Sample records for catagenesis
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Problem of regional catagenesis
Energy Technology Data Exchange (ETDEWEB)
Sen' kovskiy, Y N
1980-01-01
Based on a study of authigenic minerals of alumina (x-ray amorphous opal, opal-crystobalite, low-temperature crystobalite, quartz) and detection of the laws governing their dispersal in depth in Mesozoic-Cenozoic deposits of southwest East European platform and the Ciscarpathian trough, a zone is isolated of early catagenesis with subdivision of the latter into opal, crystobalite and quartz-halcedon subzones. Comparison of the zones of early catagenesis of the continental block and the bed of the world ocean demonstrated that in the oceanic sedimentary mass, zonality in distribution by depth of the x-ray amorphous opal, opal-crystobalite and alpha-crystobalite is expressed considerably more weakly than on the continent. Mineralogical and crystal-chemical studies of the sedimentary alumina could help to reveal the nature of individual types of rock-collectors and together with other geological data enable a more effective prediciting of their spatial arrangment in the section.
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Directory of Open Access Journals (Sweden)
N.V. Pronina
2017-05-01
Full Text Available The Timan-Pechora basin still has a large importance and as a potential region for the hydrocarbons mining in Russia. At present, new facts are emerging from oil and gas exploration. The authors studied more than 50 samples from 11 wells. Most samples in this series were related to the Middle-Late-Frasnian sediments (Late Devonian, which are allocated in «domanic» horizon. Organic macerals of the studed samples are represented both by fragments of humic macerals and sapropelic OM (formed from algal material. The common organic macerals in Timan-Pechora basin are bituminites. They were met in all samples without exception and provide total content of OM,% in the rock. Bituminites are regularly distributed among mineral matter and color the rock in gray or more dark colors. Bituminite was used to determine the reflectance index (RB,% that later was converted into the corresponding equivalent of vitrinite reflectance index (RVeq,%. This is particularly important as authors’ information was used together with the results of earlier studies. ID-modeling has been made in the program PetroMod (2015.1 Schlumberger and helped to understand evolution in Timan-Pechora basin and maturity degree of rocks. The concept of the model was coordinated with the main evolution stages of the northeast European Platform and the foredeep Ural trough. The thicknesses of catagenesis zones and position of boundaries between them are indicators of thermal regime in the analyzed regions. The heat flow used in the modelling was one and the same for most tectonic regions (except foredeep Ural trough and Khoreiverskaja depression. According to the classification of the sedimentary basins by P. Robert (1985, 5 regions belong to regions with a normal or slightly hypothermal geothermal regime (heat flow 45-65 mV/m2 and foredeep Ural trough with heat flow up to 74 mV/m2 is a region with a high hyperthermal regime.
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Koopmans, M.P.; De Leeuw, J. W.; Lewan, M.D.; Sinninghe, Damste J.S.
1996-01-01
Hydrous pyrolysis of an immature (R(a)??? 0.25%) sulphur-rich marl from the Gessoso-solfifera Formation (Messinian) in the Vena del Gesso Basin was carried out at 160C ??? T ???330 C for 72 h, to study the effect of progressive diagenesis and early catagenesis on the abundance and distribution of sulphur-containing and sulphur- and oxygen-linked carbon skeletons in low-molecular-weight and highmolecular-weight fractions (e.g. kerogen). To this end, compounds in the saturated hydrocarbon fraction, monoaromatic hydrocarbon fraction, polyaromatic hydrocarbon fraction, alkylsulphide fraction and ketone fraction were quantified, as well as compounds released after desulphurisation of the polar fraction and HI/LiAIH4 treatment of the desulphurised polar fraction. Sulphur-bound phytane and (20R)-5??,14??,17??(H) and (20R)-5??,14??,17??(H) C27 C29 steranes in the polar fraction become less abundant with increasing maturation temperature, whereas the amount of their corresponding hydrocarbons increases in the saturated hydrocarbon fraction. Carbon skeletons that are bound in the kerogen by multiple bonds (e.g. C38 n-alkane and isorenieratane) are first released into the polar fraction, and then as free hydrocarbons. These changes occur at relatively low levels of thermal maturity (R(a) <0.6%), as evidenced by the 'immature' values of biomarker maturity parameters such as the ????/(????+ ???? + ????) C35 hopane ratio and the 22S/(22S + 22R)-17??,21??(H) C35 hopane ratio. Sulphur- and oxygen-bound moieties, present in the polar fraction, are not stable with increasing thermal maturation. However, alkylthiophenes, ketones. 1,2-di-n-alkylbenzenes and free n-alkanes seem to be stable thermal degradation products of these sulphur- and oxygen-bound moieties. Thus, apart from free n-alkanes, which are abundantly present in more mature sedimentary rocks and crude oils, alkylthiophenes, 1,2-di-n-alkylbenzenes and ketones can also be expected to occur. The positions of the thiophene
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New Zealand Coals - A Potential Feedstock for Deep Microbial Life
DEFF Research Database (Denmark)
Glombitza, Clemens
2010-01-01
into the surrounding. Previous studies showed that especially oxygen containing compounds are lost from the macromolecular matrix during diagenesis and early catagenesis. Oxygen containing low molecular weight organic acids (LMWOAs) such as formate, acetate and oxalate represent important substrates for microbial...... reactions. Formate, acetate and oxalate were found to decrease continously from early diagenesis to early catagenesis. This suggests a constant release of these compounds during this maturation interval providing a suitable feedstock for microbial ecosystems in geological time spans. Investigation...... of kerogen-bound high molecular weight fatty acids show for the long chain fatty acids (C20-C30), representing a terrestrial plant material signal, a constant decrease during diagenesis and early catagenesis. In contrast the short chain fatty acids (mainly C16 and C18) show an increase again during early...
