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Claude Largeau - One of the best experts on this subject based on the ideXlab platform.
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comparison of the bulk geochemical features and thermal reactivity of Kerogens from mol boom clay bure callovo oxfordian argillite and tournemire toarcian shales underground research laboratories
Science of The Total Environment, 2008Co-Authors: I Deniau, Sylvie Derenne, Françoise Behar, I Devolbrown, Claude LargeauAbstract:Abstract Deep argillaceous formations are potential repositories for the long-term disposal of nuclear waste because of their low permeability and high sorption capacity with respect to radioelements and heavy metals. Such sedimentary rocks contain organic matter, mostly macromolecular and insoluble (Kerogen). Upon temperature elevation related to high-level long-lived radioactive waste disposal, the Kerogen may release significant quantities of gaseous and liquid effluents, especially oxygen-containing ones, which may influence the ability of the clay to retain radionuclides. The aim of the present study is to assess the global geochemical features and the thermal reactivity of the Kerogens isolated from samples collected in the Bure and Tournemire sites, France (Callovo–Oxfordian Clay and Toarcian Shales, respectively) and to draw comparisons with data previously obtained for the Mol site, Belgium (Boom Clay). The study is based on a combination of elemental, spectroscopic (FTIR, solid state 13 C NMR) and pyrolytic (Rock-Eval pyrolysis, Curie point pyrolysis–gas chromatography/mass spectrometry) analyses. Different levels of maturity and resulting differences in the relative abundance of oxygen-containing groups were thus observed for the three Kerogens. This is linked with differences in their ability to generate CO 2 and various oxygen-containing, low molecular weight, water-soluble compounds under thermal stress, decreasing from Mol to Bure and to Tournemire.
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Kerogen origin, evolution and structure
Organic Geochemistry, 2007Co-Authors: M. Vandenbroucke, Claude LargeauAbstract:Kerogen, commonly defined as the insoluble macromolecular organic matter (OM) dispersed in sedimentary rocks, is by far the most abundant form of OM on Earth. This fossil material is of prime importance as the source of oil and natural gas; moreover, Kerogen can provide essential information on major topics such as past environments, climates and biota. This review reports the main advances in Kerogen studies since the comprehensive synthesis edited by Durand [Durand, B. (Ed.), Kerogen, Insoluble Organic Matter from Sedimentary Rocks. Editions Technip, Paris, 1980.]. It is organized into eight sections. The first two are concerned with the successive definitions of Kerogen and the definition used here, the different techniques used for Kerogen isolation without loss or degradation and basic Kerogen analysis. The third and fourth focus on sedimentary OM sources and preservation processes in relation to depositional environment, including sedimentation conditions favourable for Kerogen accumulation, and extrapolation to past geological time. Great strides have been made in the latter topics over the last 25 years, owing to a combination of classical studies in organic geochemistry and studies in other domains such as biogeochemistry, oceanography, hydrology and soil science, along with the development of powerful analytical tools. The next two sections deal with the different Kerogen classifications by type and Kerogen evolution and maturation upon burial in sediments. Structural modelling of coal and Kerogen, based on physical and/or chemical structural analysis, is described in the following section. Although, only statistical, the models thus derived provide a synthetic view of the main structural resemblances and differences among various samples in relation to source, maturity or physicochemical properties. Finally, the last section explores some of the advances in Kerogen understanding expected for the near future. The review includes a list containing about 500 references.
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Cyanobacterial resistant biopolymers. Geochemical implications of the properties of Schizothrix sp. resistant material
Organic Geochemistry, 2003Co-Authors: S. Chalansonnet, Claude Largeau, Eliette Casadevall, C. Berkaloff, G. Peniguel, Remy CoudercAbstract:Biopolymers highly resistant to drastic chemical treatments occur in the walls of some microalgae. A large level of resistant material, termed PRB, was detected in the green colonial alga Botryococcus braunii. A close relationship between the chemical structure of PRB and of immature Torbanite demonstrated that selective preservation of the resistant material played a major role in the formation of this algal Kerogen. Cyanobacterial derived matter probably provided an important contribution to the formation of numerous amorphous Kerogens, including stromatolites. On the other hand, five species of cyanobacteria, of six tested, were shown to contain various levels of resistant biopolymer and a quite high content was noted in Schizothrix sp. The resistant materials of Schizothrix sp., Anacystis montana and Oscillatoria rubescens show similar chemical structure but sharply differ from PRB. Accordingly the existence of a new group of resistant biopolymers appears likely in cyanobacteria. Cyanobacterial resistant biopolymers are located in the cell envelope and exhibit an amorphous nature. Such features are in agreement with observations both on Recent mats and stromatolites and may account, firstly, for the formation of cyanobacterial Kerogens mainly via selective preservation of resistant envelope constituents and, secondly, for the amorphous nature of such Kerogens, well documented in the case of stromatolites.
