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Chemical (REE and major elements) and isotope (δ13C, δ18O) composition of carbonate manganese ores and manganese-bearing carbonates of the Usa deposit (Siberia, Russia) were studied. Received data on the composition of REE exhibit both the distinct negative (Ce/Ce*PAAS < 1) and positive (Ce/Ce*PAAS˃1) cerium anomalies and the positive Eu-anomaly (Eu/Eu*PAAS˃1). Negative Eu-anomalies are not observed. The contents of Mn, Fe, REE, and Ce-anomalies show a positive correlation with each other. Ce-anomalies and the amount of manganese and REE in relation to the carbon isotope composition (δ13C) show a negative relationship and indicate that oxidized carbon of organic matter played an important role in the concentration of manganese and REE in manganese ores. The chemical and isotope composition of examined rocks indicates on secondary formation of Mn-ores. Two major phases and sources are distinguished in the ore-forming process characterized by different chemical (REE and ore elements) and isotope composition: (i) high-grade manganese ores (with high contents of REE and light carbon isotope composition) and (ii) low-grade manganese ores (with low contents of REE and heavy carbon isotope composition). [ABSTRACT FROM AUTHOR]

The paper presents the results of the study of rock samples from Bazhenov deposits before and after laboratory modelling of hydrothermal processes in autoclaves. To evaluate the influence of hydrothermal influence on rocks of different degrees of transformation, 3 samples from the well, the rocks in which are located at the very beginning of the main zone of oil formation (PK3–MK1), and 4 samples from the well, the rocks in which are located in the middle of generation (MK2–MK3) were studied. Comparison of samples before and after heating was carried out by means of pyrolytic, coal petrography studies and analyses of polished section under scanning electron microscope. It is shown that at 350 °C there is a change in pyrolytic characteristics of the rock, which depends on the nature of organic matter and the degree of catagenetic transformation of kerogen at the time of exposure. It was found that as a result of exposure the initial macerals decrease in size and change their luminescence in ultraviolet light, secondary (kerogenic) porosity appears in onychite fragments. New minerals, in particular barium zeolites, are formed in the rocks. Identification of such formations in natural objects may indicate the occurrence of local temperature processes, which may lead to heterogeneity of organic matter transformation in Bazhenov sediments and should be taken into account to identify local zones of increased catagenesis.

Сatagenetic transformations of asphaltenes of organic matter (OM) from recent sediments and fossil rocks were studied on rocks sampled from different sedimentary basins (Timan-Pechora, Mezen, West Siberian, Kuznetsk, Aldan-Maya and Middle Amur) of Russia. Changes in the elemental composition of asphaltenes were analyzed with the Veselovsky’s model of the formation of major groups of fossil fuels using cO parameter (cO = (O/8 – N)/(C/3)) as compared with the total carbon based on elemental analysis. Just as the Van-Krevelen diagram, the plot built in C–cO coordinates for OM of various genetic forms demonstrates a significant difference in the asphaltenes composition evolution during catagenesis. At the same time, the cO parameter has notably increased in asphaltenes of both types of OM. Structural transformations of asphaltenes during catagenesis were identified in the course of high-resolution NMR (nuclear magnetic resonance) spectroscopy. The research results comprise data on carbon distributions in the aromatic and aliphatic groups in the investigated asphaltenes of different type OM of sediments and rocks at different stages of lithogenesis. A correlation between the asphaltene composition and structural parameters depending on thermocatalytic transformations is revealed. The asphaltenes of terrestrial organic matter are distinguished by higher cO values and different carbon yields of aromatics (higher) and aliphatics (lower) throughout the catagenesis phase. The highly transformed marine OM is marked by surge condensation of aromatic rings in asphaltenes, which makes them similar to asphaltenes of the terrestrial type OM.