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DEFF Research Database (Denmark)
Glombitza, Clemens; Mangelsdorf, Kai; Horsfield, Brian
2009-01-01
A rank series of lignites and coals of low to moderate maturation levels (vitrinite reflectance (R0): 0.27–0.8%) from the New Zealand Coal Band were investigated using alkaline ester cleavage experiments to reveal compositional changes of ester bound components (fatty acids and alcohols) during...... increase during early catagenesis before decreasing again during main catagenesis. This intermittent increase was related to the short chain fatty acids. To obtain a maturity related signal and to eliminate facies related scattering in the amounts of fatty acids in the coal samples, the carbon preference...
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Energy Technology Data Exchange (ETDEWEB)
Glombitza, C.; Mangelsdorf, K.; Horsfield, B. [German Research Cemter of Geoscience GFZ, Potsdam (Germany)
2009-10-15
Several lignites and coals of low to moderate maturation levels from the New Zealand Coal Band were investigated using alkaline ester cleavage experiments to reveal compositional changes of ester bound components during increasing maturation. Ester bound alcohols are found to be present in highest amounts in the very immature lignite samples but show a rapid decrease during early diagenesis. Ester bound fatty acids also show an initial exponential decrease during diagenesis but reveal an intermittent increase during early catagenesis before decreasing again during main catagenesis. This was related to the short chain fatty acids. To obtain a maturity related signal and to eliminate facies related scattering in the amounts of fatty acids in the coal samples, the carbon preference index of fatty acids (CPIFA) parameter is introduced. For the long chain fatty acids the CPIFA decreases with increasing maturity. During diagenesis, the same trend can be observed for the short chain fatty acids but the intermittent increase in the amounts of short chain fatty acids is also accompanied by high CPIFA values. This indicates less altered organic biomass at this maturation level and is in contrast to the mature CPIFA signal of the long chain fatty acids of the same samples. Thus could be due to extremely different amounts of short and long chain fatty acids in the original source organic matter or it could due to the incorporation of immature bacterial biomass from deep microbial communities containing C{sub 16} and C{sub 18} fatty acids as main cell membrane components. Deep microbial life might be stimulated at this interval by the increasing release of thermally generated potential substrates from the organic matrix during early catagenesis. The high amounts of alcohols in the immature lignite samples are also visible in the alkene distribution from the open system pyrolysis experiments of the organic matrix before and after saponification.
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International Nuclear Information System (INIS)
Gauthier-Lafaye, F.; Weber, F.
1984-01-01
New data about fluid inclusions associated to a siliceous diagenesis show that a deformation phase in the first stage of catagenesis disturbed their microthermometric behaviour. Nevertheless, temperature and pressure of fluids associated to the uraniferous paragenesis and contemporary with the Oklo natural reactors are estimated at 140-160 0 C and 250-500 bar [fr
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Horsfield, B.; Schenk, H. J.; Zink, K.; Ondrak, R.; Dieckmann, V.; Kallmeyer, J.; Mangelsdorf, K.; di Primio, R.; Wilkes, H.; Parkes, R. J.; Fry, J.; Cragg, B.
2006-06-01
Earth's largest reactive carbon pool, marine sedimentary organic matter, becomes increasingly recalcitrant during burial, making it almost inaccessible as a substrate for microorganisms, and thereby limiting metabolic activity in the deep biosphere. Because elevated temperature acting over geological time leads to the massive thermal breakdown of the organic matter into volatiles, including petroleum, the question arises whether microorganisms can directly utilize these maturation products as a substrate. While migrated thermogenic fluids are known to sustain microbial consortia in shallow sediments, an in situ coupling of abiotic generation and microbial utilization has not been demonstrated. Here we show, using a combination of basin modelling, kinetic modelling, geomicrobiology and biogeochemistry, that microorganisms inhabit the active generation zone in the Nankai Trough, offshore Japan. Three sites from ODP Leg 190 have been evaluated, namely 1173, 1174 and 1177, drilled in nearly undeformed Quaternary and Tertiary sedimentary sequences seaward of the Nankai Trough itself. Paleotemperatures were reconstructed based on subsidence profiles, compaction modelling, present-day heat flow, downhole temperature measurements and organic maturity parameters. Today's heat flow distribution can be considered mainly conductive, and is extremely high in places, reaching 180 mW/m 2. The kinetic parameters describing total hydrocarbon generation, determined by laboratory pyrolysis experiments, were utilized by the model in order to predict the timing of generation in time and space. The model predicts that the onset of present day generation lies between 300 and 500 m below sea floor (5100-5300 m below mean sea level), depending on well location. In the case of Site 1174, 5-10% conversion has taken place by a present day temperature of ca. 85 °C. Predictions were largely validated by on-site hydrocarbon gas measurements. Viable organisms in the same depth range have been proven using 14C-radiolabelled substrates for methanogenesis, bacterial cell counts and intact phospholipids. Altogether, these results point to an overlap of abiotic thermal degradation reactions going on in the same part of the sedimentary column as where a deep biosphere exists. The organic matter preserved in Nankai Trough sediments is of the type that generates putative feedstocks for microbial activity, namely oxygenated compounds and hydrocarbons. Furthermore, the rates of thermal degradation calculated from the kinetic model closely resemble rates of respiration and electron donor consumption independently measured in other deep biosphere environments. We deduce that abiotically driven degradation reactions have provided substrates for microbial activity in deep sediments at this convergent continental margin.
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Directory of Open Access Journals (Sweden)
Behar F.