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factors controlling the survival of proteinaceous material in late tithonian Kerogens kashpir oil shales russia
Organic Geochemistry, 2002Co-Authors: Armelle Riboulleau, Sylvie Derenne, François Baudin, Thierry Mongenot, Claude LargeauAbstract:Thermochemolysis experiments with tetramethylammonium hydroxide (TMAH), on three Late Jurassic Kerogens with contrasting features, confirmed the major role of encapsulation into aliphatic structures for the survival of proteinaceous moieties in Kerogens, probably via lipid sulphurisation. It also appeared that (i) some amino acid moieties survived even in the Kerogen of a sediment deposited under oxic conditions, although in lower relative abundance compared to the other two Kerogens, (ii) the survival of amino acids on geological time scales, within an organic matrix, is probably rather common in Kerogens, especially for glycine and alanine, and (iii) thermochemolysis of Kerogen sub-units with a lower degree of cross-linking rather than direct thermochemolysis of whole Kerogens is recommended to test the presence of amino acid moieties, so as to avoid dilution problems and to increase the accessibility of the TMAH.
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Sulfur speciation in Kerogens of the Orbagnoux deposit (Upper Kimmeridgian, Jura) by XANES spectroscopy and pyrolysis
Organic Geochemistry, 2002Co-Authors: Géraldine Sarret, Sylvie Derenne, Masoud Kasrai, Thierry Mongenot, Jacques Connan, G. Michael Bancroft, Claude LargeauAbstract:Abstract Thermally immature, extremely sulfur-rich Kerogens from the Orbagnoux deposit have been extensively studied over the last few years for their chemical structure, source organisms and depositional conditions. However, important uncertainties remain concerning sulfur speciation in these Kerogens and changes in sulfur functionality that occur upon thermal stress. In the present study sulfur speciation for isolated Kerogens from the five facies recognized in the deposit was established via K- and L-edge X-ray Absorption Near Edge Structure (XANES) spectroscopy. A representative sample of the most organic-rich facies of the deposit, the dark parallel laminae, was examined by “direct” pyrolysis at 400 °C and the results compared with those previously derived from “indirect” pyrolysis (carried out under the same conditions but from Kerogen pre-heated at 300 °C). XANES examination was performed on the unheated Kerogen, the pre-heated Kerogen, the insoluble pyrolysis residues and the effluents obtained via these two pyrolyses. Sulphur distribution was also determined via elemental analyses and measurements of evolved H2S. Identification of the pyrolysis products of the “direct” experiment was performed by gas chromatographic/mass spectrometric analyses, before and after desulfurization, of the crude pyrolysate and of separated fractions and sub-fractions. Substantial quantitative and qualitative differences are thus noted between the “direct” and “indirect” pyrolyses at 400 °C, as a result of the cleavage and aromatization of some sulfide bridges occurring upon pre-heating at 300 °C. Thus, the “indirect” pyrolysis appears somewhat less efficient for the thermal cracking of the macromolecular structure of the Kerogen. Nevertheless, it provides more detailed information on the intermolecularly sulfur-linked carbon skeletons that build up the bulk of this structure owing to (i) the release of OSC with higher carbon numbers and (ii) the much easier desulfurization of the molecular aggregates probably due to a lower degree of cross-linking. XANES spectroscopy showed that (i) thiophenes are the main sulfur species in the unheated Kerogens and (ii) substantial aromatization of the non-thiophenic sulfur forms occurs upon the thermal treatments.
Mohammed Hail Hakimi - One of the best experts on this subject based on the ideXlab platform.
