based higher bulk density and lower porosity, and higher electrical resistivity. All these features are in good agreement with LWD results. During this expedition, numerous special core sampling operations (PCAT) were carried out, keeping its insitu pressure in a pressure-tight vessel. They enabled acquiring insitu P-wave velocity and gamma-ray attenuation density measurements. In-situ X-CT images exhibit very clear hydrate distribution as lower density patches. Hydrate-bearing sediments exhibit a Vp-density trend that is clearly different from the ordinary formation. Vp values are significantly higher than 2 km/s whereas the density remains constant at 2-2.2 g/cm3 in hydrate zones. At some hydrate-bearing sediments, we noticed that Vp is negatively correlated to the density in the deeper portion (235-285 mbsf). On the other hand, in the shallower portion they are positively correlated. From lithostratigraphy the shallower portion consists of sand, whereas deeper portion are silty-clay dominant. We infer that the sand-dominant, shallower hydrate is a pore-filling type, and Vp is correlated positively to density. On the other hand, the clay-dominant, deeper hydrate is filled in vertical veins, and Vp is negatively correlated to density. Negative

An innovative approach to enhance methane hydrate formation kinetics with leucine for energy storage application

International Nuclear Information System (INIS)

Veluswamy, Hari Prakash; Kumar, Asheesh; Kumar, Rajnish; Linga, Praveen

2017-01-01

Highlights: • Innovative combinatorial hybrid approach to reduce nucleation stochasticity and enhance hydrate growth. • Methane hydrate growth curves are similar in UTR and STR configurations in presence of leucine. • Amalgamation of stirred (STR) and unstirred (UTR) configuration is demonstrated. • Reliable method for scale up and commercial production of Solidified Natural Gas (SNG). - Abstract: Natural gas storage in clathrate hydrates or solidified natural gas (SNG) offers the safest, cleanest and the most compact mode of storage aided by the relative ease in natural gas (NG) recovery with minimal cost compared to known conventional methods of NG storage. The stochastic nature of hydrate nucleation and the slow kinetics of hydrate growth are major challenges that needs to be addressed on the SNG production side. A deterministic and fast nucleation coupled with rapid crystallization kinetics would empower this beneficial technology for commercial application. We propose a hybrid combinatorial approach of methane hydrate formation utilizing the beneficial aspect of environmentally benign amino acid (leucine) as a kinetic promoter by combining stirred and unstirred reactor operation. This hybrid approach is simple, can easily be implemented and scaled-up to develop an economical SNG technology for efficient storage of natural gas on a large scale. Added benefits include the minimal energy requirement during hydrate growth resulting in overall cost reduction for SNG technology.

Do Pleistocene Glacial-Interglacial Cycles Control Methane Hydrate Formation? An Example from Green Canyon, Gulf of Mexico

Science.gov (United States)

Oryan, B.; Malinverno, A.; Goldberg, D.; Fortin, W.

2017-12-01

Well GC955-H was drilled in the Green Canyon region under the Gulf of Mexico Gas Hydrates Joint Industry Project in 2009. Logging-while-drilling resistivity logs obtained at the well indicate that the saturation of gas hydrate varies between high and low values in an alternating fashion. This trend is observed from 180 to 360mbsf, depths that correspond to the Late Pleistocene. Similar gas hydrate saturation patterns have been observed in other Gulf of Mexico locations (Walker Ridge sites WR313-G and 313-H) in Late Pleistocene sediments. Our hypothesis is that these variations in saturation can be explained by sea level changes through time during glacial-interglacial cycles. A higher amount of organic matter is deposited and buried in the sediment column during glacial intervals when sea level is low. Microbes in the sediment column degrade organic matter and produce methane gas as a byproduct. Higher availability of organic matter in the sediment column can increase the concentration of methane in the sediment pore water and in turn lead to the formation of gas hydrate. We use a time-dependent numerical model of the formation of gas hydrate to test this hypothesis. The model predicts the volume and distribution of gas hydrates using mass balance equations. Model inputs include in situ porosity determined from bulk density logs; local thermal gradient estimated from the depth of the bottom of the gas hydrate stability zone in proximity to the well; and sedimentation rate determined using the biostratigraphy of an industry well in the vicinity of GC955-H. Initial results show a good match between gas hydrate saturation predicted by the model and resistivity logs obtained in the well. We anticipate that this correlation will establish whether a causal link exists between the saturation of gas hydrate in this reservoir and glacioeustatic sea level changes in the Late Pleistocene.

Gas Hydrate Storage of Natural Gas

Energy Technology Data Exchange (ETDEWEB)

Rudy Rogers; John Etheridge

2006-03-31

Environmental and economic benefits could accrue from a safe, above-ground, natural-gas storage process allowing electric power plants to utilize natural gas for peak load demands; numerous other applications of a gas storage process exist. A laboratory study conducted in 1999 to determine the feasibility of a gas-hydrates storage process looked promising. The subsequent scale-up of the process was designed to preserve important features of the laboratory apparatus: (1) symmetry of hydrate accumulation, (2) favorable surface area to volume ratio, (3) heat exchanger surfaces serving as hydrate adsorption surfaces, (4) refrigeration system to remove heat liberated from bulk hydrate formation, (5) rapid hydrate formation in a non-stirred system, (6) hydrate self-packing, and (7) heat-exchanger/adsorption plates serving dual purposes to add or extract energy for hydrate formation or decomposition. The hydrate formation/storage/decomposition Proof-of-Concept (POC) pressure vessel and supporting equipment were designed, constructed, and tested. This final report details the design of the scaled POC gas-hydrate storage process, some comments on its fabrication and installation, checkout of the equipment, procedures for conducting the experimental tests, and the test results. The design, construction, and installation of the equipment were on budget target, as was the tests that were subsequently conducted. The budget proposed was met. The primary goal of storing 5000-scf of natural gas in the gas hydrates was exceeded in the final test, as 5289-scf of gas storage was achieved in 54.33 hours. After this 54.33-hour period, as pressure in the formation vessel declined, additional gas went into the hydrates until equilibrium pressure/temperature was reached, so that ultimately more than the 5289-scf storage was achieved. The time required to store the 5000-scf (48.1 hours of operating time) was longer than designed. The lower gas hydrate formation rate is attributed to a

Experimental Study on Methane Hydrate Formation and Transport from Emulsions in a “Gas Lift” Riser in a Flowloop

OpenAIRE

Pham , Trung-Kien; Cameirao , Ana ,; Herri , Jean-Michel; Glenat , Philippe

2017-01-01

Session : Flow Assurance: Transportability Strategies - GasHyDyn : Logiciel de simulation de la composition et de la stabilité des hydrates de gaz; International audience; Production of crude oil with natural gas and water at low temperature and high pressure favours conditions for gas hydrate formation which can cause many troubles, up to blockage of pipelines. This work deals with hydrate kinetics of crystallization and agglomeration together with slurry transport and deposition under flowi...

Insights into the dynamics of in situ gas hydrate formation and dissociation at the Bush Hill gas hydrate field, Gulf of Mexico

Energy Technology Data Exchange (ETDEWEB)

Solomon, Evan A.; Kastner, Miriam; Robertson, Gretchen; Jannasch, Hans; Weinstein, Yishai

2005-07-01

Four newly designed flux meters called the MOSQUITO (Multiple Orifice Sampler and Quantitative Injection Tracer Observer), capable of measuring fluid flow rates and sampling pore fluid chemistry simultaneously, and two temperature loggers were deployed for 430 days adjacent to the Bush Hill hydrate mound in the northern Gulf of Mexico (GC 185). The main objective of the deployment was to understand how chemistry, temperature, and subsurface hydrology dynamically influence the growth and dissociation of the gas hydrate mound. The flux meters were deployed in a mussel field, in bacterial mats, in a tubeworm field, and at a background site approximately 100 m southwest of the hydrate mound. Results from the longterm chemical monitoring suggest that this system is not in dynamic equilibrium. Gas hydrate actively formed within the mussel field adjacent to the most active gas vent, in the tubeworm field, and at the background site. The hydrology is variable with upward flow rates ranging from 1-90 cm/yr and downward flow rates from 3-130 cm/yr. Two distinct hydrologic pulsing events were sampled across the three mound sites, which advect a fluid from depth that further stabilizes the gas hydrate deposit. The hydrogeochemistry at Bush Hill seems to be influenced by multiple mechanisms such as active formation of gas hydrate, fluid influx and outflux due to active venting of CH4 at transient methane seeps at and near the mound, local salt tectonics, and density driven convection. The fluxes of fluid, solutes, and methane may have a significant impact on the seafloor biochemical environment and the water column chemistry at Bush Hill. (Author)

Study on molecular controlled mining system of methane hydrate; Methane hydrate no bunshi seigyo mining ni kansuru kenkyu

Energy Technology Data Exchange (ETDEWEB)

Kuriyagawa, M; Saito, T; Kobayashi, H; Karasawa, H; Kiyono, F; Nagaoki, R; Yamamoto, Y; Komai, T; Haneda, H; Takahashi, Y [National Institute for Resources and Environment, Tsukuba (Japan); Nada, H [Science and Technology Agency, Tokyo (Japan)

1997-02-01

Basic studies are conducted for the collection of methane from the methane hydrate that exists at levels deeper than 500m in the sea. The relationship between the hydrate generation mechanism and water cluster structure is examined by use of mass spectronomy. It is found that, among the stable liquid phase clusters, the (H2O)21H{sup +} cluster is the most stable. Stable hydrate clusters are in presence in quantities, and participate in the formation of hydrate crystal nuclei. For the elucidation of the nucleus formation mechanism, a kinetic simulation is conducted of molecules in the cohesion system consisting of water and methane molecules. Water molecules that array near methane molecules at the normal pressure is disarrayed under a higher pressure for rearray into a hydrate structure. Hydrate formation and breakdown in the three-phase equilibrium state of H2O, CH4, and CO2 at a low temperature and high pressure are tested, which discloses that supercooling is required for formation, that it is possible to extract CH4 first for replacement by guest molecule CO2 since CO2 is stabler than CH4 at a lower pressure or higher temperature, and that formation is easier to take place when the grain diameter is larger at the formation point since larger grain diameters result in a higher formation temperature. 3 figs.

Modeling of tri-chloro-fluoro-methane hydrate formation in a w/o emulsion submitted to steady cooling

Energy Technology Data Exchange (ETDEWEB)

Avendano-Gomez, Juan Ramon; Limas-Ballesteros, Roberto [Laboratorio de Investigacion en Ingenieria Quimica Ambiental, SEPI-ESIQIE, Instituto Politecnico Nacional, Unidad Profesional Adolfo Lopez Mateos, Zacatenco, Edificio 8, 3. piso 07738, Mexico DF (Mexico); Garcia-Sanchez, Fernando [Laboratorio de Termodinamica, Programa de Ingenieria Molecular, Instituto Mexicano del Petroleo, Eje Central Lazaro Cardenas 152, 07730 Mexico DF (Mexico)

2006-05-15

The aim of this work is to study the modeling of the thermal evolution inside an hydrate forming system which is submitted to an imposed steady cooling. The study system is a w/o emulsion where the formulation considers the CCl{sub 3}F as the hydrate forming molecule dissolved in the oil phase. The hydrate formation occurs in the aqueous phase of the emulsion, i.e. in the dispersed phase. The model equation is based on the resolution of the continuity equation in terms of a heat balance for the dispersed phase. The crystallization of the CCl{sub 3}F hydrate occurs at supercooling conditions (T{sub c}hydrate crystallization. Three time intervals characterize the evolution of temperature during the steady cooling of the w/o emulsion: (1) steady cooling, (2) hydrate formation with a release of heat, (3) a last interval of steady cooling. (author)

Basics of development of gas hydrate deposits

Energy Technology Data Exchange (ETDEWEB)

Makogon, Yuri F.; Holditch, Stephen A.; Makogon, Taras Y.

2005-07-01

Natural gas hydrate deposits could possibly be an important energy resource during this century. However, many problems associated with producing these deposits must first be solved. The industry must develop new technologies to produce the gas, to forecast possible tectonic cataclysms in regions of gas hydrate accumulations, and to prevent damage to the environment. These global issues must be addressed by every company or country who wants to produce gas hydrate deposits. Cooperative research between industry and universities can lead to technology breakthroughs in coming years. This paper reviews the Messoyakha field and the Blake Ridge and Nankai areas to explain a methodology for estimating how much gas might be producible from gas hydrate deposits (GHDs) under various conditions. The Messoyakha field is located on land, while the Blake Ridge and Nankai areas are offshore. Messoyakha is the first and the only GHD where gas production from hydrates has reached commercial flow rates. The Blake Ridge GHD has been studied for 20 years and 11 wells have been drilled to collect gas-hydrate samples. The potential resources of gas (gas in place) from Blake Ridge is estimated at 37.7Oe10{sup 12} m{sup 3} (1.330 Tcf) in hydrate form and 19.3Oe10{sup 12}m{sup 3} (681 Bcf) [5] in free gas. To estimate how much of the potential resource can be produced we need a thorough understanding of both the geologic and the thermodynamic characteristics of the formations. (Author)

Kinetics of the Formation and Dissociation of Gas Hydrates from CO₂-CH₄ Mixtures

Directory of Open Access Journals (Sweden)

Devinder Mahajan

2012-07-01

Full Text Available Sequestration of carbon dioxide (CO₂ in the form of its hydrates in natural methane (CH₄ hydrate reservoirs, via CO₂/CH₄ exchange, is an attractive pathway that also yields valuable CH₄ gas as product. In this paper, we describe a macroscale experiment to form CO₂ and CH₄-CO₂ hydrates, under seafloor-mimic conditions, in a vessel fitted with glass windows that provides visualization of hydrates throughout formation and dissociation processes. Time resolved pressure and temperature data as well as images of hydrates are presented. Quantitative gas conversions with pure CO₂, calculated from gas chromatographic measurements yielded values that range from 23 – 59% that correspond to the extent of formed hydrates. In CH₄-rich CH₄-CO₂ mixed gas systems, CH₄ hydrates were found to form preferentially.

Carbon dioxide storage in marine sediments - dissolution, transport and hydrate formation kinetics from high-pressure experiments

Science.gov (United States)

Bigalke, N. K.; Savy, J. P.; Pansegrau, M.; Aloisi, G.; Kossel, E.; Haeckel, M.

2009-12-01

By satisfying thermodynamic framework conditions for CO2 hydrate formation, pressures and temperatures of the deep marine environment are unique assets for sequestering CO2 in clathrates below the seabed. However, feasibility and safety of this storage option require an accurate knowledge of the rate constants governing the speed of physicochemical reactions following the injection of the liquefied gas into the sediments. High-pressure experiments designed to simulate the deep marine environment open the possibility to obtain the required parameters for a wide range of oceanic conditions. In an effort to constrain mass transfer coefficients and transport rates of CO2 in(to) the pore water of marine sediments first experiments were targeted at quantifying the rate of CO2 uptake by de-ionized water and seawater across a two-phase interface. The nature of the interface was controlled by selecting p and T to conditions within and outside the hydrate stability field (HSF) while considering both liquid and gaseous CO2. Concentration increase and hydrate growth were monitored by Raman spectroscopy. The experiments revealed anomalously fast transport rates of dissolved CO2 at conditions both inside and outside the HSF. While future experiments will further elucidate kinetics of CO2 transport and hydrate formation, these first results could have major significance to safety-related issues in the discussion of carbon storage in the marine environment.

Experimental study on hydration damage mechanism of shale from the Longmaxi Formation in southern Sichuan Basin, China

Directory of Open Access Journals (Sweden)

Xiangjun Liu

2016-03-01

Full Text Available As a serious problem in drilling operation, wellbore instability restricts efficient development of shale gas. The interaction between the drilling fluid and shale with hydration swelling property would have impact on the generation and propagation mechanism of cracks in shale formation, leading to wellbore instability. In order to investigate the influence of the hydration swelling on the crack propagation, mineral components and physicochemical properties of shale from the Lower Silurian Longmaxi Formation (LF were investigated by using the XRD analysis, cation exchange capabilities (CEC analysis, and SEM observation, and we researched the hydration mechanism of LF shale. Results show that quartz and clay mineral are dominated in mineral composition, and illite content averaged 67% in clay mineral. Meanwhile, CEC of the LF shale are 94.4 mmol/kg. The process of water intruding inside shale along microcracks was able to be observed through high power microscope, meanwhile, the hydration swelling stress would concentrate at the crack tip. The microcracks would propagate, bifurcate and connect with each other, with increase of water immersing time, and it would ultimately develop into macro-fracture. Moreover, the macrocracks extend and coalesce along the bedding, resulting in the rock failure into blocks. Hydration swelling is one of the major causes that lead to wellbore instability of the LF shale, and therefore improving sealing capacity and inhibition of drilling fluid system is an effective measure to stabilize a borehole.

Thermodynamics of Uranyl Minerals: Enthalpies of Formation of Uranyl Oxide Hydrates

Energy Technology Data Exchange (ETDEWEB)

K. Kubatko; K. Helean; A. Navrotsky; P.C. Burns

2005-05-11

The enthalpies of formation of seven uranyl oxide hydrate phases and one uranate have been determined using high-temperature oxide melt solution calorimetry: [(UO{sub 2}){sub 4}O(OH){sub 6}](H{sub 2}O){sub 5}, metaschoepite; {beta}-UO{sub 2}(OH){sub 2}; CaUO{sub 4}; Ca(UO{sub 2}){sub 6}O{sub 4}(OH){sub 6}(H{sub 2}O){sub 8}, becquerelite; Ca(UO{sub 2}){sub 4}O{sub 3}(OH){sub 4}(H{sub 2}O){sub 2}; Na(UO{sub 2})O(OH), clarkeite; Na{sub 2}(UO{sub 2}){sub 6}O{sub 4}(OH){sub 6}(H{sub 2}O){sub 7}, the sodium analogue of compreignacite and Pb{sub 3}(UO{sub 2}){sub 8}O{sub 8}(OH){sub 6}(H{sub 2}O){sub 2}, curite. The enthalpy of formation from the binary oxides, {Delta}H{sub f-ox}, at 298 K was calculated for each compound from the respective drop solution enthalpy, {Delta}H{sub ds}. The standard enthalpies of formation from the elements, {Delta}H{sub f}{sup o}, at 298 K are -1791.0 {+-} 3.2, -1536.2 {+-} 2.8, -2002.0 {+-} 3.2, -11389.2 {+-} 13.5, -6653.1 {+-} 13.8, -1724.7 {+-} 5.1, -10936.4 {+-} 14.5 and -13163.2 {+-} 34.4 kJ mol{sup -1}, respectively. These values are useful in exploring the stability of uranyl oxide hydrates in auxiliary chemical systems, such as those expected in U-contaminated environments.

Calibration and validation of a numerical model against experimental data of methane hydrate formation and dissociation in a sandy porous medium

Science.gov (United States)

Yin, Z.; Moridis, G. J.; Chong, Z. R.; Linga, P.

2017-12-01

Methane hydrates (MH) are known to trap enormous amounts of CH4 in oceanic and permafrost-associated deposits, and are being considered as a potential future energy source. Several powerful numerical simulators were developed to describe the behavior of natural hydrate-bearing sediments (HBS). The complexity and strong nonlinearities in HBS do not allow analytical solutions for code validation. The only reliable method to develop confidence in these models is through comparisons to laboratory and/or field experiments. The objective of this study is to reproduce numerically the results from earlier experiments of MH formation and depressurization (and the corresponding fluid production) in 1.0L reactor involving unconsolidated sand, thus validating and calibrating the TOUGH+Hydrate v1.5 simulator. We faithfully describe the reactor geometry and the experimental process that involves both hydrate formation and dissociation. We demonstrate that the laboratory experiments can only be captured by a kinetic hydration model. There is an excellent agreement between observations and predictions (a) of the cumulative gas depletion (during formation) and production (during dissociation) and (b) of pressure over time. The temperature agreement is less satisfactory, and the deviations are attributed to the fixed locations of the limited number of sensors that cannot fully capture the hydrate heterogeneity. We also predict the spatial distributions over time of the various phase (gas, aqueous and hydrate) saturations. Thus, hydrates form preferentially along the outer boundary of the sand core, and the hydrate front moves inward leaving a significant portion of the sand at the center hydrate-free. During depressurization, dissociation advances again inward from the reactor boundary to the center of the reactor. As expected, methane gas accumulates initially at the locations of most intense dissociation, and then gradually migrates to the upper section of the reactor because of

Experimental and theoretical investigations on the carbon dioxide gas hydrate formation kinetics at the onset of turbidity regarding CO2 capture and sequestration processes

International Nuclear Information System (INIS)

ZareNezhad, Bahman; Mottahedin, Mona; Varaminian, Farshad

2013-01-01

The carbon dioxide gas hydrate formation kinetics at the onset of turbidity is experimentally and theoretically investigated. It is shown that the time-dependent heterogeneous nucleation and growth kinetics are simultaneously governing the hydrate formation process at the onset of turbidity. A new approach is also presented for determination of gas hydrate-liquid interfacial tension. The CO 2 hydrate-liquid interfacial tension according to the suggested heterogeneous nucleation mechanism is found to be about 12.7 mJ/m 2 . The overall average absolute deviation between predicted and measured CO 2 molar consumption is about 0.61%, indicating the excellent accuracy of the proposed model for studying the hydrate-based CO 2 capture and sequestration processes over wide ranges of pressures and temperatures

Rheological properties of hydrate suspensions in asphaltenic crude oils; Proprietes rheologiques de suspensions d'hydrate dans des bruts asphalteniques

Energy Technology Data Exchange (ETDEWEB)

Marques de Toledo Camargo, R.

2001-03-01

The development of offshore oil exploitation under increasing water depths has forced oil companies to increase their understanding of gas hydrate formation and transportation in multiphase flow lines in which a liquid hydrocarbon phase is present. This work deals with the flow behaviour of hydrate suspensions in which a liquid hydrocarbon is the continuous phase. Three different liquid hydrocarbons are used: an asphaltenic crude oil, a condensate completely free of asphaltenes and a mixture between the asphaltenic oil and heptane. The rheological characterisation of hydrate suspensions is the main tool employed. Two original experimental devices are used: a PVT cell adapted to operate as a Couette type rheometer and a semi-industrial flow loop. Hydrate suspensions using the asphaltenic oil showed shear-thinning behaviour and thixotropy. This behaviour is typically found in flocculated systems, in which the particles attract each other forming flocs of aggregated particles at low shear rates. The suspensions using the condensate showed Newtonian behaviour. Their relative viscosities were high, which suggests that an aggregation process between hydrate particles takes. place during hydrate formation. Finally, hydrate suspensions using the mixture asphaltenic oil-heptane showed shear-thinning behaviour, thixotropy and high relative viscosity. From these results it can be inferred that, after the achievement of the hydrate formation process, the attractive forces between hydrate particles are weak. making unlikely pipeline obstruction by an aggregation process. Nevertheless, during the hydrate formation, these attractive forces can be sufficiently high. It seems that the hydrate surface wettability is an important parameter in this phenomena. (author)

Natural gas storage in hydrates with the presence of promoters

International Nuclear Information System (INIS)

Sun Zhigao; Wang Ruzhu; Ma Rongsheng; Guo Kaihua; Fan Shuanshi

2003-01-01

Hydrate technology is being developed for the storage and transport of natural gas. Micellar surfectant solutions were found to increase the gas hydrate formation rate and storage capacity. An anionic surfactant, a nonionic surfactant, their mixtures and cyclopentane were used to improve the hydrate formation of a synthetic natural gas (methane=92.05 mol%, ethane=4.96 mol%, propane=2.99 mol%) in a quiescent system in this work. The effect of an anionic surfactant (sodium dodecyl sulfate) on natural gas storage in hydrates is more pronounced compared to the effect of a nonionic surfactant (dodecyl polysaccharide glycoside). Cyclopentane could reduce hydrate formation induction time but could not improve the hydrate formation rate and storage capacity

Hydrates plugs dissociation in pipelines; Dissociation des bouchons d'hydrates de gaz dans les conduites petrolieres sous-marines

Energy Technology Data Exchange (ETDEWEB)

Nguyen Hong, D.

2005-03-15

Natural gas hydrates plugs cause problems during drilling, well operations, production, transportation and processing of oil and gas. Especially, it is a very serious problem in off-shore oil transportation where low temperature and high pressure become more and more favourable to gas hydrate formation as the new production wells are more and more deeper. Up to now, although many studies have been developed concerning the possibility of preventing pipe plugging, there is limited information in open literature on hydrate plugs dissociation and all models in literature are numerically complicated. In this study, hydrate plugs are formed from water in n-dodecane mixture with addition of a dispersant E102B in two different experimental apparatus in order to obtain hydrates plugs with different sizes (diameter of 7, 10.75 and 12 cm). Then, the plugs are dissociated by the method of two-sided depressurization. In this paper, we propose a numerical model which describes the dissociation of gas hydrate plugs in pipelines. The numerical model, which is constructed for cylindrical coordinates and for two-sided pressurization, is based on enthalpy method. We present also an approximate analytical model which has an average error 2.7 % in comparison with the numerical model. The excellent agreement between our experimental results, literature data and the two models shows that the models give a good prediction independently of the pipeline diameter, plug porosity and gas. The simplicity of the analytical model will make it easier in industrial applications. (author)

Formation of Sclerotic Hydrate Deposits in a Pipe for Extraction of a Gas from a Dome Separator

Science.gov (United States)

Urazov, R. R.; Chiglinstev, I. A.; Nasyrov, A. A.

2017-09-01

The theory of formation of hydrate deposits on the walls of a pipe for extraction of a gas from a dome separator designed for the accident-related collection of hydrocarbons on the ocean floor is considered. A mathematical model has been constructed for definition of a steady movement of a gas in such a pipe with gas-hydrate deposition under the conditions of changes in the velocity, temperature, pressure, and moisture content of the gas flow.

Hydrate-Bearing Clayey Sediments: Morphology, Physical Properties, Production and Engineering/Geological Implications

Energy Technology Data Exchange (ETDEWEB)

Dai, Sheng [Georgia Tech Research Corporation, Atlanta, GA (United States); Santamarina, J. Carlos [King Abdulaziz Univ., Jeddah (Saudi Arabia)

2017-12-30

Fine-grained sediments host more than 90 percent of global gas hydrate accumulation. However, hydrate formation in clay-dominated sediments is less understood and characterized than other types of hydrate occurrence. There is an inadequate understanding of hydrate formation mechanisms, segregation structures, hydrate lens topology, system connectivity, and physical macro-scale properties of clay-dominated hydrate-bearing sediments. This situation hinders further analyses of the global carbon budget as well as engineering challenges/solutions related to hydrate instability and production. This project studies hydrate-bearing clay-dominated sediments with emphasis on the enhanced fundamental understanding of hydrate formation and resulting morphology, the development laboratory techniques to emulate natural hydrate formations, the assessment of analytical tools to predict physical properties, the evaluation of engineering and geological implications, and the advanced understanding of gas production potential from finegrained sediments.

Comparison of Freezing and Hydrate Formation Methods in Removing Chloride and Bromide Ions from Brine

Directory of Open Access Journals (Sweden)

Marzieh Fattahi

2018-01-01

Full Text Available The growing population and enhanced industrial activities coupled with limitations on freshwater availability have led to efforts to desalinate salt water from the seas. Membrane and thermal technologies are the two commonly used for this purpose. In this study, the direct freezing and hydrate formation techniques were used for salt water desalination. Materials and Methods: Distilled water, sodium chloride, and sodium bromide were used as raw materials in the experiments. The experimental setup included a stationary reactor with two coaxial cylinders, in which ice crystals were deposited outside the cool inner cylinder to increase the salt concentration in the residual brine. An electrical conductivity instrument was used to measure sal removal. Results: Salt removal was shown to decrease with increasing salt concentration in the direct freeze method. A different trend was, however, observed in the hydrate formation method; salt removal was negligible at low concentrations in this method but increased at high concentrations before a constant value was reached. Overall, the hydrate formation recorded a higher salt removal efficiency than the other method. To investigate the effect of anion size on salt removal efficiency, experiments were carried out using NaCl and NaBr, which have the same cation but different anion sizes. Result showed that removal efficiency increased with increasing anion size. Conclusion: It was found that increasing ion radius leads to the lower likelihood of ion presence in the crystal lattice, thereby reducing salt removal efficiency. On the other hand, low concentrations of salt serve as site for the generation of cores, which naturally serve as removal accelerators.

Kinetic of formation for single carbon dioxide and mixed carbon dioxide and tetrahydrofuran hydrates in water and sodium chloride aqueous solution

NARCIS (Netherlands)

Sabil, K.M.; Duarte, A.R.C.; Zevenbergen, J.F.; Ahmad, M.M.; Yusup, S.; Omar, A.A.; Peters, C.J.

2010-01-01

A laboratory-scale reactor system is built and operated to measure the kinetic of formation for single and mixed carbon dioxide-tetrahydrofuran hydrates. The T-cycle method, which is used to collect the kinetic data, is briefly discussed. For single carbon dioxide hydrate, the induction time

Geological evolution and analysis of confirmed or suspected gas hydrate localities: Volume 10, Basin analysis, formation and stability of gas hydrates of the Aleutian Trench and the Bering Sea

Energy Technology Data Exchange (ETDEWEB)

Krason, J.; Ciesnik, M.

1987-01-01

Four major areas with inferred gas hydrates are the subject of this study. Two of these areas, the Navarin and the Norton Basins, are located within the Bering Sea shelf, whereas the remaining areas of the Atka Basin in the central Aleutian Trench system and the eastern Aleutian Trench represent a huge region of the Aleutian Trench-Arc system. All four areas are geologically diverse and complex. Particularly the structural features of the accretionary wedge north of the Aleutian Trench still remain the subjects of scientific debates. Prior to this study, suggested presence of the gas hydrates in the four areas was based on seismic evidence, i.e., presence of bottom simulating reflectors (BSRs). Although the disclosure of the BSRs is often difficult, particularly under the structural conditions of the Navarin and Norton basins, it can be concluded that the identified BSRs are mostly represented by relatively weak and discontinuous reflectors. Under thermal and pressure conditions favorable for gas hydrate formation, the relative scarcity of the BSRs can be attributed to insufficient gas supply to the potential gas hydrate zone. Hydrocarbon gas in sediment may have biogenic, thermogenic or mixed origin. In the four studied areas, basin analysis revealed limited biogenic hydrocarbon generation. The migration of the thermogenically derived gases is probably diminished considerably due to the widespread diagenetic processes in diatomaceous strata. The latter processes resulted in the formation of the diagenetic horizons. The identified gas hydrate-related BSRs seem to be located in the areas of increased biogenic methanogenesis and faults acting as the pathways for thermogenic hydrocarbons.

Investigations into surfactant/gas hydrate relationship

Energy Technology Data Exchange (ETDEWEB)

Rogers, Rudy; Zhang, Guochang; Dearman, Jennifer; Woods, Charles [Swalm School of Chemical Engineering, Mississippi State University, Mississippi State, MS 39762 (United States)

2007-03-15

Gas hydrates have unique physical properties portending useful industrial applications of gas storage, gas separation, or water desalination. When gas hydrates were found in the early 1990s to occur naturally and abundantly in seafloors, three other primary interests and concerns emerged: potential new energy source, climate threat from their greenhouse gases, and seafloor instabilities. This paper presents research showing how anionic synthetic surfactants helped develop an industrial gas hydrate storage process for natural gas and how naturally-occurring in-situ anionic biosurfactants influence the formation and placement of gas hydrates in ocean sediments. The catalytic effects, mechanisms, and surface specificities imparted by synthetic surfactants in the gas storage process and imparted by biosurfactants in porous media are discussed. The Bacillus subtilis bacterium that is indigenous to gas hydrate mounds in the Gulf of Mexico was cultured in the laboratory. Its biosurfactant was separated and found to catalyze gas hydrates in porous media. The experiments indicate that seafloor-biosurfactants can be produced rapidly in-situ to achieve threshold concentrations whereby hydrates are promoted. The biosurfactants accumulate and promote hydrate formation on specific mineral surfaces such as sodium montmorillonite. (author)

CALCIUM ORTHOPHOSPHATES HYDRATES: FORMATION, STABILITY AND INFLUENCE ON STANDARD PROPERTIES OF PORTLAND CEMENT

Directory of Open Access Journals (Sweden)

Kaziliunas A.

2013-12-01

Full Text Available Preparation of phosphogypsum to produce the binders requires a much higher input than preparation of natural gypsum stone. This makes it uncompetitive material. The investigations presented therein are meant to reduce this input by looking for the ways of rendering impurities harmless. Soluble acid orthophosphates are the main harmful impurity of phosphogypsum. The studies show that dry insoluble calcium orthophosphates hydrates (1.09 % and 2.18 % P2O5 in gypsum have little effect on W/C, setting times and soundness of Portland cement pastes. Insoluble calcium orthophosphates hydrates {CaHPO4∙2H2O, Ca8(HPO42(PO44∙5H2O and Ca9(HPO4(PO45(OH∙4H2O} formed in acidic medium (pH = 4.2 - 5.9 have been destroyed in alkaline medium and reduce standard compressive strength of cement up to 28 %. Calcium orthophosphates hydrates of hydroxyapatite group are stable in alcaline medium, while in dry state they reduce the standard compressive strength of cement until 10 %, but their suspensions prolong setting times of Portland cement as soluble orthophosphates – 2 - 3 times. Alkalis in cement increase pH of paste, but do not change the process of formation of calcium orthophosphates hydrates of hydroxyapatite group: it takes place through an intermediate phase - CaHPO4·2H2O, whose transformation into apatite lasts for 2 - 3 months.

Morphology studies on gas hydrates interacting with silica gel

Energy Technology Data Exchange (ETDEWEB)

Beltran, J.; Servio, P. [McGill Univ., Montreal, PQ (Canada). Dept. of Chemical Engineering

2008-07-01

Clathrate hydrates or gas hydrates are non-stoichiometric, crystalline compounds that form when small molecules come in contact with water at certain temperatures and pressures. Natural gas hydrates are found in the ocean bottom and in permafrost regions. It is thought that the amount of energy stored in natural hydrates is at least twice that of all other fossil fuels combined. In addition, trapping carbon dioxide as a hydrate in the bottom of the ocean has been suggested as an alternative means of reducing atmospheric carbon dioxide levels. Naturally occurring clathrates are found in close interaction with fine grained particles of very small mean pore diameters. Even though an increasing amount of hydrate equilibrium data for small diameter porous media has become available, the morphological behavior of hydrates subject to such conditions is yet to be explored. This paper presented a study that visually examined hydrate formation and decomposition of gas hydrates while interacting with fine grains of silica gel. The study showed still frames from high-resolution video recordings for hydrate formation and decomposition. The paper discussed the experiment including the apparatus as well as the results of hydrate formation and hydrate dissociation. This study enabled for the first time to observe clathrate morphology while hydrates interacted closely with fine grain particles with small mean pore diameters. 9 refs., 8 figs.

Gas hydrates forming and decomposition conditions analysis

Directory of Open Access Journals (Sweden)

А. М. Павленко

2017-07-01

Full Text Available The concept of gas hydrates has been defined; their brief description has been given; factors that affect the formation and decomposition of the hydrates have been reported; their distribution, structure and thermodynamic conditions determining the gas hydrates formation disposition in gas pipelines have been considered. Advantages and disadvantages of the known methods for removing gas hydrate plugs in the pipeline have been analyzed, the necessity of their further studies has been proved. In addition to the negative impact on the process of gas extraction, the hydrates properties make it possible to outline the following possible fields of their industrial use: obtaining ultrahigh pressures in confined spaces at the hydrate decomposition; separating hydrocarbon mixtures by successive transfer of individual components through the hydrate given the mode; obtaining cold due to heat absorption at the hydrate decomposition; elimination of the open gas fountain by means of hydrate plugs in the bore hole of the gushing gasser; seawater desalination, based on the hydrate ability to only bind water molecules into the solid state; wastewater purification; gas storage in the hydrate state; dispersion of high temperature fog and clouds by means of hydrates; water-hydrates emulsion injection into the productive strata to raise the oil recovery factor; obtaining cold in the gas processing to cool the gas, etc.

Molecular analysis of petroleum derived compounds that adsorb onto gas hydrate surfaces

International Nuclear Information System (INIS)

Borgund, Anna E.; Hoiland, Sylvi; Barth, Tanja; Fotland, Per; Askvik, Kjell M.

2009-01-01

Field observations have shown that some streams of water, gas and crude oil do not form gas hydrate plugs during petroleum production even when operating within thermodynamic conditions for hydrate formation. Also, when studied under controlled laboratory conditions, some oils are found to form hydrate dispersed systems whereas others form plugs. Oils with low tendency to form hydrate plugs are believed to contain natural hydrate plug inhibiting components (NICs) that adsorb onto the hydrate surface, making them less water-wet and preventing the particles from agglomerating into large hydrate clusters. The molecular structure of the NICs is currently unknown. In this work, hydrate adsorbing components were extracted from crude oils using freon hydrates as an extraction phase. The fractions were found to be enriched in polar material, and more polar material is associated with hydrates generated in biodegraded crude oils than in non-biodegraded oils. Various fractionation schemes and analytical techniques have been applied in the search for molecular characterisation. The average molecular weights were found to be approximately 500 g/mole. GC-MS chromatograms show a large UCM (Unresolved Complex Mixture). Thus, GC-MS has a limited potential for identification of compounds. A commercial biosurfactant was used as a model compound in the search for similar structures in the extracts. The results from analysis of the hydrate adsorbing components suggest that the type and structure are more important for hydrate morphology than the amount of material adsorbed.

Well log characterization of natural gas-hydrates

Science.gov (United States)

Collett, Timothy S.; Lee, Myung W.

2012-01-01

In the last 25 years there have been significant advancements in the use of well-logging tools to acquire detailed information on the occurrence of gas hydrates in nature: whereas wireline electrical resistivity and acoustic logs were formerly used to identify gas-hydrate occurrences in wells drilled in Arctic permafrost environments, more advanced wireline and logging-while-drilling (LWD) tools are now routinely used to examine the petrophysical nature of gas-hydrate reservoirs and the distribution and concentration of gas hydrates within various complex reservoir systems. Resistivity- and acoustic-logging tools are the most widely used for estimating the gas-hydrate content (i.e., reservoir saturations) in various sediment types and geologic settings. Recent integrated sediment coring and well-log studies have confirmed that electrical-resistivity and acoustic-velocity data can yield accurate gas-hydrate saturations in sediment grain-supported (isotropic) systems such as sand reservoirs, but more advanced log-analysis models are required to characterize gas hydrate in fractured (anisotropic) reservoir systems. New well-logging tools designed to make directionally oriented acoustic and propagation-resistivity log measurements provide the data needed to analyze the acoustic and electrical anisotropic properties of both highly interbedded and fracture-dominated gas-hydrate reservoirs. Advancements in nuclear magnetic resonance (NMR) logging and wireline formation testing (WFT) also allow for the characterization of gas hydrate at the pore scale. Integrated NMR and formation testing studies from northern Canada and Alaska have yielded valuable insight into how gas hydrates are physically distributed in sediments and the occurrence and nature of pore fluids(i.e., free water along with clay- and capillary-bound water) in gas-hydrate-bearing reservoirs. Information on the distribution of gas hydrate at the pore scale has provided invaluable insight on the mechanisms

Non-spherical particle formation induced by repulsive hydration forces during spray drying

Energy Technology Data Exchange (ETDEWEB)

Suh, Yong Jae; Lee, Jin-Woo; Chang, Hankwon; Jang, Hee-Dong, E-mail: hdjang@kigam.re.kr; Cho, Kuk, E-mail: kukcho@pusan.ac.kr [Korea Institute of Geoscience and Mineral Resources (Korea, Republic of)

2013-09-15

Non-spherical particles were produced during a spray-drying process, but the exact mechanism of their formation was unknown. The non-spherical particles form when the strength of the colloidal droplets is exceeded by external stress stemming from drag in the velocity gradient. Here, we show that repulsive hydration forces reduce the mechanical strength of the droplets; this is critical to the formation of non-spherical particles. Toroidal or ellipsoidal particles were prepared from low-concentration hydrophilic SiO{sub 2}, TiO{sub 2}, and CuO colloidal solutions, but not from hydrophobic ZnO colloidal solutions. The surface properties of the solid particulates are crucial for the morphology of particles formed during spray drying.