2006-11-01
Full Text Available Dans cet article nous proposons des modèles de structures chimiques de kérogènes et d'asphaltènes de roche. Nous avons choisi de représenter les kérogènes appartenant aux trois types classiques de matières organiques aux stades d'évolution suivants : - début de la diagenèse sensu-stricto; - début de la catagenèse (formation de l'huile; - fin de la catagenèse (formation du gaz. Les asphaltènes représentés correspondent à la phase de formation de l'huile. Nous avons tenu compte des données d'analyse obtenues sur des échantillons naturels : analyse élémentaire, microscopie électronique, RMN 13C, thermogravimétrie, analyse fonctionnelle, dégradation par pyrolyse. Afin d'obtenir une représentation chimique ayant une valeur statistique suffisante, nous avons choisi une masse moléculaire de 25 000 environ, identique pour les trois kérogènes au début de la diagenèse, et une masse de 8000 environ pour les asphaltènes associés. Nous avons ensuite dessiné à l'échelle moléculaire les structures correspondantes. This paper proposes models for the chemical structures of kerogens and asphaltenes from rocks. The kerogens belonging to the three conventional types of organic matter are represented in the following stages of evolution: (1 beginning of diagenesis sensu stricto,(2 beginning of catagenesis (formation of oil, and (3 end of catagenesis (formation of gas. The asphaltenes represented here correspond to the phase of oil formation. Models are based on analytical data obtained on natural samples, i. e. elemental analysis, electron microscopy, 13C NMR, thermogravimetry, functional analysis and pyrolysis. To get enough statistical value for the chemical modelling, a same molecular mass of about 25 000 was chosen for the three kerogens at the beginning of diagenesis. A molecular mass of about 8000 was chosen for the related asphaltenes. The chemical structures were then constructed at the molecular scale.
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Koopmans, M.P.; Rijpstra, W.I.C.; De Leeuw, J. W.; Lewan, M.D.; Damste, J.S.S.
1998-01-01
An immature (Ro=0.39%), S-rich (S(org)/C = 0.07), organic matter-rich (19.6 wt. % TOC) limestone from the Ghareb Formation (Upper Cretaceous) in Jordan was artificially matured by hydrous pyrolysis (200, 220 ..., 300??C; 72 h) to study the effect of progressive diagenesis and early catagenesis on the amounts and distributions of hydrocarbons, organic sulfur compounds and S-rich geomacromolecules. The use of internal standards allowed the determination of absolute amounts. With increasing thermal maturation, large amounts of alkanes and alkylthiophenes with predominantly linear carbon skeletons are generated from the kerogen. The alkylthiophene isomer distributions do not change significantly with increasing thermal maturation, indicating the applicability of alkylthiophenes as biomarkers at relatively high levels of thermal maturity. For a given carbon skeleton, the saturated hydrocarbon, alkylthiophenes and alkylbenzo[b]thiophenes are stable forms at relatively high temperatures, whereas the alkylsulfides are not stable. The large amount of alkylthiophenes produced relative to the alkanes may be explained by the large number of monosulfide links per carbon skeleton. These results are in good agreement with those obtained previously for an artificial maturation series of an immature S-rich sample from the Gessoso-solfifera Formation.An immature (Ro = 0.39%), S-rich (Sorg/C = 0.07), organic matter-rich (19.6 wt.% TOC) limestone from the Ghareb Formation (Upper Cretaceous) in Jordan was artificially matured by hydrous pyrolysis (200, 220, ..., 300??C; 72 h) to study the effect of progressive diagenesis and early catagenesis on the amounts and distributions of hydrocarbons, organic sulfur compounds and S-rich geomacromolecules. The use of internal standards allowed the determination of absolute amounts. With increasing thermal maturation, large amounts of alkanes and alkylthiophenes with predominantly linear carbon skeletons are generated from the kerogen. The
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Release of organic nitrogen compounds from Kerogen via catalytic hydropyrolysis
Directory of Open Access Journals (Sweden)
Bennett B
2000-12-01
Full Text Available High hydrogen pressure pyrolysis (hydropyrolysis was performed on samples of solvent extracted Kimmeridge Clay Formation source rock with a maturity equivalent to ca. 0.35% vitrinite reflectance. We describe the types and distributions of organic nitrogen compounds in the pyrolysis products (hydropyrolysates using GC-MS. Compounds identified included alkyl-substituted indoles, carbazoles, benzocarbazoles, quinolines and benzoquinolines. The distributions of the isomers of methylcarbazoles, C2-alkylcarbazoles and benzocarbazoles in the hydropyrolysates were compared to a typical North Sea oil. The hydropyrolysates compared to the North Sea oil, showed increased contributions from alkylcarbazole isomers where the nitrogen group is "exposed" (no alkyl substituents adjacent to the nitrogen functionality and appreciable levels of benzo[b]carbazole relative to benzo[a]- and benzo[c]carbazoles. Hydropyrolysis is found to be an ideal technique for liberating appreciable quantities of heterocyclic organic nitrogen compounds from geomacromolecules. The products released from the immature Kimmeridge Clay are thought to represent a potential source of nitrogen compounds in the bound phase (kerogen able to contribute to the free bitumen phase during catagenesis.
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Middle to late Jurassic in Poland; Mellem - Oevre jura i Polen
Energy Technology Data Exchange (ETDEWEB)
Poulsen, N.E.; Bojesen-Koefoed, J.; Drewniak, A.; Glowniak, E.; Ineson, J.; Matyja, B.A.; Merta, T.; Wierzbowski, A.