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organic geochemistry and basin modeling of late cretaceous harshiyat formation in the onshore and offshore basins in yemen implications for effective source rock potential and hydrocarbon generation
Marine and Petroleum Geology, 2020Co-Authors: Mohammed Hail Hakimi, Adeeb Ahmed, Ali Y Kahal, Osman Salad Hersi, Hussain Al J Faifi, Saleh QaysiAbstract:Abstract The purpose of this study is to present the source rock characteristics of Late Cretaceous Harshiyat Formation source rock in the onshore and offshore basins of Yemen (i.e. Mukalla-Sayhut, Sayun–Masila, and Jeza-Qamar). Source rock geochemical characterizations were completed and integrated to perform 1-D basin modeling to back-predict source rock thermal maturation, oil generation and expulsion. The geochemical findings revealed that mudstone intervals within the Harshiyat Formation comprised favorable source rocks, with total organic carbon (TOC) content between 0.50 and 35.10 wt %. The organic matter intervals in the Harshiyat mudstones are mainly Types II/III and III Kerogens, with certain amount of Type II and I Kerogens based on Rock-Eval HI values, ranging from 40 to 923 mg HC/g TOC. Mixed Kerogen types were consistent with vitrinite and sapropelic organic matters provided by terrigenous plant inputs, as observed by visual Kerogen examination and the distribution of biomarker fingerprints. The existence of mixed types I, II, and III organic matter suggests that the Harshiyat mudstones could contribute to oil and gas at sufficient thermal maturity levels. The biomarker data of the organic matter in the Harshiyat mudstones show the source rock contains a mix marine phytoplanktonic-bacteria/terrestrial land plant enthronement and were deposited in suboxic-anoxic conditions. Results of chemical and optical maturity indicators led to the conclusion of varying maturity stages from immature to late oil window levels for the mudstones of the Harshiyat Formation. Thermal maturation distributions inferred from the analyzed samples indicate that mudstone intervals in the offshore Mukalla-Sayhut Basin are extremely mature, compatible with the late-mature oil window and may have generated significant amounts of oil. This interpretation was supported by strong geochemical similarity between the organic matter in the mudstones and those of the oils found in the offshore Mukalla-Sayhut Basin and demonstrated by the concentrations of n-alkanes and isoprenoids as well as carbon isotopes. In the offshore Ras-Ghashwah-1X well, burial and thermal models were constructed and used to address the effect of tectonic events in triggering oil generation and expulsion from mature Harshiyat source rock in the offshore area. Kinetic database models for Type II and III Kerogen mixtures indicate that the initial conversion of Kerogen to oil occurred since the Late Oligocene with transformation ratios (TR) that span between 10% and 50%. Furthermore, the oil was expelled from organic matter intervals in the Harshiyat source rock starting from Late Oligocene and continuing until Late Miocene, with TRs of 50%–72%. From that period up to the present, the retained oil was cracked into wet gas in the gas window with an Easy %Ro greater than 1.30, and with peak TR ratios greater than 72%.
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late jurassic safer salt member in the al jawf sub basin of nw sabatayn basin yemen geochemical evaluation of organic rich oil source rock potential
Petroleum Science and Technology, 2019Co-Authors: Mohammed Hail Hakimi, Hussain Al J Faifi, Abdulwahab S Alaug, Gamal A Alramisy, Aref LashinAbstract:AbstractLate Jurassic Safer shales in the Al-Jawf sub-basin are analyzed to evaluate the organic matter input, depositional conditions and petroleum generation potential. The shales have high organic matter, with TOC values of 1.0-13.5% and they contain predominantly Types II and III Kerogen, referring to mainly oil- and gas-prone. These Kerogens are indicative for dominate marine algal component and some terrestrial organic matter input as indicated from biomarkers. Moreover, the presence of the gammacerane also confirmed a high salinity stratification condition and suggests that the dominate Type II Kerogen is rich-sulphur Kerogen (Type II-S). The vitrinite reflectance (VRo%) and Rock-Eval pyrolysis Tmax data indicate that the analyzed shales are immature.
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source rock characteristics of the lower cretaceous abu gabra formation in the muglad basin sudan and its relevance to oil generation studies