Non-spherical particle formation induced by repulsive hydration forces during spray drying

International Nuclear Information System (INIS)

Suh, Yong Jae; Lee, Jin-Woo; Chang, Hankwon; Jang, Hee-Dong; Cho, Kuk

2013-01-01

Non-spherical particles were produced during a spray-drying process, but the exact mechanism of their formation was unknown. The non-spherical particles form when the strength of the colloidal droplets is exceeded by external stress stemming from drag in the velocity gradient. Here, we show that repulsive hydration forces reduce the mechanical strength of the droplets; this is critical to the formation of non-spherical particles. Toroidal or ellipsoidal particles were prepared from low-concentration hydrophilic SiO 2 , TiO 2 , and CuO colloidal solutions, but not from hydrophobic ZnO colloidal solutions. The surface properties of the solid particulates are crucial for the morphology of particles formed during spray drying

[Skin hydration and hydrating products].

Science.gov (United States)

Duplan, H; Nocera, T

2018-05-01

One of the skin's principal functions is to protect the body against its environment by maintaining an effective epidermal barrier, not only against external factors, but also to prevent water loss from the body. Indeed, water homeostasis is vital for the normal physiological functioning of skin. Hydration levels affect not only visible microscopic parameters such as the suppleness and softness of skin, but also molecular parameters, enzyme activities and cellular signalling within the epidermis. The body is continually losing some of its water, but this phenomenon is limited and the optimal hydration gradient in skin is ensured via a set of sophisticated regulatory processes that rely on the functional and dynamic properties of the uppermost level of the skin consisting of the stratum corneum. The present article brings together data recently acquired in the fields of skin hydration and the characterisation of dehydrated or dry skin, whether through study of the regulatory processes involved or as a result of changes in the techniques used for in situ measurement, and thus in optimisation of management. Copyright © 2018. Published by Elsevier Masson SAS.

Hydrate phase equilibrium and structure for (methane + ethane + tetrahydrofuran + water) system

International Nuclear Information System (INIS)

Sun Changyu; Chen Guangjin; Zhang Lingwei

2010-01-01

The separation of methane and ethane through forming hydrate is a possible choice in natural gas, oil processing, or ethylene producing. The hydrate formation conditions of five groups of (methane + ethane) binary gas mixtures in the presence of 0.06 mole fraction tetrahydrofuran (THF) in water were obtained at temperatures ranging from (277.7 to 288.2) K. In most cases, the presence of THF in water can lower the hydrate formation pressure of (methane + ethane) remarkably. However, when the composition of ethane is as high as 0.832, it is more difficult to form hydrate than without THF system. Phase equilibrium model for hydrates containing THF was developed based on a two-step hydrate formation mechanism. The structure of hydrates formed from (methane + ethane + THF + water) system was also determined by Raman spectroscopy. When THF concentration in initial aqueous solution was only 0.06 mole fraction, the coexistence of structure I hydrate dominated by ethane and structure II hydrate dominated by THF in the hydrate sample was clearly demonstrated by Raman spectroscopic data. On the contrary, only structure II hydrate existed in the hydrate sample formed from (methane + ethane + THF + water) system when THF concentration in initial aqueous solution was increased to 0.10 mole fraction. It indicated that higher THF concentration inhibited the formation of structure I hydrate dominated by ethane and therefore lowered the trapping of ethane in hydrate. It implies a very promising method to increase the separation efficiency of methane and ethane.

[Laser Raman Spectroscopy and Its Application in Gas Hydrate Studies].

Science.gov (United States)

Fu, Juan; Wu, Neng-you; Lu, Hai-long; Wu, Dai-dai; Su, Qiu-cheng

2015-11-01

Gas hydrates are important potential energy resources. Microstructural characterization of gas hydrate can provide information to study the mechanism of gas hydrate formation and to support the exploitation and application of gas hydrate technology. This article systemly introduces the basic principle of laser Raman spectroscopy and summarizes its application in gas hydrate studies. Based on Raman results, not only can the information about gas composition and structural type be deduced, but also the occupancies of large and small cages and even hydration number can be calculated from the relative intensities of Raman peaks. By using the in-situ analytical technology, laser Raman specstropy can be applied to characterize the formation and decomposition processes of gas hydrate at microscale, for example the enclathration and leaving of gas molecules into/from its cages, to monitor the changes in gas concentration and gas solubility during hydrate formation and decomposition, and to identify phase changes in the study system. Laser Raman in-situ analytical technology has also been used in determination of hydrate structure and understanding its changing process under the conditions of ultra high pressure. Deep-sea in-situ Raman spectrometer can be employed for the in-situ analysis of the structures of natural gas hydrate and their formation environment. Raman imaging technology can be applied to specify the characteristics of crystallization and gas distribution over hydrate surface. With the development of laser Raman technology and its combination with other instruments, it will become more powerful and play a more significant role in the microscopic study of gas hydrate.

Thermal conductivity of hydrate-bearing sediments

Science.gov (United States)

Cortes, Douglas D.; Martin, Ana I.; Yun, Tae Sup; Francisca, Franco M.; Santamarina, J. Carlos; Ruppel, Carolyn D.

2009-01-01

A thorough understanding of the thermal conductivity of hydrate-bearing sediments is necessary for evaluating phase transformation processes that would accompany energy production from gas hydrate deposits and for estimating regional heat flow based on the observed depth to the base of the gas hydrate stability zone. The coexistence of multiple phases (gas hydrate, liquid and gas pore fill, and solid sediment grains) and their complex spatial arrangement hinder the a priori prediction of the thermal conductivity of hydrate-bearing sediments. Previous studies have been unable to capture the full parameter space covered by variations in grain size, specific surface, degree of saturation, nature of pore filling material, and effective stress for hydrate-bearing samples. Here we report on systematic measurements of the thermal conductivity of air dry, water- and tetrohydrofuran (THF)-saturated, and THF hydrate–saturated sand and clay samples at vertical effective stress of 0.05 to 1 MPa (corresponding to depths as great as 100 m below seafloor). Results reveal that the bulk thermal conductivity of the samples in every case reflects a complex interplay among particle size, effective stress, porosity, and fluid-versus-hydrate filled pore spaces. The thermal conductivity of THF hydrate–bearing soils increases upon hydrate formation although the thermal conductivities of THF solution and THF hydrate are almost the same. Several mechanisms can contribute to this effect including cryogenic suction during hydrate crystal growth and the ensuing porosity reduction in the surrounding sediment, increased mean effective stress due to hydrate formation under zero lateral strain conditions, and decreased interface thermal impedance as grain-liquid interfaces are transformed into grain-hydrate interfaces.

Inhibition of Methane Hydrate Formation by Ice-Structuring Proteins

DEFF Research Database (Denmark)

Jensen, Lars; Ramløv, Hans; Thomsen, Kaj

2010-01-01

, assumed biodegradable, are capable of inhibiting the growth of methane hydrate (a structure I hydrate). The ISPs investigated were type III HPLC12 (originally identified in ocean pout) and ISP type III found in meal worm (Tenebrio molitor). These were compared to polyvinylpyrrolidone (PVP) a well...... of inhibitors. The profile of the nonlinear growth was concentration-dependent but also dependent on the stirring rate. ISP type III HPLC12 decreased the growth rate of methane hydrate during the linear growth period by 17−75% at concentrations of 0.01−0.1 wt % (0.014−0.14 mM) while ISP from Tenebrio molitor...... and PVP decreased the growth rate by 30% and 39% at concentrations of 0.004 wt % (0.005 mM) and 0.1 wt % (0.1 mM), respectively. Considering the low concentration of Tenebrio molitor ISP used, these results indicate that ISP from Tenebrio molitor is the most effective hydrate inhibitor among those...

Hydrothermal Formation Of Hemi-hydrate Calcium Sulfate Whiskers In The Presence Of Additives

International Nuclear Information System (INIS)

Luo, K. B.; Li, C. M.; Li, H. P.; Ning, P.; Xiang, L.

2010-01-01

The influence of addictives on the hydrothermal formation of hemi-hydrate calcium sulfate (CaSO 4 ·0.5H 2 O) whiskers were discussed in this paper, using CaCl 2 and Na 2 SO 4 as the reactants. The presence of NaCl, CaCl 2 or Na 2 SO 4 increased the concentrations of Ca 2+ and SO 4 2- , leading to the formation of CaSO 4 ·0.5H 2 O whiskers with aspect ratio lower than 50. The one dimensional growth of CaSO 4 ·0.5H 2 O whiskers was enhanced in water with no additives owing to the low super-saturation, leading to the formation of uniform whiskers with a length of 200-2000 μm and an aspect ratio higher than 100.

Suspension hydration of C3S [tricalcium silicate] at constant pH. II. Effect of previously formed hydrates and of additives

NARCIS (Netherlands)

McCurdy, K.G.; Stein, H.N.

1973-01-01

A retardation shown by the hydration of C3S at pH=11.5 can be prevented if before the addition of C3S there are present hydrate particles in the aqueous medium. These hydrate particles probably have the composition CSHn. This indicates a hydrate CSHn, precipitated from solution, as the retarding

Can hydrate dissolution experiments predict the fate of a natural hydrate system?

Energy Technology Data Exchange (ETDEWEB)

Hester, K.C.; Peltzer, E.T.; Dunk, R.M.; Walz, P.M.; Brewer, P.G. [Monterey Bay Aquarium Research Inst., Moss Landing, CA (United States); Dendy Sloan, E. [Colorado School of Mines, Golden, CO (United States). Center for Hydrate Research

2008-07-01

Gas hydrates are naturally occurring compounds found in permafrost regions and in oceans. In the natural environment, sufficient temperature and pressure conditions for hydrate formation exist over a significant portion of the ocean. However, in addition to pressure and temperature, the chemical potential of the gas in the hydrate must be equal to the surrounding waters. If the concentration of the gas in surrounding water is under-saturated with respect to the gas in the hydrate, the hydrate will dissolve to drive the system towards chemical equilibrium. This paper presented a dissolution study of exposed hydrate from outcrops at Barkley Canyon, located off Vancouver Island, British Columbia. A previous field experiment on synthetic methane hydrate samples had demonstrated that mass transfer controlled dissolution in under-saturated seawater. However, seafloor hydrate outcrops have been shown to have significant longevity compared to expected dissolution rates based upon convective boundary layer diffusion calculations. An in-situ dissolution experiment was performed on two distinct natural hydrate fabrics in order to help resolve this apparent disconnect between the dissolution rates of synthetic and natural hydrate. The paper presented a map of Barkley Canyon and discussed the field measurements and methods for the study. Exposed outcrops of gas hydrates were cored using a specially constructed stainless steel coring device and a hydraulic ram was located inside the corer. Hydrate samples were cored directly using the a manipulator arm and then injected into a sampling cell. The hydrate was then added to an open mesh exposure container, which allowed for exposure to ambient benthic currents with minimal disturbance. As well, in order to observe the slow dissolution of the hydrate in seawater at Barkley Canyon, time-lapse photography was employed. Last, the paper presented the results of the hydrate fabric porosities and hydrate dissolution rates. It was

Desalination of Produced Water via Gas Hydrate Formation and Post Treatment

OpenAIRE

Niu, Jing

2012-01-01

This study presents a two-step desalination process, in which produced water is cleaned by forming gas hydrate in it and subsequently dewatering the hydrate to remove the residual produced water trapped in between the hydrate crystals. All experiments were performed with pressure in the range of 450 to 800psi and temperature in the range of -1 to 1°C using CO? as guest molecule for the hydrate crystals. The experiments were conducted using artificial produced waters containing different amoun...

An Experimental and Theoretical Study of CO2 Hydrate Formation Systems

OpenAIRE

Tzirakis, Fragkiskos; Kontogeorgis, Georgios; Coquelet, Christophe; von Solms, Nicolas; Stringari, Paolo

2016-01-01

Hydrate krystallisering kan blive en vigtig kulstofopsamling metode, forudsat at denne teknologi undergår yderligere forskning. Med henblik på dette mål, forsøger denne undersøgelse at kaste lys over en helt nyt emne for forskning: hydrat forfremmelse.Hydrate forfremmelse indebærer produktion af hydrat ved lavere tryk (og dermed lavere supplerende driftsomkostninger) ved brug af specielle kemikalier (promotore). I første omgang har et omfattende litteraturstudie vist at både eksperimentelle d...

Spatial resolution of gas hydrate and permeability changes from ERT data in LARS simulating the Mallik gas hydrate production test

Science.gov (United States)

Priegnitz, Mike; Thaler, Jan; Spangenberg, Erik; Schicks, Judith M.; Abendroth, Sven

2014-05-01

The German gas hydrate project SUGAR studies innovative methods and approaches to be applied in the production of methane from hydrate-bearing reservoirs. To enable laboratory studies in pilot scale, a large reservoir simulator (LARS) was realized allowing for the formation and dissociation of gas hydrates under simulated in-situ conditions. LARS is equipped with a series of sensors. This includes a cylindrical electrical resistance tomography (ERT) array composed of 25 electrode rings featuring 15 electrodes each. The high-resolution ERT array is used to monitor the spatial distribution of the electrical resistivity during hydrate formation and dissociation experiments over time. As the present phases of poorly conducting sediment, well conducting pore fluid, non-conducting hydrates, and isolating free gas cover a wide range of electrical properties, ERT measurements enable us to monitor the spatial distribution of these phases during the experiments. In order to investigate the hydrate dissociation and the resulting fluid flow, we simulated a hydrate production test in LARS that was based on the Mallik gas hydrate production test (see abstract Heeschen et al., this volume). At first, a hydrate phase was produced from methane saturated saline water. During the two months of gas hydrate production we measured the electrical properties within the sediment sample every four hours. These data were used to establish a routine estimating both the local degrees of hydrate saturation and the resulting local permeabilities in the sediment's pore space from the measured resistivity data. The final gas hydrate saturation filled 89.5% of the total pore space. During hydrate dissociation, ERT data do not allow for a quantitative determination of free gas and remaining gas hydrates since both phases are electrically isolating. However, changes are resolved in the spatial distribution of the conducting liquid and the isolating phase with gas being the only mobile isolating phase

THERMODYNAMIC MODEL OF GAS HYDRATES

OpenAIRE

Недоступ, В. И.; Недоступ, О. В.

2015-01-01

The interest to gas hydrates grows last years. Therefore working out of reliable settlement-theoretical methods of definition of their properties is necessary. The thermodynamic model of gas hydrates in which the central place occupies a behaviour of guest molecule in cell is described. The equations of interaction of molecule hydrate formative gas with cell are received, and also an enthalpy and energy of output of molecule from a cell are determined. The equation for calculation of thermody...

Gas hydrate cool storage system

Science.gov (United States)

Ternes, M.P.; Kedl, R.J.

1984-09-12

The invention presented relates to the development of a process utilizing a gas hydrate as a cool storage medium for alleviating electric load demands during peak usage periods. Several objectives of the invention are mentioned concerning the formation of the gas hydrate as storage material in a thermal energy storage system within a heat pump cycle system. The gas hydrate was formed using a refrigerant in water and an example with R-12 refrigerant is included. (BCS)

HYDRATE CORE DRILLING TESTS

Energy Technology Data Exchange (ETDEWEB)

John H. Cohen; Thomas E. Williams; Ali G. Kadaster; Bill V. Liddell

2002-11-01

The ''Methane Hydrate Production from Alaskan Permafrost'' project is a three-year endeavor being conducted by Maurer Technology Inc. (MTI), Noble, and Anadarko Petroleum, in partnership with the U.S. DOE National Energy Technology Laboratory (NETL). The project's goal is to build on previous and ongoing R&D in the area of onshore hydrate deposition. The project team plans to design and implement a program to safely and economically drill, core and produce gas from arctic hydrates. The current work scope includes drilling and coring one well on Anadarko leases in FY 2003 during the winter drilling season. A specially built on-site core analysis laboratory will be used to determine some of the physical characteristics of the hydrates and surrounding rock. Prior to going to the field, the project team designed and conducted a controlled series of coring tests for simulating coring of hydrate formations. A variety of equipment and procedures were tested and modified to develop a practical solution for this special application. This Topical Report summarizes these coring tests. A special facility was designed and installed at MTI's Drilling Research Center (DRC) in Houston and used to conduct coring tests. Equipment and procedures were tested by cutting cores from frozen mixtures of sand and water supported by casing and designed to simulate hydrate formations. Tests were conducted with chilled drilling fluids. Tests showed that frozen core can be washed out and reduced in size by the action of the drilling fluid. Washing of the core by the drilling fluid caused a reduction in core diameter, making core recovery very difficult (if not impossible). One successful solution was to drill the last 6 inches of core dry (without fluid circulation). These tests demonstrated that it will be difficult to capture core when drilling in permafrost or hydrates without implementing certain safeguards. Among the coring tests was a simulated hydrate

Methane Hydrate Formation from Enhanced Organic Carbon Burial During Glacial Lowstands: Examples from the Gulf of Mexico

Science.gov (United States)

Malinverno, A.; Cook, A.; Daigle, H.; Oryan, B.

2017-12-01

Methane hydrates in fine-grained marine sediments are often found within veins and fractures occupying discrete depth intervals that are surrounded by hydrate-free sediments. As they are not connected with gas sources beneath the base of the methane hydrate stability zone (MHSZ), these isolated hydrate-bearing intervals have been interpreted as formed by in situ microbial methane. We investigate here the hypothesis that these hydrate deposits form in sediments that were deposited during glacial lowstands and contain higher amounts of labile particulate organic carbon (POC), leading to enhanced microbial methanogenesis. During Pleistocene lowstands, river loads are deposited near the steep top of the continental slope and turbidity currents transport organic-rich, fine-grained sediments to deep waters. Faster sedimentation rates during glacial periods result in better preservation of POC because of decreased exposure times to oxic conditions. The net result is that more labile POC enters the methanogenic zone and more methane is generated in these sediments. To test this hypothesis, we apply an advection-diffusion-reaction model with a time-dependent deposition of labile POC at the seafloor controlled by glacioeustatic sea level variations in the last 250 kyr. The model is run for parameters estimated at three sites drilled by the 2009 Gulf of Mexico Joint Industry Project: Walker Ridge in the Terrebonne Basin (WR313-G and WR313-H) and Green Canyon near the canyon embayment into the Sigsbee Escarpment (GC955-H). In the model, gas hydrate forms in sediments with higher labile POC content deposited during the glacial cycle between 230 and 130 kyr (marine isotope stages 6 and 7). The corresponding depth intervals in the three sites contain hydrates, as shown by high bulk electrical resistivities and resistive subvertical fracture fills. This match supports the hypothesis that enhanced POC burial during glacial lowstands can result in hydrate formation from in situ

Methane Hydrate Formation from Enhanced Organic Carbon Burial During Glacial Lowstands: Examples from the Gulf of Mexico

Energy Technology Data Exchange (ETDEWEB)

Malinverno, Alberto; Cook, Ann; Daigle, Hugh; Oryan, Bar

2017-12-15

Methane hydrates in fine-grained marine sediments are often found within veins and fractures occupying discrete depth intervals that are surrounded by hydrate-free sediments. As they are not connected with gas sources beneath the base of the methane hydrate stability zone (MHSZ), these isolated hydrate-bearing intervals have been interpreted as formed by in situ microbial methane. We investigate here the hypothesis that these hydrate deposits form in sediments that were deposited during glacial lowstands and contain higher amounts of labile particulate organic carbon (POC), leading to enhanced microbial methanogenesis. During Pleistocene lowstands, river loads are deposited near the steep top of the continental slope and turbidity currents transport organic-rich, fine-grained sediments to deep waters. Faster sedimentation rates during glacial periods result in better preservation of POC because of decreased exposure times to oxic conditions. The net result is that more labile POC enters the methanogenic zone and more methane is generated in these sediments. To test this hypothesis, we apply an advection-diffusion-reaction model with a time-dependent deposition of labile POC at the seafloor controlled by glacioeustatic sea level variations in the last 250 kyr. The model is run for parameters estimated at three sites drilled by the 2009 Gulf of Mexico Joint Industry Project: Walker Ridge in the Terrebonne Basin (WR313-G and WR313-H) and Green Canyon near the canyon embayment into the Sigsbee Escarpment (GC955-H). In the model, gas hydrate forms in sediments with higher labile POC content deposited during the glacial cycle between 230 and 130 kyr (marine isotope stages 6 and 7). The corresponding depth intervals in the three sites contain hydrates, as shown by high bulk electrical resistivities and resistive subvertical fracture fills. This match supports the hypothesis that enhanced POC burial during glacial lowstands can result in hydrate formation from in situ

Novel understanding of calcium silicate hydrate from dilute hydration

KAUST Repository

Zhang, Lina

2017-05-13

The perspective of calcium silicate hydrate (C-S-H) is still confronting various debates due to its intrinsic complicated structure and properties after decades of studies. In this study, hydration at dilute suspension of w/s equaling to 10 was conducted for tricalcium silicate (C3S) to interpret long-term hydration process and investigate the formation, structure and properties of C-S-H. Based on results from XRD, IR, SEM, NMR and so forth, loose and dense clusters of C-S-H with analogous C/S ratio were obtained along with the corresponding chemical formulae proposed as Ca5Si4O13∙6.2H2O. Crystalline structure inside C-S-H was observed by TEM, which was allocated at the foil-like proportion as well as the edge of wrinkles of the product. The long-term hydration process of C3S in dilute suspension could be sketchily described as migration of calcium hydroxide and in-situ growth of C-S-H with equilibrium silicon in aqueous solution relatively constant and calcium varied.

Nuclear Well Log Properties of Natural Gas Hydrate Reservoirs

Science.gov (United States)

Burchwell, A.; Cook, A.

2015-12-01

Characterizing gas hydrate in a reservoir typically involves a full suite of geophysical well logs. The most common method involves using resistivity measurements to quantify the decrease in electrically conductive water when replaced with gas hydrate. Compressional velocity measurements are also used because the gas hydrate significantly strengthens the moduli of the sediment. At many gas hydrate sites, nuclear well logs, which include the photoelectric effect, formation sigma, carbon/oxygen ratio and neutron porosity, are also collected but often not used. In fact, the nuclear response of a gas hydrate reservoir is not known. In this research we will focus on the nuclear log response in gas hydrate reservoirs at the Mallik Field at the Mackenzie Delta, Northwest Territories, Canada, and the Gas Hydrate Joint Industry Project Leg 2 sites in the northern Gulf of Mexico. Nuclear logs may add increased robustness to the investigation into the properties of gas hydrates and some types of logs may offer an opportunity to distinguish between gas hydrate and permafrost. For example, a true formation sigma log measures the thermal neutron capture cross section of a formation and pore constituents; it is especially sensitive to hydrogen and chlorine in the pore space. Chlorine has a high absorption potential, and is used to determine the amount of saline water within pore spaces. Gas hydrate offers a difference in elemental composition compared to water-saturated intervals. Thus, in permafrost areas, the carbon/oxygen ratio may vary between gas hydrate and permafrost, due to the increase of carbon in gas hydrate accumulations. At the Mallik site, we observe a hydrate-bearing sand (1085-1107 m) above a water-bearing sand (1107-1140 m), which was confirmed through core samples and mud gas analysis. We observe a decrease in the photoelectric absorption of ~0.5 barnes/e-, as well as an increase in the formation sigma readings of ~5 capture units in the water-bearing sand as

Cisplatin enhances the formation of DNA single- and double-strand breaks by hydrated electrons and hydroxyl radicals.

Science.gov (United States)

Rezaee, Mohammad; Sanche, Léon; Hunting, Darel J

2013-03-01

The synergistic interaction of cisplatin with ionizing radiation is the clinical rationale for the treatment of several cancers including head and neck, cervical and lung cancer. The underlying molecular mechanism of the synergy has not yet been identified, although both DNA damage and repair processes are likely involved. Here, we investigate the indirect effect of γ rays on strand break formation in a supercoiled plasmid DNA (pGEM-3Zf-) covalently modified by cisplatin. The yields of single- and double-strand breaks were determined by irradiation of DNA and cisplatin/DNA samples with (60)Co γ rays under four different scavenging conditions to examine the involvement of hydrated electrons and hydroxyl radicals in inducing the DNA damage. At 5 mM tris in an N2 atmosphere, the presence of an average of two cisplatins per plasmid increased the yields of single- and double-strand breaks by factors of 1.9 and 2.2, respectively, relative to the irradiated unmodified DNA samples. Given that each plasmid of 3,200 base pairs contained an average of two cisplatins, this represents an increase in radiosensitivity of 3,200-fold on a per base pair basis. When hydrated electrons were scavenged by saturating the samples with N2O, these enhancement factors decreased to 1.5 and 1.2, respectively, for single- and double-strand breaks. When hydroxyl radicals were scavenged using 200 mM tris, the respective enhancement factors were 1.2 and 1.6 for single- and double-strand breaks, respectively. Furthermore, no enhancement in DNA damage by cisplatin was observed after scavenging both hydroxyl radicals and hydrated electrons. These findings show that hydrated electrons can induce both single- and double-strand breaks in the platinated DNA, but not in unmodified DNA. In addition, cisplatin modification is clearly an extremely efficient means of increasing the formation of both single- and double-strand breaks by the hydrated electrons and hydroxyl radicals created by ionizing

Dynamic morphology of gas hydrate on a methane bubble in water: Observations and new insights for hydrate film models

Science.gov (United States)

Warzinski, Robert P.; Lynn, Ronald; Haljasmaa, Igor; Leifer, Ira; Shaffer, Frank; Anderson, Brian J.; Levine, Jonathan S.

2014-10-01

Predicting the fate of subsea hydrocarbon gases escaping into seawater is complicated by potential formation of hydrate on rising bubbles that can enhance their survival in the water column, allowing gas to reach shallower depths and the atmosphere. The precise nature and influence of hydrate coatings on bubble hydrodynamics and dissolution is largely unknown. Here we present high-definition, experimental observations of complex surficial mechanisms governing methane bubble hydrate formation and dissociation during transit of a simulated oceanic water column that reveal a temporal progression of deep-sea controlling mechanisms. Synergistic feedbacks between bubble hydrodynamics, hydrate morphology, and coverage characteristics were discovered. Morphological changes on the bubble surface appear analogous to macroscale, sea ice processes, presenting new mechanistic insights. An inverse linear relationship between hydrate coverage and bubble dissolution rate is indicated. Understanding and incorporating these phenomena into bubble and bubble plume models will be necessary to accurately predict global greenhouse gas budgets for warming ocean scenarios and hydrocarbon transport from anthropogenic or natural deep-sea eruptions.

Prospects of gas hydrate presence in the Chukchi sea

Directory of Open Access Journals (Sweden)

Т. В. Матвеева

2017-08-01

Full Text Available The purpose of this study is to forecast the scale and distribution character of gas hydrate stability zone in the Chukchi Sea under simulated natural conditions and basing on these results to estimate resource potential of gas hydrates within this area. Three types of stability zone have been identified. A forecast map of gas hydrate environment and potentially gas hydrate-bearing water areas in the Chukchi Sea has been plotted to a scale of 1:5 000 000. Mapping of gas hydrate stability zone allowed to give a justified forecast based on currently available data on geologic, fluid dynamic, cryogenic, geothermal and pressure-temperature conditions of gas hydrate formation in the Chukchi Sea. It is the first forecast of such kind that focuses on formation conditions for hydrates of various types and compositions in the Arctic seas offshore Russia. Potential amount of gas, stored beneath the Chukchi Sea in the form of hydrates, is estimated based on mapping of their stability zone and falls into the interval of 7·1011-11.8·1013 m3.

A DFT-based comparative equilibrium study of thermal dehydration and hydrolysis of CaCl2 hydrates and MgCl2 hydrates for seasonal heat storage

NARCIS (Netherlands)

Pathak, A.D.; Gaastra-Nedea, S.V.; Zondag, H.A.; Rindt, C.C.M.; Smeulders, D.M.J.

2016-01-01

Salt hydrates store solar energy in chemical form via a reversible dehydration–hydration reaction. However, as a side reaction to dehydration, hydrolysis (HCl formation) may occur in chloride based salt hydrates (specially in MgCl2 hydrates), affecting the durability of the storage system. The

Towards CO2 sequestration and applications of CO2 hydrates: the effects of tetrahydrofuran on the phase equilibria of CO2 hydrates

International Nuclear Information System (INIS)

Khalik, M.S.; Peters, C.J.

2006-01-01

The increasing quantity of carbon dioxide (CO 2 ) in the atmosphere has caused widespread global concerns. Capturing CO 2 from its sources and stored it in the form of gas hydrates and application of CO 2 hydrates are among the proposed methods to overcome this problem. In order to make hydrate-based process more attractive, the use of cyclic ethers as promoters is suggested to reduce the required hydrate formation pressure and enhancing the corresponding kinetic rate. In the present work, tetrahydrofuran (THF) is chosen as a hydrate promoter, participating in forming hydrates and produces mixed hydrate together with CO 2 . The pressure and temperature ranges of hydrate stability region are carefully determined through phase equilibrium measurement of the ternary CO 2 , tetrahydrofuran (THF) and water systems. From the experimental results, it is confirmed that the presence of THF in CO 2 + water systems will extend the hydrate formation region to higher temperature at a constant pressure. The extension of the hydrate stability region is depended on the overall concentration of the ternary system. Moreover, four-phase equilibrium of H-Lw-Lv-V is observed in the system, which may be due to a liquid phase split. In the region where the four-phase equilibrium exists, the ternary system loses its concentration dependency of the hydrate equilibrium conditions. (Author)

A new aluminium-hydrate species in hydrated Portland cements characterized by 27Al and 29Si MAS NMR spectroscopy

International Nuclear Information System (INIS)

Andersen, Morten Daugaard; Jakobsen, Hans J.; Skibsted, Jorgen

2006-01-01

Recent 27 Al MAS NMR studies of hydrated Portland cements and calcium-silicate-hydrate (C-S-H) phases have shown a resonance from Al in octahedral coordination, which cannot be assigned to the well-known aluminate species in hydrated Portland cements. This resonance, which exhibits the isotropic chemical shift δ iso = 5.0 ppm and the quadrupole product parameter P Q = 1.2 MHz, has been characterized in detail by 27 Al MAS and 27 Al{ 1 H} CP/MAS NMR for different hydrated white Portland cements and C-S-H phases. These experiments demonstrate that the resonance originates from an amorphous or disordered aluminate hydrate which contains Al(OH) 6 3- or O x Al(OH) 6-x (3+x)- units. The formation of the new aluminate hydrate is related to the formation of C-S-H at ambient temperatures, however, it decomposes by thermal treatment at temperatures of 70-90 o C. From the experiments in this work it is proposed that the new aluminate hydrate is either an amorphous/disordered aluminate hydroxide or a calcium aluminate hydrate, produced as a separate phase or as a nanostructured surface precipitate on the C-S-H phase. Finally, the possibilities of Al 3+ for Ca 2+ substitution in the principal layers and interlayers of the C-S-H structure are discussed

Overview: Nucleation of clathrate hydrates.

Science.gov (United States)

Warrier, Pramod; Khan, M Naveed; Srivastava, Vishal; Maupin, C Mark; Koh, Carolyn A

2016-12-07

Molecular level knowledge of nucleation and growth of clathrate hydrates is of importance for advancing fundamental understanding on the nature of water and hydrophobic hydrate formers, and their interactions that result in the formation of ice-like solids at temperatures higher than the ice-point. The stochastic nature and the inability to probe the small length and time scales associated with the nucleation process make it very difficult to experimentally determine the molecular level changes that lead to the nucleation event. Conversely, for this reason, there have been increasing efforts to obtain this information using molecular simulations. Accurate knowledge of how and when hydrate structures nucleate will be tremendously beneficial for the development of sustainable hydrate management strategies in oil and gas flowlines, as well as for their application in energy storage and recovery, gas separation, carbon sequestration, seawater desalination, and refrigeration. This article reviews various aspects of hydrate nucleation. First, properties of supercooled water and ice nucleation are reviewed briefly due to their apparent similarity to hydrates. Hydrate nucleation is then reviewed starting from macroscopic observations as obtained from experiments in laboratories and operations in industries, followed by various hydrate nucleation hypotheses and hydrate nucleation driving force calculations based on the classical nucleation theory. Finally, molecular simulations on hydrate nucleation are discussed in detail followed by potential future research directions.

Overview: Nucleation of clathrate hydrates

Science.gov (United States)

Warrier, Pramod; Khan, M. Naveed; Srivastava, Vishal; Maupin, C. Mark; Koh, Carolyn A.

2016-12-01

Molecular level knowledge of nucleation and growth of clathrate hydrates is of importance for advancing fundamental understanding on the nature of water and hydrophobic hydrate formers, and their interactions that result in the formation of ice-like solids at temperatures higher than the ice-point. The stochastic nature and the inability to probe the small length and time scales associated with the nucleation process make it very difficult to experimentally determine the molecular level changes that lead to the nucleation event. Conversely, for this reason, there have been increasing efforts to obtain this information using molecular simulations. Accurate knowledge of how and when hydrate structures nucleate will be tremendously beneficial for the development of sustainable hydrate management strategies in oil and gas flowlines, as well as for their application in energy storage and recovery, gas separation, carbon sequestration, seawater desalination, and refrigeration. This article reviews various aspects of hydrate nucleation. First, properties of supercooled water and ice nucleation are reviewed briefly due to their apparent similarity to hydrates. Hydrate nucleation is then reviewed starting from macroscopic observations as obtained from experiments in laboratories and operations in industries, followed by various hydrate nucleation hypotheses and hydrate nucleation driving force calculations based on the classical nucleation theory. Finally, molecular simulations on hydrate nucleation are discussed in detail followed by potential future research directions.

A study of the process of joint formation of methane gas-hydrate and authigenic carbonates in bottom sediments in the Sea of Okhotsk

Energy Technology Data Exchange (ETDEWEB)

Esikov, A D [AN SSSR, Moscow (USSR). Water Problems Inst.; Pashkina, V I [AN SSSR, Moscow (USSR). Inst. Okeanologii

1990-01-01

The discovery of gas-hydrates in bottom sediments in the Sea of Okhotsk has allowed isotope fractionation of oxygen and hydrogen to be determined in the formation of the crystal lattice. It was established that the structure of gas-hydrate selectively included the heavier isotopes of oxygen and hydrogen, so that the gas-hydrate water had values of {delta}{sup 18}O = +1.9 per mille and {delta}D = +23 per mille, whereas the interstitial water was ''lighter'' in isotopes, with the values of {delta}{sup 18}O = -0.5 per mille and {delta}D = -5 per mille (relative to SMOW (standard mean ocean water)). The formation of gas-hydrates under the conditions of underwater discharge of methane alters the chemical composition of interstitial water, so that the carbonate equilibrium is shifted, and carbonates of authigenic origin are formed. The isotope composition of the carbonates is characterized by a low content of {sup 13}C({delta}{sup 13}C from -39.3 to -51.8 per mille PDB) and a high content of {sup 18}O({delta}{sup 18}O from + 2.7 to +6.3 per mille PDB) in comparison with carbonates of sea origin. These characteristics of the isotope composition suggest the participation of methane in the formation of authigenic carbonates, due to its anaerobic oxidation and the involvement of sulfate in the silt water. (author).

Observed gas hydrate morphologies in marine sediment

Energy Technology Data Exchange (ETDEWEB)

Holland, M.; Schultheiss, P.; Roberts, J.; Druce, M. [Geotek Ltd., Daventry, Northamptonshire (United Kingdom)

2008-07-01

The morphology of gas hydrate in marine sediments determines the basic physical properties of the sediment-hydrate matrix and provides information regarding the formation of gas hydrate deposits, and the nature of the disruption that will occur on dissociation. Small-scale morphology is useful in estimating the concentrations of gas hydrate from geophysical data. It is also important for predicting their response to climate change or commercial production. Many remote techniques for gas hydrate detection and quantification depend on hydrate morphology. In this study, morphology of gas hydrate was examined in HYACINTH pressure cores from recent seagoing expeditions. Visual and infrared observations from non-pressurized cores were also used. The expeditions and pressure core analysis were described in detail. This paper described the difference between two types of gas hydrate morphologies, notably pore-filling and grain-displacing. Last, the paper addressed the impact of hydrate morphology. It was concluded that a detailed morphology of gas hydrate is an essential component for a full understanding of the past, present, and future of any gas hydrate environment. 14 refs., 4 figs.

Carbon dioxide gas hydrates accumulation in freezing and frozen sediments

Energy Technology Data Exchange (ETDEWEB)

Chuvilin, E.; Guryeva, O. [Moscow State Univ., Moscow (Russian Federation). Dept. of Geology

2008-07-01

Carbon dioxide (CO{sub 2}) hydrates and methane hydrates can be formed, and exist under natural conditions. The permafrost area has been considered as an environment for the potential disposal of CO{sub 2}. The favorable factors for preserving CO{sub 2} in liquid and gas hydrate states in frozen sediments and under permafrost horizons are great thickness of frozen sediments; low permeability in comparison with thawed sediments; and favourable conditions for hydrates formation. Therefore, research on the formation and existence conditions of CO{sub 2} gas hydrates in permafrost and under permafrost sediments are of great importance for estimation of CO{sub 2} disposal conditions in permafrost, and for working out specific sequestration schemes. This paper presented the results of an experimental study on the process of carbon dioxide (CO{sub 2}) gas hydrates formation in the porous media of sediments under positive and negative temperatures. Sediment samples of various compositions including those selected in the permafrost area were used. The research was conducted in a special pressure chamber, which allowed to monitor pressure and temperature. The study used the monitoring results in order to make quantitative estimation of the kinetics of CO{sub 2} hydrates accumulation in the model sediments. Results were presented in terms of kinetics of CO{sub 2} hydrates accumulation in the porous media at positive and negative temperatures; kinetics of CO{sub 2} hydrates accumulation in various porous media; gas hydrate-former influence on kinetics of hydrates accumulation in frozen sediments; and influence of freezing on CO{sub 2} hydrates accumulation in porous media. It was concluded that hydrate accumulation took an active place in porous media not only under positive, but also under high negative temperatures, when the water was mainly in the form of ice in porous media. 27 refs., 3 tabs., 5 figs.

Impact of Compound Hydrate Dynamics on Phase Boundary Changes

Science.gov (United States)

Osegovic, J. P.; Max, M. D.