1998-12-01
Results of this project have contributed to the renewed research in the area of the Middle Jurassic ammonite stratigraphy. Upper Jurassic ammonite stratigraphy is a very actively researched field at the Geological Institute of the Warsaw University. The stratigraphical distribution of dinoflagellate cysts within the Upper Bajocian-Bathonian-Lower Callovian has provided a detailed correlation between the Polish Submediterranean Province (northern Tethyan realm) and the Subboreal Province of the North Sea area (chronostratigraphy and dinoflagellate zonation). One of the most interesting results is the improved correlation of the Oxfordian/Kimmeridgean boundary between these two provinces. The source mineral research contributed new data about the oil/gas potential of megafacies in the central Poland. The planned model development of catagenesis of Middle Jurassic clay sediments in relation to salt deposits could not be established from the found low TOC values and very low hydrogen index values between 6 and 141. The organic material can be characterized as kerogen-type III/IV. Kerogen is considered generally immature with regard to oil/gas formation. The detailed study of sponge bioherms in North-Western Poland has resulted in better understanding of the architecture and evolution of these bioherms. (EG)
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Prus, Wojciech; Fabiańska, Monika J; Łabno, Radosław
2015-06-15
The organic contamination of Antarctic soils and terrestrial sediments from nearby of five polar scientific stations on King George Island (Antarctica) was investigated. Gas chromatography-mass spectrometry (GC-MS) was applied to find composition of dichloromethane extracts of soil and terrestrial sediments. The presence of geochemical markers, such as n-alkanes, steranes, pentacyclic triterpenoids, and alkyl PAHs, their distribution types, and values of their ratios indicates the predominating source of organic fossil fuels and products of their refining rather than from the natural Antarctic environment. Fossil fuel-originated compounds well survived in conditions of Antarctic climate over long times thus enabling to characterize geochemical features of source fossil fuel identified as petroleum expelled from kerogen II of algal/bacterial origins deposited in sub-oxic conditions and being in the middle of catagenesis. Both microbial activity and water leaching play an important role in degradation of terrestrial oil spills in the Antarctica climate, and petroleum alteration occurs lowly over long periods of time. Synthetic anthropogenic compounds found in terrestrial Antarctica sediments included diisopropylnaphthalenes, products of their sulfonates degradation in paper combustion, and organophosporus compounds used as retardants and plasticizers. Copyright © 2015 Elsevier B.V. All rights reserved.
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International Nuclear Information System (INIS)
Lerche, I.
1993-01-01
The 1600 yr half-life of radium restricts the time and thus the distance over which radium can migrate in sediments. The dominant source of unsupported radium in sandstone reservoir brines must then be close by and is likely in shales adjacent to the oil-field reservoirs. The chemical similarity of calcium and radium can be used to argue for a local shale-source contribution to the calcium in reservoir sands -suggesting the probability of calcite cementation early in the sedimentary sequence. Helium production by radium decay increases with time. Concentrations of helium found in reservoir oil field brines are then used to suggest that: (a) such reservoirs are dominantly closed systems over geological times; (b) neither methane nor helium in the reservoirs have migrated any significant distance; and (c) the mechanism responsible for the observed helium in the brine is a continuous on-going process operative today. Diagenetic studies should then deal with both sands and shales interdependently, the two are not separable. Shales control the transport mechanisms of migration so that the primary migration of hydrocarbons, the result of kerogen catagenesis in shales, should occur sufficiently early in the sedimentary sequence in order to avoid exclusion from the reservoir by calcite cementation in association with radium transport. (author)
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DEFF Research Database (Denmark)
Glombitza, Clemens; Mangelsdorf, Kai; Horsfield, Brian
2016-01-01
network. Application of the carbon preference index for fatty acids (CPIFA) of bitumen and kerogen-bound acids revealed a linear correlation to the Tmax maturity parameter. This shows that the CPIFA has a clear relation to thermal stability and, thus, reactivity of the buried organic matter....... The difference in slopes of CPIFA vs. Tmax for short and long chain as well as bitumen and kerogen-bound acids may indicate their different degradation susceptibilities. The short chain fatty acids of the bitumen show the highest susceptibility whereas the kerogen-bound long chain fatty acids seem to be most...
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A Study of Porphyrins in Petroleum Source Rocks
Energy Technology Data Exchange (ETDEWEB)
Huseby, Berit
1997-12-31
This thesis discusses several aspects of porphyrin geochemistry. Degradation experiments have been performed on the Messel oil shale (Eocene, Germany) to obtain information on porphyrins bound or incorporated into macromolecular structures. Thermal heating of the preextracted kerogen by hydrous pyrolysis was used to study the release of porphyrins and their temperature dependent changes during simulated diagenesis and catagenesis. Selective chemical degradation experiments were performed on the preextracted sediment to get more detailed information about porphyrins that are specifically bound to the macromolecular structures via ester bonds. From the heating experiments, in a separate study, the porphyrin nitrogen content in the generated bitumens was compared to the bulk of organic nitrogen compounds in the fraction. The bulk nitrogen contents in the generated bitumens, the water phase and the residual organic matter was recorded to establish the distribution of nitrogen between the kerogen and product phases. Porphyrins as biomarkers were examined in naturally matured Kimmeridge clay source rocks (Upper Jurassic, Norway), and the use of porphyrins as general indicators of maturity was evaluated. Underlying maturity trends in the biomarker data was investigated by Partial Least Squares analysis. Porphyrin as indicators of depositional conditions was also addressed, where the correlations between the (amounts) abundance of nickel and vanadyl porphyrins were mapped together with other descriptors that are assumed to be indicative of redox depositional conditions. 252 refs., 28 figs., 4 tabs.