Marine and Petroleum Geology, 2015Co-Authors: Yousif M Makeen, Mohammed Hail Hakimi, Wan Hasiah Abdullah, Khairul Azlan MustaphaAbstract:Organic-rich shale and claystone are present within the Lower Cretaceous Abu Gabra Formation of the Muglad Basin, representing excellent oil source rocks. The source rock potential of Abu Gabra organicrich whole rock samples from two oilfields in the Muglad Basin was investigated using bulk and quantitative pyrolysis techniques. The analytical program included TOC, pyrolysis (SRA), pyrolysis GC, bulk kinetics, elemental analysis and Kerogen microscopy. The results were used to characterize the Kerogen composition and type of petroleum generated from these Abu Gabra organic-rich sediments to clarify the structural variability of the organic matter in the Abu Gabra source rock. The investigated Abu Gabra organic-rich sediments proved to contain excellent quality lacustrine Kerogens. The samples have moderate to high hydrogen index (HI) values (267e837 mg HC/g rock), consistent with predominantly oil-prone Types I and II Kerogen with a minor contribution of Type IIeIII Kerogens. This is supported by the abundant liptinitic materials (i.e., lipid-rich structured algae, structureless (amorphous) alginite, and sporinite) and high atomic hydrogen-to-carbon (H/C) ratio. However, pyrolysis GC analysis proved that all the investigated Abu Gabra samples contain homogeneous Type I Kerogen that produces mainly waxy oil. Bulk Kinetic experiments on these samples indicate that the source rock facies derived from a homogenous organic matter, spans an extremely narrow distribution of activation energy (Ea) ranges from 49 kcal/mol to 51 kcal/mol. The magnitude order of frequency factors (A) also show a narrow distribution range from 10
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thermal maturity history and petroleum generation modelling for the upper jurassic madbi source rocks in the marib shabowah basin western yemen
Marine and Petroleum Geology, 2015Co-Authors: Mohammed Hail Hakimi, Wan Hasiah AbdullahAbstract:Abstract Widely exposed in the Marib-Shabowah Basin, the early Upper Jurassic Madbi Formation is divided into two units (Lam and Meem, youngest to oldest) believed to be major source rocks. The Madbi source rocks are characterized by relatively high total organic carbon contents (TOC) ranging from 0.5 to 10.0 wt%, meeting the standard as a fair to excellent source rock generative potential. They contain Type II Kerogen grading to mixed Type II/III Kerogens and Type III Kerogen with HI values between 40 and 620 mg HC/g TOC. Vitrinite reflectance values range from 0.41 to 2.61% R o , indicating sufficient thermal maturity for both oil and gas generation. Burial/thermal history models indicate that the Upper Jurassic Madbi source rocks passed the peak of oil generation stage and convert the oil to dry gas in the Late Jurassic to Late Cretaceous time. Oil generation began immediately after deposition in the Late Jurassic time (150–145 Ma) and maximum rates of oil with significant gas have been generated during Late Cretaceous time (110–65 Ma). The peak gas generation occurred during the early Tertiary. The modelled hydrocarbon expulsion evolution suggests that the timing of hydrocarbon expulsion from the Madbi source rocks began in the early Cretaceous (140 Ma) persisted to present-day. The modelling results also indicate that the peak hydrocarbon generation and expulsion from Madbi source rocks in the studied area occurs well after deposition of the seal rock and formation of traps, ensuring entrapment and preservation of migrated hydrocarbons.
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geochemistry and organic petrology study of kimmeridgian organic rich shales in the marib shabowah basin yemen origin and implication for depositional environments and oil generation potential
Marine and Petroleum Geology, 2014Co-Authors: Mohammed Hail Hakimi, Wan Hasiah Abdullah, Mohamed Ragab Shalaby, Gamal A AlramisyAbstract:Kimmeridgian organic-rich shales of the Madbi Formation from the Marib-Shabowah Basin in western Yemen were analysed to evaluate the type of organic matter, origin and depositional environments as well as their oil-generation potential. Results of the current study establishes the organic geochemical characteristics of the Kimmeridgian organic-rich shales and identifies the Kerogen type based on their organic petrographic characteristics as observed under reflected white light and blue light excitation. Kerogen microscopy shows that the Kimmeridgian organic-rich shales contain a large amount of organic matter, consisting predominantly of yellow fluorescing alginite and amorphous organic matter with marine-microfossils (e.g., dinoflagellate cysts and micro-foraminiferal linings). Terrigenous organic matters (e.g., vitrinite, spores and pollen) are also present in low quantities. The high contributions of marine organic matter with minor terrigenous organic matter are also confirmed by carbon isotopic values. The organic richness of the Kimmeridgian shales is mainly due to good preservation under suboxic to relatively anoxic conditions, as indicated by the percent of numerous pyritized fragments associated with the organic matter. The biomarker parameters obtained from mass spectrometer data on m/z 191 and m/z 217 also indicate that these organic-rich shales contain mixed organic matter that were deposited in a marine environment and preserved under suboxic to relatively anoxic conditions. The Kimmeridgian organic-rich shales thus have high oil and low gas-generation potential due to oil window maturities and the nature of the organic matter, with high content of hydrogen-rich Type II and mixed Type II-III Kerogens with minor contributions of Type III Kerogen.
Jinzhong Liu - One of the best experts on this subject based on the ideXlab platform.