2006-12-01

Compound hydrate reactions are affected by the local concentration of hydrate forming materials (HFM). The relationship between HFM composition and the phase boundary is as significant as temperature and pressure. Selective uptake and sequestration of preferred hydrate formers (PF) has wide ranging implications for the state and potential use of natural hydrate formation, including impact on climate. Rising mineralizing fluids of hydrate formers (such as those that occur on Earth and are postulated to exist elsewhere in the solar system) will sequester PF before methane, resulting in a positive relationship between depth and BTU content as ethane and propane are removed before methane. In industrial settings the role of preferred formers can separate gases. When depressurizing gas hydrate to release the stored gas, the hydrate initial composition will set the decomposition phase boundary because the supporting solution takes on the composition of the hydrate phase. In other settings where hydrate is formed, transported, and then dissociated, similar effects can control the process. The behavior of compound hydrate systems can primarily fit into three categories: 1) In classically closed systems, all the material that can form hydrate is isolated, such as in a sealed laboratory vessel. In such systems, formation and decomposition are reversible processes with observed hysteresis related to mass or heat transfer limitations, or the order and magnitude in which individual hydrate forming gases are taken up from the mixture and subsequently released. 2) Kinetically closed systems are exposed to a solution mass flow across a hydrate mass. These systems can have multiple P-T phase boundaries based on the local conditions at each face of the hydrate mass. A portion of hydrate that is exposed to fresh mineralizing solution will contain more preferred hydrate formers than another portion that is exposed to a partially depleted solution. Examples of kinetically closed

Investigating the Metastability of Clathrate Hydrates for Energy Storage

Energy Technology Data Exchange (ETDEWEB)

Koh, Carolyn Ann [Colorado School of Mines, Golden, CO (United States)

2014-11-18

Important breakthrough discoveries have been achieved from the DOE award on the key processes controlling the synthesis and structure-property relations of clathrate hydrates, which are critical to the development of clathrate hydrates as energy storage materials. Key achievements include: (i) the discovery of key clathrate hydrate building blocks (stable and metastable) leading to clathrate hydrate nucleation and growth; (ii) development of a rapid clathrate hydrate synthesis route via a seeding mechanism; (iii) synthesis-structure relations of H2 + CH4/CO2 binary hydrates to control thermodynamic requirements for energy storage and sequestration applications; (iv) discovery of a new metastable phase present during clathrate hydrate structural transitions. The success of our research to-date is demonstrated by the significant papers we have published in high impact journals, including Science, Angewandte Chemie, J. Am. Chem. Soc. Intellectual Merits of Project Accomplishments: The intellectual merits of the project accomplishments are significant and transformative, in which the fundamental coupled computational and experimental program has provided new and critical understanding on the key processes controlling the nucleation, growth, and thermodynamics of clathrate hydrates containing hydrogen, methane, carbon dioxide, and other guest molecules for energy storage. Key examples of the intellectual merits of the accomplishments include: the first discovery of the nucleation pathways and dominant stable and metastable structures leading to clathrate hydrate formation; the discovery and experimental confirmation of new metastable clathrate hydrate structures; the development of new synthesis methods for controlling clathrate hydrate formation and enclathration of molecular hydrogen. Broader Impacts of Project Accomplishments: The molecular investigations performed in this project on the synthesis (nucleation & growth)-structure-stability relations of clathrate

Stochastic Approach to Determine CO2 Hydrate Induction Time in Clay Mineral Suspensions

Science.gov (United States)

Lee, K.; Lee, S.; Lee, W.

2008-12-01

A large number of induction time data for carbon dioxide hydrate formation were obtained from a batch reactor consisting of four independent reaction cells. Using resistance temperature detector(RTD)s and a digital microscope, we successfully monitored the whole process of hydrate formation (i.e., nucleation and crystal growth) and detected the induction time. The experiments were carried out in kaolinite and montmorillonite suspensions at temperatures between 274 and 277 K and pressures ranging from 3.0 to 4.0 MPa. Each set of data was analyzed beforehand whether to be treated by stochastic manner or not. Geochemical factors potentially influencing the hydrate induction time under different experimental conditions were investigated by stochastic analyses. We observed that clay mineral type, pressure, and temperature significantly affect the stochastic behavior of the induction times for CO2 hydrate formation in this study. The hydrate formation kinetics along with stochastic analyses can provide basic understanding for CO2 hydrate storage in deep-sea sediment and geologic formation, securing its stability under the environments.

Three types of gas hydrate reservoirs in the Gulf of Mexico identified in LWD data

Science.gov (United States)

Lee, Myung Woong; Collett, Timothy S.

2011-01-01

High quality logging-while-drilling (LWD) well logs were acquired in seven wells drilled during the Gulf of Mexico Gas Hydrate Joint Industry Project Leg II in the spring of 2009. These data help to identify three distinct types of gas hydrate reservoirs: isotropic reservoirs in sands, vertical fractured reservoirs in shale, and horizontally layered reservoirs in silty shale. In general, most gas hydratebearing sand reservoirs exhibit isotropic elastic velocities and formation resistivities, and gas hydrate saturations estimated from the P-wave velocity agree well with those from the resistivity. However, in highly gas hydrate-saturated sands, resistivity-derived gas hydrate-saturation estimates appear to be systematically higher by about 5% over those estimated by P-wave velocity, possibly because of the uncertainty associated with the consolidation state of gas hydrate-bearing sands. Small quantities of gas hydrate were observed in vertical fractures in shale. These occurrences are characterized by high formation resistivities with P-wave velocities close to those of water-saturated sediment. Because the formation factor varies significantly with respect to the gas hydrate saturation for vertical fractures at low saturations, an isotropic analysis of formation factor highly overestimates the gas hydrate saturation. Small quantities of gas hydrate in horizontal layers in shale are characterized by moderate increase in P-wave velocities and formation resistivities and either measurement can be used to estimate gas hydrate saturations.

Cryogenic-SEM investigation of CO{sub 2} hydrate morphologies

Energy Technology Data Exchange (ETDEWEB)

Camps, A.P.; Milodowski, A.; Rochelle, C.; Williams, J.F.; Jackson, P. D. [British Geological Survey, Keyworth, Nottinghamshire (United Kingdom); Camps, A.P; Lovell, M.; Williams, J.F. [Leicester Univ., Leicester (United Kingdom). Dept. of Geology

2008-07-01

Gas hydrates occur naturally around the world in the shallow-marine geosphere, and are seen as a drilling hazard in the petroleum industry due to their role in the carbon cycle, and their possible contribution in past and present climate change. Hydrates are ice-like structures composed of cages of water molecules containing one or more guest molecules, such as methane and carbon dioxide (CO{sub 2}). CO{sub 2} hydrates also occur naturally on earth and are being investigated for their potential to store large volumes of CO{sub 2} to reduce atmospheric emissions of greenhouse gases as a climate change mitigation strategy. However, the mineralogy and formation processes of hydrates are relatively poorly understood. Different imaging techniques have been utilized to study gas hydrates, such as nuclear magnetic resonance, magnetic resonance imaging, and x-ray computed tomography. Scanning Electron Microscopy (SEM) at cryogenic temperatures is another technique to study hydrates, and has been used successfully for investigation of methane and CO{sub 2} hydrates. This paper presented a study that investigated CO{sub 2} hydrates formed in laboratories, using a cryogenic-SEM. The paper presented the study methods and observations, including euhedral crystalline carbon dioxide hydrate; acicular carbon dioxide hydrate; granoblastic carbon dioxide hydrate; and gas rich carbon dioxide hydrate. It was concluded that the investigation produced various different hydrate morphologies resulting from different formation conditions. Morphologies ranged from well-defined euhedral crystals to acicular needles, and more complex, intricate forms. 22 refs., 6 figs., 1 appendix.

In-situ gas hydrate hydrate saturation estimated from various well logs at the Mount Elbert Gas Hydrate Stratigraphic Test Well, Alaska North Slope

Science.gov (United States)

Lee, M.W.; Collett, T.S.

2011-01-01

In 2006, the U.S. Geological Survey (USGS) completed detailed analysis and interpretation of available 2-D and 3-D seismic data and proposed a viable method for identifying sub-permafrost gas hydrate prospects within the gas hydrate stability zone in the Milne Point area of northern Alaska. To validate the predictions of the USGS and to acquire critical reservoir data needed to develop a long-term production testing program, a well was drilled at the Mount Elbert prospect in February, 2007. Numerous well log data and cores were acquired to estimate in-situ gas hydrate saturations and reservoir properties.Gas hydrate saturations were estimated from various well logs such as nuclear magnetic resonance (NMR), P- and S-wave velocity, and electrical resistivity logs along with pore-water salinity. Gas hydrate saturations from the NMR log agree well with those estimated from P- and S-wave velocity data. Because of the low salinity of the connate water and the low formation temperature, the resistivity of connate water is comparable to that of shale. Therefore, the effect of clay should be accounted for to accurately estimate gas hydrate saturations from the resistivity data. Two highly gas hydrate-saturated intervals are identified - an upper ???43 ft zone with an average gas hydrate saturation of 54% and a lower ???53 ft zone with an average gas hydrate saturation of 50%; both zones reach a maximum of about 75% saturation. ?? 2009.

CO2 injection into submarine, CH4-hydrate bearing sediments: Parameter studies towards the development of a hydrate conversion technology

Science.gov (United States)

Deusner, Christian; Bigalke, Nikolaus; Kossel, Elke; Haeckel, Matthias

2013-04-01

In the recent past, international research efforts towards exploitation of submarine and permafrost hydrate reservoirs have increased substantially. Until now, findings indicate that a combination of different technical means such as depressurization, thermal stimulation and chemical activation is the most promising approach for producing gas from natural hydrates. Moreover, emission neutral exploitation of CH4-hydrates could potentially be achieved in a combined process with CO2 injection and storage as CO2-hydrate. In the German gas hydrate initiative SUGAR, a combination of experimental and numerical studies is used to elucidate the process mechanisms and technical parameters on different scales. Experiments were carried out in the novel high-pressure flow-through system NESSI (Natural Environment Simulator for sub-Seafloor Interactions). Recent findings suggest that the injection of heated, supercritical CO2 is beneficial for both CH4 production and CO2 retention. Among the parameters tested so far are the CO2 injection regime (alternating vs. continuous injection) and the reservoir pressure / temperature conditions. Currently, the influence of CO2 injection temperature is investigated. It was shown that CH4 production is optimal at intermediate reservoir temperatures (8 ° C) compared to lower (2 ° C) and higher temperatures (10 ° C). The reservoir pressure, however, was of minor importance for the production efficiency. At 8 ° C, where CH4- and CO2-hydrates are thermodynamically stable, CO2-hydrate formation appears to be slow. Eventual clogging of fluid conduits due to CO2-rich hydrate formation force open new conduits, thereby tapping different regions inside the CH4-hydrate sample volume for CH4gas. In contrast, at 2 ° C immediate formation of CO2-hydrate results in rapid and irreversible obstruction of the entire pore space. At 10 ° C pure CO2-hydrates can no longer be formed. Consequently the injected CO2 flows through quickly and interaction with

Methane Hydrate in Confined Spaces: An Alternative Storage System.

Science.gov (United States)

Borchardt, Lars; Casco, Mirian Elizabeth; Silvestre-Albero, Joaquin

2018-03-14

Methane hydrate inheres the great potential to be a nature-inspired alternative for chemical energy storage, as it allows to store large amounts of methane in a dense solid phase. The embedment of methane hydrate in the confined environment of porous materials can be capitalized for potential applications as its physicochemical properties, such as the formation kinetics or pressure and temperature stability, are significantly changed compared to the bulk system. We review this topic from a materials scientific perspective by considering porous carbons, silica, clays, zeolites, and polymers as host structures for methane hydrate formation. We discuss the contribution of advanced characterization techniques and theoretical simulations towards the elucidation of the methane hydrate formation and dissociation process within the confined space. We outline the scientific challenges this system is currently facing and look on possible future applications for this technology. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

The phase equilibria of multicomponent gas hydrate in methanol/ethylene glycol solution based formation water

International Nuclear Information System (INIS)

Xu, Shurui; Fan, Shuanshi; Yao, Haiyuan; Wang, Yanhong; Lang, Xuemei; Lv, Pingping; Fang, Songtian

2017-01-01

Highlights: • The equilibrium data in THI solution based formation water is first investigated. • The 0.55 mass fraction concentration of EG 0.55 mass fraction fills the vacancy of this area. • The testing pressure range from 4.22 MPa to 34.72 MPa was rare in published data. - Abstract: In this paper, the three-phase coexistence points are generated for multicomponent gas hydrate in methanol (MeOH) solution for (0.05, 0.10, 0.15, and 0.35) mass fraction and ethylene glycol (EG) solution for (0.05, 0.10, 0.15, 0.35, 0.40 and 0.55) mass fraction. The phase equilibrium curves of different system were obtained by an isochoric pressure-search method on high pressure apparatus. The phase equilibrium regions of multicomponent gas hydrate were measured using the same composition of natural gas distributed in the South China Sea. And the different concentration solutions were prepared based formation water. The experimental data were measured in a wide range temperature from 267.74 to 298.53 K and a wide range pressure from 4.22 MPa to 34.72 MPa. The results showed that the hydrate phase equilibrium curves shifted to the inhibition region in accordance with the increased inhibitor concentration. In addition, the equilibrium temperature would decrease about 2.7 K when the concentration of MeOH increased 0.05 mass fraction. Besides, the suppression temperature was 1.25 K with the 0.05 mass fraction increase of EG concentration in the range of 0.05 mass fraction to 0.15 mass fraction. While in high EG concentration region, the suppression temperature was 3.3 K with the same increase of EG concentration (0.05 mass fraction).

Origins of hydration differences in homochiral and racemic crystals of aspartic acid.

Science.gov (United States)

Juliano, Thomas R; Korter, Timothy M

2015-02-26

The propensity for crystalline hydrates of organic molecules to form is related to the strength of the interactions between molecules, including the chiral composition of the molecular solids. Specifically, homochiral versus racemic crystalline samples can exhibit distinct differences in their ability to form energetically stable hydrates. The focus of the current study is a comparison of the crystal structures and intermolecular forces found in solid-state L-aspartic acid, DL-aspartic acid, and L-aspartic acid monohydrate. The absence of experimental evidence for the DL-aspartic acid monohydrate is considered here in terms of the enhanced thermodynamic stability of the DL-aspartic acid anhydrate crystal as compared to the L-aspartic acid anhydrate as revealed through solid-state density functional theory calculations and terahertz spectroscopic measurements. The results indicate that anhydrous DL-aspartic acid is the more stable solid, not due to intermolecular forces alone but also due to the improved conformations of the molecules within the racemic solid. Hemihydrated and monohydrated forms of DL-aspartic acid have been computationally evaluated, and in each case, the hydrates produce destabilized aspartic acid conformations that prevent DL-aspartic acid hydrate formation from occurring.

TOUGH+Hydrate v1.0 User's Manual: A Code for the Simulation of System Behavior in Hydrate-Bearing Geologic Media

Energy Technology Data Exchange (ETDEWEB)

Moridis, George; Moridis, George J.; Kowalsky, Michael B.; Pruess, Karsten

2008-03-01

TOUGH+HYDRATE v1.0 is a new code for the simulation of the behavior of hydrate-bearing geologic systems. By solving the coupled equations of mass and heat balance, TOUGH+HYDRATE can model the non-isothermal gas release, phase behavior and flow of fluids and heat under conditions typical of common natural CH{sub 4}-hydrate deposits (i.e., in the permafrost and in deep ocean sediments) in complex geological media at any scale (from laboratory to reservoir) at which Darcy's law is valid. TOUGH+HYDRATE v1.0 includes both an equilibrium and a kinetic model of hydrate formation and dissociation. The model accounts for heat and up to four mass components, i.e., water, CH{sub 4}, hydrate, and water-soluble inhibitors such as salts or alcohols. These are partitioned among four possible phases (gas phase, liquid phase, ice phase and hydrate phase). Hydrate dissociation or formation, phase changes and the corresponding thermal effects are fully described, as are the effects of inhibitors. The model can describe all possible hydrate dissociation mechanisms, i.e., depressurization, thermal stimulation, salting-out effects and inhibitor-induced effects. TOUGH+HYDRATE is the first member of TOUGH+, the successor to the TOUGH2 [Pruess et al., 1991] family of codes for multi-component, multiphase fluid and heat flow developed at the Lawrence Berkeley National Laboratory. It is written in standard FORTRAN 95, and can be run on any computational platform (workstation, PC, Macintosh) for which such compilers are available.

Permeability of sediment cores from methane hydrate deposit in the Eastern Nankai Trough, Japan

Science.gov (United States)

Konno, Y.; Yoneda, J.; Egawa, K.; Ito, T.; Jin, Y.; Kida, M.; Suzuki, K.; Nakatsuka, Y.; Nagao, J.

2013-12-01

Effective and absolute permeability are key parameters for gas production from methane-hydrate-bearing sandy sediments. Effective and/or absolute permeability have been measured using methane-hydrate-bearing sandy cores and clayey and silty cores recovered from Daini Atsumi Knoll in the Eastern Nankai Trough during the 2012 JOGMEC/JAPEX Pressure coring operation. Liquid-nitrogen-immersed cores were prepared by rapid depressurization of pressure cores recovered by a pressure coring system referred to as the Hybrid PCS. Cores were shaped cylindrically on a lathe with spraying of liquid nitrogen to prevent hydrate dissociation. Permeability was measured by a flooding test or a pressure relaxation method under near in-situ pressure and temperature conditions. Measured effective permeability of hydrate-bearing sediments is less than tens of md, which are order of magnitude less than absolute permeability. Absolute permeability of clayey cores is approximately tens of μd, which would perform a sealing function as cap rocks. Permeability reduction due to a swelling effect was observed for a silty core during flooding test of pure water mimicking hydrate-dissociation-water. Swelling effect may cause production formation damage especially at a later stage of gas production from methane hydrate deposits. This study was financially supported by the Research Consortium for Methane Hydrate Resources in Japan (MH21 Research Consortium) that carries out Japan's Methane Hydrate R&D Program conducted by the Ministry of Economy, Trade and Industry (METI).

Fire extinction utilizing carbon dioxide hydrate

Energy Technology Data Exchange (ETDEWEB)

Hatakeyama, T.; Aida, E.; Yokomori, T.; Ohmura, R.; Ueda, T. [Keio Univ., Hiyoshi, Kohoku-ku, Yokohama (Japan)

2008-07-01

Clathrate hydrates formed with nonflammable gases may be suitable for use as fire extinguishing agents because dissociation of the hydrates results in the temperature decrease in the combustion field and the nonflammable gases released from the dissociated hydrates prevent the supply of the oxygen to the combustion field. This paper discussed experiments in which ordinary ice and dry ice were used to evaluate the performance of CO{sub 2} hydrate as a fire extinguishing agent. The paper described the apparatus and procedure for the preparation of CO{sub 2} hydrate crystals. A schematic of the reactor to form CO{sub 2} hydrate and a photograph of CO{sub 2} hydrate crystal formed in the study were also presented. Other illustrations, photographs, and tables that were presented included a schematic diagram of the experimental apparatus used for the flame extinction experiments; a photograph of CO{sub 2} hydrate powder; sequential video graphs of the flame extinction by the supply of CO{sub 2} hydrate crystals to the methanol pool flame and the relevant illustration; and heat of CO{sub 2} hydrate dissociation, water vaporization and sublimation of dry ice. It was concluded that the critical mass of the CO{sub 2} hydrate required to extinguish a flame was much less than that of ordinary ice, indicating the superiority of CO{sub 2} hydrate to the ice. In addition, the experiments also revealed that the size of the CO{sub 2} hydrate particles had a significant effect on the performance of flame extinction. 5 refs., 2 tabs., 7 figs.

Formation of hydrated layers in PMMA thin films in aqueous solution

Energy Technology Data Exchange (ETDEWEB)

Akers, Peter W. [School of Chemical Sciences, University of Auckland, Auckland (New Zealand); Nelson, Andrew R.J. [The Bragg Institute, Australian Nuclear Science and Technology Organisation, Menai, NSW (Australia); Williams, David E. [School of Chemical Sciences, University of Auckland, Auckland (New Zealand); MacDiarmid Institute of Advanced Materials and Nanotechnology, Wellington (New Zealand); McGillivray, Duncan J., E-mail: d.mcgillivray@auckland.ac.nz [School of Chemical Sciences, University of Auckland, Auckland (New Zealand); MacDiarmid Institute of Advanced Materials and Nanotechnology, Wellington (New Zealand)

2015-10-30

Graphical abstract: - Highlights: • Homogeneous thin PMMA films prepared on Si/SiOx substrates and measured in air and water. • Reproducible formation of highly hydrated layer containing 50% water at the PMMA/SiOx interface. • When heated the films swell at 50 °C without loss of material. • Upon re-cooling to 25 °C the surface roughens and material is lost. - Abstract: Neutron reflectometry (NR) measurements have been made on thin (70–150 Å) poly(methylmethacrylate) (PMMA) films on Si/SiOx substrates in aqueous conditions, and compared with parameters measured using ellipsometry and X-Ray reflectometry (XRR) on dry films. All techniques show that the thin films prepared using spin-coating techniques were uniform and had low roughness at both the silicon and subphase interfaces, and similar surface energetics to thicker PMMA films. In aqueous solution, NR measurements at 25 °C showed that PMMA forms a partially hydrated layer at the SiOx interface 10 Å under the film, while the bulk film remains intact and contains around 4% water. Both the PMMA film layer and the sublayer showed minimal swelling over a period of 24 h. At 50 °C, PMMA films in aqueous solution roughen and swell, without loss of PMMA material at the surface. After cooling back to 25 °C, swelling and roughening increases further, with loss of material from the PMMA layer.

Formation of hydrated layers in PMMA thin films in aqueous solution

International Nuclear Information System (INIS)

Akers, Peter W.; Nelson, Andrew R.J.; Williams, David E.; McGillivray, Duncan J.

2015-01-01

Graphical abstract: - Highlights: • Homogeneous thin PMMA films prepared on Si/SiOx substrates and measured in air and water. • Reproducible formation of highly hydrated layer containing 50% water at the PMMA/SiOx interface. • When heated the films swell at 50 °C without loss of material. • Upon re-cooling to 25 °C the surface roughens and material is lost. - Abstract: Neutron reflectometry (NR) measurements have been made on thin (70–150 Å) poly(methylmethacrylate) (PMMA) films on Si/SiOx substrates in aqueous conditions, and compared with parameters measured using ellipsometry and X-Ray reflectometry (XRR) on dry films. All techniques show that the thin films prepared using spin-coating techniques were uniform and had low roughness at both the silicon and subphase interfaces, and similar surface energetics to thicker PMMA films. In aqueous solution, NR measurements at 25 °C showed that PMMA forms a partially hydrated layer at the SiOx interface 10 Å under the film, while the bulk film remains intact and contains around 4% water. Both the PMMA film layer and the sublayer showed minimal swelling over a period of 24 h. At 50 °C, PMMA films in aqueous solution roughen and swell, without loss of PMMA material at the surface. After cooling back to 25 °C, swelling and roughening increases further, with loss of material from the PMMA layer.

Stages of Gas-Hydrate Evolution on the Northern Cascadia Margin

Directory of Open Access Journals (Sweden)

the IODP Expedition 311 Scientists

2006-09-01

Full Text Available Natural gas hydrate occurs beneath many continental slopes and in arctic permafrost areas. Recent studies have indicated that the largest deposits of gas hydrate might lie in nearly horizontal layers several hundred meters beneath the seafloor of continental slopes, especially in the large, accretionary sedimentary prisms of subduction zones. Expedition 311 of the Integrated Ocean Drilling Program (IODP investigated the formation of gas hydrate in the accretionary prism of the Cascadia subduction zone (Fig. 1. The primary objectives of Expedition 311 were to test and constraingeological models of gas hydrate formation by upward fluidand methane transport in accretionary prisms. We specifi -cally sought to (a determine the mechanisms that controlthe nature, magnitude, and distribution of the gas hydrate,(b find the pathways of the fluid migration required to formlarge concentrations of gas hydrate, (c examine the effectsof gas hydrate on the physical properties of the host sediment,and (d investigate the microbiology and geochemistryassociated with the occurrence of gas hydrate. Furthermore,we concentrated on the contrast between methane transportby focused fl ow in fault zones and by dispersed pervasiveupward flow at various scales of permeability.

Catalysis of gas hydrates by biosurfactants in seawater-saturated sand/clay

Energy Technology Data Exchange (ETDEWEB)

Rogers, R. E.; Kothapalli, C.; Lee, M.S. [Mississippi State University, Swalm School of Chemical Engineering, MS (United States); Woolsey, J. R. [University of Mississippi, Centre of Marine Resources and Environmental Technology, MS (United States)

2003-10-01

Large gas hydrate mounds have been photographed in the seabed of the Gulf of Mexico and elsewhere. According to industry experts, the carbon trapped within gas hydrates is two or three times greater than all known crude oil, natural gas and coal reserves in the world. Gas hydrates, which are ice-like solids formed from the hydrogen bonding of water as water temperature is lowered under pressure to entrap a suitable molecular-size gas in cavities of the developing crystal structure, are found below the ocean floor to depths exhibiting temperature and pressure combinations within the appropriate limits. The experiments described in this study attempt to ascertain whether biosurfactant byproducts of microbial activity in seabeds could catalyze gas hydrate formation. Samples of five possible biosurfactants classifications were used in the experiments. Results showed that biosurfactants enhanced hydrate formation rate between 96 per cent and 288 percent, and reduced hydrate induction time 20 per cent to 71 per cent relative to the control. The critical micellar concentration of rhamnolipid/seawater solution was found to be 13 ppm at hydrate-forming conditions. On the basis of these results it was concluded that minimal microbial activity in sea floor sands could achieve the threshold concentration of biosurfactant that would greatly promote hydrate formation. 28 refs., 2 tabs., 4 figs.

TOUGH+HYDRATE v1.2 User's Manual: A Code for the Simulation of System Behavior in Hydrate-Bearing Geologic Media

Energy Technology Data Exchange (ETDEWEB)

Moridis, George J. [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Kowalsky, Michael B. [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Pruess, Karsten [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)

2012-08-01

TOUGH+HYDRATE v1.2 is a code for the simulation of the behavior of hydratebearing geologic systems, and represents the second update of the code since its first release [Moridis et al., 2008]. By solving the coupled equations of mass and heat balance, TOUGH+HYDRATE can model the non-isothermal gas release, phase behavior and flow of fluids and heat under conditions typical of common natural CH4-hydrate deposits (i.e., in the permafrost and in deep ocean sediments) in complex geological media at any scale (from laboratory to reservoir) at which Darcy’s law is valid. TOUGH+HYDRATE v1.2 includes both an equilibrium and a kinetic model of hydrate formation and dissociation. The model accounts for heat and up to four mass components, i.e., water, CH4, hydrate, and water-soluble inhibitors such as salts or alcohols. These are partitioned among four possible phases (gas phase, liquid phase, ice phase and hydrate phase). Hydrate dissociation or formation, phase changes and the corresponding thermal effects are fully described, as are the effects of inhibitors. The model can describe all possible hydrate dissociation mechanisms, i.e., depressurization, thermal stimulation, salting-out effects and inhibitor-induced effects. TOUGH+HYDRATE is a member of TOUGH+, the successor to the TOUGH2 [Pruess et al., 1991] family of codes for multi-component, multiphase fluid and heat flow developed at the Lawrence Berkeley National Laboratory. It is written in standard FORTRAN 95/2003, and can be run on any computational platform (workstation, PC, Macintosh) for which such compilers are available.

Effect of hydration on the organo-noble gas molecule HKrCCH: role of krypton in the stabilization of hydrated HKrCCH complexes.

Science.gov (United States)

Biswas, Biswajit; Singh, Prashant Chandra

2015-11-11

The effect of hydration on the fluorine free organo-noble gas compound HKrCCH and the role of krypton in the stabilization of the hydrated HKrCCH complexes have been investigated using the quantum chemical calculations on the HKrCCH-(H2O)n=1-6 clusters. Structure and energetics calculations show that water stabilizes HKrCCH through the π hydrogen bond in which the OH group of water interacts with the C[triple bond, length as m-dash]C group of HKrCCH. A maximum of four water molecules can directly interact with the C[triple bond, length as m-dash]C of HKrCCH and after that only inter-hydrogen bonding takes place between the water molecules indicating that the primary hydration shell contains four water molecules. Atom in molecule analysis depicts that π hydrogen bonded complexes of the hydrated HKrCCH are cyclic structures in which the OKr interaction cooperates in the formation of strong O-HC[triple bond, length as m-dash]C interaction. Structure, energetics and charge analysis clearly established that krypton plays an important role in the stabilization as well as the formation of the primary hydration shell of hydrated HKrCCH complexes.

Simulating the effect of hydrate dissociation on wellhead stability during oil and gas development in deepwater

Science.gov (United States)

Li, Qingchao; Cheng, Yuanfang; Zhang, Huaiwen; Yan, Chuanliang; Liu, Yuwen

2018-02-01

It is well known that methane hydrate has been identified as an alternative resource due to its massive reserves and clean property. However, hydrate dissociation during oil and gas development (OGD) process in deep water can affect the stability of subsea equipment and formation. Currently, there is a serious lack of studies over quantitative assessment on the effects of hydrate dissociation on wellhead stability. In order to solve this problem, ABAQUS finite element software was used to develop a model and to evaluate the behavior of wellhead caused by hydrate dissociation. The factors that affect the wellhead stability include dissociation range, depth of hydrate formation and mechanical properties of dissociated hydrate region. Based on these, series of simulations were carried out to determine the wellhead displacement. The results revealed that, continuous dissociation of hydrate in homogeneous and isotropic formations can causes the non-linear increment in vertical displacement of wellhead. The displacement of wellhead showed good agreement with the settlement of overlying formations under the same conditions. In addition, the shallower and thicker hydrate formation can aggravate the influence of hydrate dissociation on the wellhead stability. Further, it was observed that with the declining elastic modulus and Poisson's ratio, the wellhead displacement increases. Hence, these findings not only confirm the effect of hydrate dissociation on the wellhead stability, but also lend support to the actions, such as cooling the drilling fluid, which can reduce the hydrate dissociation range and further make deepwater operations safer and more efficient.

Thermodynamic studies on semi-clathrate hydrates of TBAB + gases containing carbon dioxide

International Nuclear Information System (INIS)

Eslamimanesh, Ali

2012-01-01

CO 2 capture has become an important area of research mainly due to its drastic greenhouse effects. Gas hydrate formation as a separation technique shows tremendous potential, both from a physical feasibility as well as an envisaged lower energy utilization criterion. Briefly, gas (clathrate) hydrates are non-stoichiometric, ice-like crystalline compounds formed through a combination of water and suitably sized guest molecule(s) under low-temperatures and elevated pressures. As the pressure required for gas hydrate formation is generally high, therefore, aqueous solution of tetra-n-butyl ammonium bromide (TBAB) is added to the system as a gas hydrate promoter. TBAB generally reduces the required hydrate formation pressure and/or increases the formation temperature as well as modifies the selectivity of hydrate cages to capture CO 2 molecules. TBAB also takes part in the hydrogen-bonded cages. Such hydrates are called 'semi-clathrate' hydrates. Evidently, reliable and accurate phase equilibrium data, acceptable thermodynamic models, and other thermodynamic studies should be provided to design efficient separation processes using the aforementioned technology. For this purpose, phase equilibria of clathrate/semi-clathrate hydrates of various gas mixtures containing CO 2 (CO 2 + CH 4 /N 2 /H 2 ) in the presence of pure water and aqueous solutions of TBAB have been measured in this thesis. In the theoretical section of the thesis, a thermodynamic model on the basis of the van der Waals and Platteeuw (vdW-P) solid solution theory along with the modified equations for determination of the Langmuir constants of the hydrate formers has been successfully developed to represent/predict equilibrium conditions of semi-clathrate hydrates of CO 2 , CH 4 , and N 2 . Later, several thermodynamic consistency tests on the basis of Gibbs-Duhem equation as well as a statistical approach have been applied on the phase equilibrium data of the systems of mixed/simple clathrate hydrates

Flow assurance intervention, hydrates remediation

Energy Technology Data Exchange (ETDEWEB)

Mancini, Christopher S. [Oceaneering International Inc., Houston, TX (United States)

2012-07-01

This paper addresses the issues of removing hydrates in sub sea flow lines and associated equipment with an Remotely Operated Vehicle (ROV) of opportunity and a multi-service-vessel (MSV). The paper is split into three topics: the equipment used with the ROV, assessing the interface points and handling fluids produced from drawing down the pressure. Each section is explained thoroughly and backed up with real world experience. The equipment section details information from actual jobs performed and why the particular components were utilized. The system is generally contained in an ROV mounted skid. Pumps are utilized to draw down the pressure inside the hydrated section of equipment, removing one of the three necessary components for hydrates formation. Once the section is pumped down, several options exist for handling the fluids pumped out of the system: pumping to surface, re-injection into the well, or injection into an operating flow line. This method of hydrates remediation is both economical and timely. Hydrate blockages form in low temperatures and high pressures. Reducing the pressure or increasing the temperature so the conditions lie to the right of the hydrate dissociation curve will slowly decompose the blockage. Depressurization and the use of MEG or methanol will give favorable conditions to remove the hydrate plug. Oceaneering has the capabilities to remove hydrates using the FRS in conjunction with an installation vessel to dispose of the gas and fluid removed from the flow line. Hydrate remediation techniques should be implemented into the initial design to reduce costs later. The cost of stopped production combined with the day rate for equipment needed for hydrate removal outweighs the costs if no technique is utilized. (author)

Free energy of hydration of niobium oxide

International Nuclear Information System (INIS)

Plodinec, M.J.

1996-01-01

Some of the glasses being formulated by SRTC researchers contain niobium oxide. In this report, the free energy of hydration of the oxide is calculated from the free energies of formation of the oxide, the hydroxide, and water. This value can be used in calculations of the free energy of hydration of glasses containing niobium

METHANE HYDRATE PRODUCTION FROM ALASKAN PERMAFROST

Energy Technology Data Exchange (ETDEWEB)

Richard Sigal; Kent Newsham; Thomas Williams; Barry Freifeld; Timothy Kneafsey; Carl Sondergeld; Shandra Rai; Jonathan Kwan; Stephen Kirby; Robert Kleinberg; Doug Griffin

2005-02-01

Natural-gas hydrates have been encountered beneath the permafrost and considered a nuisance by the oil and gas industry for years. Engineers working in Russia, Canada and the USA have documented numerous drilling problems, including kicks and uncontrolled gas releases, in arctic regions. Information has been generated in laboratory studies pertaining to the extent, volume, chemistry and phase behavior of gas hydrates. Scientists studying hydrate potential agree that the potential is great--on the North Slope of Alaska alone, it has been estimated at 590 TCF. However, little information has been obtained on physical samples taken from actual rock containing hydrates. The work scope drilled and cored a well The Hot Ice No. 1 on Anadarko leases beginning in FY 2003 and completed in 2004. An on-site core analysis laboratory was built and utilized for determining the physical characteristics of the hydrates and surrounding rock. The well was drilled from a new Anadarko Arctic Platform that has a minimal footprint and environmental impact. The final efforts of the project are to correlate geology, geophysics, logs, and drilling and production data and provide this information to scientists developing reservoir models. No gas hydrates were encountered in this well; however, a wealth of information was generated and is contained in this report. The Hot Ice No. 1 well was drilled from the surface to a measured depth of 2300 ft. There was almost 100% core recovery from the bottom of surface casing at 107 ft to total depth. Based on the best estimate of the bottom of the methane hydrate stability zone (which used new data obtained from Hot Ice No. 1 and new analysis of data from adjacent wells), core was recovered over its complete range. Approximately 580 ft of porous, mostly frozen, sandstone and 155 of conglomerate were recovered in the Ugnu Formation and approximately 215 ft of porous sandstone were recovered in the West Sak Formation. There were gas shows in the bottom

[Prospects for Application of Gases and Gas Hydrates to Cryopreservation].

Science.gov (United States)

Shishova, N V; Fesenko, E E

2015-01-01

In the present review, we tried to evaluate the known properties of gas hydrates and gases participating in the formation of gas hydrates from the point of view of the mechanisms of cryoinjury and cryoprotection, to consider the papers on freezing biological materials in the presence of inert gases, and to analyze the perspectives for the development of this direction. For the purpose, we searched for the information on the physical properties of gases and gas hydrates, compared processes occured during the formation of gas hydrates and water ice, analyzed the influence of the formation and growth of gas hydrates on the structure of biological objects. We prepared a short review on the biological effects of xenon, krypton, argon, carbon dioxide, hydrogen sulfide, and carbon monoxide especially on hypothermal conditions and probable application of these properties in cryopreservation technologies. The description of the existing experiments on cryopreservation of biological objects with the use of gases was analyzed. On the basis of the information we found, the most perspective directions of work in the field of cryopreservation of biological objects with the use of gases were outlined. An attempt was made to forecast the potential problems in this field.

Vibrational dynamics of hydration water in amylose

CERN Document Server

Cavatorta, F; Albanese, G; Angelini, N

2002-01-01

We present a study of the dynamical properties of hydration water associated with amylose helices, based on low-temperature vibrational spectra collected using the TOSCA inelastic spectrometer at ISIS. The structural constraints of the polysaccharidic chains favour the formation of a high-density structure for water, which has been suggested by Imberty and Perez on the basis of conformational analysis. According to this model, hydration water can only enter the pores formed by six adjacent helices and completely fills the pores at a hydration level of about 0.27-g water/g dry amylose. Our measurements show that the dynamical behaviour of hydration water is similar to that observed in high-density amorphous ice. (orig.)

Kinetic studies of methane-ethane mixed gas hydrates by neutron diffraction and Raman spectroscopy.

Science.gov (United States)

Murshed, M Mangir; Kuhs, Werner F

2009-04-16

In situ formations of CH(4)-C(2)H(6) mixed gas hydrates were made using high flux neutron diffraction at 270 K and 5 MPa. For this purpose, a feed gas composition of CH(4) and C(2)H(6) (95 mol% CH(4)) was employed. The rates of transformation of spherical grains of deuterated ice Ih into hydrates were measured by time-resolved neutron powder diffraction on D20 at ILL, Grenoble. Phase fractions of the crystalline constituents were obtained from Rietveld refinements. A concomitant formation of structure type I (sI) and structure type II (sII) hydrates were observed soon after the gas pressure was applied. The initial fast formation of sII hydrate reached its maximum volume and started declining very slowly. The formation of sI hydrate followed a sigmoid growth kinetics that slowed down due to diffusion limitation. This observation has been interpreted in terms of a kinetically favored nucleation of the sII hydrate along with a slow transformation into sI. Both powder diffraction and Raman spectroscopic results suggest that a C(2)H(6)-rich sII hydrate was formed at the early part of the clathration, which slowly decreased to approximately 3% after a reaction of 158 days as confirmed by synchrotron XRD. The final persistence of a small portion of sII hydrate points to a miscibility gap between CH(4)-rich sI and C(2)H(6)-rich sII hydrates.

Study on gas hydrate as a new energy resource in the twenty first century

Energy Technology Data Exchange (ETDEWEB)

Ryu, Byung Jae; Kim, Won Sik; Oh, Jae Ho [Korea Institute of Geology Mining and Materials, Taejon (Korea)] [and others

1998-12-01

Methane hydrate, a special type of clathrate hydrates, is a metastable solid compound mainly consisted of methane and water and generally called as gas hydrate. It is stable in the specific low- temperature/high-pressure conditions. Very large amount of methane that is the main component of natural gas, is accumulated in the form of methane hydrate subaquatic areas. Methane hydrate are the major reservoir of methane on the earth. On the other hand, the development and transmission through pipeline of oil and natural gas in the permafrost and deep subaquatic regions are significantly complicated by formation and dissociation of methane hydrate. The dissociation of natural methane hydrates caused by increasing temperature and decreasing pressure could cause the atmospheric pollution and geohazard. The formation, stable existence and dissociation of natural methane hydrates depend on the temperature, pressure, and composition of gas and characteristics of the interstitial waters. For the study on geophysical and geological conditions for the methane hydrate accumulation and to find BSR in the East Sea, Korea, the geophysical surveys using air-gun system, multibeam echo sounder, SBP were implemented in last September. The water temperature data vs. depth were obtained to determine the methane hydrate stability zone in the study area. The experimental equilibrium condition of methane hydrate was also measured in 3 wt.% sodium chloride solution. The relationship between Methane hydrate formation time and overpressure was analyzed through the laboratory work. (author). 49 refs., 6 tabs., 26 figs.

Behaviour of gas production from type 3 hydrate reservoirs

Energy Technology Data Exchange (ETDEWEB)

Pooladi-Darvish, M. [Calgary Univ., AB (Canada). Dept. of Chemical and Petroleum Engineering]|[Fekete Associates Inc., Calgary, AB (Canada); Zatsepina, O. [Calgary Univ., AB (Canada). Dept. of Chemical and Petroleum Engineering; Hong, H. [Fekete Associates Inc., Calgary, AB (Canada)

2008-07-01

The possible role of gas hydrates as a potential energy resource was discussed with particular reference to methods for estimating the rate of gas production from hydrate reservoirs under different operating conditions. This paper presented several numerical simulations studies of gas production from type 3 hydrate reservoirs in 1-D and 2-D geometries. Type 3 reservoirs include gas production from hydrate-reservoirs that lie totally within the hydrate stability zone and are sandwiched by impermeable layers on top and bottom. The purpose of this study was to better understand hydrate decomposition by depressurization. The study questioned whether 1-D modeling of type 3 hydrate reservoirs is a reasonable approximation. It also determined whether gas rate increases or decreases with time. The important reservoir characteristics for determining the rate of gas production were identified. Last, the study determined how competition between fluid and heat flow affects hydrate decomposition. This paper also described the relation and interaction between the heat and fluid flow mechanisms in depressurization of type 3 hydrate reservoirs. All results of 1-D and 2-D numerical simulation and analyses were generated using the STARS simulator. It was shown that the rate of gas production depends on the initial pressure/temperature conditions and permeability of the hydrate bearing formation. A high peak rate may be achieved under favourable conditions, but this peak rate is obtained after an initial period where the rate of gas production increases with time. The heat transfer in the direction perpendicular to the direction of fluid flow is significant, requiring 2D modeling. The hydraulic diffusivity is low because of the low permeability of hydrate-bearing formations. This could result in competition between heat and fluid flow, thereby influencing the behaviour of decomposition. 6 refs., 3 tabs., 12 figs.