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A Study of Porphyrins in Petroleum Source Rocks
Energy Technology Data Exchange (ETDEWEB)
Huseby, Berit
1996-12-31
This thesis discusses several aspects of porphyrin geochemistry. Degradation experiments have been performed on the Messel oil shale (Eocene, Germany) to obtain information on porphyrins bound or incorporated into macromolecular structures. Thermal heating of the preextracted kerogen by hydrous pyrolysis was used to study the release of porphyrins and their temperature dependent changes during simulated diagenesis and catagenesis. Selective chemical degradation experiments were performed on the preextracted sediment to get more detailed information about porphyrins that are specifically bound to the macromolecular structures via ester bonds. From the heating experiments, in a separate study, the porphyrin nitrogen content in the generated bitumens was compared to the bulk of organic nitrogen compounds in the fraction. The bulk nitrogen contents in the generated bitumens, the water phase and the residual organic matter was recorded to establish the distribution of nitrogen between the kerogen and product phases. Porphyrins as biomarkers were examined in naturally matured Kimmeridge clay source rocks (Upper Jurassic, Norway), and the use of porphyrins as general indicators of maturity was evaluated. Underlying maturity trends in the biomarker data was investigated by Partial Least Squares analysis. Porphyrin as indicators of depositional conditions was also addressed, where the correlations between the (amounts) abundance of nickel and vanadyl porphyrins were mapped together with other descriptors that are assumed to be indicative of redox depositional conditions. 252 refs., 28 figs., 4 tabs.
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Energy Technology Data Exchange (ETDEWEB)
Maowen Li; Snowdon, L.R. [Geological Survey of Canada, Calgary (Canada); Renzi Lin; Peirong Wang [Jianghan Petroleum Institute, Hubei (China); Yongsheng Liao; Peilong Li [Shengli Petroleum Administrative Bureau, Shandong (China)
1999-07-01
This study shows that the oils and condensates in the Kekeya Field in the Tarim Basin, NW China, belong to a single family, most likely derived from marine shale source rocks deposited under oxic-suboxic conditions with mixed terrigenous and algal-bacterial organic inputs. The maturity data clearly indicate that the paraffinic condensates were not formed by thermal cracking of oil during late catagenesis (R{sub o} > 1.2%). Both the oils and condensates were generated within the normal oil window, whereas addition of gaseous hydrocarbons from a separate source resulted in migration fractionation and hence spuriously high heptane indices. Age specific biomarkers show that the oils and condensates were not generated from the Mesozoic-Cenozoic strata, but from the Carboniferous-Permian sections. 1D basin modelling results are consistent with this interpretation, suggesting that the Mesozoic-Eocene strata are currently immature with respect to hydrocarbon generation and expulsion. Deep-seated faults may have provided routes for upward fluid migration at the time of active deformation during several pulses of the Himalayan orogeny. The favoured targets for further petroleum exploration in front of the Kunlun Mountains include the deep structures within the Carboniferous-Permian strata for indigenous petroleum accumulations and anticlines and stratigraphic traps within the Mesozoic-Cenozoic sections that are cut by deep-seated thrust faults where secondary petroleum accumulations most likely occurred. (author)
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Investigation of water-soluble organic matter extracted from shales during leaching experiments
Zhu, Yaling; Vieth-Hillebrand, Andrea; Wilke, Franziska D. H.; Horsfield, Brian
2017-04-01
The huge volumes and unknown composition of flowback and produced waters cause major public concerns about the environmental and social compatibility of hydraulic fracturing and the exploitation of gas from unconventional reservoirs. Flowback and produced waters contain not only residues of fracking additives but also chemical species that are dissolved from the shales themselves during fluid-rock interaction. Knowledge of the composition, size and structure of dissolved organic carbon (DOC) as well as the main controls on the release of DOC are a prerequisite for a better understanding of these interactions and its effects on composition of flowback and produced water. Black shales from four different geological settings and covering a maturity range Ro = 0.3-2.6% were extracted with deionized water. The DOC yields were found to decrease rapidly with increasing diagenesis and remain low throughout catagenesis. Four DOC fractions have been qualitatively and quantitatively characterized using size-exclusion chromatography. The concentrations of individual low molecular weight organic acids (LMWOA) decrease with increasing maturity of the samples except for acetate extracted from the overmature Posidonia shale, which was influenced by hydrothermal brines. The oxygen content of the shale organic matter also shows a significant influence on the release of organic acids, which is indicated by the positive trend between oxygen index (OI) and the concentrations of formate and acetate. Based on our experiments, both the properties of the organic matter source and the thermal maturation progress of the shale organic matter significantly influence the amount and quality of extracted organic compounds during the leaching experiments.
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Yang, Shengyu; Schulz, Hans-Martin; Horsfield, Brian; Schovsbo, Niels H.; Noah, Mareike; Panova, Elena; Rothe, Heike; Hahne, Knut
2018-05-01
An interdisciplinary study was carried out to unravel organic-inorganic interactions caused by the radiogenic decay of uranium in the immature organic-rich Alum Shale (Middle Cambrian-Lower Ordovician). Based on pyrolysis experiments, uranium content is positively correlated with the gas-oil ratios and the aromaticities of both the free hydrocarbons residing in the rock and the pyrolysis products from its kerogen, indicating that irradiation has had a strong influence on organic matter composition overall and hence on petroleum potential. The Fourier Transform Ion Cyclotron Resonance mass spectrometry data reveal that macro-molecules in the uranium-rich Alum Shale samples are less alkylated than less irradiated counterparts, providing further evidence for structural alteration by α-particle bombardment. In addition, oxygen containing-compounds are enriched in the uranium-rich samples but are not easily degradable into low-molecular-weight products due to irradiation-induced crosslinking. Irradiation has induced changes in organic matter composition throughout the shale's entire ca. 500 Ma history, irrespective of thermal history. This factor has to be taken into account when reconstructing petroleum generation history. The Alum Shale's kerogen underwent catagenesis in the main petroleum kitchen area 420-340 Ma bp. Our calculations suggest the kerogen was much more aliphatic and oil-prone after deposition than that after extensive exposure to radiation. In addition, the gas sorption capacity of the organic matter in the Alum Shale can be assumed to have been less developed during Palaeozoic times, in contrast to results gained by sorption experiments performed at the present day, for the same reason. The kerogen reconstruction method developed here precludes overestimations of gas generation and gas retention in the Alum Shale by taking irradiation exposure into account and can thus significantly mitigate charge risk when applied in the explorations for both
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Phan, Thai T.; Gardiner, James B.; Capo, Rosemary C.; Stewart, Brian W.