The evolution of the elemental composition of dispersed organic matter (DOM) heterocyclic components during catagenesis was traced via studying samples from the Tyumen (SG-6) and Srednevylyuy-27 (SV-27) super-deep wells of Siberia. During mesocatagenesis, the composition of terrigenous DOM asphaltenes and resins undergoes directed changes: a decrease in hydrogen and oxygen content, enrichment with carbon, and graphitization of the structure. During apocatagenesis, due to high-temperature destruction, on the one hand, there is a condensation of individual blocks of asphaltenes and their transition to an insoluble form (formation of epiasphaltenic kerogens – EPAK). On the other hand, the lighter part of the asphaltenes goes into the formation of hydrocarbons and gas formation – a relative increase in the concentration of the former in % by mass of residual bitumoids is noted, as well as structural redistributions within benzene and spirit-benzene resins. In all studied parameters of the elemental composition, a symmetrical (unidirectional) transformation of resinous and asphaltene components of bitumoids from the SG-6 and SV-27 wells under harsh thermobaric conditions is noted. The obtained results should be taken into account when predicting new oil and gas accumulation zones in deep-laid horizons.

The article considers the elements of organic geochemistry in the regional aspect, which aims to separate quantitative prediction of oil and gas content of regions. The principles and results of balance calculations of generation and emission of liquid and gaseous hydrocarbons for different faciesgenetic types of organic matter and methods for calculating the scale of hydrocarbon emission are considered. Finally, a list of the main regularities of organic geochemistry is given.

A model of the activity of hydrothermal-metasomatic systems confined to certain structural elements is proposed in the present article. The model is based on the analysis of a large volume of traditional studies: measurements of porosity coefficients, permeability, pyrolytic measurements - together with specific measurements: isotopic composition of carbonate rocks, temperature of homogenization of gas-liquid inclusions, studies of the composition of rocks with a scanning electron microscope, a description of petrographic thin sections. The model allows to generalize the results of the impact of hydrothermal-metasomatic systems on the reservoir properties of the rocks of the BazhenovAbalak complex: constructive – leaching processes and increasing reservoir properties, and destructive – massive mineral formation that fills the pore space, up to the formation of secondary seals.

Studies have been carried out to assess the qualitative features of fluids, aimed at identifying the regularities in the differentiation of the properties of naphthides during the formation of hydrocarbon deposits outside anticlinal structures. Due to the exhaustion of hydrocarbon reserves associated with anticlinal traps, the main attention is paid to the composition of fluids confined specifically to non-anticlinal structures – to traps of a combined structure. Physicochemical properties, trace element (TE) composition, phase states of naphthides in deposits affected by hypergenetic or catagenetic processes have been analyzed using specific examples; in regions with a possible additional inflow of hydrocarbons (Romashkino group of fields in the Republic of Tatarstan); in the crystalline basement of sedimentary basins. The results of the analysis make it possible to predict the characteristic features of fluids in traps of various types at certain levels of the processes of oil formation, secondary transformation and destruction of accumulations, mainly due to the tectonic regime of the sedimentary basin. With prolonged lateral migration, at great depths with good isolation from surface weathering agents, light oils, depleted in TE, more often of nickel specialization, are found in lithologically and stratigraphically screened traps, and gas condensate accumulations are possible. At shallow depths with poor regional or local seals, heavy, highly viscous hypergene-transformed oils, natural bitumens with high concentrations of industrially significant metals V, Ni, Co, Mo Cd, U were found in traps of pinch-out zones and various types of trap screening. tectonically-screened traps) with a multiphase filling of traps and, at the same time, the influence and inflow of deep ones, i.e. more catagenically transformed fluids, it is possible to detect light oils of the nickel type or gas condensates enriched with elements of “magmatic emanations” – As, Hg, Al, B, rare earth elements. Oils filling combined traps in the crystalline basement within platform oil and gas basins, as a rule, do not differ in their compositional peculiarities in comparison with oils in overlying or adjacent parts of the sedimentary section.

A series of kerogen samples were isolated from Domanik oil shale before and after hydrothermal treatment in an autoclave (at 250–375°C, for 24 h). Than composition of the C1–C5 hydrocarbon gases generated in stepwise (300–800°C) pyrolysis of these kerogens was characterized by gas chromatography. According to the calculated EASY %Ro and Rock-Eval pyrolysis data, the highest maturity level of the organic matter reached by the hydrothermal treatment corresponded to the MC4 stage. As the hydrothermal treatment temperature of the oil shale was elevated up to 325°C, the dry pyrolysis of residual kerogen led to the predominant generation of wet gases in which C2+ prevailed over methane; at temperatures above 325°C, methane was predominant. Based on the pattern of the generation curves plotted individually for C1, C2, C3, C2–C5, and C4–C5 gases, methane was found to have additional sources in the kerogen structure, compared to C2+ gases. Ethane and ethylene are generated simultaneously via the free-radical decomposition of alkyl structures; moreover, at high pyrolysis temperatures, ethane and ethylene have some precursors other than those of C3+ gases. [ABSTRACT FROM AUTHOR]