The U.S. Geological Survey’s Gas Hydrates Project

Science.gov (United States)

Ruppel, Carolyn D.

2018-01-17

The Gas Hydrates Project at the U.S. Geological Survey (USGS) focuses on the study of methane hydrates in natural environments. The project is a collaboration between the USGS Energy Resources and the USGS Coastal and Marine Geology Programs and works closely with other U.S. Federal agencies, some State governments, outside research organizations, and international partners. The USGS studies the formation and distribution of gas hydrates in nature, the potential of hydrates as an energy resource, and the interaction between methane hydrates and the environment. The USGS Gas Hydrates Project carries out field programs and participates in drilling expeditions to study marine and terrestrial gas hydrates. USGS scientists also acquire new geophysical data and sample sediments, the water column, and the atmosphere in areas where gas hydrates occur. In addition, project personnel analyze datasets provided by partners and manage unique laboratories that supply state-of-the-art analytical capabilities to advance national and international priorities related to gas hydrates.

Modeling the kinetics of hydrates formation using phase field method under similar conditions of petroleum pipelines; Modelagem da cinetica de formacao de hidratos utilizando o Modelo do Campo de Fase em condicoes similares a dutos de petroleo

Energy Technology Data Exchange (ETDEWEB)

Oliveira, Mabelle Biancardi; Castro, Jose Adilson de; Silva, Alexandre Jose da [Universidade Federal Fluminense (UFF), Volta Redonda, RJ (Brazil). Programa de Pos-Graduacao em Engenharia Metalurgica], e-mails: mabelle@metal.eeimvr.uff.br; adilson@metal.eeimvr.uff.br; ajs@metal.eeimvr.uff.br

2008-10-15

Natural hydrates are crystalline compounds that are ice-like formed under oil extraction transportation and processing. This paper deals with the kinetics of hydrate formation by using the phase field approach coupled with the transport equation of energy. The kinetic parameters of the hydrate formation were obtained by adjusting the proposed model to experimental results in similar conditions of oil extraction. The effect of thermal and nucleation conditions were investigated while the rate of formation and morphology were obtained by numerical computation. Model results of kinetics growth and morphology presented good agreement with the experimental ones. Simulation results indicated that super-cooling and pressure were decisive parameters for hydrates growth, morphology and interface thickness. (author)

Optimum potassium chloride concentration to reduce hydration capacity of clay formations; Concentracao otima de cloreto de potassio para reduzir a capacidade de hidratacao das formacoes argilosas

Energy Technology Data Exchange (ETDEWEB)

Machado, Jose Carlos Vieira [PETROBRAS, Salvador, BA (Brazil). Centro de Recursos Humanos Norte-Nordeste. Setor de Programas de Perfuracao; Oliveira, Manoel Martins de [PETROBRAS, BA (Brazil). Distrito de Perfuracao. Div. de Tecnicas de Perfuracao

1988-12-31

An experimental method for ascertaining the optimal concentration of potassium chloride for reducing the hydration and dispersion capacity of clayey formations sensitive to water-based fluids is described. Under this method, filtering time for disperse systems prepared from clayey formation samples is measured. A discussion is offered on theoretical aspects of hydration, expansion, and dispersion of clayey rocks in response to the variations in stress equilibrium states produced by these phenomena when a hole (well) is opened in the rock. The state of the art of this technological branch is also described. (author) 10 refs., 5 figs., 4 tabs.

Critical guest concentration and complete tuning pattern appearing in the binary clathrate hydrates

Energy Technology Data Exchange (ETDEWEB)

Cha, J.H.; Lee, H. [Korea Advanced Inst. of Science and Technology, Yuseong-gu, Daejeon (Korea, Republic of). Dept. of Chemical and Biomolecular Engineering; Kim, D.Y. [SK Engineering and Construction, Jongno-gu, Seoul (Korea, Republic of); Park, J. [Hanwha Chemical R and D Center, Yuseong-gu, Daejeon (Korea, Republic of); Lee, J.W. [Kongju National Univ., Cheonan, Chungnam (Korea, Republic of); Ripmeester, J.A. [National Research Council of Canada, Ottawa, ON (Canada). Steacie Inst. for Molecular Sciences

2008-07-01

Clathrate hydrates, or gas hydrates, are stabilized by van der Waals interaction between a guest molecule and a host framework. Because of their property, they are a potential resource in the exploitation of natural gas hydrates, as a material for the sequestration of carbon dioxide (CO{sub 2}), as a means of storage and transportation of natural gas, as well as hydrogen storage. Clathrate hydrate research can be divided into two categories that emphasize either macroscopic or microscopic approaches. However, these two approaches need to be closely linked for a better understanding of the structures and processes involving both natural phenomena and hydrates for industrial processes. Details on the molecular scale that concern the less usual properties of clathrate hydrates remain unknown. This paper presented the results of a study that reported on the existence of a critical guest concentration (CGC) and established the complete tuning pattern that occurred in the binary hydrates, including water-soluble hydrate formers (promoters) and water-insoluble guests. The paper presented the experimental procedures, including formation of the methane (CH{sub 4}) and tetrahydrofuran (THF) binary hydrate; a schematic diagram of the experimental apparatus; and formation of the CH{sub 4} and t-BuNH{sub 2} binary hydrate. Nuclear magnetic resonance (NMR) spectroscopic measurements and thermodynamic measurements were also presented. It was concluded that the CGC value appeared to primarily depend on the chemical nature of a liquid guest component participating in the binary hydrate formation. 10 refs., 2 tabs., 9 figs.

Comparative Assessment of Advanced Gay Hydrate Production Methods

Energy Technology Data Exchange (ETDEWEB)

M. D. White; B. P. McGrail; S. K. Wurstner

2009-06-30

Displacing natural gas and petroleum with carbon dioxide is a proven technology for producing conventional geologic hydrocarbon reservoirs, and producing additional yields from abandoned or partially produced petroleum reservoirs. Extending this concept to natural gas hydrate production offers the potential to enhance gas hydrate recovery with concomitant permanent geologic sequestration. Numerical simulation was used to assess a suite of carbon dioxide injection techniques for producing gas hydrates from a variety of geologic deposit types. Secondary hydrate formation was found to inhibit contact of the injected CO{sub 2} regardless of injectate phase state, thus diminishing the exchange rate due to pore clogging and hydrate zone bypass of the injected fluids. Additional work is needed to develop methods of artificially introducing high-permeability pathways in gas hydrate zones if injection of CO{sub 2} in either gas, liquid, or micro-emulsion form is to be more effective in enhancing gas hydrate production rates.

Indian National Gas Hydrate Program Expedition 01 report

Science.gov (United States)

Collett, Timothy S.; Riedel, M.; Boswell, R.; Presley, J.; Kumar, P.; Sathe, A.; Sethi, A.; Lall, M.V.; ,

2015-01-01

Gas hydrate is a naturally occurring “ice-like” combination of natural gas and water that has the potential to serve as an immense resource of natural gas from the world’s oceans and polar regions. However, gas-hydrate recovery is both a scientific and a technical challenge and much remains to be learned about the geologic, engineering, and economic factors controlling the ultimate energy resource potential of gas hydrate. The amount of natural gas contained in the world’s gas-hydrate accumulations is enormous, but these estimates are speculative and range over three orders of magnitude from about 2,800 to 8,000,000 trillion cubic meters of gas. By comparison, conventional natural gas accumulations (reserves and undiscovered, technically recoverable resources) for the world are estimated at approximately 440 trillion cubic meters. Gas recovery from gas hydrate is hindered because the gas is in a solid form and because gas hydrate commonly occurs in remote Arctic and deep marine environments. Proposed methods of gas recovery from gas hydrate generally deal with disassociating or “melting” in situ gas hydrate by heating the reservoir beyond the temperature of gas-hydrate formation, or decreasing the reservoir pressure below hydrate equilibrium. The pace of energy-related gas hydrate assessment projects has accelerated over the past several years.

Anti-Agglomerator of Tetra-n-Butyl Ammonium Bromide Hydrate and Its Effect on Hydrate-Based CO2 Capture

Directory of Open Access Journals (Sweden)

Rong Li

2018-02-01

Full Text Available Tetra-n-butyl ammonium bromide (TBAB was widely used in the research fields of cold storage and CO2 hydrate separation due to its high phase change latent heat and thermodynamic promotion for hydrate formation. Agglomeration always occurred in the process of TBAB hydrate generation, which led to the blockage in the pipeline and the separation apparatus. In this work, we screened out a kind of anti-agglomerant that can effectively solve the problem of TBAB hydrate agglomeration. The anti-agglomerant (AA is composed of 90% cocamidopropyl dimethylamine and 10% glycerol, which can keep TBAB hydrate of 19.3–29.0 wt. % in a stable state of slurry over 72 h. The microscopic observation of the morphology of the TBAB hydrate particles showed that the addition of AA can greatly reduce the size of the TBAB hydrate particles. CO2 gas separation experiments found that the addition of AA led to great improvement on gas storage capacity, CO2 split fraction and separation factor, due to the increasing of contact area between gas phase and hydrate particles. The CO2 split fraction and separation factor with AA addition reached up to 70.3% and 42.8%, respectively.

Investigation of Kinetic Hydrate Inhibition Using a High Pressure Micro Differential Scanning Calorimeter

DEFF Research Database (Denmark)

Daraboina, Nagu; Malmos, Christine; von Solms, Nicolas

2013-01-01

of hydrate growth. Additionally, hydrate formed in the presence of inhibitor decomposed at higher temperatures compared to pure water, indicating that while hydrate formation is initially inhibited; once hydrates form, they are more stable in the presence of inhibitor. Overall, this method proved a viable......Methane hydrate formation and decomposition were investigated in the presence of the kinetic inhibitor (Luvicap EG) and synergist (polyethylene oxide; PEO) using a high pressure micro-differential scanning calorimeter (HP-μDSC) with both temperature ramping and isothermal temperature programs....... These investigations were performed using small samples in four different capillary tubes in the calorimeter cell. When the isothermal method was employed, it was found that Luvicap EG significantly delays the hydrate nucleation time as compared to water. The results obtained from the ramping method demonstrated...

Low-δD hydration rinds in Yellowstone perlites record rapid syneruptive hydration during glacial and interglacial conditions

Science.gov (United States)

Bindeman, Ilya N.; Lowenstern, Jacob B.

2016-01-01

Hydration of silicic volcanic glass forms perlite, a dusky, porous form of altered glass characterized by abundant “onion-skin” fractures. The timing and temperature of perlite formation are enigmatic and could plausibly occur during eruption, during post-eruptive cooling, or much later at ambient temperatures. To learn more about the origin of natural perlite, and to fingerprint the hydration waters, we investigated perlitic glass from several synglacial and interglacial rhyolitic lavas and tuffs from the Yellowstone volcanic system. Perlitic cores are surrounded by a series of conchoidal cracks that separate 30- to 100-µm-thick slivers, likely formed in response to hydration-induced stress. H2O and D/H profiles confirm that most D/H exchange happens together with rapid H2O addition but some smoother D/H variations may suggest separate minor exchange by deuterium atom interdiffusion following hydration. The hydrated rinds (2–3 wt% H2O) transition rapidly (within 30 µm, or by 1 wt% H2O per 10 µm) to unhydrated glass cores. This is consistent with quenched “hydration fronts” where H2O diffusion coefficients are strongly dependent on H2O concentrations. The chemical, δ18O, and δD systematics of bulk glass records last equilibrium between ~110 and 60 °C without chemical exchange but with some δ18O exchange. Similarly, the δ18O of water extracted from glass by rapid heating suggests that water was added to the glass during cooling at higher rates of diffusion at 60–110 °C temperatures, compared with values expected from extrapolation of high-temperature (>400 °C) experimental data. The thick hydration rinds in perlites, measuring hundreds of microns, preserve the original D/H values of hydrating water as a recorder of paleoclimate conditions. Measured δD values in perlitic lavas are −150 to −191 or 20–40 ‰ lower than glass hydrated by modern Yellowstone waters. This suggests that Yellowstone perlites record the low-δD signature

Generalized hypothesis of the origin of the living-matter simplest elements, transformation of the Archean atmosphere, and the formation of methane-hydrate deposits

International Nuclear Information System (INIS)

Ostrovskii, Viktor E; Kadyshevich, Elena A

2007-01-01

The original hydrate hypothesis of the origin of living-matter simplest elements (LMSEs), i.e., the 'Life Origination Hydrate hypothesis,' abbreviated as the LOH hypothesis, is discussed. It includes notions of the interdependence and interconditionality of processes leading to the life origin, to the transformation of the primary atmosphere, and to the underground methane-hydrate formation. Saturation of the young earth's crust with nebular hydrogen is taken into consideration for the first time. The origin of LMSEs is regarded as a result of regular and thermodynamically caused inevitable chemical transformations and of the universal physical and chemical laws. According to the LOH hypothesis, LMSEs originated repeatedly and, maybe, are now originating from methane (or other simple hydrocarbons), niter, and phosphate within boundary layers of the solid phases of the hydrates of the simplest hydrocarbons. It is assumed that the phenomenon of monochirality of nucleic acids is caused by geometric features of the structure matrix. (reviews of topical problems)

Generalized hypothesis of the origin of the living-matter simplest elements, transformation of the Archean atmosphere, and the formation of methane-hydrate deposits

Energy Technology Data Exchange (ETDEWEB)

Ostrovskii, Viktor E [L. Ya. Karpov Institute of Physical Chemistry, Moscow (Russian Federation); Kadyshevich, Elena A [A.M. Obukhov Institute of Atmospheric Physics, Russian Academy of Sciences, Moscow (Russian Federation)

2007-02-28

The original hydrate hypothesis of the origin of living-matter simplest elements (LMSEs), i.e., the 'Life Origination Hydrate hypothesis,' abbreviated as the LOH hypothesis, is discussed. It includes notions of the interdependence and interconditionality of processes leading to the life origin, to the transformation of the primary atmosphere, and to the underground methane-hydrate formation. Saturation of the young earth's crust with nebular hydrogen is taken into consideration for the first time. The origin of LMSEs is regarded as a result of regular and thermodynamically caused inevitable chemical transformations and of the universal physical and chemical laws. According to the LOH hypothesis, LMSEs originated repeatedly and, maybe, are now originating from methane (or other simple hydrocarbons), niter, and phosphate within boundary layers of the solid phases of the hydrates of the simplest hydrocarbons. It is assumed that the phenomenon of monochirality of nucleic acids is caused by geometric features of the structure matrix. (reviews of topical problems)

Irrigation port hydration in phacoemulsification surgery

Directory of Open Access Journals (Sweden)

Suzuki H

2018-01-01

Full Text Available Hisaharu Suzuki,1 Yoichiro Masuda,2 Yuki Hamajima,1 Hiroshi Takahashi3 1Department of Ophthalmology, Nippon Medical School Musashikosugi Hospital, Kawasaki City, Kanagawa, 2Department of Ophthalmology, The Jikei University, Katsushika Medical Center, Tokyo, 3Department of Ophthalmology, Nippon Medical School, Tokyo, Japan Background: In most cases, hydration is performed by water injection into the stromal tissue with a needle. The technique is simple, however it is sometimes troublesome.Purpose: We describe a simple technique for hydrating the corneal stroma in cataract surgery using an irrigation port.Patients and methods: The technique began by pushing the irrigation port against the corneal stroma for a few seconds during phacoemulsification, which generated edema in the corneal incision that subsequently prevented leakage. This procedure is called the hydration using irrigation port (HYUIP technique. A total of 60 eyes were randomized and placed in two groups, 30 eyes underwent surgeries using the HYUIP technique (HYUIP group and 30 eyes underwent surgeries without the HYUIP technique (control. The three points evaluated during each surgery included 1 the occurrence of anterior chamber collapse during the pulling out of the I/A tip after inserting the intraocular lens, 2 the need for conventional hydration, and 3 watertight completion at the end stage of surgery.Results: The anterior chamber collapse and the need for conventional hydration were significantly smaller in the HYUIP group compared to the control group. Regarding the self-sealing completion, no significant difference was observed between the two groups.Conclusion: The HYUIP technique is an effective method for creating self-sealing wound. In addition, this technique helps to prevent anterior chamber collapse. Keywords: cataract surgery, hydration, irrigation and aspiration, phacoemulsification, wound, self-sealing 

The genetic source and timing of hydrocarbon formation in gas hydrate reservoirs in Green Canyon, Block GC955

Science.gov (United States)

Moore, M. T.; Darrah, T.; Cook, A.; Sawyer, D.; Phillips, S.; Whyte, C. J.; Lary, B. A.

2017-12-01

Although large volumes of gas hydrates are known to exist along continental slopes and below permafrost, their role in the energy sector and the global carbon cycle remains uncertain. Investigations regarding the genetic source(s) (i.e., biogenic, thermogenic, mixed sources of hydrocarbon gases), the location of hydrocarbon generation, (whether hydrocarbons formed within the current reservoir formations or underwent migration), rates of clathrate formation, and the timing of natural gas formation/accumulation within clathrates are vital to evaluate economic potential and enhance our understanding of geologic processes. Previous studies addressed some of these questions through analysis of conventional hydrocarbon molecular (C1/C2+) and stable isotopic (e.g., δ13C-CH4, δ2H-CH4, δ13C-CO2) composition of gases, water chemistry and isotopes (e.g., major and trace elements, δ2H-H2O, δ18O-H2O), and dissolved inorganic carbon (δ13C-DIC) of natural gas hydrate systems to determine proportions of biogenic and thermogenic gas. However, the effects from contributions of mixing, transport/migration, methanogenesis, and oxidation in the subsurface can complicate the first-order application of these techniques. Because the original noble gas composition of a fluid is preserved independent of microbial activity, chemical reactions, or changes in oxygen fugacity, the integration of noble gas data can provide both a geochemical fingerprint for sources of fluids and an additional insight as to the uncertainty between effects of mixing versus post-genetic modification. Here, we integrate inert noble gases (He, Ne, Ar, and associated isotopes) with these conventional approaches to better constrain the source of gas hydrate formation and the residence time of fluids (porewaters and natural gases) using radiogenic 4He ingrowth techniques in cores from two boreholes collected as part of the University of Texas led UT-GOM2-01 drilling project. Pressurized cores were extracted from

Assessing the conditions favorable for the occurrence of gas hydrate in the Tuonamu area Qiangtang basin, Qinghai–Tibetan, China

International Nuclear Information System (INIS)

He Jianglin; Wang Jian; Fu Xiugen; Zheng Chenggang; Chen Yanting

2012-01-01

Highlights: ► This is a pioneer research on the exploration of gas hydrate in Qiangtang basin. ► The factors influencing the stable of gas hydrate in Tuonamu area were studied. ► Simulation shows that gas hydrate stable zone is about 300 m thick in target area. ► Source condition is the key factor for the formation of gas hydrate in this area. ► The areas around the deeper faults are favorable targets for gas hydrate. - Abstract: Qiangtang basin, which is located in the largest continuous permafrost area in Qinghai–Tibetan Plateau, is expected to be a strategic area of gas hydrate exploitation in China. However, relatively little work has been done on the exploration of gas hydrate in this area. In this work, we evaluated the factors controlling the formation of gas hydrate in the Tuonamu area and provided a preliminary insight into gas hydrate distribution in it on the basis of the core samples, seismic data and laboratory analysis. It can be concluded that the source rock in the deeper formation would be dominant thermogenic source for the formation of gas hydrate in Tuonamu area. The thickness of gas hydrate stable zone in this area is about 300 m. The gas hydrate in the area most probably is in the form of gas-hydrate-water. The source condition is the key factor for the formation of gas hydrate and the gas hydrate layer would be mainly present in the form of interlayer in this area. The areas around the deeper faults are the favorable targets for the exploration of gas hydrate in the Tuonamu area.

Class H cement hydration at 180 deg. C and high pressure in the presence of added silica

International Nuclear Information System (INIS)

Jupe, Andrew C.; Wilkinson, Angus P.; Luke, Karen; Funkhouser, Gary P.

2008-01-01

Under deep oil-well conditions of elevated temperature and pressure, crystalline calcium silicate hydrates are formed during Portland cement hydration. The use of silica rich mineral additives leads to the formation of crystalline hydrates with better mechanical properties than those formed without the additive. The effects of silica flour, silica fume (amorphous silica), and a natural zeolite mixture on the hydration of Class H cement slurries at 180 deg. C under externally applied pressures of 7 and 52 MPa are examined in real time using in-situ synchrotron X-ray diffraction. For some compositions examined, but not all, pressure was found to have a large effect on the kinetics of crystalline hydrate formation. The use of silica fume delayed both C 3 S hydration and the formation of crystalline silicate hydrates compared to what was seen with other silica sources

A possible reason behind the initial formation of pentagonal dodecahedron cavities in sI-methane hydrate nucleation: A DFT study

Science.gov (United States)

Mondal, Sukanta; Goswami, Tamal; Jana, Gourhari; Misra, Anirban; Chattaraj, Pratim Kumar

2018-01-01

In this letter, a possible reason behind selective host-guest organization in the initial stage of sI methane hydrate nucleation is provided, through density functional theory based calculations. In doing so, we have connected earlier experimental and theoretical observations on the structure and energetics of sI methane hydrate to our findings. Geometry and relative stability of small (H2O)5 and (H2O)6 clusters, presence of CH4 guest, integrity and cavity radius of (H2O)20 and (H2O)24, as well as the weak van der Waals type of forces, particularly dispersion interaction, are major factors responsible for initial formation of methane encapsulated dodecahedron cavity over tetrakaidecahedron.

Impact of CO{sub 2} hydrates on ocean carbon dioxide deposition options

Energy Technology Data Exchange (ETDEWEB)

Lund, P C

1995-04-01

The objective of the research project described in this report was to contribute to the research on greenhouse gases and the global environment. The focus is on the concept of storing large amounts of CO{sub 2} in the ocean. The project was divided into three subtasks: (1) a comprehensive study of the thermodynamic, physical and chemical properties of the seawater/CO{sub 2}/hydrate system, (2) establishment of a micro-scale kinetic model for CO{sub 2} hydrate formation and stability, based on (1), and (3) establishment of macro-scale models for various ocean deposition options based on (2). A database of selected thermodynamic functions has been set up. A large database of oceanic data has also been made; for any given coordinates at sea a computer program provides the temperature, salinity and oxygen profiles from the sea surface to the sea floor. The kinetic model predicts the formation and pseudo-stability of a very thin hydrate film which acts as an inhibitor for diffusion of CO{sub 2} into the sea water. The model predicts that the hydrate film reduces the overall flux from a liquid CO{sub 2} source with about 90%. Thermodynamically, pure CO{sub 2} in contact with water might form hydrates at depths below about 400 m, which would indicate that hydrate formation could play a role for all ocean CO{sub 2} deposition options. However, this study shows that other mechanisms significantly reduce the role of hydrate formation. It is finally concluded that although more modelling and experimental work is required within this field of research, the hydrate film may play an important role for all options except from shallow water injection. 86 refs., 32 figs., 16 tabs.

Protocol for Measuring the Thermal Properties of a Supercooled Synthetic Sand-water-gas-methane Hydrate Sample.

Science.gov (United States)

Muraoka, Michihiro; Susuki, Naoko; Yamaguchi, Hiroko; Tsuji, Tomoya; Yamamoto, Yoshitaka

2016-03-21

Methane hydrates (MHs) are present in large amounts in the ocean floor and permafrost regions. Methane and hydrogen hydrates are being studied as future energy resources and energy storage media. To develop a method for gas production from natural MH-bearing sediments and hydrate-based technologies, it is imperative to understand the thermal properties of gas hydrates. The thermal properties' measurements of samples comprising sand, water, methane, and MH are difficult because the melting heat of MH may affect the measurements. To solve this problem, we performed thermal properties' measurements at supercooled conditions during MH formation. The measurement protocol, calculation method of the saturation change, and tips for thermal constants' analysis of the sample using transient plane source techniques are described here. The effect of the formation heat of MH on measurement is very small because the gas hydrate formation rate is very slow. This measurement method can be applied to the thermal properties of the gas hydrate-water-guest gas system, which contains hydrogen, CO2, and ozone hydrates, because the characteristic low formation rate of gas hydrate is not unique to MH. The key point of this method is the low rate of phase transition of the target material. Hence, this method may be applied to other materials having low phase-transition rates.

Development of hydrate risk quantification in oil and gas production

Science.gov (United States)

Chaudhari, Piyush N.

Subsea flowlines that transport hydrocarbons from wellhead to the processing facility face issues from solid deposits such as hydrates, waxes, asphaltenes, etc. The solid deposits not only affect the production but also pose a safety concern; thus, flow assurance is significantly important in designing and operating subsea oil and gas production. In most subsea oil and gas operations, gas hydrates form at high pressure and low temperature conditions, causing the risk of plugging flowlines, with a undesirable impact on production. Over the years, the oil and gas industry has shifted their perspective from hydrate avoidance to hydrate management given several parameters such as production facility, production chemistry, economic and environmental concerns. Thus, understanding the level of hydrate risk associated with subsea flowlines is an important in developing efficient hydrate management techniques. In the past, hydrate formation models were developed for various flow-systems (e.g., oil dominated, water dominated, and gas dominated) present in the oil and gas production. The objective of this research is to extend the application of the present hydrate prediction models for assessing the hydrate risk associated with subsea flowlines that are prone to hydrate formation. It involves a novel approach for developing quantitative hydrate risk models based on the conceptual models built from the qualitative knowledge obtained from experimental studies. A comprehensive hydrate risk model, that ranks the hydrate risk associated with the subsea production system as a function of time, hydrates, and several other parameters, which account for inertial, viscous, interfacial forces acting on the flow-system, is developed for oil dominated and condensate systems. The hydrate plugging risk for water dominated systems is successfully modeled using The Colorado School of Mines Hydrate Flow Assurance Tool (CSMHyFAST). It is found that CSMHyFAST can be used as a screening tool in

Halogen systematics in the Mallik 5L-38 gas hydrate production research well, Northwest Territories, Canada: Implications for the origin of gas hydrates under terrestrial permafrost conditions

International Nuclear Information System (INIS)

Tomaru, Hitoshi; Fehn, Udo; Lu, Zunli; Matsumoto, Ryo

2007-01-01

The authors report here halogen concentrations in pore waters and sediments collected from the Mallik 5L-38 gas hydrate production research well, a permafrost location in the Mackenzie Delta, Northwest Territories, Canada. Iodine and Br are commonly enriched in waters associated with CH 4 , reflecting the close association between these halogens and source organic materials. Pore waters collected from the Mallik well show I enrichment, by one order of magnitude above that of seawater, particularly in sandy layers below the gas hydrate stability zone (GHSZ). Although Cl and Br concentrations increase with depth similar to the I profile, they remain below seawater values. The increase in I concentrations observed below the GHSZ suggests that I-rich fluids responsible for the accumulation of CH 4 in gas hydrates are preferentially transported through the sandy permeable layers below the GHSZ. The Br and I concentrations and I/Br ratios in Mallik are considerably lower than those in marine gas hydrate locations, demonstrating a terrestrial nature for the organic materials responsible for the CH 4 at the Mallik site. Halogen systematics in Mallik suggest that they are the result of mixing between seawater, freshwater and an I-rich source fluid. The comparison between I/Br ratios in pore waters and sediments speaks against the origin of the source fluids within the host formations of gas hydrates, a finding compatible with the results from a limited set of 129 I/I ratios determined in pore waters, which gives a minimum age of 29 Ma for the source material, i.e. at the lower end of the age range of the host formations. The likely scenario for the gas hydrate formation in Mallik is the derivation of CH 4 together with I from the terrestrial source materials in formations other than the host layers through sandy permeable layers into the present gas hydrate zones

Thermodynamic promotion of carbon dioxide-clathrate hydrate formation by tetrahydrofuran, cyclopentane and their mixtures

DEFF Research Database (Denmark)

Herslund, Peter Jørgensen; Thomsen, Kaj; Abildskov, Jens

2013-01-01

Gas clathrate hydrate dissociation pressures are reported for mixtures of carbon dioxide, water and thermodynamic promoters forming structure II hydrates.Hydrate (H)-aqueous liquid (Lw)-vapour (V) equilibrium pressures for the ternary system composed of water, tetrahydrofuran (THF), and carbon....... It is shown that upon adding THF to the pure aqueous phase to form a 4mass percent solution, the equilibrium pressure of the formed hydrates may be lowered compared to the ternary system of water, cyclopentane and carbon dioxide. © 2013 Elsevier Ltd....... dioxide (CO2), with 5.0mole percent THF in the initial aqueous phase, are presented in the temperature range from 283.3K to 285.2K. At 283.3K, the three-phase equilibrium pressure is determined to be 0.61MPa (absolute pressure).Four-phase hydrate (H)-aqueous liquid (Lw)-organic liquid (La)-vapour (V...

Gas hydrate drilling transect across northern Cascadia margin - IODP Expedition 311

Science.gov (United States)

Riedel, M.; Collett, T.; Malone, M.J.; Collett, T.S.; Mitchell, M.; Guerin, G.; Akiba, F.; Blanc-Valleron, M.; Ellis, M.; Hashimoto, Y.; Heuer, V.; Higashi, Y.; Holland, M.; Jackson, P.D.; Kaneko, M.; Kastner, M.; Kim, J.-H.; Kitajima, H.; Long, P.E.; Malinverno, A.; Myers, Gwen E.; Palekar, L.D.; Pohlman, J.; Schultheiss, P.; Teichert, B.; Torres, M.E.; Trehu, A.M.; Wang, Jingyuan; Worthmann, U.G.; Yoshioka, H.

2009-01-01

A transect of four sites (U1325, U1326, U1327 and U1329) across the northern Cascadia margin was established during Integrated Ocean Drilling Program Expedition 311 to study the occurrence and formation of gas hydrate in accretionary complexes. In addition to the transect sites, a fifth site (U1328) was established at a cold vent with active fluid flow. The four transect sites represent different typical geological environments of gas hydrate occurrence across the northern Cascadia margin from the earliest occurrence on the westernmost first accreted ridge (Site U1326) to the eastward limit of the gas hydrate occurrence in shallower water (Site U1329). Expedition 311 complements previous gas hydrate studies along the Cascadia accretionary complex, especially ODP Leg 146 and Leg 204 by extending the aperture of the transect sampled and introducing new tools to systematically quantify the gas hydrate content of the sediments. Among the most significant findings of the expedition was the occurrence of up to 20 m thick sand-rich turbidite intervals with gas hydrate concentrations locally exceeding 50% of the pore space at Sites U1326 and U1327. Moreover, these anomalous gas hydrate intervals occur at unexpectedly shallow depths of 50-120 metres below seafloor, which is the opposite of what was expected from previous models of gas hydrate formation in accretionary complexes, where gas hydrate was predicted to be more concentrated near the base of the gas hydrate stability zone just above the bottom-simulating reflector. Gas hydrate appears to be mainly concentrated in turbidite sand layers. During Expedition 311, the visual correlation of gas hydrate with sand layers was clearly and repeatedly documented, strongly supporting the importance of grain size in controlling gas hydrate occurrence. The results from the transect sites provide evidence for a structurally complex, lithology-controlled gas hydrate environment on the northern Cascadia margin. Local shallow

Free energy landscape and molecular pathways of gas hydrate nucleation

Energy Technology Data Exchange (ETDEWEB)

Bi, Yuanfei; Porras, Anna; Li, Tianshu, E-mail: tsli@gwu.edu [Department of Civil and Environmental Engineering, George Washington University, Washington DC 20052 (United States)

2016-12-07

Despite the significance of gas hydrates in diverse areas, a quantitative knowledge of hydrate formation at a molecular level is missing. The impediment to acquiring this understanding is primarily attributed to the stochastic nature and ultra-fine scales of nucleation events, posing a great challenge for both experiment and simulation to explore hydrate nucleation. Here we employ advanced molecular simulation methods, including forward flux sampling (FFS), p{sub B} histogram analysis, and backward flux sampling, to overcome the limit of direct molecular simulation for exploring both the free energy landscape and molecular pathways of hydrate nucleation. First we test the half-cage order parameter (H-COP) which we developed for driving FFS, through conducting the p{sub B} histogram analysis. Our results indeed show that H-COP describes well the reaction coordinates of hydrate nucleation. Through the verified order parameter, we then directly compute the free energy landscape for hydrate nucleation by combining both forward and backward flux sampling. The calculated stationary distribution density, which is obtained independently of nucleation theory, is found to fit well against the classical nucleation theory (CNT). Subsequent analysis of the obtained large ensemble of hydrate nucleation trajectories show that although on average, hydrate formation is facilitated by a two-step like mechanism involving a gradual transition from an amorphous to a crystalline structure, there also exist nucleation pathways where hydrate crystallizes directly, without going through the amorphous stage. The CNT-like free energy profile and the structural diversity suggest the existence of multiple active transition pathways for hydrate nucleation, and possibly also imply the near degeneracy in their free energy profiles among different pathways. Our results thus bring a new perspective to the long standing question of how hydrates crystallize.

Free energy landscape and molecular pathways of gas hydrate nucleation

International Nuclear Information System (INIS)

Bi, Yuanfei; Porras, Anna; Li, Tianshu

2016-01-01

Despite the significance of gas hydrates in diverse areas, a quantitative knowledge of hydrate formation at a molecular level is missing. The impediment to acquiring this understanding is primarily attributed to the stochastic nature and ultra-fine scales of nucleation events, posing a great challenge for both experiment and simulation to explore hydrate nucleation. Here we employ advanced molecular simulation methods, including forward flux sampling (FFS), p B histogram analysis, and backward flux sampling, to overcome the limit of direct molecular simulation for exploring both the free energy landscape and molecular pathways of hydrate nucleation. First we test the half-cage order parameter (H-COP) which we developed for driving FFS, through conducting the p B histogram analysis. Our results indeed show that H-COP describes well the reaction coordinates of hydrate nucleation. Through the verified order parameter, we then directly compute the free energy landscape for hydrate nucleation by combining both forward and backward flux sampling. The calculated stationary distribution density, which is obtained independently of nucleation theory, is found to fit well against the classical nucleation theory (CNT). Subsequent analysis of the obtained large ensemble of hydrate nucleation trajectories show that although on average, hydrate formation is facilitated by a two-step like mechanism involving a gradual transition from an amorphous to a crystalline structure, there also exist nucleation pathways where hydrate crystallizes directly, without going through the amorphous stage. The CNT-like free energy profile and the structural diversity suggest the existence of multiple active transition pathways for hydrate nucleation, and possibly also imply the near degeneracy in their free energy profiles among different pathways. Our results thus bring a new perspective to the long standing question of how hydrates crystallize.

Free energy landscape and molecular pathways of gas hydrate nucleation.

Science.gov (United States)

Bi, Yuanfei; Porras, Anna; Li, Tianshu

2016-12-07

Despite the significance of gas hydrates in diverse areas, a quantitative knowledge of hydrate formation at a molecular level is missing. The impediment to acquiring this understanding is primarily attributed to the stochastic nature and ultra-fine scales of nucleation events, posing a great challenge for both experiment and simulation to explore hydrate nucleation. Here we employ advanced molecular simulation methods, including forward flux sampling (FFS), p B histogram analysis, and backward flux sampling, to overcome the limit of direct molecular simulation for exploring both the free energy landscape and molecular pathways of hydrate nucleation. First we test the half-cage order parameter (H-COP) which we developed for driving FFS, through conducting the p B histogram analysis. Our results indeed show that H-COP describes well the reaction coordinates of hydrate nucleation. Through the verified order parameter, we then directly compute the free energy landscape for hydrate nucleation by combining both forward and backward flux sampling. The calculated stationary distribution density, which is obtained independently of nucleation theory, is found to fit well against the classical nucleation theory (CNT). Subsequent analysis of the obtained large ensemble of hydrate nucleation trajectories show that although on average, hydrate formation is facilitated by a two-step like mechanism involving a gradual transition from an amorphous to a crystalline structure, there also exist nucleation pathways where hydrate crystallizes directly, without going through the amorphous stage. The CNT-like free energy profile and the structural diversity suggest the existence of multiple active transition pathways for hydrate nucleation, and possibly also imply the near degeneracy in their free energy profiles among different pathways. Our results thus bring a new perspective to the long standing question of how hydrates crystallize.

Characterization of un-hydrated and hydrated BioAggregate™ and MTA Angelus™.

Science.gov (United States)

Camilleri, J; Sorrentino, F; Damidot, D

2015-04-01

high calcium ion release early, which was maintained over the 28-day period as opposed to MTA Angelus, which demonstrated low early calcium ion release which increased as the material aged. The mineralogical composition of BioAggregate was different to MTA Angelus. As opposed to MTA Angelus, BioAggregate did not contain aluminium and contained additives such as calcium phosphate and silicon dioxide. As a consequence, BioAggregate reacted more slowly and formation of calcium hydroxide and leaching of calcium ions in solution were not evident as the material aged. The additives in BioAggregate modify the kinetics and the end products of hydration. Although newer generation tricalcium silicate-based materials contain similar constituents to MTA, they do not undergo the same setting reactions, and thus, their clinical performance will not be comparable to that of MTA.

Structural and hydration properties of amorphous tricalcium silicate

International Nuclear Information System (INIS)

Mori, K.; Fukunaga, T.; Shiraishi, Y.; Iwase, K.; Xu, Q.; Oishi, K.; Yatsuyanagi, K.; Yonemura, M.; Itoh, K.; Sugiyama, M.; Ishigaki, T.; Kamiyama, T.; Kawai, M.

2006-01-01

Mechanical milling was carried out to synthesize amorphous tricalcium silicate (Ca 3 SiO 5 ) sample, where Ca 3 SiO 5 is the most principal component of Portland cement. The partial phase transformation from the crystalline to the amorphous state was observed by X-ray and neutron diffractions. Moreover, it was found that the structural distortion on the Ca-O correlation exists in the milled Ca 3 SiO 5 . The hydration of the milled Ca 3 SiO 5 with D 2 O proceeds as follows: the formation of hydration products such as Ca(OD) 2 rapidly occurs in the early hydration stage, and then proceeds slowly after about 15 h. The induction time for the hydration of the milled Ca 3 SiO 5 is approximately one half shorter than that for the hydration of the unmilled one. This result means that the mechanical milling brings about the chemical activity of Ca 3 SiO 5 for hydration, and may be particularly useful for increasing the reactivity in the early hydration stage

Thermal conductivity measurements in unsaturated hydrate-bearing sediments

Science.gov (United States)

Dai, Sheng; Cha, Jong-Ho; Rosenbaum, Eilis J.; Zhang, Wu; Seol, Yongkoo

2015-08-01

Current database on the thermal properties of hydrate-bearing sediments remains limited and has not been able to capture their consequential changes during gas production where vigorous phase changes occur in this unsaturated system. This study uses the transient plane source (TPS) technique to measure the thermal conductivity of methane hydrate-bearing sediments with various hydrate/water/gas saturations. We propose a simplified method to obtain thermal properties from single-sided TPS signatures. Results reveal that both volume fraction and distribution of the pore constituents govern the thermal conductivity of unsaturated specimens. Thermal conductivity hysteresis is observed due to water redistribution and fabric change caused by hydrate formation and dissociation. Measured thermal conductivity increases evidently when hydrate saturation Sh > 30-40%, shifting upward from the geometric mean model prediction to a Pythagorean mixing model. These observations envisage a significant drop in sediment thermal conductivity when residual hydrate/water saturation falls below ~40%, hindering further gas production.