2018-02-01
We investigate sediment sources, depositional conditions and diagenetic processes affecting the Middle Devonian Marcellus Shale in the Appalachian Basin, eastern USA, a major target of natural gas exploration. Multiple proxies, including trace metal contents, rare earth elements (REE), the Sm-Nd and Rb-Sr isotope systems, and U isotopes were applied to whole rock digestions and sequentially extracted fractions of the Marcellus shale and adjacent units from two locations in the Appalachian Basin. The narrow range of εNd values (from -7.8 to -6.4 at 390 Ma) is consistent with derivation of the clastic sedimentary component of the Marcellus Shale from a well-mixed source of fluvial and eolian material of the Grenville orogenic belt, and indicate minimal post-depositional alteration of the Sm-Nd system. While silicate minerals host >80% of the REE in the shale, data from sequentially extracted fractions reflect post-depositional modifications at the mineralogical scale, which is not observed in whole rock REE patterns. Limestone units thought to have formed under open ocean (oxic) conditions have δ238U values and REE patterns consistent with modern seawater. The δ238U values in whole rock shale and authigenic phases are greater than those of modern seawater and the upper crust. The δ238U values of reduced phases (the oxidizable fraction consisting of organics and sulfide minerals) are ∼0.6‰ greater than that of modern seawater. Bulk shale and carbonate cement extracted from the shale have similar δ238U values, and are greater than δ238U values of adjacent limestone units. We suggest these trends are due to the accumulation of chemically and, more likely, biologically reduced U from anoxic to euxinic bottom water as well as the influence of diagenetic reactions between pore fluids and surrounding sediment and organic matter during diagenesis and catagenesis.
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Energy Technology Data Exchange (ETDEWEB)
Kalaitzidis, Stavros; Siavalas, George; Christanis, Kimon [Dept. of Geology, University of Patras, 26504 Rio-Patras (Greece); Skarpelis, Nikos [Dept. of Geology and Geoenvironment, University of Athens, 15784 Zografou (Greece); Araujo, Carla Viviane [Petrobras-Cenpes GEOQ/PDEXP, Rua Horacio Macedo n 950, Cidade Universitaria - Ilha do Fundao, 21941-915 Rio de Janeiro (Brazil)
2010-04-01
The Pera-Lakkos coal located on top of bauxite deposits in the Ghiona mining district (Central Greece), is the only known Mesozoic (Late Cretaceous) coal in the country. It was derived from herbaceous plants and algae growing in mildly brackish mires that formed behind a barrier system during a regression of the sea, on a karstified limestone partly filled in with bauxitic detritus. Petrological, mineralogical and geochemical data point to the predominance of reducing conditions and intense organic matter degradation in the palaeomires. O/C vs. H/C and OI vs. HI plots, based on elemental analysis and Rock-Eval data, characterize kerogen types I/II. This reflects the relatively high liptinite content of the coal. Besides kerogen composition, O/C vs. H/C plot for the Pera-Lakkos coals is in accordance with a catagenesis stage of maturation in contrast with vitrinite reflectance and T{sub max} from Rock-Eval pyrolysis, which indicate the onset of oil window maturation stage. Suppression of vitrinite reflectance should be considered and the high liptinite content corroborates this hypothesis. Despite some favourable aspects for petroleum generation presented by the Pera-Lakkos coal, its maximum thickness (up to 50 cm) points to a restricted potential for petroleum generation. Coal oxidation took place either during the late stage of peat formation, due to wave action accompanying the subsequent marine transgression, or epigenetically after the emergence of the whole sequence due to percolation of drainage waters. Both options are also supported by the REE shale-normalized profiles, which demonstrate an upwards depletion in the coal layer. Oxidation also affected pyrite included in the coal; this led to the formation of acidic (sulfate-rich) solutions, which percolated downwards resulting in bleaching of the upper part of the underlying bauxite. (author)
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Shuai, Yanhua; Douglas, Peter M. J.; Zhang, Shuichang; Stolper, Daniel A.; Ellis, Geoffrey S.; Lawson, Michael; Lewan, Michael D.; Formolo, Michael; Mi, Jingkui; He, Kun; Hu, Guoyi; Eiler, John M.