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chemical structure changes of lacustrine type ii Kerogen under semi open pyrolysis as investigated by solid state 13c nmr and ft ir spectroscopy
Marine and Petroleum Geology, 2020Co-Authors: Lianhua Hou, Xia Luo, Shizhen Tao, Ping Guan, Jinzhong LiuAbstract:Abstract At present, there is a lack of research on the structural changes of lacustrine Type-II Kerogen, which is regionally distributed but has significant potential for hydrocarbon resources. In our previous work, a series of non-hydrous, temperature-based semi-open pyrolysis experiments have been performed on the Chang 7 oil shale to simulate the thermal maturation (from 0.53 %Ro to 1.68 %Ro) of lacustrine Type-II Kerogen. In that work, the parallel reaction pathway for Kerogen decomposition was supported. The aim of this work is to reveal the structural changes of the post-pyrolysis Kerogen. Integrated analysis including elemental analysis, programmed pyrolysis (Rock-Eval), Fourier transform infrared (FT-IR) spectroscopy, and solid-state 13C nuclear magnetic resonance (13C NMR) spectroscopy were conducted on the native unheated and post-pyrolysis rocks and Kerogens. Based on the compositional features of the hydrocarbon products, structural changes of the post-pyrolysis Kerogen were investigated, and insights on the initial chemical structure of the Kerogen were also obtained. Before the peak hydrocarbon-generating stage (Ro 1.09%), the reactions in the previous two stages produce a highly aromatic Kerogen. The increased aromaticity of the highly matured Kerogen is most likely to be caused by aromatization or dehydrogenation of hydroaromatics and coking of aromatic bitumen, not by fusing or condensation of aromatic rings.
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role of bitumen and nsos during the decomposition process of a lacustrine type ii Kerogen in semi open pyrolysis system
Fuel, 2020Co-Authors: Lianhua Hou, Jinzhong Liu, Xia Luo, Shizhen Tao, Ping Guan, Senhu LinAbstract:Abstract The purpose of this work is to investigate the generation characteristics of bitumen, NSO compounds, oil, and HC compounds during the artificial maturation of a lacustrine Type-II Kerogen (which has not been given enough attention before) in order to determine its decomposition process. The analysis is based on the data itself, on the premise of jumping out of the generally accepted sequential reaction model. By taking the Kerogen of the Chang 7 shale as an example, seven parallel experiments, in the temperature range from 300 °C to 420 °C were conducted on newly designed temperature-based semi-open pyrolysis system. The overall products are classified into oil and bitumen according to their phase, the C15+ fractions are classified into C15+sat, C15+aro and NSOs based on chemical compositions, and the NSOs are further classified into n-pentane NSOs and DCM NSOs according to Behar et al., (2008) and (2010). Results show that large proportion of oil is not merely a result of thermal cracking of bitumen, but also directly from the decomposition of Kerogen itself. Both C15+sat and C15+aro are generated as soon as Kerogen starts to decompose. It is not until the initial productivity of Kerogen is basically exhausted that NSOs become the main precursor of hydrocarbons. The comparison with Behar et al. [2008, organic geochemistry 39, 1–22] further reveals that, for Chang 7 Kerogen, initial decomposition of Kerogen generates much more HCs than DCM NSOs. These results contradict the sequential reaction model described as: Kerogen → bitumen → oil or Kerogen → NSOs → hydrocarbons. Instead, they confirm the “alternate pathway” mechanism proposed by Burnham et al. [ACS symposium, 1989] in which hydrocarbons can be formed immediately from Kerogen in parallel with NSOs and the formation of the two species are controlled by bond-breaking reactions that are independent of each other. This study adds geochemical insights into the decomposition mechanism of lacustrine Type-II Kerogen.
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the effect of oil expulsion or retention on further thermal degradation of Kerogen at the high maturity stage a pyrolysis study of type ii Kerogen from pingliang shale china
Organic Geochemistry, 2014Co-Authors: Wanglu Jia, Qiuling Wang, Jinzhong Liu, Pingan PengAbstract:High maturity oil and gas are usually generated after primary oil expulsion from source rocks, especially from oil prone type I/II Kerogen. However, the detailed impacts of oil expulsion, or retention in source rock on further thermal degradation of Kerogen at the high maturity stage remain unknown. In the present study, we collected an Ordovician Pingliang shale sample containing type II Kerogen. The Kerogens, which had previously generated and expelled oil and those which had not, were prepared and pyrolyzed in a closed system, to observe oil expulsion or oil retention effects on later oil and gas generation from Kerogen. The results show that oil expulsion and retention strongly impacts on further oil and gas generation in terms of both the amount and composition in the high maturity stage. Gas production will be reduced by 50% when the expulsion coefficient reaches 58%, and gas from oil-expelled Kerogen (less oil retained) is much drier than that from fresh Kerogen. The oil expulsion also causes n-alkanes and gas compounds to have heavier carbon isotopic compositions at high maturity stages. The enrichment of 13C in n-alkanes and gas hydrocarbons are 1‰ and 4–6‰ respectively, compared to fresh Kerogen. Oil expulsion may act as open system opposite to the oil retention that influences the data pattern in crossplots of δ13C2–δ13C3 versus C2/C3, δ13C2–δ13C3 versus δ13C1 and δ13C1–δ13C2 versus ln(C1/C2), which are widely used for identification of gas from Kerogen cracking or oil cracking. These results suggest that the reserve estimation and gas/source correlation in deep burial basins should consider the proportion of oil retention to oil expulsion the source rocks have experienced.