Investigating the influence of lithologic heterogeneity on gas hydrate formation and methane recycling at the base of the gas hydrate stability zone in channelized systems

Energy Technology Data Exchange (ETDEWEB)

Daigle, Hugh; Nole, Michael; Cook, Ann; Malinverno, Alberto

2017-12-14

In marine environments, gas hydrate preferentially accumulates in coarse-grained sediments. At the meso- to micro-scale, however, hydrate distribution in these coarse-grained units is often heterogeneous. We employ a methane hydrate reservoir simulator coupling heat and mass transfer as well as capillary effects to investigate how capillary controls on methane solubility affect gas and hydrate accumulations in reservoirs characterized by graded bedding and alternating sequences of coarse-grained sands and fine-grained silt and clay. Simulations bury a channelized reservoir unit encased in homogeneous, fine-grained material characterized by small pores (150 nm) and low permeability (~1 md in the absence of hydrate). Pore sizes within each reservoir bed between vary between coarse sand and fine silt. Sands have a median pore size of 35 microns and a lognormal pore size distribution. We also investigate how the amount of labile organic carbon (LOC) affects hydrate growth due to microbial methanogenesis within the sediments. In a diffusion-dominated system, methane movies into reservoir layers along spatial gradients in dissolved methane concentration. Hydrate grows in such a way as to minimize these concentration gradients by accumulating slower in finer-grained reservoir layers and faster in coarser-grained layers. Channelized, fining-upwards sediment bodies accumulate hydrate first along their outer surfaces and thence inward from top to bottom. If LOC is present in thin beds within the channel, higher saturations of hydrate will be distributed more homogeneously throughout the unit. When buried beneath the GHSZ, gas recycling can occur only if enough hydrate is present to form a connected gas phase upon dissociation. Simulations indicate that this is difficult to achieve for diffusion-dominated systems, especially those with thick GHSZs and/or small amounts of LOC. However, capillary-driven fracturing behavior may be more prevalent in settings with thick GHSZs.

On the electrolytic generation of hydrated electron

International Nuclear Information System (INIS)

Ghosh Mazumdar, A.S.; Guha, S.N.

1975-01-01

Investigations on the electrolytic generation of hydrated electron in oxygenated as well as oxygen-free solutions at different pH were undertaken. Since sup(-e)aq is known to react rapidly with O 2 yielding the transient O 2 - ion, the latter was looked for through its interaction with phosphite ions resulting in their oxidation near the cathode. It appears from the results that in electrolytic processes, the primary electron (esup(-)sub(cathode)) probably reacts directly with reactive solutes like oxygen, bypassing the hydration step. Data obtained in oxygen-free solutions, however, support the possible formation of hydrated electron at least in alkaline solutions. (author)

Phase equilibrium conditions of semi-calthrate hydrates of (tetra-n-butyl ammonium chloride + carbon dioxide)

International Nuclear Information System (INIS)

Sun, Zhi-Gao; Jiao, Li-Jun; Zhao, Zhi-Gui; Wang, Gong-Liang; Huang, Hai-Feng

2014-01-01

Highlights: • Carbon dioxide hydrate stability zone was enlarged with the help of TBAC. • Carbon dioxide uptake into TBAC semi-clathrate hydrates is confirmed. • Equilibrium pressure of hydrate decreased with the increase of TBAC mass concentration. • The addition of TBAC reduces the formation pressures of carbon dioxide hydrate by 2.5 MPa. - Abstract: In the present work, hydrate equilibrium conditions for (tetra-n-butyl ammonium chloride (TBAC) + carbon dioxide + water) mixtures were investigated. Tetra-n-butyl ammonium chloride was reported to form a semi-clathrate hydrate. The experiments were carried out within the TBAC mass fraction range of (0.05 to 0.3). The experimental results showed that the presence of TBAC decreased the formation pressure of carbon dioxide double hydrate within the experimental temperature range. Moreover, pressure reduction was dependent on the TBAC concentration

Measurements of gas permeability and non-Darcy flow in gas-water-hydrate systems

Energy Technology Data Exchange (ETDEWEB)

Ersland, G.; Husebo, J.; Graue, A.; Kvamme, B. [Bergen Univ., Bergen (Norway). Dept. of Physics and Technology; Baldwin, B. [Green Country Petrophysics LLC, Dewey, OK (United States); Stevens, J.; Howard, J. [ConocoPhillips, OK (United States)

2008-07-01

Storage of carbon dioxide (CO{sub 2}) in natural gas hydrate reservoirs may offer stable long-term storage of a greenhouse gas while benefiting from methane production, without requiring heat. By exposing hydrate to a thermodynamically preferred hydrate former, CO{sub 2}, the hydrate may be maintained macroscopically in the solid state and retain the stability of the formation. However, there is concern over the flow capacity in such reservoirs. This depends on several factors, notably thermodynamic destabilization of hydrate in small pores due to capillary effects; the presence of liquid channels separating the hydrate from the mineral surfaces; and, the connectivity of gas or liquid filled pores and channels. This paper described a technique for measuring gas permeability in gas-water-hydrate systems. It reported on several experiments that measured gas permeability during stages of hydrate growth in sandstone core plugs. Interactions between minerals and surrounding molecules were also discussed. The formation of methane hydrate in porous media was monitored and quantified with magnetic resonance imaging (MRI). MRI images of hydrate growth within the porous rock were provided along with measurements of gas permeability and non-Darcy flow effects at various hydrate saturations. Gas permeability was measured at steady state flow of methane through the hydrate-bearing core sample. Significant gas permeability was recorded for porous sandstone even when hydrates occupied up to 60 per cent of the pore space. It was concluded that MRI imaging can be used effectively to map and quantify hydrate saturation in sandstone core plugs. 27 refs., 2 tabs., 10 figs.

Study on gas hydrate as a new energy resource in the 21th century

Energy Technology Data Exchange (ETDEWEB)

Ryu, Byeong-Jae; Kwak Young-Hoon; Kim, Won-Sik [Korea Institute of Geology Mining and Materials, Taejon (KR)] (and others)

1999-12-01

Natural gas hydrate, a special type of clathrate hydrates, is a metastable solid compound which mainly consists of methane and water, and generally called as gas hydrate. It is stable in the specific low-temperature/high-pressure conditions. Gas hydrates play an important role as major reservoir of methane on the earth. On the other hand, the formation and dissociation of gas hydrates could cause the plugging in pipeline, gas kick during production, atmospheric pollution and geohazard. To understand the formation and dissociation of the gas hydrate, the experimental equilibrium conditions of methane hydrate were measured in pure water, 3 wt.% NaCl and MgCl{sub 2} solutions. The equilibrium conditions of propane hydrates were also measured in pure water. The relationship between methane hydrate formation time and overpressure was also analyzed through the laboratory work. The geophysical surveys using air-gun system and multibeam echo sounder were implemented to develop exploration techniques and to evaluate the gas hydrate potential in the East Sea, Korea. General indicators of submarine gas hydrates on seismic data is commonly inferred from the BSR developed parallel to the see floor, amplitude blanking at the upper part of the BSR, and phase reversal and decrease of the interval velocity at BSR. The field data were processed using Geobit 2.9.5 developed by KIGAM to detect the gas hydrate indicators. The accurate velocity analysis was performed by XVA (X-window based Velocity Analysis). Processing results show that the strong reflector occurred parallel to the sea floor were shown at about 1800 ms two way travel time. The interval velocity decrease at this strong reflector and at the reflection phase reversal corresponding to the reflection at the sea floor. Gas hydrate stability field in the study area was determined using the data of measured hydrate equilibrium condition, hydrothermal gradient and geothermal gradient. The depth of BSR detected in the seismic

Research on the nanolevel influence of surfactants on structure formation of the hydrated Portland cement compositions

Directory of Open Access Journals (Sweden)

Guryanov Alexander

2016-01-01

Full Text Available The research of the structure formation process on a nanolevel of the samples of hydrated Portland cement compositions containing the modifying additives has been conducted with the help of small angle neutron scattering method. Carbonate and aluminum alkaline slimes as well as the complex additives containing surfactants were used as additives. The influence of slimes and surfactants on structural parameters change of Portland cement compositions of the average size of the disseminating objects, fractal dimension samples is considered. These Portland cement compositions are shown to be fractal clusters.

Hydrate studies of northern Cascadia margin off Vancouver Island : a reference source

Energy Technology Data Exchange (ETDEWEB)

Hyndman, R. [Natural Resources Canada, Sidney, BC (Canada). Geological Survey of Canada, Pacific Geoscience Centre]|[Victoria Univ., BC (Canada). School of Earth and Ocean Sciences; Riedel, M. [McGill Univ., Montreal, PQ (Canada). Dept. of Earth and Planetary Sciences; Spence, G.D. [Victoria Univ., BC (Canada). School of Earth and Ocean Sciences

2008-07-01

Extensive geophysical studies have been conducted to determine the occurrence, distribution, and concentration of gas hydrate in the Cascadia subduction zone off western Canada. In this paper, the authors compiled a comprehensive reference list of studies involving marine natural gas hydrate surveys and studies on the northern Cascadia margin. The reference categories included general reviews; regional tectonic framework for northern Cascadia hydrate; prism sediment thickening, fluid expulsion and hydrate formation; and, seismic surveys. This paper first addressed the local tectonics and the sedimentary accretionary prism in which the hydrate forms, followed by a description of the geophysical and geological surveys that have been conducted. The surveys included a wide range of seismic surveys such as multichannel, ocean-bottom, high-resolution single channel and very high resolution deep towed surveys. Heat flow, electrical sounding, seafloor compliance, sediment coring, and mapping gas plumes from the seafloor were among the other geophysical studies listed in this paper. The conclusions that have resulted from this work in terms of distribution, concentrations and amounts of hydrate were presented along with a discussion on the process of hydrate formation and dissociation. 96 refs., 3 figs.

The influences of skin visco-elasticity, hydration level and aging on the formation of wrinkles: a comprehensive and objective approach.

Science.gov (United States)

Choi, Jae Woo; Kwon, Soon Hyo; Huh, Chang Hun; Park, Kyoung Chan; Youn, Sang Woong

2013-02-01

Various skin parameters including skin visco-elasticity and hydration level affect the formation of wrinkles. The aim of this study was to investigate the comprehensive and objective relationship between age, skin visco-elasticity, hydration level, and the occurrence of wrinkles using bioengineering equipments for the first time. A total number of 97 healthy women were included in this study. Age, Fitzpatrick skin type, skin mechanical parameters obtained with Cutometer(R0~R9), hydration level measured with Corneometer, as well as wrinkle parameters (SEsm, SEr, SEsc, and SEw) assessed with Visioscan, were analyzed with the Pearson's correlation test. The skin fluidity (R6) increased while the elastic recovery ratio (R7) decreased with the age. The wrinkle parameter (SEw) also increased with the age. The higher skin hysteresis values (R4 and R9) coincided with the higher SEw values. Skin hydration significantly lowered the hysteresis (R9), the wrinkles (SEw), and the depth of wrinkle furrows (R3mr). The elderly have less elastic skin and more wrinkles. Skin hysteresis most closely related with the degree of wrinkles. Drier skin showed more wrinkles and deeper furrows, with wider intervals. On the basis of these objective findings, we propose several skin parameters associated with wrinkles, and hypothesize the mechanism of wrinkle generation. © 2012 John Wiley & Sons A/S.

Geomechanical Performance of Hydrate-Bearing Sediment in Offshore Environments

Energy Technology Data Exchange (ETDEWEB)

Stephen Holditch; Tad Patzek; Jonny Rutqvist; George Moridis; Richard Plumb

2008-03-31

The objective of this multi-year, multi-institutional research project was to develop the knowledge base and quantitative predictive capability for the description of geomechanical performance of hydrate-bearing sediments (hereafter referred to as HBS) in oceanic environments. The focus was on the determination of the envelope of hydrate stability under conditions typical of those related to the construction and operation of offshore platforms. We have developed a robust numerical simulator of hydrate behavior in geologic media by coupling a reservoir model with a commercial geomechanical code. We also investigated the geomechanical behavior of oceanic HBS using pore-scale models (conceptual and mathematical) of fluid flow, stress analysis, and damage propagation. The objective of the UC Berkeley work was to develop a grain-scale model of hydrate-bearing sediments. Hydrate dissociation alters the strength of HBS. In particular, transformation of hydrate clusters into gas and liquid water weakens the skeleton and, simultaneously, reduces the effective stress by increasing the pore pressure. The large-scale objective of the study is evaluation of geomechanical stability of offshore oil and gas production infrastructure. At Lawrence Berkeley National Laboratory (LBNL), we have developed the numerical model TOUGH + Hydrate + FLAC3D to evaluate how the formation and disassociation of hydrates in seafloor sediments affects seafloor stability. Several technical papers were published using results from this model. LBNL also developed laboratory equipment and methods to produce realistic laboratory samples of sediments containing gas hydrates so that mechanical properties could be measured in the laboratory. These properties are required to run TOUGH + Hydrate + FLAC3D to evaluate seafloor stability issues. At Texas A&M University we performed a detailed literature review to determine what gas hydrate formation properties had been measured and reported in the literature. We

Electrical Conductive Mechanism of Gas Hydrate-Bearing Reservoirs in the Permafrost Region of Qilian Mountain

Science.gov (United States)

Peng, C.; Zou, C.; Tang, Y.; Liu, A.; Hu, X.

2017-12-01

In the Qilian Mountain, gas hydrates not only occur in pore spaces of sandstones, but also fill in fractures of mudstones. This leads to the difficulty in identification and evaluation of gas hydrate reservoir from resistivity and velocity logs. Understanding electrical conductive mechanism is the basis for log interpretation. However, the research is insufficient in this area. We have collected well logs from 30 wells in this area. Well logs and rock samples from DK-9, DK-11 and DK-12 wells were used in this study. The experiments including SEM, thin section, NMR, XRD, synthesis of gas hydrate in consolidated rock cores under low temperature and measurement of their resistivity and others were performed for understanding the effects of pore structure, rock composition, temperature and gas hydrate on conductivity. The results show that the porosity of reservoir of pore filling type is less than 10% and its clay mineral content is high. As good conductive passages, fractures can reduce resistivity of water-saturated rock. If fractures in the mudstone are filled by calcite, resistivity increases significantly. The resistivity of water-saturated rock at 2°C is twice of that at 18°C. The gas hydrate formation process in the sandstone was studied by resistivity recorded in real time. In the early stage of gas hydrate formation, the increase of residual water salinity may lead to the decrease of resistivity. In the late stage of gas hydrate formation, the continuity decrease of water leads to continuity increase of resistivity. In summary, fractures, rock composition, temperature and gas hydrate are important factors influencing resistivity of formation. This study is helpful for more accurate evaluation of gas hydrate from resistivity log. Acknowledgment: We acknowledge the financial support of the National Special Program for Gas Hydrate Exploration and Test-production (GZH201400302).

Onset and stability of gas hydrates under permafrost in an environment of surface climatic change : past and future

International Nuclear Information System (INIS)

Majorowicz, J.A.; Osadetz, K.; Safanda, J.

2008-01-01

This paper presented a model designed to simulate permafrost and gas hydrate formation in a changing surface temperature environment in the Beaufort-Mackenzie Basin (BMB). The numerical model simulated surface forcing due to general cooling trends that began in the late Miocene era. This study modelled the onset of permafrost formation and subsequent gas hydrate formation in the changing surface temperature environment for the BMB. Paleoclimatic data were used. The 1-D model was constrained by deep heat flow from well bottom hole temperatures; conductivity; permafrost thickness; and the thickness of the gas hydrates. The model used latent heat effects for the ice-bearing permafrost and hydrate intervals. Surface temperatures for glacial and interglacial histories for the last 14 million years were considered. The model also used a detailed Holocene temperature history as well as a scenario in which atmospheric carbon dioxide (CO 2 ) levels were twice as high as current levels. Two scenarios were considered: (1) the formation of gas hydrates from gas entrapped under geological seals; and (2) the formation of gas hydrates from gas located in free pore spaces simultaneously with permafrost formation. Results of the study showed that gas hydrates may have formed at a depth of 0.9 km only 1 million years ago. Results of the other modelling scenarios suggested that the hydrates formed 6 million years ago, when temperature changes caused the gas hydrate layer to expand both downward and upward. Detailed models of more recent glacial and interglacial histories showed that the gas hydrate zones will persist under the thick body of the BMB permafrost through current interglacial warming as well as in scenarios where atmospheric CO 2 is doubled. 28 refs., 13 figs

Hydrate-based technology for CO2 capture from fossil fuel power plants

International Nuclear Information System (INIS)

Yang, Mingjun; Song, Yongchen; Jiang, Lanlan; Zhao, Yuechao; Ruan, Xuke; Zhang, Yi; Wang, Shanrong

2014-01-01

Graphical abstract: Application of hydrate based technology on carbon dioxide capture and storage (CCS). - Highlights: • Hydrate-based CO 2 –N 2 separation data was obtained for flow in porous media. • Tetrahydrofuran and sodium dodecyl sulphate are used as additives simultaneously. • Solution movement rarely occurs when residual solution saturations are low. • Bothe of pressure and temperature have remarkable impacts on gas compositions. • A suitable operation parameter choice is proposed for hydrate-based CO 2 capture. - Abstract: Hydrate-based CO 2 capture is a promising technology. To obtain fundamental data for a flowing system, we measured the distribution of pore solution to analyse hydrate formation/dissociation and gas separation properties. An orthogonal experiment was carried out to investigate the effects of glass beads, flow rates, pressures and temperatures on it. Magnetic resonance imaging (MRI) images were obtained using a spin echo multi-slice pulse sequence. Hydrate saturations were calculated quantitatively using an MRI mean intensity. The results show that hydrate blockages were frequently present. During the hydrate formation and dissociation process, the movement of the solution occurred in cycles. However, the solution movement rarely occurred for residual solution saturations obtained with a high backpressure. The solution concentrate phenomenon occurred mostly in BZ-04. The highest hydrate saturation was 30.2%, and the lowest was 0.70%. Unlike that in BZ-01, there was no stability present in BZ-02 and BZ-04. The different CO 2 concentrations for the three processes of each cycle verified hydrate formation during the gas flow process. The highest CO 2 concentration was 38.8%, and the lowest one was 11.4%. To obtain high hydrate saturation and good separation effects, the values of 5.00 MPa, 1.0 ml min −1 and 280.00 K were chosen. For the gas flow process, only the pressure had a significant impact on gas composition, and all

The structure of hydrate bearing fine grained marine sediments

Energy Technology Data Exchange (ETDEWEB)

Priest, J.; Kingston, E.; Clayton, C. [Southampton Univ., Highfield (United Kingdom). School of Civil Engineering and the Environment; Schultheiss, P.; Druce, M. [Geotek Ltd., Daventry (United Kingdom)

2008-07-01

This paper discussed the structure of naturally occurring methane gas hydrates in fine-grained sediments from core samples recovered using in situ pressures from the eastern margin of the Indian Ocean. High resolution X-ray computed tomography (CT) images were taken of gas hydrate cores. The hydrate structure was examined and comparisons were made between low resolution X-ray images obtained on the cores prior to sub-sectioning and depressurization procedures. The X-ray images showed the presence of high-angle, sub-parallel veins within the recovered sediments. The scans indicated that the hydrates occurred as fracture filing veins throughout the core. Fracture orientation was predominantly sub-vertical. Thick millimetric hydrate veins were composed of sub-millimetric veins with variations in fracture angle. The analysis indicated that hydrate formation was episodic in nature and subject to changes in the stress regime. Results of the study showed that depressurization and subsequent freezing alter the structure of the sediment even when the gas hydrate has not been altered. A large proportion of the hydrate survived when outside of its stability region. The self-preserving behaviour of the hydrate was attributed to the endothermic nature of gas hydrate dissociation. It was concluded that the accurate physical characterization of gas hydrates can only be conducted when the core section remains under in situ stress conditions. 13 refs., 9 figs.

Supramolecular Organization of Nonstoichiometric Drug Hydrates: Dapsone

Science.gov (United States)

Braun, Doris E.; Griesser, Ulrich J.

2018-01-01

The observed moisture- and temperature dependent transformations of the dapsone (4,4′-diaminodiphenyl sulfone, DDS) 0. 33-hydrate were correlated to its structure and the number and strength of the water-DDS intermolecular interactions. A combination of characterization techniques was used, including thermal analysis (hot-stage microscopy, differential scanning calorimetry and thermogravimetric analysis), gravimetric moisture sorption/desorption studies and variable humidity powder X-ray diffraction, along with computational modeling (crystal structure prediction and pair-wise intermolecular energy calculations). Depending on the relative humidity the hydrate contains between 0 and 0.33 molecules of water per molecule DDS. The crystal structure is retained upon dehydration indicating that DDS hydrate shows a non-stoichiometric (de)hydration behavior. Unexpectedly, the water molecules are not located in structural channels but at isolated-sites of the host framework, which is counterintuitively for a hydrate with non-stoichiometric behavior. The water-DDS interactions were estimated to be weaker than water-host interactions that are commonly observed in stoichiometric hydrates and the lattice energies of the isomorphic dehydration product (hydrate structure without water molecules) and (form III) differ only by ~1 kJ mol−1. The computational generation of hypothetical monohydrates confirms that the hydrate with the unusual DDS:water ratio of 3:1 is more stable than a feasible monohydrate structure. Overall, this study highlights that a deeper understanding of the formation of hydrates with non-stoichiometric behavior requires a multidisciplinary approach including suitable experimental and computational methods providing a firm basis for the development and manufacturing of high quality drug products. PMID:29520359

Amount of gas hydrate estimated from compressional- and shear-wave velocities at the JAPEX/JNOC/GSC Mallik 2L-38 gas hydrate research well

Science.gov (United States)

Lee, M.W.

1999-01-01

The amount of in situ gas hydrate concentrated in the sediment pore space at the JAPEX/JNOC/GSC Mallik 2L-38 gas hydrate research well was estimated by using compressional-wave (P-wave) and shear-wave (S-wave) downhole log measurements. A weighted equation developed for relating the amount of gas hydrate concentrated in the pore space of unconsolidated sediments to the increase of seismic velocities was applied to the acoustic logs with porosities derived from the formation density log. A weight of 1.56 (W=1.56) and the exponent of 1 (n=1) provided consistent estimates of gas hydrate concentration from the S-wave and the P-wave logs. Gas hydrate concentration is as much as 80% in the pore spaces, and the average gas hydrate concentration within the gas-hydrate-bearing section from 897 m to 1110 m (excluding zones where there is no gas hydrate) was calculated at 39.0% when using P-wave data and 37.8% when using S-wave data.

Infrared spectroscopy for monitoring gas hydrates in aqueous solution

Energy Technology Data Exchange (ETDEWEB)

Dobbs, G.T.; Luzinova, Y.; Mizaikoff, B. [Georgia Inst. of Technology, Atlanta, GA (United States). School of Chemistry and Biochemistry; Raichlin, Y.; Katzir, A. [Tel-Aviv Univ., Tel-Aviv (Israel). Shool of Physics and Astronomy

2008-07-01

This paper introduced the first principles for monitoring gas hydrate formation and dissociation in aqueous solution by evaluating state-responsive infrared (IR) absorption features of water with fiberoptic evanescent field spectroscopy. A first order linear functional relationship was also derived according to Lambert Beer's law in order to quantify the percentage gas hydrate within the volume of water probed via the evanescent field. In addition, spectroscopic studies evaluating seafloor sediments collected from a gas hydrate site in the Gulf of Mexico revealed minimal spectral interferences from sediment matrix components. As such, evanescent field sensing strategies were established as a promising perspective for monitoring the dynamics of gas hydrates in oceanic environments. 21 refs., 5 figs.

Kinetics of CO2 and methane hydrate formation : an experimental analysis in the bulk phase

NARCIS (Netherlands)

He, Y.; Rudolph, E.S.J.; Zitha, P.L.J.; Golombok, M.

2011-01-01

Gas resources captured in the form of gas hydrates are by an order of magnitude larger than the resources available from conventional resources. In order to keep the CO2CO2 footprint in the world as small as possible, the idea is to produce methane hydrates and sequestrate CO2CO2 into hydrates in

An effective medium inversion algorithm for gas hydrate quantification and its application to laboratory and borehole measurements of gas hydrate-bearing sediments

Science.gov (United States)

Chand, S.; Minshull, T.A.; Priest, J.A.; Best, A.I.; Clayton, C.R.I.; Waite, W.F.

2006-01-01

The presence of gas hydrate in marine sediments alters their physical properties. In some circumstances, gas hydrate may cement sediment grains together and dramatically increase the seismic P- and S-wave velocities of the composite medium. Hydrate may also form a load-bearing structure within the sediment microstructure, but with different seismic wave attenuation characteristics, changing the attenuation behaviour of the composite. Here we introduce an inversion algorithm based on effective medium modelling to infer hydrate saturations from velocity and attenuation measurements on hydrate-bearing sediments. The velocity increase is modelled as extra binding developed by gas hydrate that strengthens the sediment microstructure. The attenuation increase is modelled through a difference in fluid flow properties caused by different permeabilities in the sediment and hydrate microstructures. We relate velocity and attenuation increases in hydrate-bearing sediments to their hydrate content, using an effective medium inversion algorithm based on the self-consistent approximation (SCA), differential effective medium (DEM) theory, and Biot and squirt flow mechanisms of fluid flow. The inversion algorithm is able to convert observations in compressional and shear wave velocities and attenuations to hydrate saturation in the sediment pore space. We applied our algorithm to a data set from the Mallik 2L–38 well, Mackenzie delta, Canada, and to data from laboratory measurements on gas-rich and water-saturated sand samples. Predictions using our algorithm match the borehole data and water-saturated laboratory data if the proportion of hydrate contributing to the load-bearing structure increases with hydrate saturation. The predictions match the gas-rich laboratory data if that proportion decreases with hydrate saturation. We attribute this difference to differences in hydrate formation mechanisms between the two environments.

Nonequilibrium Thermodynamics of Hydrate Growth on a Gas-Liquid Interface

Science.gov (United States)

Fu, Xiaojing; Cueto-Felgueroso, Luis; Juanes, Ruben

2018-04-01

We develop a continuum-scale phase-field model to study gas-liquid-hydrate systems far from thermodynamic equilibrium. We design a Gibbs free energy functional for methane-water mixtures that recovers the isobaric temperature-composition phase diagram under thermodynamic equilibrium conditions. The proposed free energy is incorporated into a phase-field model to study the dynamics of hydrate formation on a gas-liquid interface. We elucidate the role of initial aqueous concentration in determining the direction of hydrate growth at the interface, in agreement with experimental observations. Our model also reveals two stages of hydrate growth at an interface—controlled by a crossover in how methane is supplied from the gas and liquid phases—which could explain the persistence of gas conduits in hydrate-bearing sediments and other nonequilibrium phenomena commonly observed in natural methane hydrate systems.

Gas hydrate phase equilibria measurement techniques and phase rule considerations

International Nuclear Information System (INIS)

Beltran, Juan G.; Bruusgaard, Hallvard; Servio, Phillip

2012-01-01

Highlights: → Inconsistencies found in hydrate literature. → Clarification to the number of variables needed to satisfy and justify equilibrium data. → Application of phase rule to mixed hydrate systems. → Thermodynamically consistent format to present data. - Abstract: A brief review of the Gibbs phase rule for non-reacting systems and its correct application to clathrate hydrates is presented. Clarification is provided for a common mistake found in hydrate phase-equilibria literature, whereby initial compositions are used as intensive variables to satisfy the Gibbs phase rule instead of the equilibrium values. The system of (methane + carbon dioxide + water) under (hydrate + liquid + vapor) equilibrium is used as a case study to illustrate key points and suggestions to improve experimental techniques are proposed.

Grain-scale imaging and compositional characterization of cryo-preserved India NGHP 01 gas-hydrate-bearing cores

Science.gov (United States)

Stern, Laura A.; Lorenson, T.D.

2014-01-01

We report on grain-scale characteristics and gas analyses of gas-hydrate-bearing samples retrieved by NGHP Expedition 01 as part of a large-scale effort to study gas hydrate occurrences off the eastern-Indian Peninsula and along the Andaman convergent margin. Using cryogenic scanning electron microscopy, X-ray spectroscopy, and gas chromatography, we investigated gas hydrate grain morphology and distribution within sediments, gas hydrate composition, and methane isotopic composition of samples from Krishna–Godavari (KG) basin and Andaman back-arc basin borehole sites from depths ranging 26 to 525 mbsf. Gas hydrate in KG-basin samples commonly occurs as nodules or coarse veins with typical hydrate grain size of 30–80 μm, as small pods or thin veins 50 to several hundred microns in width, or disseminated in sediment. Nodules contain abundant and commonly isolated macropores, in some places suggesting the original presence of a free gas phase. Gas hydrate also occurs as faceted crystals lining the interiors of cavities. While these vug-like structures constitute a relatively minor mode of gas hydrate occurrence, they were observed in near-seafloor KG-basin samples as well as in those of deeper origin (>100 mbsf) and may be original formation features. Other samples exhibit gas hydrate grains rimmed by NaCl-bearing material, presumably produced by salt exclusion during original hydrate formation. Well-preserved microfossil and other biogenic detritus are also found within several samples, most abundantly in Andaman core material where gas hydrate fills microfossil crevices. The range of gas hydrate modes of occurrence observed in the full suite of samples suggests a range of formation processes were involved, as influenced by local in situconditions. The hydrate-forming gas is predominantly methane with trace quantities of higher molecular weight hydrocarbons of primarily microbial origin. The composition indicates the gas hydrate is Structure I.

Guideline adherence for identification and hydration of high-risk hospital patients for contrast-induced nephropathy.

NARCIS (Netherlands)

Schilp, J.; Blok, C. de; Langelaan, M.; Spreeuwenberg, P.; Wagner, C.

2014-01-01

Background: Contrast-induced nephropathy (CIN) is a common cause of acute renal failure in hospital patients. To prevent CIN, identification and hydration of high-risk patients is important. Prevention of CIN by hydration of high-risk patients was one of the themes to be implemented in the Dutch

Guideline adherence for identification and hydration of high-risk hospital patients for contrast-induced nephropathy

NARCIS (Netherlands)

Schilp, J.; de Blok, C.; Langelaan, M.; Spreeuwenberg, P.; Wagner, C.

2014-01-01

Background: Contrast-induced nephropathy (CIN) is a common cause of acute renal failure in hospital patients. To prevent CIN, identification and hydration of high-risk patients is important. Prevention of CIN by hydration of high-risk patients was one of the themes to be implemented in the Dutch

Influence of Physical Activity and Ambient Temperature on Hydration: The European Hydration Research Study (EHRS

Directory of Open Access Journals (Sweden)

Ricardo Mora-Rodriguez

2016-04-01

Full Text Available This study explored the effects of physical activity (PA and ambient temperature on water turnover and hydration status. Five-hundred seventy three healthy men and women (aged 20–60 years from Spain, Greece and Germany self-reported PA, registered all food and beverage intake, and collected 24-h urine during seven consecutive days. Fasting blood samples were collected at the onset and end of the study. Food moisture was assessed using nutritional software to account for all water intake which was subtracted from daily urine volume to allow calculation of non-renal water loss (i.e., mostly sweating. Hydration status was assessed by urine and blood osmolality. A negative association was seen between ambient temperature and PA (r = −0.277; p < 0.001. Lower PA with high temperatures did not prevent increased non-renal water losses (i.e., sweating and elevated urine and blood osmolality (r = 0.218 to 0.163 all p < 0.001. When summer and winter data were combined PA was negatively associated with urine osmolality (r = −0.153; p = 0.001. Our data suggest that environmental heat acts to reduce voluntary PA but this is not sufficient to prevent moderate dehydration (increased osmolality. On the other hand, increased PA is associated with improved hydration status (i.e., lower urine and blood osmolality.

Reconsideration on Hydration of Sodium Ion: From Micro-Hydration to Bulk Hydration

Science.gov (United States)

Yongquan, Zhou; Chunhui, Fang; Yan, Fang; Fayan, Zhu; Haiwen, Ge; Hongyan, Liu

2017-12-01

Micro hydration structures of the sodium ion, [Na(H2O) n ]+, n = 1-12, were probed by density functional theory (DFT) at B3LYP/aug-cc-pVDZ level in both gaseous and aqueous phase. The predicted equilibrium sodium-oxygen distance of 0.240 nm at the present level of theory. The four-, five- and six-coordinated cluster can transform from each other at the ambient condition. The analysis of the successive water binding energy and natural charge population (NBO) on Na+ clearly shows that the influence of Na+ on the surrounding water molecules goes beyond the first hydration shell with the hydration number of 6. The Car-Parrinello molecular dynamic simulation shows that only the first hydration sphere can be found, and the hydration number of Na+ is 5.2 and the hydration distance ( r Na-O) is 0.235 nm. All our simulations mentioned in the present paper show an excellent agreement with the diffraction result from X-ray scattering study.

Putting the Deep Biosphere and Gas Hydrates on the Map

Science.gov (United States)

Sikorski, Janelle J.; Briggs, Brandon R.

2016-01-01

Microbial processes in the deep biosphere affect marine sediments, such as the formation of gas hydrate deposits. Gas hydrate deposits offer a large source of natural gas with the potential to augment energy reserves and affect climate and seafloor stability. Despite the significant interdependence between life and geology in the ocean, coverage…

Magnetic resonance microscopy for assessment of morphological changes in hydrating hydroxypropylmethylcellulose matrix tablets in situ-is it possible to detect phenomena related to drug dissolution within the hydrated matrices?

Science.gov (United States)

Kulinowski, Piotr; Młynarczyk, Anna; Jasiński, Krzysztof; Talik, Przemysław; Gruwel, Marco L H; Tomanek, Bogusław; Węglarz, Władysław P; Dorożyński, Przemysław

2014-09-01

So far, the hydrated part of the HPMC matrix has commonly been denoted as a "gel" or "pseudogel" layer. No MRI-based results have been published regarding observation of internal phenomena related to drug dissolution inside swelling polymeric matrices during hydration. The purpose of the study was to detect such phenomena. Multiparametric, spatially and temporally resolved T2 MR relaxometry, in situ, was applied to study formation of the hydration progress in HPMC matrix tablets loaded with L-dopa and ketoprofen using a 11.7 T MRI system. Two spin-echo based pulse sequences were used, one of them specifically designed to study short T2 signals. Two components in the T2 decay envelope were estimated and spatial distributions of their parameters, i.e. amplitudes and T2 values, were obtained. Based on the data, different region formation patterns (i.e. multilayer structure) were registered depending on drug presence and solubility. Inside the matrix with incorporated sparingly soluble drug a specific layer formation due to drug dissolution was detected, whereas a matrix with very slightly soluble drug does not form distinct external "gel-like" layer. We have introduced a new paradigm in the characterization of hydrating matrices using (1)H MRI methods. It reflects molecular mobility and concentration of water inside the hydrated matrix. For the first time, drug dissolution related phenomena, i.e. particular front and region formation, were observed by MRI methods.

Dynamics of Permafrost Associated Methane Hydrate in Response to Climate Change

Science.gov (United States)

You, K.; Flemings, P. B.

2014-12-01

The formation and melting of methane hydrate and ice are intertwined in permafrost regions. A shortage of methane supply leads to formation of hydrate only at depth, below the base of permafrost. We consider a system with the ground surface initially at 0 oC with neither ice nor hydrate present. We abruptly decrease the temperature from 0 to -10 oC to simulate the effect of marine regression/ global cooling. A low methane supply rate of 0.005 kg m-2 yr-1 from depth leads to distinct ice and hydrate layers: a 100 m continuous hydrate layer is present beneath 850 m at 80 k.y.. However, a high methane supply rate of 0.1 kg m-2 yr-1 leads to 50 m ice-bonded methane hydrate at the base of permafrost, and the hydrate layer distributes between the depth of 350 and 700 m at 80 k.y.. We apply our model to illuminate future melting of hydrate at Mallik, a known Arctic hydrate accumulation. We assume a 600 m thick ice saturated (average 90%) layer extending downward from the ground surface. We increase the surface temperature linearly from -6 to 0 oC for 300 yr and then keep the surface temperature at 0 oC to reflect future climate warming caused by doubling of CO2. Hydrate melting is initiated at the base of the hydrate layer after 15 k.y.. Methane gas starts to vent to the atmosphere at 38 k.y. with an average flux of ~ 0.35 g m-2 yr-1. If the 600 m thick average ice saturation is decreased to half (45%) (or to zero), methane gas starts to vent to the atmosphere at 29 k.y. (or at 20 k.y.) with the same average flux. These results are found by a newly-developed fully-coupled multiphase multicomponent fluid flow and heat transport model. Our thermodynamic equilibrium-based model emphasizes the role of salinity in both ice and hydrate dynamics.

Experimental Investigation into the Combustion Characteristics of Propane Hydrates in Porous Media

Directory of Open Access Journals (Sweden)

Xiang-Ru Chen

2015-02-01

Full Text Available The combustion characteristics of both pure propane hydrates and the mixtures of hydrates and quartz sands were investigated by combustion experiments. The flame propagation, flame appearance, burning time and temperature in different hydrate layers were studied. For pure propane hydrate combustion, the initial flame falls in the “premixed” category. The flame propagates very rapidly, mainly as a result of burnt gas expansion. The flame finally self-extinguishes with some proportion of hydrates remaining unburned. For the hydrate-sand mixture combustion, the flame takes the form of many tiny discontinuous flames appearing and disappearing at different locations. The burn lasts for a much shorter amount of time than pure hydrate combustion. High porosity and high hydrate saturation is beneficial to the combustion. The hydrate combustion is the combustion of propane gas resulting from the dissociation of the hydrates. In both combustion test scenarios, the hydrate-dissociated water plays a key role in the fire extinction, because it is the main resistance that restrains the heat transfer from the flame to the hydrates and that prevents the hydrate-dissociated gas from releasing into the combustion zone.

Effect of temperature dependence of the Langmuir constant molecular pair potentials on gas hydrates formation mechanism

Energy Technology Data Exchange (ETDEWEB)

Mokhtari, B.; Enayati, M. [Iranian Offshore Oil Co., Tehran (Iran, Islamic Republic of); Heidaryan, E. [Islamic Azad Univ., Tehran (Iran, Islamic Republic of). Masjidosolayman Branch

2008-07-01

Theoretical methods show that crystalline hydrates can form from single-phase systems consisting of both vapor water with gaseous hydrate former and liquid water with dissolved hydrate former. Two phase systems consist of both liquid water with gaseous hydrate former and with liquid hydrate former on the surface. This paper presented a Langmuir constant related model for the prediction of equilibrium pressures and cage occupancies of pure component hydrates. Intermolecular potentials were fit to quantum mechanical energies to obtain the Langmuir constants, which differed from the procedure utilized with the vdWP model. The paper described the experimental method and model calculations. This included the Fugacity model and Van der Waals and Platteeuw model. The paper also discussed pair potential of non-spherical molecules, including the multicentre (site-site) potential; Gaussian overlap potential; Lennard-Jones potential; and Kihara generalized pair potential. It was concluded that fraction of occupied cavities is a function of pair potentials between hard core and empty hydrate lattice. These pair potentials could be calculated from some model as Kihara cell potential, Gaussian potential, Lennard-Jones potential and multicentre pair potential. 49 refs., 3 figs.