2018-02-01
Multiply isotopically substituted molecules ('clumped' isotopologues) can be used as geothermometers because their proportions at isotopic equilibrium relative to a random distribution of isotopes amongst all isotopologues are functions of temperature. This has allowed measurements of clumped-isotope abundances to be used to constrain formation temperatures of several natural materials. However, kinetic processes during generation, modification, or transport of natural materials can also affect their clumped-isotope compositions. Herein, we show that methane generated experimentally by closed-system hydrous pyrolysis of shale or nonhydrous pyrolysis of coal yields clumped-isotope compositions consistent with an equilibrium distribution of isotopologues under some experimental conditions (temperature-time conditions corresponding to 'low,' 'mature,' and 'over-mature' stages of catagenesis), but can have non-equilibrium (i.e., kinetically controlled) distributions under other experimental conditions ('high' to 'over-mature' stages), particularly for pyrolysis of coal. Non-equilibrium compositions, when present, lead the measured proportions of clumped species to be lower than expected for equilibrium at the experimental temperature, and in some cases to be lower than a random distribution of isotopes (i.e., negative Δ18 values). We propose that the consistency with equilibrium for methane formed by relatively low temperature pyrolysis reflects local reversibility of isotope exchange reactions involving a reactant or transition state species during demethylation of one or more components of kerogen. Non-equilibrium clumped-isotope compositions occur under conditions where 'secondary' cracking of retained oil in shale or wet gas hydrocarbons (C2-5, especially ethane) in coal is prominent. We suggest these non-equilibrium isotopic compositions are the result of the expression of kinetic isotope effects during the irreversible generation of methane from an alkyl
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Black shales and naftogenesis. A review
International Nuclear Information System (INIS)
Yudovich, Yu.E.; Ketris, M.P.
1993-01-01
A genetic relation between petroleum plus hydrocarbon gases and bio organic authigenic matter has been well established. As black shales are enriched in organic matter they may serve as potential petroleum beds on the depths suitable for petroleum generation (2-5 km). The calculations made by petroleum geologists showed that hydrocarbon amounts generated by black shales made up to one fifth of the initial organic matter at the end of MK-2 stage of catagenesis. Consequently, black shales may serve as the main oil producers in many sedimentary basins. Petroleum generation in black shales has some peculiarities. Abundant masses of organic matter generate huge amounts of hydrocarbon gases which in turn produce anomalous high bed pressures followed by pulse cavitation effect. Bed pressures 1.5 times higher than normal lithostatic pressure have been detected in oil-bearing black shales of the Cis-Caucasus on the depth of 2.0-2.5 km, along with very high (6 degrees per 100 m) geothermal gradient. According to Stavropol oil geologists, there occurs an effect of rock-by-fluid-destruction after fluid pressure has greatly exceeded the lithostatic pressure. Stress tensions discharge by impulses and cracks may appear with a rate of 0.3-0.7 of the sound speed. Cavitation of gaseous bubbles is produced by sharp crack extension. Such cavitation accounts for impact waves and increased local pressure and temperature. Such an increase, in turn, fastens petroleum generation and new rock cracking. The effect of over-pressed rocks associated with black shales may serve as a process indicator. That is why the geophysical methods detect enhanced specific gravity and decreased porosity zones in such black shales. Cracks and petroleum accumulation occur on the flanks of such zones of rock-by-fluid-destruction. Some black shales may be petroleum-productive due to enhanced uranium content. There exist ideas about uranium-derived heat or radiolytic effects on the petroleum generation. Such
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Shuai, Yanhua; Etiope, Giuseppe; Zhang, Shuichang; Douglas, Peter M. J.; Huang, Ling; Eiler, John M.
2018-01-01
Abiotic hydrocarbon gas, typically generated in serpentinized ultramafic rocks and crystalline shields, has important implications for the deep biosphere, petroleum systems, the carbon cycle and astrobiology. Distinguishing abiotic gas (produced by chemical reactions like Sabatier synthesis) from biotic gas (produced from degradation of organic matter or microbial activity) is sometimes challenging because their isotopic and molecular composition may overlap. Abiotic gas has been recognized in numerous locations on the Earth, although there are no confirmed instances where it is the dominant source of commercially valuable quantities in reservoir rocks. The deep hydrocarbon reservoirs of the Xujiaweizi Depression in the Songliao Basin (China) have been considered to host significant amounts of abiotic methane. Here we report methane clumped-isotope values (Δ18) and the isotopic composition of C1-C3 alkanes, CO2 and helium of five gas samples collected from those Xujiaweizi deep reservoirs. Some geochemical features of these samples resemble previously suggested identifiers of abiotic gas (13C-enriched CH4; decrease in 13C/12C ratio with increasing carbon number for the C1-C4 alkanes; abundant, apparently non-biogenic CO2; and mantle-derived helium). However, combining these constraints with new measurements of the clumped-isotope composition of methane and careful consideration of the geological context, suggests that the Xujiaweizi depression gas is dominantly, if not exclusively, thermogenic and derived from over-mature source rocks, i.e., from catagenesis of buried organic matter at high temperatures. Methane formation temperatures suggested by clumped-isotopes (167-213 °C) are lower than magmatic gas generation processes and consistent with the maturity of local source rocks. Also, there are no geological conditions (e.g., serpentinized ultramafic rocks) that may lead to high production of H2 and thus abiotic production of CH4 via CO2 reduction. We propose
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Shuai, Yanhua; Douglas, Peter M.J.; Zhang, Shuichang; Stolper, Daniel A.; Ellis, Geoffrey S.; Lawson, Michael; Lewan, Michael; Formolo, Michael; Mi, Jingkui; He, Kun; Hu, Guoyi; Eiler, John M.