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geochemical characterization of released bound biomarkers by catalytic hydropyrolysis of ordovician source rock from tarim basin china
Energy Exploration & Exploitation, 2013Co-Authors: Qingtao Wang, Jinzhong Liu, Pingan Peng, Linxiang Jiang, Jian ZengAbstract:The Salgan and Yingan shales in the Keping area are Middle and Upper Ordovician hydrocarbon source rocks in the Tarim Basin, north-western China. Complete distribution of n-alkanes and isoprenoids can be obtained from the source rocks, while general terpanes (m/z 191) and steranes (m/z 217) were totally absent. Therefore, Kerogens in these rocks were further treated by catalytic hydropyrolysis (HyPy) to obtain more biomarker information. As an efficient technique, Hypy successfully released bound terpanes and steranes. Furthermore, some maturity parameters were calculated. Based on the values of these parameters, the effective Ro value of bound biomarkers in Salgan and Yingan shale was deduced to be in the range of 0.7-0.75% and 0.65-0.73%, respectively. Considering the artificial heating effect in HyPy technique, relatively lower values would be expected to the maturity of the bound biomarkers. Therefore, the incorporation of bound biomarkers into Kerogen should occur even earlier, before the Ro value re...
M. Vandenbroucke - One of the best experts on this subject based on the ideXlab platform.
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Kerogen origin, evolution and structure
Organic Geochemistry, 2007Co-Authors: M. Vandenbroucke, Claude LargeauAbstract:Kerogen, commonly defined as the insoluble macromolecular organic matter (OM) dispersed in sedimentary rocks, is by far the most abundant form of OM on Earth. This fossil material is of prime importance as the source of oil and natural gas; moreover, Kerogen can provide essential information on major topics such as past environments, climates and biota. This review reports the main advances in Kerogen studies since the comprehensive synthesis edited by Durand [Durand, B. (Ed.), Kerogen, Insoluble Organic Matter from Sedimentary Rocks. Editions Technip, Paris, 1980.]. It is organized into eight sections. The first two are concerned with the successive definitions of Kerogen and the definition used here, the different techniques used for Kerogen isolation without loss or degradation and basic Kerogen analysis. The third and fourth focus on sedimentary OM sources and preservation processes in relation to depositional environment, including sedimentation conditions favourable for Kerogen accumulation, and extrapolation to past geological time. Great strides have been made in the latter topics over the last 25 years, owing to a combination of classical studies in organic geochemistry and studies in other domains such as biogeochemistry, oceanography, hydrology and soil science, along with the development of powerful analytical tools. The next two sections deal with the different Kerogen classifications by type and Kerogen evolution and maturation upon burial in sediments. Structural modelling of coal and Kerogen, based on physical and/or chemical structural analysis, is described in the following section. Although, only statistical, the models thus derived provide a synthetic view of the main structural resemblances and differences among various samples in relation to source, maturity or physicochemical properties. Finally, the last section explores some of the advances in Kerogen understanding expected for the near future. The review includes a list containing about 500 references.
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Kerogen: from Types to Models of Chemical Structure
Oil & Gas Science and Technology - Revue d'IFP Energies nouvelles, 2003Co-Authors: M. VandenbrouckeAbstract:The aim of the present paper is to review the conceptual and analytical developments in the period 1970-1990 which have led, through Kerogen isolation and analysis on one hand, and case studies of petroleum systems on the other hand, to the concept of Kerogen types, evolution paths, and statistical chemical models. Kerogen is defined as the sedimentary organic matter generating petroleum, an insoluble product as opposed to its counterpart soluble in usual organic solvents, such as petroleum. As Kerogen is a complex organic material intimately mixed with minerals in sediments, the first task was to set up a robust procedure for its isolation, enabling then its study by various physicochemical analyses. The parallel development of oil exploration, resulting in geological sample availability, made the geochemical comparison of various petroleum systems possible. Comparisons concerned not only oils, source rock extracts and Kerogen compositions, but also the timing of petroleum generation. The notion of kinetic cracking of Kerogen into petroleum stemming from these case studies, associated with the observation of time and temperature compensation, resulted in the use of pyrolysis to evaluate the oil potential still to be generated by the Kerogen, and in the construction of the Rock-Eval. In the mid 70s, all main parameters on Kerogens from reference series of source rocks were available to define the notions of types and evolution paths of Kerogens upon geological maturation. A further important step for improving the knowledge of Kerogen composition was achieved in the 80s using new techniques of analytical and preparative pyrolysis and their coupling with different detectors. The pyrolysis products, small building blocks issued from the Kerogen thermal cracking, could thus be analyzed and quantified at the molecular level, without the problems of representativity associated with natural extract analyses, such as loss of volatile fractions or product migration out of source rocks. ;Contemporaneous developments in solid state 13C NMR allowed quantification of the various forms of carbon and their molecular environment in the Kerogen, whereas quantification was not possible with IR or UV spectroscopy. The quantification of molecular building blocks and their bonding functional groups in Kerogens allowed conceptual averaged molecular models of Kerogens to be proposed in order to visualize their atomic and molecular composition, and the changes occurring in this composition according to types and maturity. Although it will never be possible to represent a true Kerogen structure, simply because it is a mixture of various nonpolymeric macromolecules, an hypothetical average structure of Kerogen, representing a large amount of information from various analyses, can provide a synthetic view of the main resemblances and differences among sedimentary organic matters.