Supramolecular Organization of Nonstoichiometric Drug Hydrates: Dapsone

Directory of Open Access Journals (Sweden)

Doris E. Braun

2018-02-01

Full Text Available The observed moisture- and temperature dependent transformations of the dapsone (4,4′-diaminodiphenyl sulfone, DDS 0. 33-hydrate were correlated to its structure and the number and strength of the water-DDS intermolecular interactions. A combination of characterization techniques was used, including thermal analysis (hot-stage microscopy, differential scanning calorimetry and thermogravimetric analysis, gravimetric moisture sorption/desorption studies and variable humidity powder X-ray diffraction, along with computational modeling (crystal structure prediction and pair-wise intermolecular energy calculations. Depending on the relative humidity the hydrate contains between 0 and 0.33 molecules of water per molecule DDS. The crystal structure is retained upon dehydration indicating that DDS hydrate shows a non-stoichiometric (dehydration behavior. Unexpectedly, the water molecules are not located in structural channels but at isolated-sites of the host framework, which is counterintuitively for a hydrate with non-stoichiometric behavior. The water-DDS interactions were estimated to be weaker than water-host interactions that are commonly observed in stoichiometric hydrates and the lattice energies of the isomorphic dehydration product (hydrate structure without water molecules and (form III differ only by ~1 kJ mol−1. The computational generation of hypothetical monohydrates confirms that the hydrate with the unusual DDS:water ratio of 3:1 is more stable than a feasible monohydrate structure. Overall, this study highlights that a deeper understanding of the formation of hydrates with non-stoichiometric behavior requires a multidisciplinary approach including suitable experimental and computational methods providing a firm basis for the development and manufacturing of high quality drug products.

Preliminary Experimental Examination Of Controls On Methane Expulsion During Melting Of Natural Gas Hydrate Systems

Science.gov (United States)

Kneafsey, T. J.; Flemings, P. B.; Bryant, S. L.; You, K.; Polito, P. J.

2013-12-01

Global climate change will cause warming of the oceans and land. This will affect the occurrence, behavior, and location of subseafloor and subterranean methane hydrate deposits. We suggest that in many natural systems local salinity, elevated by hydrate formation or freshened by hydrate dissociation, may control gas transport through the hydrate stability zone. We are performing experiments and modeling the experiments to explore this behavior for different warming scenarios. Initially, we are exploring hydrate association/dissociation in saline systems with constant water mass. We compare experiments run with saline (3.5 wt. %) water vs. distilled water in a sand mixture at an initial water saturation of ~0.5. We increase the pore fluid (methane) pressure to 1050 psig. We then stepwise cool the sample into the hydrate stability field (~3 degrees C), allowing methane gas to enter as hydrate forms. We measure resistivity and the mass of methane consumed. We are currently running these experiments and we predict our results from equilibrium thermodynamics. In the fresh water case, the modeled final hydrate saturation is 63% and all water is consumed. In the saline case, the modeled final hydrate saturation is 47%, the salinity is 12.4 wt. %, and final water saturation is 13%. The fresh water system is water-limited: all the water is converted to hydrate. In the saline system, pore water salinity is elevated and salt is excluded from the hydrate structure during hydrate formation until the salinity drives the system to three phase equilibrium (liquid, gas, hydrate) and no further hydrate forms. In our laboratory we can impose temperature gradients within the column, and we will use this to investigate equilibrium conditions in large samples subjected to temperature gradients and changing temperature. In these tests, we will quantify the hydrate saturation and salinity over our meter-long sample using spatially distributed temperature sensors, spatially distributed

Remagnetization and Cementation of Unconsolidated Sediments in the Mallik 5L-38 Well (Canadian Arctic) by Solute Exclusion During Gas Hydrate Formation

Science.gov (United States)

Hamilton, T. S.; Enkin, R. J.; Esteban, L.

2007-05-01

mineralogy. Silt samples are significantly stronger than sand samples in saturation magnetization and magnetic susceptibility. The silt samples have single-domain to pseudo-single domain coercivity ratios whereas the gas hydrate bearing sands have a more multi-domain nature. Sands with current gas hydrate concentrations > 80% have less magnetic material and single domain characteristics. The source of the greigite, carbonates, and other diagenetic minerals was apparently concentrated solutes excluded from formation waters by the freezing and formation of the water dominated gas hydrate. The hydrates served as a cementing agent for the unconsolidated sediments, allowing them to fracture. Some layers have been so inflated by the introduction carbonate and sulfide cements that they resemble hydrothermal tufa and skarns with floating sand grains. In the silts, the magnetic properties reflect the mixture of primary detrital magnetite and diagenetic greigite in various grain sizes and concentrations. At Mallik, the magnetic properties are sensitive to the diagenetic mineralogy and redox state associated with the transport of methane and pore fluids and the creation of gas hydrates. Hypersaline brines, produced by solute exclusion from pore waters, fractured and inflated less permeable sediments and forced rapid disequilibrium growth of greigite without dissolving primary detrital magnetite grains.

Thermodynamic and Process Modelling of Gas Hydrate Systems in CO2 Capture Processes

DEFF Research Database (Denmark)

Herslund, Peter Jørgensen

A novel gas separation technique based on gas hydrate formation (solid precipitation) is investigated by means of thermodynamic modeling and experimental investigations. This process has previously been proposed for application in post-combustion carbon dioxide capture from power station flue gases...... formation may be performed at pressures of approximately 20 MPa and temperatures below 280 K. Thermodynamic promoters are needed, to reduce the pressure requirement of the process, thereby making it competitive to existing capture technologies. A literature study is presented focusing mainly...... on thermodynamic gas hydrate promotion by hydrate formers stabilising the classical gas clathrate hydrate structures (sI, sII and sH) at low to moderate pressures. Much literature is available on this subject. Both experimental and theoretical studies presented in the literature have pointed out cyclopentane...

Pre-combustion capture of carbon dioxide in a fixed bed reactor using the clathrate hydrate process

International Nuclear Information System (INIS)

Babu, Ponnivalavan; Kumar, Rajnish; Linga, Praveen

2013-01-01

Hydrate based gas separation (HBGS) process with silica sand and silica gel as contact medium was employed to capture CO 2 from fuel gas mixture. Gas uptake measurement at three different pressures (7.5, 8.5 and 9.0 MPa) and 274.15 K were conducted for hydrate formation kinetics and overall conversion of water to hydrate, rate of hydrate formation were determined. Water conversion of up to 36% was achieved with silica sand bed compared to 13% conversion in the silica gel bed. Effect of driving force on the rate of hydrate formation and gas consumption was significant in silica sand bed whereas it was found to be insignificant in silica gel bed. Hydrate dissociation experiments by thermal stimulation (at constant pressure) alone and a combination of depressurization and thermal stimulation were carried out for complete recovery of the hydrated gas. A driving force of 23 K was found to be sufficient to recover all the hydrated gas within 1 h. This study indicates that silica sand can be an effective porous media for separation of CO 2 from fuel gas when compared to silica gel. - Highlights: ► The clathrate process for pre-combustion capture of carbon dioxide in a novel fixed bed reactor is presented. ► Performance of two contact media (silica gel and silica sand) was investigated. ► Water to hydrate conversion was higher in a silica sand column. ► A pressure reduction and thermal stimulation approach is presented for a complete recovery of the hydrated gas

Experimental Equipment Validation for Methane (CH4) and Carbon Dioxide (CO2) Hydrates

Science.gov (United States)

Saad Khan, Muhammad; Yaqub, Sana; Manner, Naathiya; Ani Karthwathi, Nur; Qasim, Ali; Mellon, Nurhayati Binti; Lal, Bhajan

2018-04-01

Clathrate hydrates are eminent structures regard as a threat to the gas and oil industry in light of their irritating propensity to subsea pipelines. For natural gas transmission and processing, the formation of gas hydrate is one of the main flow assurance delinquent has led researchers toward conducting fresh and meticulous studies on various aspects of gas hydrates. This paper highlighted the thermodynamic analysis on pure CH4 and CO2 gas hydrates on the custom fabricated equipment (Sapphire cell hydrate reactor) for experimental validation. CO2 gas hydrate formed at lower pressure (41 bar) as compared to CH4 gas hydrate (70 bar) while comparison of thermodynamic properties between CH4 and CO2 also presented in this study. This preliminary study could provide pathways for the quest of potent hydrate inhibitors.

Prediction of Gas Hydrate Formation Conditions in Aqueous Solutions of Single and Mixed Electrolytes

DEFF Research Database (Denmark)

Zuo, You-Xiang; Stenby, Erling Halfdan

1997-01-01

In this paper, the extended Patel-Teja equation of state was modified to describe non-ideality of the liquid phase containing water and electrolytes accurately. The modified Patel-Teja equation of state (MPT EOS) was utilized to develop a predictive method for gas hydrate equilibria. The new method...... employs the Barkan and Sheinin hydrate model for the description of the hydrate phase, the original Patel-Teja equation of state for the vapor phase fugacities, and the MPT EOS (instead of the activity coefficient model) for the activity of water in the aqueous phase. The new method has succesfully...

Vertical seismic profile data from well Mallik 2L-38 for gas hydrate studies

Energy Technology Data Exchange (ETDEWEB)

Mi, Y [Calgary Univ., AB (Canada); Walia, R [Victoria Univ., BC (Canada); Hyndman, R D; Sakai, A

1999-01-01

A gas hydrate research well was drilled in the Canadian Arctic to determine gas hydrates in a permafrost setting in a collaborative research project between the Japan National Oil Corp., and the Geological Survey of Canada with the participation of other agencies. The multidisciplinary study included an electromagnetic survey, permafrost and gas hydrate coring, and comprehensive downhole geophysical logging and measurement. Laboratory studies on recovered cores and cuttings included sedimentology, physical properties, geochemistry, and reservoir characteristics of the Mallik gas accumulation. As part of the field program, a vertical seismic profiling survey was conducted at zero and offset source positions with 3 component receiver tools and horizontal and vertical vibration sources. A special effort was made to record shear wave data, and results from this work were combined with down hole logs and regional surface seismic data. The data will be used also to determine the effect of gas hydrates on formation velocities and to measure gas hydrate concentrations as a function of depth in the formation penetrated by the well. Certain conclusions followed from the initial VSP analysis. 1) Zero offset vertical vibration Z component and horizontal X component data give reliable velocity estimation within the gas hydrate formation zone, and P wave velocities from offset data indicate excellent consistency with that from zero offset data and with the sonic log. 2) The VSP data permitted reliable identification of gas hydrate bearing zones. 4 refs.

Numerical simulation studies of gas production scenarios from hydrate accumulations at the Mallik Site, McKenzie Delta, Canada

International Nuclear Information System (INIS)

Moridis, George J.; Collett, Timothy S.; Dallimore, Scott R.; Satoh, Tohru; Hancock, Stephen; Weatherill, Brian

2002-01-01

The Mallik site represents an onshore permafrost-associated gas hydrate accumulation in the Mackenzie Delta, Northwest Territories, Canada. An 1150 m deep gas hydrate research well was drilled at the site in 1998. The objective of this study is the analysis of various gas production scenarios from several gas-hydrate-bearing zones at the Mallik site. The TOUGH2 general-purpose simulator with the EOSHYDR2 module were used for the analysis. EOSHYDR2 is designed to model the non-isothermal CH(sub 4) (methane) release, phase behavior and flow under conditions typical of methane-hydrate deposits by solving the coupled equations of mass and heat balance, and can describe any combination of gas hydrate dissociation mechanisms. Numerical simulations indicated that significant gas hydrate production at the Mallik site was possible by drawing down the pressure on a thin free-gas zone at the base of the hydrate stability field. Gas hydrate zones with underlying aquifers yielded significant gas production entirely from dissociated gas hydrate, but large amounts of produced water. Lithologically isolated gas-hydrate-bearing reservoirs with no underlying free gas or water zones, and gas-hydrate saturations of at least 50% were also studied. In these cases, it was assumed that thermal stimulation by circulating hot water in the well was the method used to induce dissociation. Sensitivity studies indicated that the methane release from the hydrate accumulations increases with gas-hydrate saturation, the initial formation temperature, the temperature of the circulating water in the well, and the formation thermal conductivity. Methane production appears to be less sensitive to the rock and hydrate specific heat and permeability of the formation

Thermodynamic inhibitor performance extender that, effectively and economically prevent hydrate formation in the oil field production systems

Energy Technology Data Exchange (ETDEWEB)

Allenson, Stephen; Johnston, Angela [Nalco Energy Services, Sugar Land, TX (United States)

2008-07-01

This paper presents the development of a new additive that was developed to improve the effectiveness of the treatment two to four fold when added to the thermodynamic hydrate inhibitor (THI). Consequently, the THI/additive treatment can now enable the system to handle two to four times the amount of water production or can allow treatment of the same amount of water at half to quarter the dosage of THI. This new additive extends the performance of the THI and allows for a significant increase in production or a significant drop in the amount of THI usage with a corresponding drop in cost. This paper will further discuss the overall process of THI enhancement and will present several case studies where the enhanced THI has been successfully applied. (author)

Crack formation and prevention in colloidal drops

Science.gov (United States)

Kim, Jin Young; Cho, Kun; Ryu, Seul-A.; Kim, So Youn; Weon, Byung Mook

2015-08-01

Crack formation is a frequent result of residual stress release from colloidal films made by the evaporation of colloidal droplets containing nanoparticles. Crack prevention is a significant task in industrial applications such as painting and inkjet printing with colloidal nanoparticles. Here, we illustrate how colloidal drops evaporate and how crack generation is dependent on the particle size and initial volume fraction, through direct visualization of the individual colloids with confocal laser microscopy. To prevent crack formation, we suggest use of a versatile method to control the colloid-polymer interactions by mixing a nonadsorbing polymer with the colloidal suspension, which is known to drive gelation of the particles with short-range attraction. Gelation-driven crack prevention is a feasible and simple method to obtain crack-free, uniform coatings through drying-mediated assembly of colloidal nanoparticles.

Hydrate-CASM for modeling Methane Hydrate-Bearing Sediments

Science.gov (United States)

De La Fuente Ruiz, M.; Vaunat, J.; Marin Moreno, H.

2017-12-01

A clear understanding of the geomechanical behavior of methane hydrate-bearing sediments (MHBS) is crucial to assess the stability of the seafloor and submarine infrastructures to human and natural loading changes. Here we present the Hydrate-CASM, a new elastoplastic constitutive model to predict the geomechanical behavior of MHBS. Our model employs the critical state model CASM (Clay and Sand Model) because of its flexibility in describing the shape of the yield surface and its proven ability to predict the mechanical behavior of sands, the most commercially viable hydrate reservoirs. The model considers MHBS as a deformable elastoplastic continuum, and hydrate-related changes in the stress-strain behavior are predicted by a densification mechanism. The densification attributes the mechanical contribution of hydrate to; a reduction of the available void ratio; a decrease of the swelling line slope; and an increase of the volumetric yield stress. It is described by experimentally derived physical parameters except from the swelling slope coefficient that requires empirical calibration. The Hydrate-CASM is validated against published triaxial laboratory tests performed at different confinement stresses, hydrate saturations, and hydrate morphologies. During the validation, we focused on capturing the mechanical behavior of the host sediment and consider perturbations of the sediment's mechanical properties that could result from the sample preparation. Our model successfully captures the experimentally observed influence of hydrate saturation in the magnitude and trend of the stiffness, shear strength, and dilatancy of MHBS. Hence, we propose that hydrate-related densification changes might be a major factor controlling the geomechanical response of MHBS.

Extensin network formation in Vitis vinifera callus cells is an essential and causal event in rapid and H2O2-induced reduction in primary cell wall hydration

Science.gov (United States)

2011-01-01

Background Extensin deposition is considered important for the correct assembly and biophysical properties of primary cell walls, with consequences to plant resistance to pathogens, tissue morphology, cell adhesion and extension growth. However, evidence for a direct and causal role for the extensin network formation in changes to cell wall properties has been lacking. Results Hydrogen peroxide treatment of grapevine (Vitis vinifera cv. Touriga) callus cell walls was seen to induce a marked reduction in their hydration and thickness. An analysis of matrix proteins demonstrated this occurs with the insolubilisation of an abundant protein, GvP1, which displays a primary structure and post-translational modifications typical of dicotyledon extensins. The hydration of callus cell walls free from saline-soluble proteins did not change in response to H2O2, but fully regained this capacity after addition of extensin-rich saline extracts. To assay the specific contribution of GvP1 cross-linking and other wall matrix proteins to the reduction in hydration, GvP1 levels in cell walls were manipulated in vitro by binding selected fractions of extracellular proteins and their effect on wall hydration during H2O2 incubation assayed. Conclusions This approach allowed us to conclude that a peroxidase-mediated formation of a covalently linked network of GvP1 is essential and causal in the reduction of grapevine callus wall hydration in response to H2O2. Importantly, this approach also indicated that extensin network effects on hydration was only partially irreversible and remained sensitive to changes in matrix charge. We discuss this mechanism and the importance of these changes to primary wall properties in the light of extensin distribution in dicotyledons. PMID:21672244

The effects of ice on methane hydrate nucleation: a microcanonical molecular dynamics study.

Science.gov (United States)

Zhang, Zhengcai; Guo, Guang-Jun

2017-07-26

Although ice powders are widely used in gas hydrate formation experiments, the effects of ice on hydrate nucleation and what happens in the quasi-liquid layer of ice are still not well understood. Here, we used high-precision constant energy molecular dynamics simulations to study methane hydrate nucleation from vapor-liquid mixtures exposed to the basal, prismatic, and secondary prismatic planes of hexagonal ice (ice Ih). Although no significant difference is observed in hydrate nucleation processes for these different crystal planes, it is found, more interestingly, that methane hydrate can nucleate either on the ice surface heterogeneously or in the bulk solution phase homogeneously. Several factors are mentioned to be able to promote the heterogeneous nucleation of hydrates, including the adsorption of methane molecules at the solid-liquid interface, hydrogen bonding between hydrate cages and the ice structure, the stronger ability of ice to transfer heat than that of the aqueous solution, and the higher occurrence probability of hydrate cages in the vicinity of the ice surface than in the bulk solution. Meanwhile, however, the other factors including the hydrophilicity of ice and the ice lattice mismatch with clathrate hydrates can inhibit heterogeneous nucleation on the ice surface and virtually promote homogeneous nucleation in the bulk solution. Certainly, the efficiency of ice as a promoter and as an inhibitor for heterogeneous nucleation is different. We estimate that the former is larger than the latter under the working conditions. Additionally, utilizing the benefit of ice to absorb heat, the NVE simulation of hydrate formation with ice can mimic the phenomenon of ice shrinking during the heterogeneous nucleation of hydrates and lower the overly large temperature increase during homogeneous nucleation. These results are helpful in understanding the nucleation mechanism of methane hydrate in the presence of ice.

Constraining gas hydrate occurrence in the northern Gulf of Mexico continental slope : fine scale analysis of grain-size in hydrate-bearing sediments

Energy Technology Data Exchange (ETDEWEB)

Hangsterfer, A.; Driscoll, N.; Kastner, M. [Scripps Inst. of Oceanography, La Jolla, CA (United States). Geosciences Research Division

2008-07-01

Methane hydrates can form within the gas hydrate stability zone (GHSZ) in sea beds. The Gulf of Mexico (GOM) contains an underlying petroleum system and deeply buried, yet dynamic salt deposits. Salt tectonics and fluid expulsion upward through the sediment column result in the formation of fractures, through which high salinity brines migrate into the GHSZ, destabilizing gas hydrates. Thermogenic and biogenic hydrocarbons also migrate to the seafloor along the GOMs northern slope, originating from the thermal and biogenic degradation of organic matter. Gas hydrate occurrence can be controlled by either primary permeability, forming in coarse-grained sediment layers, or by secondary permeability, forming in areas where hydrofracture and faulting generate conduits through which hydrocarbon-saturated fluids flow. This paper presented a study that attempted to determine the relationship between grain-size, permeability, and gas hydrate distribution. Grain-size analyses were performed on cores taken from Keathley Canyon and Atwater Valley in the GOM, on sections of cores that both contained and lacked gas hydrate. Using thermal anomalies as proxies for the occurrence of methane hydrate within the cores, samples of sediment were taken and the grain-size distributions were measured to see if there was a correlation between gas hydrate distribution and grain-size. The paper described the methods, including determination of hydrate occurrence and core analysis. It was concluded that gas hydrate occurrence in Keathley Canyon and Atwater Valley was constrained by secondary permeability and was structurally controlled by hydrofractures and faulting that acted as conduits through which methane-rich fluids flowed. 11 refs., 2 tabs., 5 figs.

Lithological controls on gas hydrate saturation: Insights from signal classification of NMR downhole data

Science.gov (United States)

Bauer, Klaus; Kulenkampff, Johannes; Henninges, Jan; Spangenberg, Erik

2016-04-01

Nuclear magnetic resonance (NMR) downhole data are analyzed with a new strategy to study gas hydrate-bearing sediments in the Mackenzie Delta (NW Canada). NMR logging is a powerful tool to study geological reservoir formations. The measurements are based on interactions between the magnetic moments of protons in geological formation water and an external magnetic field. Inversion of the measured raw data provides so-called transverse relaxation time (T2) distribution curves or spectra. Different parts of the T2 curve are related with distinct pore radii and corresponding fluid components. A common practice in the analysis of T2 distribution curves is to extract single-valued parameters such as apparent total porosity. Moreover, the derived total NMR apparent porosity and the gamma-gamma density log apparent porosity can be combined to estimate gas hydrate saturation in hydrate-bearing sediments. To avoid potential loss of information, in our new approach we analyze the entire T2 distribution curves as quasi-continuous signals to characterize the rock formation. The approach is applied to NMR data measured in gas hydrate research well Mallik 5L-38. We use self-organizing maps, a neural network clustering technique, to subdivide the data set of NMR T2 distribution curves into classes with a similar and distinctive signal shape. The method includes (1) preparation of data vectors, (2) unsupervised learning, (3) cluster definition, and (4) classification and depth mapping of all NMR signals. Each signal class thus represents a specific pore size distribution which can be interpreted in terms of distinct lithologies and reservoir types. A key step in the interpretation strategy is to reconcile the NMR classes with other log data not considered in the clustering analysis, such as gamma ray, photo-electric factor, hydrate saturation, and other logs. Our results defined six main lithologies within the target zone. Gas hydrate layers were recognized by their low signal

Dissociation heat of mixed-gas hydrate composed of methane and ethane

Energy Technology Data Exchange (ETDEWEB)

Hachikubo, A.; Nakagawa, R.; Kubota, D.; Sakagami, H.; Takahashi, N.; Shoji, H. [Kitami Inst. of Technology, Kitami (Japan)

2008-07-01

Formation and dissociation processes of natural gas hydrates in permafrost, marine and lake sediments are highly controlled by their thermal properties. Dissociation heat of gas hydrates can be estimated from phase equilibrium data using the Clausius-Clapeyron equation. However, this method is applicable for pure gas hydrate and at a temperature of 0 degrees Celsius. Direct calorimetric measurements on gas hydrates using a calorimeter have been developed to obtain thermal properties of gas hydrates, including dissociation heat and heat capacity. Studies have shown that a structure 2 gas hydrate appears in appropriate gas composition of methane and ethane. This paper investigated the effect of ethane concentration on dissociation heat of mixed-gas (methane and ethane) hydrate. Raman spectroscopy was used to confirm the appearance of a structure 2 gas hydrate. The paper identified the experimental procedure and discussed sample preparation, Raman spectroscopy, and calorimetric measurements. A schematic diagram of the calorimeter was also presented. It was concluded that in most cases, two stages of dissociation were found at the dissociation process. 15 refs., 6 figs.

Balancing Accuracy and Computational Efficiency for Ternary Gas Hydrate Systems

Science.gov (United States)

White, M. D.

2011-12-01

phase transitions. This paper describes and demonstrates a numerical solution scheme for ternary hydrate systems that seeks a balance between accuracy and computational efficiency. This scheme uses a generalize cubic equation of state, functional forms for the hydrate equilibria and cage occupancies, variable switching scheme for phase transitions, and kinetic exchange of hydrate formers (i.e., CH4, CO2, and N2) between the mobile phases (i.e., aqueous, liquid CO2, and gas) and hydrate phase. Accuracy of the scheme will be evaluated by comparing property values and phase equilibria against experimental data. Computational efficiency of the scheme will be evaluated by comparing the base scheme against variants. The application of interest will the production of a natural gas hydrate deposit from a geologic formation, using the guest molecule exchange process; where, a mixture of CO2 and N2 are injected into the formation. During the guest-molecule exchange, CO2 and N2 will predominately replace CH4 in the large and small cages of the sI structure, respectively.

Rapid hydrogen hydrate growth from non-stoichiometric tuning mixtures during liquid nitrogen quenching.

Science.gov (United States)

Grim, R Gary; Kerkar, Prasad B; Sloan, E Dendy; Koh, Carolyn A; Sum, Amadeu K

2012-06-21

In this study the rapid growth of sII H(2) hydrate within 20 min of post formation quenching towards liquid nitrogen (LN(2)) temperature is presented. Initially at 72 MPa and 258 K, hydrate samples would cool to the conditions of ~60 MPa and ~90 K after quenching. Although within the stability region for H(2) hydrate, new hydrate growth only occurred under LN(2) quenching of the samples when preformed hydrate "seeds" of THF + H(2) were in the presence of unconverted ice. The characterization of hydrate seeds and the post-quenched samples was performed with confocal Raman spectroscopy. These results suggest that quenching to LN(2) temperature, a common preservation technique for ex situ hydrate analysis, can lead to rapid unintended hydrate growth. Specifically, guest such as H(2) that may otherwise need sufficiently long induction periods to nucleate, may still experience rapid growth through an increased kinetic effect from a preformed hydrate template.

Historical methane hydrate project review

Science.gov (United States)

Collett, Timothy; Bahk, Jang-Jun; Frye, Matt; Goldberg, Dave; Husebo, Jarle; Koh, Carolyn; Malone, Mitch; Shipp, Craig; Torres, Marta

2013-01-01

Blake Ridge in the Atlantic Ocean in 1995, have also contributed greatly to our understanding of the geologic controls on the formation, occurrence, and stability of gas hydrates in marine environments. For the most part methane hydrate research expeditions carried out by the ODP and IODP provided the foundation for our scientific understanding of gas hydrates. The methane hydrate research efforts under ODP-­‐IODP have mostly dealt with the assessment of the geologic controls on the occurrence of gas hydrate, with a specific goal to study the role methane hydrates may play in the global carbon cycle.Over the last 10 years, national led methane hydrate research programs, along with industry interest have led to the development and execution of major methane hydrate production field test programs. Two of the most important production field testing programs have been conducted at the Mallik site in the Mackenzie River Delta of Canada and in the Eileen methane hydrate accumulation on the North Slope of Alaska. Most recently we have also seen the completion of the world’s first marine methane hydrate production test in the Nankai Trough in the offshore of Japan. Industry interest in gas hydrates has also included important projects that have dealt with the assessment of geologic hazards associated with the presence of hydrates.The scientific drilling and associated coring, logging, and borehole monitoring technologies developed in the long list of methane hydrate related field studies are one of the most important developments and contributions associated with methane hydrate research and development activities. Methane hydrate drilling has been conducted from advanced scientific drilling platforms like the JOIDES Resolution and the D/V Chikyu, which feature highly advanced integrated core laboratories and borehole logging capabilities. Hydrate research drilling has also included the use of a wide array of industry, geotechnical and multi-­‐service ships. All of

Coupled numerical modeling of gas hydrates bearing sediments from laboratory to field-scale conditions

Science.gov (United States)

Sanchez, M. J.; Santamarina, C.; Gai, X., Sr.; Teymouri, M., Sr.

2017-12-01

Stability and behavior of Hydrate Bearing Sediments (HBS) are characterized by the metastable character of the gas hydrate structure which strongly depends on thermo-hydro-chemo-mechanical (THCM) actions. Hydrate formation, dissociation and methane production from hydrate bearing sediments are coupled THCM processes that involve, amongst other, exothermic formation and endothermic dissociation of hydrate and ice phases, mixed fluid flow and large changes in fluid pressure. The analysis of available data from past field and laboratory experiments, and the optimization of future field production studies require a formal and robust numerical framework able to capture the very complex behavior of this type of soil. A comprehensive fully coupled THCM formulation has been developed and implemented into a finite element code to tackle problems involving gas hydrates sediments. Special attention is paid to the geomechanical behavior of HBS, and particularly to their response upon hydrate dissociation under loading. The numerical framework has been validated against recent experiments conducted under controlled conditions in the laboratory that challenge the proposed approach and highlight the complex interaction among THCM processes in HBS. The performance of the models in these case studies is highly satisfactory. Finally, the numerical code is applied to analyze the behavior of gas hydrate soils under field-scale conditions exploring different features of material behavior under possible reservoir conditions.

Effect of overpressure on gas hydrate distribution

Energy Technology Data Exchange (ETDEWEB)

Bhatnagar, G.; Chapman, W.G.; Hirasaki, G.J. [Rice Univ., Houston, TX (United States). Dept. of Chemical and Biomolecular Engineering; Dickens, G.R.; Dugan, B. [Rice Univ., Houston, TX (United States). Dept. of Earth Sciences

2008-07-01

Natural gas hydrate systems can be characterized by high sedimentation rates and/or low permeability sediments, which can lead to pore pressure higher than hydrostatic. This paper discussed a study that examined this effect of overpressure on gas hydrate and free gas distribution in marine sediments. A one-dimensional numerical model that coupled sedimentation, fluid flow, and gas hydrate formation was utilized. In order to quantify the relative importance of sedimentation rates and low permeability sediments, a dimensionless sedimentation-compaction group (scN) was defined, that compared the absolute permeability of the sediments to the sedimentation rate. Higher values of scN mean higher permeability or low sedimentation rate which generally yield hydrostatic pore pressure while lower values of scN normally create pore pressure greater than hydrostatic. The paper discussed non-hydrostatic consolidation in gas hydrate systems, including mass balances; constitutive relationships; normalized variables; and dimensionless groups. A numerical solution to the problem was presented. It was concluded that simulation results demonstrated that decreasing scN not only increased pore pressure above hydrostatic values, but also lowered the lithostatic stress gradient and gas hydrate saturation. This occurred because overpressure resulted in lower effective stress, causing higher porosity and lower bulk density of the sediment. 16 refs., 5 figs., 1 appendix.

Detailed evaluation of gas hydrate reservoir properties using JAPEX/JNOC/GSC Mallik 2L-38 gas hydrate research well downhole well-log displays

Science.gov (United States)

Collett, T.S.

1999-01-01

The JAPEX/JNOC/GSC Mallik 2L-38 gas hydrate research well project was designed to investigate the occurrence of in situ natural gas hydrate in the Mallik area of the Mackenzie Delta of Canada. Because gas hydrate is unstable at surface pressure and temperature conditions, a major emphasis was placed on the downhole logging program to determine the in situ physical properties of the gas-hydrate-bearing sediments. Downhole logging tool strings deployed in the Mallik 2L-38 well included the Schlumberger Platform Express with a high resolution laterolog, Array Induction Imager Tool, Dipole Shear Sonic Imager, and a Fullbore Formation Microlmager. The downhole log data obtained from the log- and core-inferred gas-hydrate-bearing sedimentary interval (897.25-1109.5 m log depth) in the Mallik 2L-38 well is depicted in a series of well displays. Also shown are numerous reservoir parameters, including gas hydrate saturation and sediment porosity log traces, calculated from available downhole well-log and core data. The gas hydrate accumulation delineated by the Mallik 2L-38 well has been determined to contain as much as 4.15109 m3 of gas in the 1 km2 area surrounding the drill site.

Acoustical method of whole-body hydration status monitoring

Science.gov (United States)

Sarvazyan, A. P.; Tsyuryupa, S. N.; Calhoun, M.; Utter, A.

2016-07-01

An acoustical handheld hydration monitor (HM) for assessing the water balance of the human body was developed. Dehydration is a critical public health problem. Many elderly over age of 65 are particularly vulnerable as are infants and young children. Given that dehydration is both preventable and reversible, the need for an easy-to-perform method for the detection of water imbalance is of the utmost clinical importance. The HM is based on an experimental fact that ultrasound velocity in muscle is a linear function of water content and can be referenced to the hydration status of the body. Studies on the validity of HM for the assessment of whole-body hydration status were conducted in the Appalachian State University, USA, on healthy young adults and on elderly subjects residing at an assisted living facility. The HM was able to track changes in total body water during periods of acute dehydration and rehydration in athletes and day-to-day and diurnal variability of hydration in elderly. Results of human studies indicate that HM has a potential to become an efficient tool for detecting abnormal changes in the body hydration status.

Magnetic Resonance Microscopy for Assessment of Morphological Changes in Hydrating Hydroxypropylmethylcellulose Matrix Tablets In Situ–Is it Possible to Detect Phenomena Related to Drug Dissolution Within the Hydrated Matrices?

OpenAIRE

Kulinowski, Piotr; Młynarczyk, Anna; Jasiński, Krzysztof; Talik, Przemysław; Gruwel, Marco L. H.; Tomanek, Bogusław; Węglarz, Władysław P.; Dorożyński, Przemysław

2014-01-01

ABSTRACT Purpose So far, the hydrated part of the HPMC matrix has commonly been denoted as a “gel” or “pseudogel” layer. No MRI-based results have been published regarding observation of internal phenomena related to drug dissolution inside swelling polymeric matrices during hydration. The purpose of the study was to detect such phenomena. Methods Multiparametric, spatially and temporally resolved T2 MR relaxometry, in situ, was applied to study formation of the hydration progress in HPMC mat...

Fractionation of oxygen and hydrogen isotopes at the hydrate gas forming in the sea sediments

International Nuclear Information System (INIS)

Pashkina, V.I.; Esikov, A.D.

1990-01-01

The paper gives data on isotope composition of interstitial and near-bottom waters sampled in a region of gas-hydrate formation in the Sea of Okhotsk. The studies show that heavy isotopes of oxygen and hydrogen is used in gas-hydrate formation, with the result that isotope composition of its constitution water constitutes δ 18 O=+1.99per mille, δD=+23per mille relatively to SMOW. Formation of autogenic carbonates leads to isotope exchange with interstitial water wich, in turn, changes its primary isotope composition in the direction of increasing of O-18 content. The near-bottom waters are isotope-light relatively to the SMOW standard and to the mean isotope composition of interstitial water in the studied region of gas-hydrate spreading. (orig.) [de

The effect of hydrate promoters on gas uptake.

Science.gov (United States)

Xu, Chun-Gang; Yu, Yi-Song; Ding, Ya-Long; Cai, Jing; Li, Xiao-Sen

2017-08-16

Gas hydrate technology is considered as a promising technology in the fields of gas storage and transportation, gas separation and purification, seawater desalination, and phase-change thermal energy storage. However, to date, the technology is still not commercially used mainly due to the low gas hydrate formation rate and the low gas uptake. In this study, the effect of hydrate promoters on gas uptake was systematically studied and analyzed based on hydrate-based CH 4 storage and CO 2 capture from CO 2 /H 2 gas mixture experiments. Raman spectroscopy, Fourier transform infrared spectroscopy (FTIR) and gas chromatography (GC) were employed to analyze the microstructures and gas compositions. The results indicate that the effect of the hydrate promoter on the gas uptake depends on the physical and chemical properties of the promoter and gas. A strong polar ionic promoter is not helpful towards obtaining the ideal gas uptake because a dense hydrate layer is easily formed at the gas-liquid interface, which hinders gas diffusion from the gas phase to the bulk solution. For a weak polar or non-polar promoter, the gas uptake depends on the dissolution characteristics among the different substances in the system. The lower the mutual solubility among the substances co-existing in the system, the higher the independence among the substances in the system; this is so that each phase has an equal chance to occupy the hydrate cages without or with small interactions, finally leading to a relatively high gas uptake.

Hydration kinetics of cement composites with varying water-cement ratio using terahertz spectroscopy

Science.gov (United States)

Ray, Shaumik; Dash, Jyotirmayee; Devi, Nirmala; Sasmal, Saptarshi; Pesala, Bala

2015-03-01

Cement is mixed with water in an optimum ratio to form concrete with desirable mechanical strength and durability. The ability to track the consumption of major cement constituents, viz., Tri- and Dicalcium Silicates (C3S, C2S) reacting with water along with the formation of key hydration products, viz., Calcium-Silicate-Hydrate (C-S-H) which gives the overall strength to the concrete and Calcium Hydroxide (Ca(OH)2), a hydration product which reduces the strength and durability, using an efficient technique is highly desirable. Optimizing the amount of water to be mixed with cement is one of the main parameters which determine the strength of concrete. In this work, THz spectroscopy has been employed to track the variation in hydration kinetics for concrete samples with different water-cement ratios, viz., 0.3, 0.4, 0.5 and 0.6. Results show that for the sample with water-cement ratio of 0.3, significant amount of the C3S and C2S remain unreacted even after the initial hydration period of 28 days while for the cement with water-cement ratio of 0.6, most of the constituents get consumed during this stage. Analysis of the formation of Ca(OH)2 has been done which shows that the concrete sample with water-cement ratio of 0.6 produces the highest amount of Ca(OH)2 due to higher consumption of C3S/C2S in presence of excess water which is not desirable. Samples with water-cement ratio of 0.4 and 0.5 show more controlled reaction during the hydration which can imply formation of an optimized level of desired hydration products resulting in a more mechanically strong and durable concrete.

Oil and gas pipelines with hydrophobic surfaces better equipped to deal with gas hydrate flow assurance issues

DEFF Research Database (Denmark)

Perfeldt, Christine Malmos; Sharifi, Hassan; von Solms, Nicolas

2015-01-01

Gas hydrate deposition can cause plugging in oil and gas pipelines with resultant flow assurance challenges. Presently, the energy industry uses chemical additives in order to manage hydrate formation, however these chemicals are expensive and may be associated with safety and environmental...... concerns. Here we show the effect of a hydrophobically coated surface on hydrate formation in the presence of an antifreeze protein type I (AFP I) and a biodegradable synthetic polymer (LuvicapBio) in a high pressure crystallizer setup. The hydrophobic surface increased the hydrate induction time...... crystallizer. This indicates that 10 to 14 times less KHI is needed in the presence of a hydrophobically coated surface. These experimental studies suggest that the use of hydrophobic surfaces or pipelines could serve as an alternative or additional flow assurance approach for gas hydration mitigation...

Numerical studies of gas production from several CH4 hydrate zones at the Mallik site, Mackenzie Delta, Canada

Science.gov (United States)

Moridis, G.J.; Collett, T.S.; Dallimore, S.R.; Satoh, T.; Hancock, S.; Weatherill, B.

2004-01-01

The Mallik site represents an onshore permafrost-associated gas hydrate accumulation in the Mackenzie Delta, Northwest Territories, Canada. A gas hydrate research well was drilled at the site in 1998. The objective of this study is the analysis of various gas production scenarios from five methane hydrate-bearing zones at the Mallik site. In Zone #1, numerical simulations using the EOSHYDR2 model indicated that gas production from hydrates at the Mallik site was possible by depressurizing a thin free gas zone at the base of the hydrate stability field. Horizontal wells appeared to have a slight advantage over vertical wells, while multiwell systems involving a combination of depressurization and thermal stimulation offered superior performance, especially when a hot noncondensible gas was injected. Zone #2, which involved a gas hydrate layer with an underlying aquifer, could yield significant amounts of gas originating entirely from gas hydrates, the volumes of which increased with the production rate. However, large amounts of water were also produced. Zones #3, #4 and #5 were lithologically isolated gas hydrate-bearing deposits with no underlying zones of mobile gas or water. In these zones, thermal stimulation by circulating hot water in the well was used to induce dissociation. Sensitivity studies indicated that the methane release from the hydrate accumulations increased with the gas hydrate saturation, the initial formation temperature, the temperature of the circulating water in the well, and the formation thermal conductivity. Methane production appears to be less sensitive to the specific heat of the rock and of the hydrate, and to the permeability of the formation. ?? 2004 Published by Elsevier B.V.