2018-01-01
Multiply isotopically substituted molecules (‘clumped’ isotopologues) can be used as geothermometers because their proportions at isotopic equilibrium relative to a random distribution of isotopes amongst all isotopologues are functions of temperature. This has allowed measurements of clumped-isotope abundances to be used to constrain formation temperatures of several natural materials. However, kinetic processes during generation, modification, or transport of natural materials can also affect their clumped-isotope compositions. Herein, we show that methane generated experimentally by closed-system hydrous pyrolysis of shale or nonhydrous pyrolysis of coal yields clumped-isotope compositions consistent with an equilibrium distribution of isotopologues under some experimental conditions (temperature–time conditions corresponding to ‘low,’ ‘mature,’ and ‘over-mature’ stages of catagenesis), but can have non-equilibrium (i.e., kinetically controlled) distributions under other experimental conditions (‘high’ to ‘over-mature’ stages), particularly for pyrolysis of coal. Non-equilibrium compositions, when present, lead the measured proportions of clumped species to be lower than expected for equilibrium at the experimental temperature, and in some cases to be lower than a random distribution of isotopes (i.e., negative Δ18 values). We propose that the consistency with equilibrium for methane formed by relatively low temperature pyrolysis reflects local reversibility of isotope exchange reactions involving a reactant or transition state species during demethylation of one or more components of kerogen. Non-equilibrium clumped-isotope compositions occur under conditions where ‘secondary’ cracking of retained oil in shale or wet gas hydrocarbons (C2-5, especially ethane) in coal is prominent. We suggest these non-equilibrium isotopic compositions are the result of the expression of kinetic isotope effects during the irreversible generation
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Geophysical aspects of underground fluid dynamics and mineral transformation process
Khramchenkov, Maxim; Khramchenkov, Eduard
2014-05-01
The description of processes of mass exchange between fluid and poly-minerals material in porous media from various kinds of rocks (primarily, sedimentary rocks) have been examined. It was shown that in some important cases there is a storage equation of non-linear diffusion equation type. In addition, process of filtration in un-swelling soils, swelling porous rocks and coupled process of consolidation and chemical interaction between fluid and particles material were considered. In the latter case equations of physical-chemical mechanics of conservation of mass for fluid and particles material were used. As it is well known, the mechanics of porous media is theoretical basis of such branches of science as rock mechanics, soil physics and so on. But at the same moment some complex processes in the geosystems lacks full theoretical description. The example of such processes is metamorphosis of rocks and correspondent variations of stress-strain state. In such processes chemical transformation of solid and fluid components, heat release and absorption, phase transitions, rock destruction occurs. Extensive usage of computational resources in limits of traditional models of the mechanics of porous media cannot guarantee full correctness of obtained models and results. The process of rocks consolidation which happens due to filtration of underground fluids is described from the position of rock mechanics. As an additional impact, let us consider the porous media consolidating under the weight of overlying rock with coupled complex geological processes, as a continuous porous medium of variable mass. Problems of obtaining of correct storage equations for coupled processes of consolidation and mass exchange between underground fluid and skeleton material are often met in catagenesi processes description. The example of such processes is metamorphosis of rocks and correspondent variations of stress-strain state. In such processes chemical transformation of solid and fluid
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Organic geochemical study of domanik deposits, Tatarstan Republic.
Nosova, F. F.; Pronin, N. V.
2010-05-01
in reducing environments. Mass chromatograms show the distribution of regular steranes, iso-steranes, lower molecular weight C21 and C22 steranes (pregnanes) (m/z 217) and triterpanes (m/z 191). The biomarkers distribution of the domanic samples generally suggests a major marine phytoplankton contribution relative to terrigenous land plant source input. The marine affinity is evident from the relatively abundant C27 steranes, which are biomarkers for marine algal contribution to organic matter and low C29 sterane contens. In this present study, samples are dominated by 5α, 14α, 17α (H)-20R and 5β, 14α, 17α (H)-20R steranes (biological configuration). The ratios of 20S/(20S+20R) for αααC29 steranes and ββ/(αα + ββ) for 5α-C29 steranes in the samples, are 0.21 to 0.55 and to 0.12 to 0.50, respectively. The thermal maturity level, assessed by values of several biomarker parameters has been estimated to be within end of diagenesis/eginning of catagenesis and correspond to theoretical vitrinite values (R0) in the range 0.57-0.65%.
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Energy Technology Data Exchange (ETDEWEB)
Muscio, G P.A.
1995-07-01
When petroleum is produced from its reservoir at present day, it has already been submitted to a complex array of natural processes, which have left their imprint on its chemical and physical properties. These processes involve the generation of petroleum in its source rock as a function of thermal evolution, and its migration to the reservoir. In order to achieve a better understanding of the effects that these processes have on the nature and occurrence of petroleum, it is crucial to investigate a study area that represents an integrated system encompassing all processes from the beginning of crude oil formation to entrapment. The Bakken Shale petroleum system of the Williston Basin (U.S.A./Canada) appears to fulfil these requirements as it covers a broad range of maturity incorporating all stages of catagenesis, and source and reservoir are closely associated, i.e. Bakken petroleum has not been submitted to long secondary migration routes. Combined with a basinwide uniformity in kerogen type, the latter feature constrains the broad scope of potential influences, and therefore the Bakken petroleum system is an ideal candidate to study petroleum generation, its expulsion and migration under natural conditions. By using a selected set of wells/core samples which were considered to be representative for the entire Bakken petroleum system based on comprehensive screening analyses on both kerogen and bitumen, the present study focussed on the following principal aspects: (1) Evolution of petroleum generation as a function of maturation; (2) Primary migration and distribution of crude oil in a constrained natural system; (3) Occurrence of gas in the immature zone; (4) Evaluation of the natural maturity series with simulation experiments. (orig./HS) [Deutsch] Die Prozesse und Phaenomene der natuerlichen Bildung und Migration von Erdoel und Erdgas laufen waehrend der Katagenese sowohl zeitlich als auch raeumlich zu grossen Teilen parallel zueinander ab und praegen die