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thermal cracking of Kerogen in open and closed systems determination of kinetic parameters and stoichiometric coefficients for oil and gas generation
Organic Geochemistry, 1997Co-Authors: F. Behar, M. Vandenbroucke, Yongchun Tang, F Marquis, J EspitalieAbstract:Abstract The purpose of the study is to compare artificial maturation of Kerogens representative of the main types of organic matter (Kerogen Types I, II, II-S and III) in open and anhydrous closed pyrolysis systems. The generated compounds are fractionated according to their thermal stability into six chemical classes: C 1 , C 2 C 5 , C 6 C 14 , C 15+ saturates, C 15+ aromatics and NSOs, which include resins and asphaltenes. In both systems, primary cracking of Kerogen can be described by two main reactions: oil generation together with early gas generation followed by late gas production. Mass balances obtained in the two pyrolysis systems are reasonably similar, although some secondary cracking of the NSOs and underestimation of methane potential due to incomplete pyrolysis may occur in the open system. Kinetic parameters of thermal cracking are derived from experiments in the open system using an optimization procedure which determines a unique frequency factor and a weight distribution of chemical classes for a discrete series of activation energies. The resultant frequency factors are checked with those obtained for specific molecular tracers such as n -C 12 - and n -C 24 -alkanes generated from Kerogens in open and closed systems under isothermal conditions. The results show that using a unique frequency factor as determined by optimization is correct for Type I, II and II-S Kerogens. This factor is more questionable, however, when the distribution of activation energies is very broad, such as for Type III coals. Based on this study, a strategy for determination of kinetic parameters on any new source rock sample is proposed.
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experimental simulation in a confined system and kinetic modelling of Kerogen and oil cracking
Organic Geochemistry, 1992Co-Authors: Françoise Behar, S Kressmann, J L Rudkiewicz, M. VandenbrouckeAbstract:Abstract The purpose of this study is to experimentally simulate both Kerogen and oil cracking in a closed pyrolysis system and then, to model the kinetic scheme. Kerogens were isolated from their mineral matrix in order to obtain a complete recovery of the insoluble residue. Experiments were conducted under anhydrous conditions in order to calculate atomic balances for carbon, hydrogen, oxygen and sulfur. The pyrolysis products were fractionated by molecular weight and relative thermal stability. The kinetic scheme comprises four kinds of reactions: 1. depolymerization reactions for Kerogen and heavy products such as resins and asphaltenes. This type of reaction involves the most labile compounds, which are likely to be generated by CO or/and CS bond cracking. It produces heavy soluble compounds but very small amounts of gases and pure liquid hydrocarbons. 2. CC bond cracking of C6+ saturated chains. These reactions occurat higher apparent activation energies than the previous ones. They generated shorter aliphatic chains but again, very low amounts of methane and ethane. 3. demethylation reactions of aromatic structures such as C9C13 compounds, polycondensed C14 + nuclei and the insoluble residue. The generated products are mainly gaseous compounds and coke. 4. CC bond cracking of C3C5 aliphatic chains which produces mainly methane and ethane, ethane being degraded into methane. Our results show that a unique kinetic scheme can be used for secondary cracking reactions either when oil is pyrolysed alone or when bitumen is first generated during Kerogen pyrolysis. The kinetic scheme involves 11 chemical classes fractionated by molecular weight and thermal stability; among them 3 are stable (methane, a mixture comprising benzene/toluene/xylenes/naphthalene and coke), 8 are unstable (ethane, C3C5, C9C13 aromatics, C6C13 saturates, C14+ unstable aromatics, C14+ condensed aromatics and precoke). Although the two Kerogens selected in this study are degraded with the same apparent activation energy and preexponential factor, stoichiometric coefficients must be specifically determined for each equation of the kinetic scheme in which Kerogen cracking is included.