Formation of magnesium silicate hydrate (M-S-H) cement pastes using sodium hexametaphosphate

Energy Technology Data Exchange (ETDEWEB)

Zhang, Tingting [Faculty of Infrastructure Engineering, Dalian University of Technology, Dalian 116024 (China); Department of Materials, Centre for Advanced Structural Ceramics, Imperial College London, South Kensington Campus, London SW7 2AZ (United Kingdom); Department of Civil and Environmental Engineering, Imperial College London, South Kensington Campus, London SW7 2AZ (United Kingdom); Vandeperre, Luc J. [Department of Materials, Centre for Advanced Structural Ceramics, Imperial College London, South Kensington Campus, London SW7 2AZ (United Kingdom); Cheeseman, Christopher R., E-mail: c.cheeseman@imperial.ac.uk [Department of Civil and Environmental Engineering, Imperial College London, South Kensington Campus, London SW7 2AZ (United Kingdom)

2014-11-15

Magnesium silicate hydrate (M-S-H) gel is formed by the reaction of brucite with amorphous silica during sulphate attack in concrete and M-S-H is therefore regarded as having limited cementing properties. The aim of this work was to form M-S-H pastes, characterise the hydration reactions and assess the resulting properties. It is shown that M-S-H pastes can be prepared by reacting magnesium oxide (MgO) and silica fume (SF) at low water to solid ratio using sodium hexametaphosphate (NaHMP) as a dispersant. Characterisation of the hydration reactions by x-ray diffraction and thermogravimetric analysis shows that brucite and M-S-H gel are formed and that for samples containing 60 wt.% SF and 40 wt.% MgO all of the brucites react with SF to form M-S-H gel. These M-S-H cement pastes were found to have compressive strengths in excess of 70 MPa.

Changes in the solid state of anhydrous and hydrated forms of sodium naproxen under different grinding and environmental conditions: Evidence of the formation of new hydrated forms.

Science.gov (United States)

Censi, Roberta; Rascioni, Riccardo; Di Martino, Piera

2015-05-01

The aim of the present work was to investigate the solid state change of the anhydrous and hydrate solid forms of sodium naproxen under different grinding and environmental conditions. Grinding was carried out manually in a mortar under the following conditions: at room temperature under air atmosphere (Method A), in the presence of liquid nitrogen under air atmosphere (Method B), at room temperature under nitrogen atmosphere (Method C), and in the presence of liquid nitrogen under nitrogen atmosphere (Method D). Among the hydrates, the following forms were used: a dihydrate form (DSN) obtained by exposing the anhydrous form at 55% RH; a dihydrate form (CSN) obtained by crystallizing sodium naproxen from water; the tetrahydrate form (TSN) obtained by exposing the anhydrous form at 75% RH. The metastable monohydrate form (MSN), previously described in the literature, was not used because of its high physical instability. The chemical stability during grinding was firstly assessed and proven by HPLC. Modification of the particle size and shape, and changes in the solid state under different grinding methods were evaluated by scanning electron microscopy, and X-ray powder diffractometry and thermogravimetry, respectively. The study demonstrated the strong influence of starting form, grinding and environmental conditions on particle size, shape and solid state of recovered sodium naproxen forms. In particular, it was demonstrated that in the absence of liquid nitrogen (Methods A and C), either at air or at nitrogen atmosphere, the monohydrate form (MSN) was obtained from any hydrates, meaning that these grinding conditions favored the dehydration of superior hydrates. The grinding process carried out in the presence of liquid nitrogen (Method B) led to further hydration of the starting materials: new hydrate forms were identified as one pentahydrate form and one hexahydrate form. The hydration was caused by the condensation of the atmospheric water on sodium naproxen

THz characterization of hydrated and anhydrous materials

Science.gov (United States)

Sokolnikov, Andre

2011-06-01

The characterization of anhydrous and hydrated forms of materials is of great importance to science and industry. Water content poses difficulties for successful identification of the material structure by THz radiation. However, biological tissues and hydrated forms of nonorganic substances still may be investigated by THz radiation. This paper outlines the range of possibilities of the above characterization, as well as provides analysis of the physical mechanism that allows or prevents penetration of THz waves through the substance. THz-TDS is used to measure the parameters of the characterization of anhydrous and hydrated forms of organic and nonorganic samples. Mathematical methods (such as prediction models of time-series analysis) are used to help identifying the absorption coefficient and other parameters of interest. The discovered dependencies allow designing techniques for material identification/characterization (e.g. of drugs, explosives, etc. that may have water content). The results are provided.

Clustering mechanism of oxocarboxylic acids involving hydration reaction: Implications for the atmospheric models

Science.gov (United States)

Liu, Ling; Kupiainen-Määttä, Oona; Zhang, Haijie; Li, Hao; Zhong, Jie; Kurtén, Theo; Vehkamäki, Hanna; Zhang, Shaowen; Zhang, Yunhong; Ge, Maofa; Zhang, Xiuhui; Li, Zesheng

2018-06-01

The formation of atmospheric aerosol particles from condensable gases is a dominant source of particulate matter in the boundary layer, but the mechanism is still ambiguous. During the clustering process, precursors with different reactivities can induce various chemical reactions in addition to the formation of hydrogen bonds. However, the clustering mechanism involving chemical reactions is rarely considered in most of the nucleation process models. Oxocarboxylic acids are common compositions of secondary organic aerosol, but the role of oxocarboxylic acids in secondary organic aerosol formation is still not fully understood. In this paper, glyoxylic acid, the simplest and the most abundant atmospheric oxocarboxylic acid, has been selected as a representative example of oxocarboxylic acids in order to study the clustering mechanism involving hydration reactions using density functional theory combined with the Atmospheric Clusters Dynamic Code. The hydration reaction of glyoxylic acid can occur either in the gas phase or during the clustering process. Under atmospheric conditions, the total conversion ratio of glyoxylic acid to its hydration reaction product (2,2-dihydroxyacetic acid) in both gas phase and clusters can be up to 85%, and the product can further participate in the clustering process. The differences in cluster structures and properties induced by the hydration reaction lead to significant differences in cluster formation rates and pathways at relatively low temperatures.

Detection of gas hydrate with downhole logs and assessment of gas hydrate concentrations (saturations) and gas volumes on the Blake Ridge with electrical resistivity log data

Science.gov (United States)

Collett, T.S.; Ladd, J.

2000-01-01

Let 164 of the Ocean Drilling Program was designed to investigate the occurrence of gas hydrate in the sedimentary section beneath the Blake Ridge on the southeastern continental margin of North America. Site 994, and 997 were drilled on the Blake Ridge to refine our understanding of the in situ characteristics of natural gas hydrate. Because gas hydrate is unstable at surface pressure and temperature conditions, a major emphasis was placed on the downhole logging program to determine the in situ physical properties of the gas hydrate-bearing sediments. Downhole logging tool strings deployed on Leg 164 included the Schlumberger quad-combination tool (NGT, LSS/SDT, DIT, CNT-G, HLDT), the Formation MicroScanner (FMS), and the Geochemical Combination Tool (GST). Electrical resistivity (DIT) and acoustic transit-time (LSS/SDT) downhole logs from Sites 994, 995, and 997 indicate the presence of gas hydrate in the depth interval between 185 and 450 mbsf on the Blake Ridge. Electrical resistivity log calculations suggest that the gas hydrate-bearing sedimentary section on the Blake Ridge may contain between 2 and 11 percent bulk volume (vol%) gas hydrate. We have determined that the log-inferred gas hydrates and underlying free-gas accumulations on the Blake Ridge may contain as much as 57 trillion m3 of gas.

Observations of CO{sub 2} clathrate hydrate formation and dissolution under deep-ocean disposal conditions

Energy Technology Data Exchange (ETDEWEB)

Warzinski, R.P.; Cugini, A.V. [Department of Energy, Pittsburgh, PA (United States); Holder, G.D. [Univ. of Pittsburgh, Pittsburgh, PA (United States)

1995-11-01

Disposal of anthropogenic emissions of CO{sub 2} may be required to mitigate rises in atmospheric levels of this greenhouse gas if other measures are ineffective and the worst global warming scenarios begin to occur. Long-term storage of large quantities of CO{sub 2} has been proposed, but the feasibility of large land and ocean disposal options remains to be established. Determining the fate of liquid CO{sub 2} injected into the ocean at depths greater than 500 m is complicated by uncertainties associated with the physical behavior of CO{sub 2} under these conditions, in particular the possible formation of the ice-like CO{sub 2} clathrate hydrate. Resolving this issue is key to establishing the technical feasibility of this option. Experimental and theoretical work in this area is reported.

Vertical seismic profile data from well Mallik 2L-38 for gas hydrate studies

Energy Technology Data Exchange (ETDEWEB)

Mi, Y [Calgary Univ., AB (Canada). Dept. of Geology and Geophysics; Walia, R [Victoria Univ., BC (Canada) School of Earth and Ocean Sciences; Hyndman, R [Geological Survey of Canada, Sidney, BC (Canada) Pacific Geoscience Centre

1999-07-01

A gas hydrate research well was drilled in the Canadian Arctic to study gas hydrates in a permafrost setting in a collaborative research project between the Japan National Oil Corp., the Geological Survey of Canada and other agencies. The multidisciplinary study included an electromagnetic survey, permafrost and gas hydrate coring, comprehensive downhole geophysical logging and measurement. Laboratory studies concerned studies on recovered cuttings and core including sedimentology, physical properties, geochemistry, and reservoir characteristics of the Mallik gas accumulation. As part of the Mallik 2L-38 field program, a vertical seismic profiling survey was conducted at zero and other offset source positions with three component receiver tools and horizontal and vertical vibration sources. A special effort was made to record shear wave data, which will be used to estimate the effect of gas hydrate on formation velocities and to determine gas hydrate concentration as a function of the Mallik gas accumulation. From the initial VSP analysis, certain conclusions follow: 1) zero offset vertical vibration component Z and horizontal X component data give reliable velocity determination within the gas hydrate formation zone. P wave velocities from offset VSP data show an excellent consistency with that from offset data and with the sonic log. And 2) the VSP data permit reliable identification of gas hydrate bearing zones. Abstract only included.

Experimental solid state NMR of gas hydrates : problems and solutions

Energy Technology Data Exchange (ETDEWEB)

Moudrakovski, I.; Lu, H.; Ripmeester, J. [National Research Council of Canada, Ottawa, ON (Canada). Steacie Inst. for Molecular Sciences; Kumar, R.; Susilo, R. [British Columbia Univ., Vancouver, BC (Canada). Dept. of Chemical and Biological Engineering; Luzi, M. [GeoForschungsZentrum Potsdam, Potsdam (Germany)

2008-07-01

Solid State NMR is a suitable spectroscopic technique for hydrate research for several reasons, including its capability to distinguish between different structural types of hydrates, its quantitative nature and potential for both in-situ and time resolved experiments. This study illustrated the applications of solid state NMR for compositional and structural studies of clathrate hydrates, with particular emphasis on experimental techniques and potential ways to overcome technical difficulties. In order to use the method to its full capacity, some instrumental developments are needed to adapt it to the specific experimental requirements of hydrate studies, such as very low temperatures and high pressures. This presentation discussed the quantification of the Carbon-13 spectra with examples from natural and synthetic hydrates prepared from multi-component mixtures of hydrocarbons. The main approach used for the first two examples was Carbon-13 NMR with Magic Angle Spinning (MAS) at -100 degrees C. The detailed characterization of mixed hydrogen hydrates required low temperature hydrogen MAS. The quantification problems encountered during these experiments were also discussed. The purpose of these recent experimental developments was to prompt wider application of Solid State NMR in hydrate research. NMR proved to be a viable method for analyzing the composition and structure of multi-component mixed gas hydrates; characterizing natural gas hydrates; and, evaluating the formation conditions and properties of mixed hydrogen hydrates. The limitations of the method were highlighted and sensible choices of experimental conditions and techniques that ensure accurate results were discussed. 34 refs., 10 figs.

Methane hydrates in marine sediments - Untapped source of energy

Digital Repository Service at National Institute of Oceanography (India)

Jauhari, P.

(Egorov et al 1999). Many known gas seep areas and mud volcanoes are characterised by the formation of authigenic carbonates. In the Gulf of Mexico, which is the best studied area, the association of bacterial mats, gas hydrates and authigenic carbonates... of methane hydrates offshore southern Mexico. In : Watkins, J.S., Moore J.R. et al. (Eds). Initial Reports deep Sea Drilling Project Leg 66. Washington, D.C., US Government Printing Office, pp. 547-556. Singh, A., & Singh, B.D. 1999. Methane Gas...

Gas hydrates stability zone thickness map of Indian deep offshore areas - A GIS based approach

Digital Repository Service at National Institute of Oceanography (India)

Rastogi, A.; Deka, B.; Bhattacharya, G.C.; Ramprasad, T.; KameshRaju, K.A.; Srinivas, K.; Murty, G.P.S.; Chaubey, A.K.; Ramana, M.V.; Subrahmanyam, V.; Sarma, K.V.L.N.S.; Desa, M.; Paropkari, A.L.; Menezes, A.A.A.; Murty, V.S.N.; Antony, M.K.; SubbaRaju, L.V.; Desa, E.; Veerayya, M.

hydrate occurrence in offshore regions and around the Indian sub-continent. This was accomplished by estimating the gas hydrate stability zone (GHSZ) thickness from the saptial analysis of the physical parameters that control the formation and stability...

Experimental observations on the competing effect of tetrahydrofuran and an electrolyte and the strength of hydrate inhibition among metal halides in mixed CO2 hydrate equilibria

International Nuclear Information System (INIS)

Sabil, Khalik M.; Roman, Vicente R.; Witkamp, Geert-Jan; Peters, Cor J.

2010-01-01

In the present work, experimental data on the equilibrium conditions of mixed CO 2 and THF hydrates in aqueous electrolyte solutions are reported. Seven different electrolytes (metal halides) were used in this work namely sodium chloride (NaCl), calcium chloride (CaCl 2 ), magnesium chloride (MgCl 2 ), potassium bromide (KBr), sodium fluoride (NaF), potassium chloride (KCl), and sodium bromide (NaBr). All equilibrium data were measured by using Cailletet apparatus. Throughout this work, the overall concentration of CO 2 and THF were kept constant at (0.04 and 0.05) mol fraction, respectively, while the concentration of electrolytes were varied. The experimental temperature ranged from (275 to 305) K and pressure up 7.10 MPa had been applied. From the experimental results, it is concluded that THF, which is soluble in water is able to suppress the salt inhibiting effect in the range studied. In all quaternary systems studied, a four-phase hydrate equilibrium line was observed where hydrate (H), liquid water (L W ), liquid organic (L V ), and vapour (V) exist simultaneously at specific pressure and temperature. The formation of this four-phase equilibrium line is mainly due to a liquid-liquid phase split of (water + THF) mixture when pressurized with CO 2 and the split is enhanced by the salting-out effect of the electrolytes in the quaternary system. The strength of hydrate inhibition effect among the electrolytes was compared. The results shows the hydrate inhibiting effect of the metal halides is increasing in the order NaF 2 2 . Among the cations studied, the strength of hydrate inhibition increases in the following order: K + + 2+ 2+ . Meanwhile, the strength of hydrate inhibition among the halogen anion studied decreases in the following order: Br - > Cl - > F - . Based on the results, it is suggested that the probability of formation and the strength of ionic-hydrogen bond between an ion and water molecule and the effects of this bond on the ambient water

An international effort to compare gas hydrate reservoir simulators

Energy Technology Data Exchange (ETDEWEB)

Wilder, J.W. [Akron Univ., Akron, OH (United States). Dept. of Theoretical and Applied Math; Moridis, G.J. [California Univ., Berkely, CA (United States). Earth Sciences Div., Lawrence Berkely National Lab.; Wilson, S.J. [Ryder Scott Co., Denver, CO (United States); Kurihara, M. [Japan Oil Engineering Co. Ltd., Tokyo (Japan); White, M.D. [Pacific Northwest National Laboratory Hydrology Group, Richland, WA (United States); Masuda, Y. [Tokyo Univ., Tokyo (Japan). Dept. of Geosystem Engineering; Anderson, B.J. [National Energy Technology Lab., Morgantown, WV (United States)]|[West Virginia Univ., Morgantown, WV (United States). Dept. of Chemical Engineering; Collett, T.S. [United States Geological Survey, Denver, CO (United States); Hunter, R.B. [ASRC Energy Services, Anchorage, AK (United States); Narita, H. [National Inst. of Advanced Industrial Science and Technology, MEthane hydrate Research Lab., Sapporo (Japan); Pooladi-Darvish, M. [Fekete Associates Inc., Calgary, AB (Canada); Rose, K.; Boswell, R. [National Energy Technology Lab., Morgantown, WV (United States)

2008-07-01

In this study, 5 different gas hydrate production scenarios were modeled by the CMG STARS, HydateResSim, MH-21 HYDRES, STOMP-HYD and the TOUGH+HYDRATE reservoir simulators for comparative purposes. The 5 problems ranged in complexity from 1 to 3 dimensional with radial symmetry, and in horizontal dimensions of 20 meters to 1 kilometer. The scenarios included (1) a base case with non-isothermal multi-fluid transition to equilibrium, (2) a base case with gas hydrate (closed-domain hydrate dissociation), (3) dissociation in a 1-D open domain, (4) gas hydrate dissociation in a one-dimensional radial domain, similarity solutions, (5) gas hydrate dissociation in a two-dimensional radial domain. The purpose of the study was to compare the world's leading gas hydrate reservoir simulators in an effort to improve the simulation capability of experimental and naturally occurring gas hydrate accumulations. The problem description and simulation results were presented for each scenario. The results of the first scenario indicated very close agreement among the simulators, suggesting that all address the basics of mass and heat transfer, as well as overall process of gas hydrate dissociation. The third scenario produced the initial divergence among the simulators. Other differences were noted in both scenario 4 and 5, resulting in significant corrections to algorithms within several of the simulators. The authors noted that it is unlikely that these improvements would have been identified without this comparative study due to a lack of real world data for validation purposes. It was concluded that the solution for gas hydrate production involves a combination of highly coupled fluid, heat and mass transport equations combined with the potential for formation or disappearance of multiple solid phases in the system. The physical and chemical properties of the rocks containing the gas hydrate depend on the amount of gas hydrate present in the system. Each modeling and

India National Gas Hydrate Program Expedition 02 Technical Contributions

Science.gov (United States)

Collett, T. S.; Kumar, P.; Shukla, K. M.; Nagalingam, J.; Lall, M. V.; Yamada, Y.; Schultheiss, P. J.; Holland, M.; Waite, W. F.

2017-12-01

The National Gas Hydrate Program Expedition 02 (NGHP-02) was conducted from 3-March-2015 to 28-July-2015 off the eastern coast of India. The primary objective of this expedition was the exploration and discovery of highly saturated gas hydrate occurrences in sand reservoirs that would be targets of future production testing. The first 2 months of the expedition were dedicated to logging while drilling (LWD) operations with a total of 25 holes being drilled and logged. The next 3 months were dedicated to coring operations at 10 of the most promising sites. NGHP-02 downhole logging, coring and formation pressure testing have confirmed the presence of large, highly saturated, gas hydrate accumulations in coarse-grained sand-rich depositional systems throughout the Krishna-Godavari Basin within the regions defined during NGHP-02 as Area-B, Area-C, and Area-E. The nature of the discovered gas hydrate occurrences closely matched pre-drill predictions, confirming the project developed depositional models for the sand-rich depositional facies in the Krishna-Godavari and Mahanadi Basins. The existence of a fully developed gas hydrate petroleum system was established in Area-C of the Krishna-Godavari Basin with the discovery of a large slope-basin interconnected depositional system, including a sand-rich, gas-hydrate-bearing channel-levee prospect at Sites NGHP-02-08 and -09. The acquisition of closely spaced LWD and core holes in the Area-B L1 Block gas hydrate accumulation have provided one of the most complete three-dimensional petrophysical-based views of any known gas hydrate reservoir system in the world. It was concluded that Area-B and Area-C in the area of the greater Krishna-Godavari Basin contain important world-class gas hydrate accumulations and represent ideal sites for consideration of future gas hydrate production testing.

A Computationally Efficient Equation of State for Ternary Gas Hydrate Systems

Science.gov (United States)

White, M. D.

2012-12-01

the production of geologic accumulations of gas hydrates have historically suffered from relatively slow execution times, compared with other multifluid, porous media systems, due to strong nonlinearities and phase transitions. The phase equilibria for the ternary gas hydrate system within the gas hydrate stability range of composition, temperature and pressure, includes regions where the gas hydrate is in equilibrium with gas, nonaqueous liquid, or mixtures of gas and nonaqeuous liquid near the CO2-CH4-N2 mixture critical point. In these regions, solutions to cubic equations of state can be nonconvergent without accurate initial guesses. A hybrid tabular-cubic equation of state is described which avoids convergence issues, but conserves the characteristics and advantages of the cubic equation of state approaches to phase equilibria calculations. The application of interest will be the production of a natural gas hydrate deposit from a geologic formation, using the guest molecule exchange process; where, a mixture of CO2 and N2 are injected into the formation. During the guest-molecule exchange, CO2 and N2 will predominately replace CH4 in the large and small cages of the sI structure, respectively.

A numerical study of natural hydrate formation kinetics in petroleum pipelines by the phase field method: influence of the model parameters; Estudo da cinetica de formacao de hidratos em dutos de petroleo pelo metodo do campo de fase: influencia dos parametros do modelo

Energy Technology Data Exchange (ETDEWEB)

Oliveira, Mabelle Biancardi; Castro, Jose Adilson de; Silva, Alexandre Jose da; Ferreira, Alexandre Furtado [Universidade Federal Fluminense (UFF), Volta Redonda, RJ (Brazil). Pos-Graduacao em Engenharia Metalurgica], e-mail: mabelle@metal.eeimvr.uff.br, e-mail: adilson@metal.eeimvr.uff.br, e-mail: ajs@metal.eeimvr.uff.br, e-mail: furtado@metal.eeimvr.uff.br

2006-07-01

The objective of this work is to study the influence of the parameters of the phase field model field on the formation of natural hydrates. It was investigated parameters such as superficial tension, effect of the super-cooling, homogeneous and heterogeneous nucleation. The influence of these parameters was analyzed according to morphology of the interface and the rate of formation. The mathematical model to describe the evolution of the natural hydrates formation is based on the simultaneous solution of the phase and energy equations. The finite volume numerical method was used to discretize the governing differential equations. Results of the simulation indicated that the reduction of the superficial tension leads to the increase of the surface rugosity, interface thickness and instability of the interface resulting in a decrease of the rate growth. In order to investigate the nucleation effect of the natural hydrates, two conditions had been simulated a) the random distribution of nuclei: where the evolution of formed hydrates suffered coalescence and the kinetic decreased due to impingement of hydrates regions and b) Nucleation in the pipeline wall, where rough interfaces were observed. (author)

Experimental validation of kinetic inhibitor strength on natural gas hydrate nucleation

DEFF Research Database (Denmark)

Daraboina, Nagu; Pachitsas, Stylianos; von Solms, Nicolas

2015-01-01

The kinetics of natural gas hydrate formation in the presence of dissolved salts (NaCl) and crude oil ( a middle east crude with density 851.5 kg/m3 were investigated by using a standard rocking cell (RC-5) apparatus. The hydrate nucleation temperature was reduced in the presence of NaCl and oil...... management in oil and gas facilities. (C) 2014 Elsevier Ltd. All rights reserved....

Gas hydrates

Digital Repository Service at National Institute of Oceanography (India)

Ramprasad, T.

, not all of them are white like snow. Some hydrates from the deep Gulf of Mexico are richly colored in shades of yellow, orange, or even red. The ice-like masses are beautiful, and contrast with the dull gray of deep sea muds. Hydrates from the Blake... volcanoes and associated gas hydrates: Marine Geology, v. 167, p. 29-42. Milkov, A.V. and R. Sassen, 2001a, Estimate of gas hydrate resource, northwestern Gulf of Mexico continental slope: Marine Geology, v. 179, pp. 71-83. Milkov, A.V., Sassen, R...

[Pharmacotherapy for preventing calcium containing stone formation].

Science.gov (United States)

Nagata, Masao; Takayama, Tatsuya; Mugiya, Souichi; Ohzono, Seiichiro

2011-10-01

Many urinary tract stones consist of calcium, and has high relapse rate. Accordingly, it is very important to prevent calcium-containing stone formation. This paper describes about effects and mechanisms for Xanthine oxidase inhibitor, citrate formulation, magnesium formulation, thiazides, vitamin B(6), extract of Quercus salicina Blume and chorei-to (medical herb) . Recent new drugs and the elucidation of new metabolic pathways may lead to the development of prevention of urolithiasis.

Shifting Focus: From Hydration for Performance to Hydration for Health.

Science.gov (United States)

Perrier, Erica T

2017-01-01

Over the past 10 years, literature on hydration biomarkers has evolved considerably - from (de)hydration assessment towards a more global definition of biomarkers of hydration in daily life. This shift in thinking about hydration markers was largely driven by investigating the differences that existed between otherwise healthy individuals whose habitual, ad-libitum drinking habits differ, and by identifying physiological changes in low-volume drinkers who subsequently increase their water intake. Aside from obvious differences in urinary volume and concentration, a growing body of evidence is emerging that links differences in fluid intake with small, but biologically significant, differences in vasopressin (copeptin), glomerular filtration rate, and markers of metabolic dysfunction or disease. Taken together, these pieces of the puzzle begin to form a picture of how much water intake should be considered adequate for health, and represent a shifting focus from hydration for performance, toward hydration for health outcomes. This narrative review outlines the key areas of research in which the global hydration process - including water intake, urinary hydration markers, and vasopressin - has been associated with health outcomes, focusing on kidney and metabolic endpoints. It will also provide a commentary on how various hydration biomarkers may be used in hydration for health assessment. Finally, if adequate water intake can play a role in maintaining health, how might we tell if we are drinking enough? Urine output is easily measured, and can take into account differences in daily physical activity, climate, dietary solute load, and other factors that influence daily water needs. Today, targets have been proposed for urine osmolality, specific gravity, and color that may be used by researchers, clinicians, and individuals as simple indicators of optimal hydration. However, there remain a large number of incomplete or unanswered research questions regarding the

Gas Hydrate Research Database and Web Dissemination Channel

Energy Technology Data Exchange (ETDEWEB)

Micheal Frenkel; Kenneth Kroenlein; V Diky; R.D. Chirico; A. Kazakow; C.D. Muzny; M. Frenkel

2009-09-30

To facilitate advances in application of technologies pertaining to gas hydrates, a United States database containing experimentally-derived information about those materials was developed. The Clathrate Hydrate Physical Property Database (NIST Standard Reference Database {number_sign} 156) was developed by the TRC Group at NIST in Boulder, Colorado paralleling a highly-successful database of thermodynamic properties of molecular pure compounds and their mixtures and in association with an international effort on the part of CODATA to aid in international data sharing. Development and population of this database relied on the development of three components of information-processing infrastructure: (1) guided data capture (GDC) software designed to convert data and metadata into a well-organized, electronic format, (2) a relational data storage facility to accommodate all types of numerical and metadata within the scope of the project, and (3) a gas hydrate markup language (GHML) developed to standardize data communications between 'data producers' and 'data users'. Having developed the appropriate data storage and communication technologies, a web-based interface for both the new Clathrate Hydrate Physical Property Database, as well as Scientific Results from the Mallik 2002 Gas Hydrate Production Research Well Program was developed and deployed at http://gashydrates.nist.gov.

MORPHOLOGY OF METHANE HYDRATE HOST SEDIMENTS

International Nuclear Information System (INIS)

JONES, K.W.; FENG, H.; TOMOV, S.; WINTER, W.J.; EATON, M.; MAHAJAN, D.

2004-01-01

Results from simulated experiments in several laboratories show that host sediments influence hydrate formation in accord with known heterogeneity of host sediments at sites of gas hydrate occurrence (1). For example, in Mackenzie Delta, NWT Canada (Mallik 2L-38 well), coarser-grained units (pore-filling model) are found whereas in the Gulf of Mexico, the found hydrate samples do not appear to be lithologically controlled. We have initiated a systematic study of sediments, initially focusing on samples from various depths at a specific site, to establish a correlation with hydrate occurrence (or variations thereof) to establish differences in their microstructure, porosity, and other associated properties. The synchrotron computed microtomography (CMT) set-up at the X-27A tomography beam line at the National Synchrotron Light Source (NSLS), Brookhaven National Laboratory was used as a tool to study sediments from Blake Ridge at three sub bottom depths of 0.2, 50, and 667 meters. Results from the tomographic analysis of the deepest sample (667 m) are presented here to illustrate how tomography can be used to obtain new insights into the structures of methane hydrate host sediments. The investigation shows the internal grain/pore space resolution in the microstructure and a 3-D visualization of the connecting pathways obtained following data segmentation into pore space and grains within the sediment sample. The analysis gives the sample porosity, specific surface area, mean particle size, and tortuosity, as well. An earlier report on the experimental program has been given by Mahajan et al. (2)

Manufacture of Methane Hydrate using Carbon Nano Tubes

International Nuclear Information System (INIS)

Park, Sung Seek

2010-02-01

. Therefore, it is found that NaCl acts as a inhibitor. Also, when the multi wall carbon nanotubes of 0.004 wt% was added to pure water, the amount of consumed gas was about 300% higher than that in pure water and the hydrate formation time decreased at the low subcooling temperature

Impacts of Hydrate Distribution on the Hydro-Thermo-Mechanical Properties of Hydrate-Bearing Sediments

Science.gov (United States)

Dai, S.; Seol, Y.

2015-12-01

In general, hydrate makes the sediments hydraulically less conductive, thermally more conductive, and mechanically stronger; yet the dependency of these physical properties on hydrate saturation varies with hydrate distribution and morphology. Hydrate distribution in sediments may cause the bulk physical properties of their host sediments varying several orders of magnitude even with the same amount of hydrate. In natural sediments, hydrate morphology is inherently governed by the burial depth and the grain size of the host sediments. Compare with patchy hydrate, uniformly distributed hydrate is more destructive to fluid flow, yet leads to higher gas and water permeability during hydrate dissociation due to the easiness of forming percolation paths. Water and hydrate have similar thermal conductivity values; the bulk thermal conductivity of hydrate-bearing sediments depends critically on gas-phase saturation. 60% of gas saturation may result in evident thermal conductivity drop and hinder further gas production. Sediments with patchy hydrate yield lower stiffness than that with cementing hydrate but higher stiffness than that with pore filling and loading bearing hydrate. Besides hydrate distribution, the stress state and loading history also play an important role in the mechanical behavior of hydrate-bearing sediments.

Multicavity SCRF calculation of ion hydration energies

International Nuclear Information System (INIS)

Diercksen, B.H.F.; Karelson, M.; Tamm, T.

1994-01-01

The hydration energies of the proton, hydroxyl ion, and several inorganic ions were calculated using the multicavity self-consistent reaction field (MCa SCRF) method developed for the quantum-mechanical modeling of rotationally or flexible systems in dielectric media. The ionic complexes H 3 O + (H2O) 4 , OH - (H2O) 4 , NH + 4 (H2O) 4 , and Hal - (H2O) 4 , where Hal = F, Cl, or Br, have been studied. Each complex was divided between five spheres, corresponding to the central ion and four water molecules in their first coordination sphere, respectively. Each cavity was surrounded by a polarizable medium with the dielectric permittivity of water at room temperature (80). The ionic hydration energies of ions were divided into specific and nonspecific parts. After accounting for the cavity-formation energy using scaled particle theory, good agreement between the total calculated and experimental hydration energies was obtained for all ions studied

Clinical study on orofacial photonic hydration using phototherapy and biomaterials

Science.gov (United States)

Lizarelli, Rosane F. Z.; Grandi, Natália D. P.; Florez, Fernando L. E.; Grecco, Clovis; Lopes, Luciana A.

2015-06-01

Skin hydration is important to prevent aging and dysfunction of orofacial system. Nowadays, it is known that cutaneous system is linked to muscle system, then every dentist need to treat healthy facial skin, as lips, keeping orofacial functions healthy. Thirty-two patients were treated using laser and led therapy single or associated to biomaterials (dermo-cosmetics) searching for the best protocol to promote skin hydration. Using a peace of equipment to measure electric impedance, percentage of water and oil from skin, before and after different treatments were analyzed. Statistic tests using 5% and 0.1% of significance were applied and results showed that light could improve hydration of epidermis layer of facial skin. Considering just light effect, using infrared laser followed by blue led system is more effective to hydration than just blue led system application. Considering dermo-cosmetic and light, the association between both presented the best result.

Integrating Natural Gas Hydrates in the Global Carbon Cycle

Energy Technology Data Exchange (ETDEWEB)

David Archer; Bruce Buffett

2011-12-31

We produced a two-dimensional geological time- and basin-scale model of the sedimentary margin in passive and active settings, for the simulation of the deep sedimentary methane cycle including hydrate formation. Simulation of geochemical data required development of parameterizations for bubble transport in the sediment column, and for the impact of the heterogeneity in the sediment pore fluid flow field, which represent new directions in modeling methane hydrates. The model is somewhat less sensitive to changes in ocean temperature than our previous 1-D model, due to the different methane transport mechanisms in the two codes (pore fluid flow vs. bubble migration). The model is very sensitive to reasonable changes in organic carbon deposition through geologic time, and to details of how the bubbles migrate, in particular how efficiently they are trapped as they rise through undersaturated or oxidizing chemical conditions and the hydrate stability zone. The active margin configuration reproduces the elevated hydrate saturations observed in accretionary wedges such as the Cascadia Margin, but predicts a decrease in the methane inventory per meter of coastline relative to a comparable passive margin case, and a decrease in the hydrate inventory with an increase in the plate subduction rate.

Novel nanotechnology for efficient production of binary clathrate hydrates of hydrogen and other compounds

Energy Technology Data Exchange (ETDEWEB)

Di Profio, P.; Arca, S.; Germani, R.; Savelli, G. [Perugia Univ., Perugia (Italy). Dept. of Chemistry, Center of Excellence on Innovative Nanostructured Materials

2008-07-01

The development of a hydrogen-based economy depends on finding ways to store hydrogen, but current hydrogen storage methods have significant disadvantages. One main challenge in storing sufficient amounts of hydrogen (up to 4 weight per cent) into a clathrate matrix is that of a kinetic origin, in that the mass transfer of hydrogen gas into clathrate structures is significantly limited by the macroscopic scale of the gas-liquid or gas-ice interfaces involved. This paper discussed the possibility of storing hydrogen in clathrate hydrates. It presented a newly developed method for preparing binary hydrogen hydrates that is based on the formation of amphiphile-aided nanoemulsions. Nanotechnology is used to reduce the size of hydrate particles to a few nanometers, thereby minimizing the kinetic hindrance to hydrate formation. This process has potential for increasing the amount of hydrogen stored, as it has provided ca. 1 weight per cent of hydrogen. Two new co-formers were also successfully tested, namely cyclopentane and tetrahydrothiophene. 23 refs., 10 figs.

Methane accumulation and forming high saturations of methane hydrate in sandy sediments

Energy Technology Data Exchange (ETDEWEB)

Uchida, T.; Waseda, A. [JAPEX Research Center, Chiba (Japan); Fujii, T. [Japan Oil, Gas and Metals National Corp., Chiba (Japan). Upstream Technology Unit

2008-07-01

Methane supplies for marine gas hydrates are commonly attributed to the microbial conversion of organic materials. This study hypothesized that methane supplies were related to pore water flow behaviours and microscopic migration in intergranular pore systems. Sedimentology and geochemistry analyses were performed on sandy core samples taken from the Nankai trough and the Mallik gas hydrate test site in the Mackenzie Delta. The aim of the study was to determine the influence of geologic and sedimentolic controls on the formation and preservation of natural gas hydrates. Grain size distribution curves indicated that gas hydrate saturations of up to 80 per cent in pore volume occurred throughout the hydrate-dominant sand layers in the Nankai trough and Mallik areas. Water permeability measurements showed that the highly gas hydrate-saturated sands have a permeability of a few millidarcies. Pore-space gas hydrates occurred primarily in fine and medium-grained sands. Core temperature depression, core observations, and laboratory analyses of the hydrates confirmed the pore-spaces as intergranular pore fillings. Results of the study suggested that concentrations of gas hydrates may require a pore space large enough to occur within a host sediments, and that the distribution of porous and coarser-grained sandy sediments is an important factor in controlling the occurrence of gas hydrates. 11 refs., 4 figs.

3D pore-type digital rock modeling of natural gas hydrate for permafrost and numerical simulation of electrical properties

Science.gov (United States)

Dong, Huaimin; Sun, Jianmeng; Lin, Zhenzhou; Fang, Hui; Li, Yafen; Cui, Likai; Yan, Weichao

2018-02-01

Natural gas hydrate is being considered as an alternative energy source for sustainable development and has become a focus of research throughout the world. In this paper, based on CT scanning images of hydrate reservoir rocks, combined with the microscopic distribution of hydrate, a diffusion limited aggregation (DLA) model was used to construct 3D hydrate digital rocks of different distribution types, and the finite-element method was used to simulate their electrical characteristics in order to study the influence of different hydrate distribution types, hydrate saturation and formation of water salinity on electrical properties. The results show that the hydrate digital rocks constructed using the DLA model can be used to characterize the microscopic distribution of different types of hydrates. Under the same conditions, the resistivity of the adhesive hydrate digital rock is higher than the cemented and scattered type digital rocks, and the resistivity of the scattered hydrate digital rock is the smallest among the three types. Besides, the difference in the resistivity of the different types of hydrate digital rocks increases with an increase in hydrate saturation, especially when the saturation is larger than 55%, and the rate of increase of each of the hydrate types is quite different. Similarly, the resistivity of the three hydrate types decreases with an increase in the formation of water salinity. The single distribution hydrate digital rock constructed, combined with the law of microscopic distribution and influence of saturation on the electrical properties, can effectively improve the accuracy of logging identification of hydrate reservoirs and is of great significance for the estimation of hydrate reserves.

Elevated gas hydrate saturation within silt and silty clay sediments in the Shenhu area, South China Sea

Science.gov (United States)

Wang, Xiujuan; Hutchinson, Deborah R.; Wu, Shiguo; Yang, Shengxiong; Guo, Yiqun

2011-01-01

Gas hydrate saturations were estimated using five different methods in silt and silty clay foraminiferous sediments from drill hole SH2 in the South China Sea. Gas hydrate saturations derived from observed pore water chloride values in core samples range from 10 to 45% of the pore space at 190–221 m below seafloor (mbsf). Gas hydrate saturations estimated from resistivity (Rt) using wireline logging results are similar and range from 10 to 40.5% in the pore space. Gas hydrate saturations were also estimated by P wave velocity obtained during wireline logging by using a simplified three-phase equation (STPE) and effective medium theory (EMT) models. Gas hydrate saturations obtained from the STPE velocity model (41.0% maximum) are slightly higher than those calculated with the EMT velocity model (38.5% maximum). Methane analysis from a 69 cm long depressurized core from the hydrate-bearing sediment zone indicates that gas hydrate saturation is about 27.08% of the pore space at 197.5 mbsf. Results from the five methods show similar values and nearly identical trends in gas hydrate saturations above the base of the gas hydrate stability zone at depths of 190 to 221 mbsf. Gas hydrate occurs within units of clayey slit and silt containing abundant calcareous nannofossils and foraminifer, which increase the porosities of the fine-grained sediments and provide space for enhanced gas hydrate formation. In addition, gas chimneys, faults, and fractures identified from three-dimensional (3-D) and high-resolution two-dimensional (2-D) seismic data provide pathways for fluids migrating into the gas hydrate stability zone which transport methane for the formation of gas hydrate. Sedimentation and local canyon migration may contribute to higher gas hydrate saturations near the base of the stability zone.

Positron annihilation probing for the hydratation rate of cement paste

International Nuclear Information System (INIS)

Myllylae, R.; Karras, M.

1975-01-01

Positron annihilation has been found to be a possible probe for the exponential hydratation of cement paste. Both lifetime and Doppler line broadening measurements revealed the hydratation rate. With the aid of increased stability in the lifetime spectrometer it has been possible to extend the measuring sensitivity over a period of several weeks. Two main lifetimes, tau 1 = 480 +- 20 psec and tau 2 = 2.1 +- 0.1 nsec, were observed to be constant during the hydratation. The intensity of the 2.1 nsec component changed from 4 to 8% after 47 days, and simultaneously the annihilation line narrowed from 2.6 to 2.4 keV. This behaviour has been interpreted as an increase in positronium formation. The possible practical applications of positron annihilation radiation as a hydratation probe has been evaluated for use in a concrete laboratory and even for regular construction work. (orig.) [de

Dissociation behavior of methane--ethane mixed gas hydrate coexisting structures I and II.

Science.gov (United States)

Kida, Masato; Jin, Yusuke; Takahashi, Nobuo; Nagao, Jiro; Narita, Hideo

2010-09-09

Dissociation behavior of methane-ethane mixed gas hydrate coexisting structures I and II at constant temperatures less than 223 K was studied with use of powder X-ray diffraction and solid-state (13)C NMR techniques. The diffraction patterns at temperatures less than 203 K showed both structures I and II simultaneously convert to Ih during the dissociation, but the diffraction pattern at temperatures greater than 208 K showed different dissociation behavior between structures I and II. Although the diffraction peaks from structure II decreased during measurement at constant temperatures greater than 208 K, those from structure I increased at the initial step of dissociation and then disappeared. This anomalous behavior of the methane-ethane mixed gas hydrate coexisting structures I and II was examined by using the (13)C NMR technique. The (13)C NMR spectra revealed that the anomalous behavior results from the formation of ethane-rich structure I. The structure I hydrate formation was associated with the dissociation rate of the initial methane-ethane mixed gas hydrate.

Effect of gas hydrates melting on seafloor slope stability

Science.gov (United States)

Sultan, N.; Cochonat, P.; Foucher, J. P.; Mienert, J.; Haflidason, H.; Sejrup, H. P.

2003-04-01

Quantitative studies of kinetics of gas hydrate formation and dissociation is of a particular concern to the petroleum industry for an evaluation of environmental hazards in deep offshore areas. Gas hydrate dissociation can generate excess pore pressure that considerably decreases the strength of the soil. In this paper, we present a theoretical study of the thermodynamic chemical equilibrium of gas hydrate in soil, which is based on models previously reported by Handa (1989), Sloan (1998) and Henry (1999). Our study takes into account the influence of temperature, pressure, pore water chemistry, and the pore size distribution of the sediment. This model fully accounts for the latent heat effects, as done by Chaouch and Briaud (1997) and Delisle et al. (1998). It uses a new formulation based on the enthalpy form of the law of conservation of energy. The model allows for the evaluation of the excess pore pressure generated during gas hydrate dissociation using the Soave’s (1972) equation of state. Fluid flow in response to the excess pore pressure is simulated using the finite element method. In the second part of the paper, we present and discuss an application of the model through a back-analysis of the case of the giant Storegga slide on the Norwegian margin. Two of the most important changes during and since the last deglaciation (hydrostatic pressure due to the change of the sea level and the increase of the sea water temperature) were considered in the calculation. Simulation results are presented and discussed. Chaouch, A., &Briaud, J.-L., 1997. Post melting behavior of gas hydrates in soft ocean sediments, OTC-8298, in 29th offshore technology conference proceedings, v. 1, Geology, earth sciences and environmental factors: Society of Petroleum Engineers, p. 217-224. Delisle, G.; Beiersdorf, H.; Neben, S.; Steinmann, D., 1998. The geothermal field of the North Sulawesi accretionary wedge and a model on BSR migration in unstable depositional environments. in

The crucial effect of early-stage gelation on the mechanical properties of cement hydrates

Science.gov (United States)

Ioannidou, Katerina; Kanduč, Matej; Li, Lunna; Frenkel, Daan; Dobnikar, Jure; Del Gado, Emanuela

2016-07-01

Gelation and densification of calcium-silicate-hydrate take place during cement hydration. Both processes are crucial for the development of cement strength, and for the long-term evolution of concrete structures. However, the physicochemical environment evolves during cement formation, making it difficult to disentangle what factors are crucial for the mechanical properties. Here we use Monte Carlo and Molecular Dynamics simulations to study a coarse-grained model of cement formation, and investigate the equilibrium and arrested states. We can correlate the various structures with the time evolution of the interactions between the nano-hydrates during the preparation of cement. The novel emerging picture is that the changes of the physicochemical environment, which dictate the evolution of the effective interactions, specifically favour the early gel formation and its continuous densification. Our observations help us understand how cement attains its unique strength and may help in the rational design of the properties of cement and related materials.

An ab initio and AIM investigation into the hydration of 2-thioxanthine

Directory of Open Access Journals (Sweden)

Fossey John S

2010-03-01

Full Text Available Abstract Background Hydration is a universal phenomenon in nature. The interactions between biomolecules and water of hydration play a pivotal role in molecular biology. 2-Thioxanthine (2TX, a thio-modified nucleic acid base, is of significant interest as a DNA inhibitor yet its interactions with hydration water have not been investigated either computationally or experimentally. Here in, we reported an ab initio study of the hydration of 2TX, revealing water can form seven hydrated complexes. Results Hydrogen-bond (H-bond interactions in 1:1 complexes of 2TX with water are studied at the MP2/6-311G(d, p and B3LYP/6-311G(d, p levels. Seven 2TX...H2O hydrogen bonded complexes have been theoretically identified and reported for the first time. The proton affinities (PAs of the O, S, and N atoms and deprotonantion enthalpies (DPEs of different N-H bonds in 2TX are calculated, factors surrounding why the seven complexes have different hydrogen bond energies are discussed. The theoretical infrared and NMR spectra of hydrated 2TX complexes are reported to probe the characteristics of the proposed H-bonds. An improper blue-shifting H-bond with a shortened C-H bond was found in one case. NBO and AIM analysis were carried out to explain the formation of improper blue-shifting H-bonds, and the H-bonding characteristics are discussed. Conclusion 2TX can interact with water by five different H-bonding regimes, N-H...O, O-H...N, O-H...O, O-H...S and C-H...O, all of which are medium strength hydrogen bonds. The most stable H-bond complex has a closed structure with two hydrogen bonds (N(7-H...O and O-H...O, whereas the least stable one has an open structure with one H-bond. The interaction energies of the studied complexes are correlated to the PA and DPE involved in H-bond formation. After formation of H-bonds, the calculated IR and NMR spectra of the 2TX-water complexes change greatly, which serves to identify the hydration of 2TX.

Naphthenic acids hydrates of gases: influence of the water/oil interface on the dispersing properties of an acidic crude oil; Acides naphteniques hydrates de gaz de l'interface eau/huile sur les proprietes dispersantes d'un brut acide

Energy Technology Data Exchange (ETDEWEB)

Arla, D.

2006-01-15

Nowadays, the development of offshore oil production under increasing water depths (high pressures and low temperatures) has led oil companies to focus on gas hydrates risks. Hydrates are crystals containing gas and water molecules which can plug offshore pipelines. It has been shown that some asphaltenic crude oils stabilize water-in-oil emulsions (W/O) during several months and exhibit very good anti-agglomerant properties avoiding hydrate plugs formation. In this work, we have studied the 'anti-hydrate' properties of a West African acidic crude oil called crude AH. This oil contains naphthenic acids, RCOOH hydrocarbons which are sensitive to both the pH and the salinity of the water phase.The emulsifying properties of the crude AH have firstly been explored. It has been shown that heavy resins and asphaltenes are the main compounds of the crude AH responsible for the long term stability of the W/O emulsions whereas the napthenates RCOO{sup -} lead to less stable W/O emulsions. Dealing with hydrates, the crude AH exhibits moderate anti-agglomerant properties due to the presence of heavy resins and asphaltenes. However, the naphthenates RCOO{sup -} drastically increase the formation of hydrate plugs. Moreover, it has been pointed out that hydrate particles agglomeration accelerates the kinetics of hydrate formation and enhances the water/oil separation. In order to explain these behaviours, a mechanism of agglomeration by 'sticking' between a hydrate particle and a water droplet has been proposed. Finally, we have developed a model which describes the physico-chemical equilibria of the naphthenic acids in the binary system water/crude AH, in order to transpose the results obtained in the laboratory to the real oil field conditions. (author)

Experimental preparation of Kr/Xe hydrate at pressures up to 160 bar

International Nuclear Information System (INIS)

Simonis, R.

1985-06-01

A compound called gas (mixture) hydrate is formed under pressurized atmosphere by reaction of krypton, xenon and a mixture of both with water. The study under review reports on preparing such hydrates experimentally under pressures up to 160 bar. The dissociation function of the hydrates is determined by low and medium-pressure experiments. Observing the formation process it was found that a hydrate layer is formed at the interface of gas and water, its separating effect almost inhibiting continuance of hydrate reactions. Strong stirring will avoid or destroy the separating layer. It is shown that at pressures above 50 bar the dissociation function psub(D) (T) gets non-linear with logarithmic pressure plotting above the absolute, reciprocal temperature. The medium-temperature experiments show that the density of the gas consisting of Xe or Kr and Xe, respectively, reaches higher values than that of the water. In this case, the system collapses and the gas is found at the bottom of the pressure flask, and the water in the top region. The gas samples taken during the mixed hydrate preparation show that Kr is accumulated in the gaseous phase, and Xe in the hydrate phase. (orig./RB) [de

Influence of pozzolana on C4AF hydratio n and the effects of chloride and sulfate io ns on the hydrates formed

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RIMVYDAS KAMINSKAS

2011-09-01

Full Text Available This study investigated the influence of natural pozzolana additive on the hydration of C4AF (aluminoferrite and the effects of chloride and sulfate ions on the hydrates formed. In the samples, 25% (by weight of the C4AF was replaced with pozzolana. The mixture was then hardened for 28 days in water, soaked in a saturated NaCl solution for 3 months, and then soaked in a 5% Na2SO4 solution for 3 months at 20°C. It is estimated that under normal conditions, pozzolana additive accelerates the formation of CO32-–AFm (monocarboaluminate and gibbsite, however, impede the formation of cubic aluminum hydrates. Also, part of the amorphous SiO2 penetrates into the structure of hydrates of C4AF and initiates the formation of hydrated alumino-silicate (gismondine. Monocarboaluminate affected by NaCl becomes unstable and takes part in reactions producing Ca2Al(OH6Cl·2H2O (hydrocalumite-M. After samples were transferred from a saturated NaCl solution to a 5% Na2SO4 solution, hydrocalumite-M was the source of aluminates for the formation of ettringite. In samples with pozzolana additive, the hydrated alumino-silicate and gibbsite compounds that were formed remained stable in an environment containing chloride and sulfate ions and retarded the corrosion reaction of C4AF hydrates.

Replacement of CH4 in the hydrate by use of liquid CO2

International Nuclear Information System (INIS)

Ota, Masaki; Morohashi, Kenji; Abe, Yuki; Watanabe, Masaru; Smith, Richard Lee Jr.; Inomata, Hiroshi

2005-01-01

The dynamics of CH 4 replacement in the CH 4 hydrate with saturated liquid CO 2 at 273.2 K was measured with a high pressure optical cell. The results showed that CH 4 in the hydrate gradually moved to the liquid CO 2 phase while CO 2 in the liquid phase penetrated into the hydrate from the quantitative analysis. The decomposing process of the CH 4 hydrate during the replacement was analyzed with in situ Raman spectroscopy, which allowed us to distinguish the cage structure of the CH 4 hydrate and discuss the microscopic view of the replacement in the hydrate. It was found that the decomposition of the medium cage (M-cage) in the CH 4 hydrate proceeded faster than that of the small cage (S-cage). The observed rate difference could be related to the stability of the S-cage in the CH 4 hydrate or the re-formation tendency of CH 4 and water molecules in the S-cage after decomposing the hydrate structure, whereas the guest molecule exchange of CH 4 with CO 2 could occur in the M-cage. Based on the experimental data, we developed a kinetic model for calculation of the CH 4 remaining in the hydrate considering the decomposition rate difference between the M-cage and S-cage in the CH 4 hydrate. The results indicate that the driving force could be the fugacity difference between the fluid phase and the hydrate phase for the replacement process

Ad libitum fluid intake does not prevent dehydration in suboptimally hydrated young soccer players during a training session of a summer camp.

Science.gov (United States)

Arnaoutis, Giannis; Kavouras, Stavros A; Kotsis, Yiannis P; Tsekouras, Yiannis E; Makrillos, Michalis; Bardis, Costas N

2013-06-01

There is a lack of studies concerning hydration status of young athletes exercising in the heat. To assess preexercise hydration status in young soccer players during a summer sports camp and to evaluate body- water balance after soccer training sessions. Initial hydration status was assessed in 107 young male soccer players (age 11-16 yr) during the 2nd day of the camp. Seventy-two athletes agreed to be monitored during 2 more training sessions (3rd and 5th days of the camp) to calculate dehydration via changes in body weight, while water drinking was allowed ad libitum. Hydration status was assessed via urine specific gravity (USG), urine color, and changes in total body weight. Mean environmental temperature and humidity were 27.2 ± 2 °C and 57% ± 9%, respectively. According to USG values, 95 of 107 of the players were hypohydrated (USG ≥ 1.020) before practice. The prevalence of dehydration observed was maintained on both days, with 95.8% and 97.2% of the players being dehydrated after the training sessions on the 3rd and 5th days, respectively. Despite fluid availability, 54 of the 66 (81.8%) dehydrated players reduced their body weight (-0.35 ± 0.04 kg) as a response to training, while 74.6% (47 out of the 63) further reduced their body weight (-0.22 ± 0.03 kg) after training on the 5th day. Approximately 90% of the young soccer players who began exercising under warm weather conditions were hypohydrated, while drinking ad libitum during practice did not prevent further dehydration in already dehydrated players.

Gas hydrate formation in deep-sea sediments - on the role of sediment-mechanical process determination; Gashydratbildung in Tiefseesedimenten - zur Rolle der sedimentmechanischen Prozesssteuerung

Energy Technology Data Exchange (ETDEWEB)

Feeser, V. [Kiel Univ. (Germany). Geologisch-Palaeontologisches Inst.

1997-12-31

Slope failures in gas hydrate regions are encountered throughout the oceans. The stability of seafloor slopes can be assessed and predicted by means of calculation methods based on mechanical laws and parameters which describe the deformation behaviour and/or mechanical strength of the slope-forming sediments. Thermodynamic conditions conducive to the formation of gas hydrates in marine sediments differ from conditions prevailing in exclusively water-filled systems. The present contribution describes the relevant energetic conditions on the basis of a simple spherical model giving due consideration to petrographic parameters. Depending on pore size distribution, lithological stress conditions, pore water pressure, and sediment strength gas hydrates will either develop as a cementing phase or as segregated lenses. (MSK) [Deutsch] In den Weltmeeren ereignen sich immer wieder Hangrutschungen in Gashydratgebieten. Die zur Beurteilung und Prognonse von Hangstabilitaeten zu verwendenden Berechnungsverfahren erfordern Stoffgesetze und Parameter, welche das Deformations-und/oder Festigkeitsverhalten der hangbildenden Sedimente beschreiben. Die thermodynamischen Bildungsbedingungen von Gashydraten in marinen Sedimenten unterscheiden sich von den Bedingungen in ausschliesslich wassergefuellten Systemen. Unter Einbeziehung petrographischer Eigenschaften werden die energetischen Bedingungen beschrieben. Dazu dient ein einfaches Kugelmodell. Je nach vorhandenem Porenraumspektrum, lithostatischen Spannungsverhaeltnissen, Porenwasserdruck und Sedimentfestigkeit wachsen Gashydrate als Porenraumzement oder als segregierte Linsen.

Effect of changes in seafloor temperature and sea-level on gas hydrate stability

Energy Technology Data Exchange (ETDEWEB)

Garg, S.K.; Pritchett, W. [Science Applications International Corp., San Diego, CA (United States)

2008-07-01

Natural gas hydrates occur in oceanic sediments and in permafrost regions around the world. As a greenhouse gas, large amounts of methane released from the global hydrate reservoir would have a significant impact on Earth's climate. The role of methane released by hydrate dissociation in climate change is uncertain. However, changes in global climate such as glaciation and warming can destabilize the hydrates. During the last glacial maximum, the sea level dropped about 100 meters. It has been suggested that the sea-level fall was associated with gas hydrate instability and seafloor slumping. This paper investigated the effect of changes in seafloor temperature and sea level on gas hydrate stability and on gas venting at the seafloor. A one-dimensional numerical computer model (simulator) was developed to describe methane hydrate formation, decomposition, reformation, and distribution with depth below the seafloor in the marine environment. The simulator was utilized to model hydrate distributions at two sites, notably Blake Ridge, located offshore South Carolina and Hydrate Ridge, located off the coast of Oregon. The numerical models for the two sites were conditioned by matching the sulfate, chlorinity, and hydrate distribution measurements. The effect of changes in seafloor temperature and sea-level on gas hydrate stability were then investigated. It was concluded that for Blake Ridge, changes in hydrate concentration were small. Both the changes in seafloor temperature and sea-level led to a substantial increase in gas venting at the seafloor for Hydrate Ridge. 17 refs., 8 figs.

Hydration of the sulfuric acid-methylamine complex and implications for aerosol formation.

Science.gov (United States)

Bustos, Danielle J; Temelso, Berhane; Shields, George C

2014-09-04

The binary H2SO4-H2O nucleation is one of the most important pathways by which aerosols form in the atmosphere, and the presence of ternary species like amines increases aerosol formation rates. In this study, we focus on the hydration of a ternary system of sulfuric acid (H2SO4), methylamine (NH2CH3), and up to six waters to evaluate its implications for aerosol formation. By combining molecular dynamics (MD) sampling with high-level ab initio calculations, we determine the thermodynamics of forming H2SO4(NH2CH3)(H2O)n, where n = 0-6. Because it is a strong acid-base system, H2SO4-NH2CH3 quickly forms a tightly bound HSO4(-)-NH3CH3(+) complex that condenses water more readily than H2SO4 alone. The electronic binding energy of H2SO4-NH2CH3 is -21.8 kcal mol(-1) compared with -16.8 kcal mol(-1) for H2SO4-NH3 and -12.8 kcal mol(-1) for H2SO4-H2O. Adding one to two water molecules to the H2SO4-NH2CH3 complex is more favorable than adding to H2SO4 alone, yet there is no systematic difference for n ≥ 3. However, the average number of water molecules around H2SO4-NH2CH3 is consistently higher than that of H2SO4, and it is fairly independent of temperature and relative humidity.

Growth mode transition of tetrahydrofuran clathrate hydrates in the guest/host concentration boundary layer.

Science.gov (United States)

Sabase, Yuichiro; Nagashima, Kazushige

2009-11-19

Clathrate hydrates are known to form a thin film along a guest/host boundary. We present here the first report of tetrahydrofuran (THF) clathrate hydrate formation in a THF/water concentration boundary layer. We found that the THF-water system also forms a hydrate film separating the guest/host phases. The lateral growth rate of the film increases as supercooling increases. The thickness of the film at the growth tip decreases as supercooling and the lateral growth rate increase. These tendencies are consistent with reports of experiments for other hydrates and predictions of heat-transfer models. After film formation and slight melting, two types of growth modes are observed, depending on temperature T. At T = 3.0 degrees C, the film slowly thickens. The thickening rate is much lower than the lateral growth rate, as reported for other hydrates. At T agglomerate of small polycrystalline hydrates forms in each phase. Grain boundaries in the film and pore spaces in the agglomerate act as paths for permeation of each liquid. Timing when continuous nucleation starts is dominantly controlled by the time of initiation of liquid permeation through the film. Digital particle image velocimetry analysis of the agglomerate shows that it expands not by growth at the advancing front but rather by continuous nucleation in the interior. Expansion rates of the agglomerate tend to be higher for the cases of multipermeation paths in the film and the thinner film. We suppose that the growth mode transition to continuous nucleation is caused by the memory effect due to slight melting of the hydrate film.

Le problème des hydrates dans le contexte de la production et du transport polyphasiques des pétroles bruts et des gaz naturels. Deuxième partie : les solutions possibles aux difficultés d'exploitation générées par les hydrates Hydrates Problem Within the Framework of Multiphase Production and Transport of Crude Oils and Natural Gases. Part Two: Possible Solutions to Exploitation Difficulties Generated by Hydrates

Directory of Open Access Journals (Sweden)

Behar E.

2006-11-01

Full Text Available L'exploitation en mer des gisements de combustibles fossiles fluides a amplifié le besoin d'accroître nos connaissances sur les hydrates qui sont susceptibles de boucher les installations de production, de traitement et de transport. La première partie rappelait la structure moléculaire des hydrates I, Il et H et décrivait ensuite succinctement l'analyse physico-chimique de leur formation, tant sur les plans thermodynamique que cinétique. Dans cette deuxième partie, les remèdes possibles aux problèmes rencontrés par les compagnies opératrices sont indiqués, essentiellement les inhibiteurs thermodynamiques classiques tels que les alcools ou les sels qui diminuent la température de formation des hydrates, et les additifs dispersants qui évitent la croissance et/ou l'agglomération des cristaux. Pour terminer, une boucle pilote de circulation originale est présentée, ses caractéristiques qui permettent la validation des additifs dispersants dans des conditions hydrodynamiques et physico-chimiques représentatives étant soulignées. Offshore exploitation of fossil fluid fuels has emphasized the need of improving our knowledge on hydrates which can plug production, treatment and transport facilities. The first part recalled the molecular structure of I, II and H hydrates, then the physical-chemistry of their formation was briefly reviewed from both the thermodynamic and the kinetic points of view. In this second part, the possible remedies to the problems met by operating companies are described, mainly classical thermodynamic inhibitors such as alcohols or salts which decrease the hydrates formation temperature, and dispersant additives which avoid crystals growth and/or agglomeration. At last an original circulation loop at pilot scale is presented, its characteristics which allow the testing of dispersant additives under representative hydrodynamic and physico-chemical conditions being outlined.

Experimental setting for assessing mechanical strength of gas hydrate pellet

Energy Technology Data Exchange (ETDEWEB)

Jeong, S.J.; Choi, J.H.; Koh, B.H. [Dongguk Univ., Phil-dong, Chung-gu, Seoul (Korea, Republic of). Dept. of Mechanical Engineering

2008-07-01

Due to the constant increase in global demand for clean energy, natural gas production from stranded medium and small size gas wells has drawn significant interest. Because the ocean transport of natural gas in the form of solid hydrate pellets (NGHP) has been estimated to be economically feasible, several efforts have been made to develop a total NGHP ocean transport chain. The investigation of mechanical strength of solid-form hydrate pellet has been an important task in fully exploiting the benefit of gas hydrate in the perspective of mass transportation and storage. This paper provided the results of a preliminary study regarding the assessment of mechanical properties of the gas hydrate pellet. The preliminary study suggested some of the key issues regarding formation and strength of gas hydrate pellets. Instead of utilizing the gas hydrate pellet, the study focused on a preliminary test setup for developing the ice pellet which was readily applied to the gas hydrate pellet in the future. The paper described the pelletization of ice powder as well as the experimental setup. Several photographs were illustrated, including samples of ice pellets; compression test for ice pellet using air press and load cell; and the initiation of crack in the cross section of an ice pellet. It was found that mechanical strength, especially, compression strength was not significantly affected by different level of press-forming force up to a certain level. 4 refs., 1 tab., 4 figs.

Risk factors of methane hydrate resource development in the concentrated zones distributed in the eastern Nankai Trough

Science.gov (United States)

Yamamoto, K.; Nagakubo, S.

2009-04-01

, low pressure. Deformation and subsidence of the sea floor may be unavoidable but does not cause serious concern on the safety. Some have argued that hydrate dissociations in wide area may cause landslide due to weakened formation by dissociation. To manage the concern, the test site should be chosen carefully and formation property alternation should be well known. One common misunderstanding widespread in public is that methane hydrate is "unstable material." Indeed, the hydrate is stable in the original temperature and pressure conditions, and the endothermic process of hydrate dissociation leads negative feedback to the formation conditions from the altered states by artificial depressurization. Also the hydrate dissociation in the sandy sediments is governed by relatively slow heat and fluid transport phenomena in porous media, so the process is gradual. Therefore, a catastrophic chain reaction which many people imagine is surely unlikely. As mentioned above, at present, risks of methane hydrate resource development in the concentrated zones distributed in the eastern Nankai trough are not significant, and comparable or less serious than conventional oil and gas production, we concluded. Of course, this evaluation should be verified with offshore production tests in the future, and new knowledge should be reflected to the safe and environmentally friendly production system designs. The nature of unconsolidated formation after the hydrate dissociation is key issue of such investigation. MH21 consortium has studied the issue in many aspects, and will continue the investigation.

Implications of hydration depletion in the in vitro starch digestibility of white bread crumb and crust.

Science.gov (United States)

Martínez, Mario M; Román, Laura; Gómez, Manuel

2018-01-15

The objective of this study was to provide understanding about the efficacy of decreasing dough hydration to slow down starch digestibility in white bread. Breads were made with 45 (low hydration bread, LHB), 60 (intermediate hydration bread, IHB) and 75% (high hydration bread, HHB) water (flour basis). A hydration depletion down to 45%, which is close to the minimum hydration found in commercially available white bread, did not prevent the starch in the crumb from complete gelatinization. However, LHB and IHB crumbs were more resistant to physical breakdown during in vitro digestion than HHB crumbs, resulting in a 96.81% increase of slowly digestible starch (SDS) from 75 to 45% dough hydration. The degree of gelatinization in crust samples was significantly reduced with a depletion in the dough hydration, ranging from 29.90 to 44.36%, which led to an increase of SDS from 7.41 in HHB to 13.78% in LHB (bread basis). Copyright © 2017 Elsevier Ltd. All rights reserved.

Preventing Pressure Sores

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Process for prevention of water build-up in cryogenic distillation column

International Nuclear Information System (INIS)

Hopewell, R.B.

1988-01-01

In a process for the separation of a hydrocarbon and acid gas containing feed stream in a cryogenic distillation column, a zone of the column which is operated at a temperature of 60 0 F or less, wherein free water accumulates or forms hydrates in the column from water vapor in the feed stream during the cryogenic process, and which process comprises separating the feed stream in the column into an overhead stream and a bottom stream, this patent describes the improvement which comprises: withdrawing a hydrocarbon and acid gas vapor stream which stream is enriched in water vapor with respect to the feed stream, thereby preventing the excess accumulation of free water or the formation of hydrates in the cryogenic column

Experimental observations on the competing effect of tetrahydrofuran and an electrolyte and the strength of hydrate inhibition among metal halides in mixed CO{sub 2} hydrate equilibria

Energy Technology Data Exchange (ETDEWEB)

Sabil, Khalik M., E-mail: khalik_msabil@petronas.com.m [Delft University of Technology, Laboratory of Process Equipment, Mechanical, Maritime and Materials Engineering, Leeghwaterstraat 44, 2628 CA Delft (Netherlands); Universiti Teknologi PETRONAS, Chemical Engineering Programme, Bandar Seri Iskandar, 31750 Tronoh, Perak (Malaysia); Roman, Vicente R.; Witkamp, Geert-Jan [Delft University of Technology, Laboratory of Process Equipment, Mechanical, Maritime and Materials Engineering, Leeghwaterstraat 44, 2628 CA Delft (Netherlands); Peters, Cor J., E-mail: C.J.Peters@tudelft.n [Delft University of Technology, Laboratory of Process Equipment, Mechanical, Maritime and Materials Engineering, Leeghwaterstraat 44, 2628 CA Delft (Netherlands); Petroleum Institute, Chemical Engineering Program, Bu Hasa Building, Room 2207A, P.O. Box 2533, Abu Dhabi (United Arab Emirates)

2010-03-15

In the present work, experimental data on the equilibrium conditions of mixed CO{sub 2} and THF hydrates in aqueous electrolyte solutions are reported. Seven different electrolytes (metal halides) were used in this work namely sodium chloride (NaCl), calcium chloride (CaCl{sub 2}), magnesium chloride (MgCl{sub 2}), potassium bromide (KBr), sodium fluoride (NaF), potassium chloride (KCl), and sodium bromide (NaBr). All equilibrium data were measured by using Cailletet apparatus. Throughout this work, the overall concentration of CO{sub 2} and THF were kept constant at (0.04 and 0.05) mol fraction, respectively, while the concentration of electrolytes were varied. The experimental temperature ranged from (275 to 305) K and pressure up 7.10 MPa had been applied. From the experimental results, it is concluded that THF, which is soluble in water is able to suppress the salt inhibiting effect in the range studied. In all quaternary systems studied, a four-phase hydrate equilibrium line was observed where hydrate (H), liquid water (L{sub W}), liquid organic (L{sub V}), and vapour (V) exist simultaneously at specific pressure and temperature. The formation of this four-phase equilibrium line is mainly due to a liquid-liquid phase split of (water + THF) mixture when pressurized with CO{sub 2} and the split is enhanced by the salting-out effect of the electrolytes in the quaternary system. The strength of hydrate inhibition effect among the electrolytes was compared. The results shows the hydrate inhibiting effect of the metal halides is increasing in the order NaF < KBr < NaCl < NaBr < CaCl{sub 2} < MgCl{sub 2}. Among the cations studied, the strength of hydrate inhibition increases in the following order: K{sup +} < Na{sup +} < Ca{sup 2+} < Mg{sup 2+}. Meanwhile, the strength of hydrate inhibition among the halogen anion studied decreases in the following order: Br{sup -} > Cl{sup -} > F{sup -}. Based on the results, it is suggested that the probability of formation and

Simulating the gas hydrate production test at Mallik using the pilot scale pressure reservoir LARS

Science.gov (United States)

Heeschen, Katja; Spangenberg, Erik; Schicks, Judith M.; Priegnitz, Mike; Giese, Ronny; Luzi-Helbing, Manja

2014-05-01

LARS, the LArge Reservoir Simulator, allows for one of the few pilot scale simulations of gas hydrate formation and dissociation under controlled conditions with a high resolution sensor network to enable the detection of spatial variations. It was designed and built within the German project SUGAR (submarine gas hydrate reservoirs) for sediment samples with a diameter of 0.45 m and a length of 1.3 m. During the project, LARS already served for a number of experiments simulating the production of gas from hydrate-bearing sediments using thermal stimulation and/or depressurization. The latest test simulated the methane production test from gas hydrate-bearing sediments at the Mallik test site, Canada, in 2008 (Uddin et al., 2011). Thus, the starting conditions of 11.5 MPa and 11°C and environmental parameters were set to fit the Mallik test site. The experimental gas hydrate saturation of 90% of the total pore volume (70 l) was slightly higher than volumes found in gas hydrate-bearing formations in the field (70 - 80%). However, the resulting permeability of a few millidarcy was comparable. The depressurization driven gas production at Mallik was conducted in three steps at 7.0 MPa - 5.0 MPa - 4.2 MPa all of which were used in the laboratory experiments. In the lab the pressure was controlled using a back pressure regulator while the confining pressure was stable. All but one of the 12 temperature sensors showed a rapid decrease in temperature throughout the sediment sample, which accompanied the pressure changes as a result of gas hydrate dissociation. During step 1 and 2 they continued up to the point where gas hydrate stability was regained. The pressure decreases and gas hydrate dissociation led to highly variable two phase fluid flow throughout the duration of the simulated production test. The flow rates were measured continuously (gas) and discontinuously (liquid), respectively. Next to being discussed here, both rates were used to verify a model of gas

Protecting exposed tissues with external ultrasonic super-hydration.

Science.gov (United States)

Silberg, Barry Neil

2006-01-01

The author contends that a technique preventing dehydration of exposed tissues, such as external ultrasonic super-hydration, will result in a lower morbidity rate, decreasing deep tissue pain, susceptibility to infection, fat necrosis, wound dehiscence, and improving recovery times. He discusses how he uses this technique in his aesthetic surgery practice.

Hydrogeochemical and isotopic signatures of gas hydrate-forming fluids offshore NE Sakhalin (the sea of Okhotsk): Results from the CHAOS-2003 cruises

International Nuclear Information System (INIS)

Mazurenko, Leonid; Matveeva, Tatiana; Soloviev, Valery; Prasolov, Eduard; Logvina, Elizaveta; Shoji, Hitoshi; Hachikubo, Akihiro; Minami, Hirotsugi; Sakagami, Hirotoshi

2005-01-01

During the CHAOS-2003 cruises of R/V Akademik Lavrentyev three new gas hydrate accumulations named the Chaos, the Hieroglyph and the Kitami were discovered offshore NE Sakhalin (the Sea of Okhotsk) in association with fluid venting. The main goal of this paper is to clarify the origin and the composition of gas and water involving the accumulation of vent-related gas hydrates and to reveal their mechanism of formation. Discharging of deeper sourced water is not observed based on data of the major ion distribution. Observed isotope anomalies of hydrogen (up to 2.52%) and oxygen (up to 0.36%) are higher than fractionation coefficient under gas hydrate formation (1.8% and 0.3%, respectively). These features could be explained by two processes: a) an influence of residual water during gas hydrates formation or b) involving to the process of gas hydrate formation of deep-sourced water. The latter process is most probably influence on the isotopic composition of the pore water. Studied pore water samples consist from three end members: Gas hydrate water, seawater (or in situ pore water of the basin) and deep-sourced water. Results of isotopic studies of water testify that discharged fluid is characterized by light (delta)D (up to approx. 0.11% ) and (delta) 18 O (up to approx. 0.12%). Two mechanisms of gas hydrate accumulation are distinguished: Precipitation from infiltrating gas-saturated water and segregation of pore water by diffusing gas. (Author)

Skin hydration of the heel with fissure in patients with diabetes: a cross-sectional observational study

Directory of Open Access Journals (Sweden)

Oe M

2018-06-01

Full Text Available Makoto Oe,1 Kimie Takehara,2 Hiroshi Noguchi,3 Yumiko Ohashi,4 Mayu Fukuda,1 Takashi Kadowaki,5 Hiromi Sanada1,6 1Global Nursing Research Center, 2Department of Advanced Nursing Technology, 3Department of Life Support Technology (Molten, Graduate School of Medicine, The University of Tokyo, 4Department of Nursing, The University of Tokyo Hospital, 5Department of Diabetes and Metabolic Diseases, 6Department of Gerontological Nursing/Wound Care Management, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan Purpose: Foot fissure should be prevented in patients with diabetes due to the likelihood of subsequent diabetic ulcer. The purpose of this study was to investigate a cutoff point for skin hydration with fissure and the factors associated with low skin hydration in patients with diabetes. Subjects and methods: Subjects were patients with diabetes who visited the diabetic foot clinic and were evaluated for skin hydration on the heel between April 2008 and March 2015. Information about fissure, skin hydration, age, sex, autonomic neuropathy, angiopathy, and tinea pedis were collected from the medical charts. Skin hydration on the heel was measured using a moisture checker. Skin hydration was compared between heels with and without fissure, and a cutoff for skin hydration with fissure was determined using receiver operating characteristic analysis. Based on the determined cutoff, factors associated with lower skin hydration were analyzed using logistic regression analysis. Results: Participants comprised 693 patients. Mean±SD age was 66.8±10.8 years, and 57.0% of subjects were male. The frequency of fissures on the heels was 10.4%. Area under the receiver operating characteristic curve for skin hydration in the presence of fissure was 0.717. Twenty percent was selected as the cutoff point, offering sensitivity of 0.478 and specificity of 0.819. Logistic regression analysis showed correlations between three factors (male sex, tinea

Direct measurement of methane hydrate composition along the hydrate equilibrium boundary

Science.gov (United States)

Circone, S.; Kirby, S.H.; Stern, L.A.

2005-01-01

The composition of methane hydrate, namely nW for CH 4??nWH2O, was directly measured along the hydrate equilibrium boundary under conditions of excess methane gas. Pressure and temperature conditions ranged from 1.9 to 9.7 MPa and 263 to 285 K. Within experimental error, there is no change in hydrate composition with increasing pressure along the equilibrium boundary, but nW may show a slight systematic decrease away from this boundary. A hydrate stoichiometry of n W = 5.81-6.10 H2O describes the entire range of measured values, with an average composition of CH4??5.99(??0.07) H2O along the equilibrium boundary. These results, consistent with previously measured values, are discussed with respect to the widely ranging values obtained by thermodynamic analysis. The relatively constant composition of methane hydrate over the geologically relevant pressure and temperature range investigated suggests that in situ methane hydrate compositions may be estimated with some confidence. ?? 2005 American Chemical Society.

Modelling the effects of waste components on cement hydration

NARCIS (Netherlands)

van Eijk, R.J.; Brouwers, Jos

2000-01-01

Ordinary Portland Cement (OPC) is often used for the Solidification/Stabilization (S/S) of waste containing heavy metals and salts. These waste componenents will precipitate in the form of insoluble compounds onto unreacted cement clinker grains preventing further hydration. In this study the long

Development of a compound energy system for cold region houses using small-scale natural gas cogeneration and a gas hydrate battery

International Nuclear Information System (INIS)

Obara, Shin'ya; Kikuchi, Yoshinobu; Ishikawa, Kyosuke; Kawai, Masahito; Yoshiaki, Kashiwaya

2015-01-01

In this study, an independent energy system for houses in cold regions was developed using a small-scale natural gas CGS (cogeneration), air-source heat pump, heat storage tank, and GHB (gas hydrate battery). Heat sources for the GHB were the ambient air and geothermal resources of the cold region. The heat cycle of CO 2 hydrate as a source of energy was also experimentally investigated. To increase the formation speed of CO 2 hydrates, a ferrous oxide–graphite system catalyst was used. The ambient air of cold regions was used as a heat source for the formation process (electric charge) of the GHB, and the heat supplied by a geothermal heat exchanger was used for the dissociation process (electric discharge). Using a geothermal heat source, fuel consumption was halved because of an increased capacity for hydrate formation in the GHB, a shortening of the charging and discharging cycle, and a decrease in the freeze rate of hydrate formation space. Furthermore, when the GHB was introduced into a cold region house, the application rate of renewable energy was 47–71% in winter. The spread of the GHB can greatly reduce fossil fuel consumption and the associated greenhouse gases released from houses in cold regions. - Highlights: • Compound energy system for cold region houses by a gas hydrate battery was proposed. • Heat sources of a gas hydrate battery are exhaust heat of the CGS and geothermal. • Drastic reduction of the fossil fuel consumption in a cold region is realized

Gas hydrate in nature

Science.gov (United States)

Ruppel, Carolyn D.

2018-01-17

Gas hydrate is a naturally occurring, ice-like substance that forms when water and gas combine under high pressure and at moderate temperatures. Methane is the most common gas present in gas hydrate, although other gases may also be included in hydrate structures, particularly in areas close to conventional oil and gas reservoirs. Gas hydrate is widespread in ocean-bottom sediments at water depths greater than 300–500 meters (m; 984–1,640 feet [ft]) and is also present in areas with permanently frozen ground (permafrost). Several countries are evaluating gas hydrate as a possible energy resource in deepwater or permafrost settings. Gas hydrate is also under investigation to determine how environmental change may affect these deposits.

Hydration Properties of Ground Granulated Blast-Furnace Slag (GGBS Under Different Hydration Environments

Directory of Open Access Journals (Sweden)

Shuhua LIU

2017-02-01

Full Text Available The hydration properties of various cementitious materials containing Ground Granulated Blast-furnace Slag (GGBS, two alkali-activated slag cements (AAS-1 and AAS-2 in which sodium silicate and sodium hydroxide act as alkaline activators respectively, supersulfated cement (SSC and slag Portland cement(PSC, are compared with ordinary Portland cement (OPC to investigate the effect of activating environment on the hydration properties in this study by determining the compressive strength of the pastes, the hydration heat of binders within 96 hours, and the hydration products at age of 28 days. The results show that C-S-H gels are the main hydrated products for all cementitious systems containing GGBS. Ca(OH2 is the hydration products of OPC and PSC paste. However, ettringite and gypsum crystals instead of Ca(OH2 are detected in SSC paste. Additionally, tobermorite, a crystalline C-S-H, and calcite are hydrated products in AAS-1. Tobermorite, cowlesite and calcite are hydrated products of AAS-2 as well. Based on strength results, AAS-1 paste exhibits the highest compressive strength followed by POC, PSC, SSC in order at all testing ages and AAS-2 give the lowest compressive strength except for the early age at 3 days, which is higher than SSC but still lower than PSC. From hydration heat analysis, alkalinity in the reaction solution is a vital factor influencing the initial hydration rate and the initial hydration rate from higher to lower is AAS-2, AAS-1, OPC, PSC and SSC. Although AAS possesses a faster reaction rate in the initial hours, cumulative hydration heat of AAS is comparably lower than that of OPC, but higher than those of PSC and SSC in turn, which indicates that the hydration heat of clinkers is much higher than that of slag.DOI: http://dx.doi.org/10.5755/j01.ms.23.1.14934