Pingan Peng - One of the best experts on this subject based on the ideXlab platform.
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the effect of oil expulsion or retention on further thermal degradation of Kerogen at the high maturity stage a pyrolysis study of type ii Kerogen from pingliang shale china
Organic Geochemistry, 2014Co-Authors: Wanglu Jia, Qiuling Wang, Jinzhong Liu, Pingan PengAbstract:High maturity oil and gas are usually generated after primary oil expulsion from source rocks, especially from oil prone type I/II Kerogen. However, the detailed impacts of oil expulsion, or retention in source rock on further thermal degradation of Kerogen at the high maturity stage remain unknown. In the present study, we collected an Ordovician Pingliang shale sample containing type II Kerogen. The Kerogens, which had previously generated and expelled oil and those which had not, were prepared and pyrolyzed in a closed system, to observe oil expulsion or oil retention effects on later oil and gas generation from Kerogen. The results show that oil expulsion and retention strongly impacts on further oil and gas generation in terms of both the amount and composition in the high maturity stage. Gas production will be reduced by 50% when the expulsion coefficient reaches 58%, and gas from oil-expelled Kerogen (less oil retained) is much drier than that from fresh Kerogen. The oil expulsion also causes n-alkanes and gas compounds to have heavier carbon isotopic compositions at high maturity stages. The enrichment of 13C in n-alkanes and gas hydrocarbons are 1‰ and 4–6‰ respectively, compared to fresh Kerogen. Oil expulsion may act as open system opposite to the oil retention that influences the data pattern in crossplots of δ13C2–δ13C3 versus C2/C3, δ13C2–δ13C3 versus δ13C1 and δ13C1–δ13C2 versus ln(C1/C2), which are widely used for identification of gas from Kerogen cracking or oil cracking. These results suggest that the reserve estimation and gas/source correlation in deep burial basins should consider the proportion of oil retention to oil expulsion the source rocks have experienced.
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geochemical characterization of released bound biomarkers by catalytic hydropyrolysis of ordovician source rock from tarim basin china
Energy Exploration & Exploitation, 2013Co-Authors: Qingtao Wang, Jinzhong Liu, Pingan Peng, Linxiang Jiang, Jian ZengAbstract:The Salgan and Yingan shales in the Keping area are Middle and Upper Ordovician hydrocarbon source rocks in the Tarim Basin, north-western China. Complete distribution of n-alkanes and isoprenoids can be obtained from the source rocks, while general terpanes (m/z 191) and steranes (m/z 217) were totally absent. Therefore, Kerogens in these rocks were further treated by catalytic hydropyrolysis (HyPy) to obtain more biomarker information. As an efficient technique, Hypy successfully released bound terpanes and steranes. Furthermore, some maturity parameters were calculated. Based on the values of these parameters, the effective Ro value of bound biomarkers in Salgan and Yingan shale was deduced to be in the range of 0.7-0.75% and 0.65-0.73%, respectively. Considering the artificial heating effect in HyPy technique, relatively lower values would be expected to the maturity of the bound biomarkers. Therefore, the incorporation of bound biomarkers into Kerogen should occur even earlier, before the Ro value re...
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kinetics of oil group type generation and expulsion an integrated application to dongying depression bohai bay basin china
Organic Geochemistry, 2012Co-Authors: Zhifu Wei, Yanrong Zou, Yulan Cai, Lei Wang, Xiaorong Luo, Pingan PengAbstract:Pyrolysis of two Kerogens isolated from the E2-3s 3 3 and E2-3s 1 4 source rocks in the Niuzhuang sag, Dongying Depression, Bohai Bay Basin, China, was performed in a confined system. The products were extracted with solvent and separated using micro-column chromatography into group-type fractions (saturates, aromatics, resins and asphaltenes) with the Kerogen residue in each case undergoing swelling with a variety of solvents. The kinetics for generation and retention of crude oil and its group-type fractions from the Kerogens were studied and the kinetic parameters applied to modeling generation and retention of crude oil and its fractions from the E2-3s 3 3 and E2-3s 1 4 source rocks on the basis of burial and thermal history of the Niuzhuang sag. The results show that the ‘‘normal oil’’ was generated at about 4.26 Ma and 24.85 Ma ago, but expelled at about 3.96 Ma and 17.46 Ma ago, respectively, from E2-3s 3 3 and E2-3s 1 4 source rocks. The current proportions of the expelled saturates, aromatics and NSOs are about 60%, 15% and 25%, respectively.