The composition of hydrocarbon gases formed by pyrolysis of residual Domanik shale kerogen at 800°C, preceded by hydrothermal treatment at 250–375°С, was studied by pyrolytic gas chromatography. Starting from the autoclave temperature of 320–325°C, the hydrothermal treatment of the shale affects the kerogen structures responsible for the formation of C2+ gases in pyrolysis at 800°C. An increase in the temperature of the shale hydrothermal treatment leads to a monotonic increase in the С1/С2+ ratio in the products of the residual kerogen pyrolysis at 800°C. The methane yield at 800°C does not correlate with the content of alkyl structures, determined in kerogen by IR spectroscopy, and the yield of С2+ gases linearly correlates with the content of alkyl structures. [ABSTRACT FROM AUTHOR]

Localization of the finds of natural bitumen in archipelagos in the western segment of the Russian Arctic is considered. The nature of their appearance in relation with the subsurface geothermal regime is discussed. Based on numerical simulation, temperatures and heat flow density are calculated in 2D geometry along seismogeological profiles and in 3D geometry for the isometric structure of Franz Josef Land. It is concluded that all the noted natural bitumen manifestations are genetically related to hydrothermal activity, with signs adequately recorded in the geotemperature field. [ABSTRACT FROM AUTHOR]

Abstract—It has been established that the average values of some hydrocarbons biomarker coefficients of bitumens from the Domanik deposits and oils from the Domanik–Tournaisian complex coincide. These are the proportions of C27–C29 steranes, tri-/pentacyclanes ratio, and coefficients 2 × С17/С16 + С18 and 2 × С27/С26 + С28 calculated from n-alkane composition. Such indicators as the Pr/Ph, (Pr + Ph)/(n‑C17 + n‑C18), dia-/reg-steranes, and the sterane/hopane ratios in oils are slightly lower than in the bitumen. The average values of δ13C in asphaltene, resin, aromatic hydrocarbons, and aliphatic hydrocarbons fractions from oils of the Domanik genotype and in the studied bitumens are similar. The carbon isotope composition of asphaltenes in oils is depleted in 13С compared to those of resins and aromatic hydrocarbons, and vice versa in bitumens. A heterogeneous composition of the bacterial flora in the sediments of the Domanik Sea is suggested. In some places, species with high concentrations of diplopterol or hexafunctional bacteriohopanes likely dominated over bacteriohopantetrol. [ABSTRACT FROM AUTHOR]

Hydrothermal liquefaction (HTL) of sewage sludge is considered in the article as an analogue of the natural processes of oil formation (catagenesis). A comparison of the physicochemical composition of primary and secondary sludge with type II kerogen (natural precursor of oil) showed their similarity. Both types of sludge have a slightly higher level of oxygen and nitrogen. The study tested the hypothesis that the elements included in the inorganic part of the oil source rocks can have a catalytic effect on the oil formation processes. For the conducted studies of sludge HTL, the catalysts containing cations and substances found in oil source rocks were chosen: as homogeneous catalysts (KOH, NaOH, NH4Fe(SO4)2, CoCl6, NiSO4, CuSO4, ZnSO4, MoO3) and as heterogeneous catalysts (MgO, Zeolite, Al2O3). The effectiveness of catalysts containing metal ions, zeolite and aluminum oxide has been proven. The highest biocrude yield was achieved in a process with NiSO4 as the catalyst in a dose 2 g per 10 g of sludge: oil yield increased by 34.9% and 63.4% in the processing of primary and secondary sludge, respectively. The use of catalysts provided an increase in fuel HHV by 10.8–12.5%, which is associated with a decrease in oxygen content (by 10.8–43.2%) with a simultaneous increase in carbon (by 7.9–10.9%) and hydrogen (by 6.5–18.7%) content. [ABSTRACT FROM AUTHOR]

Evolutionary transformations of the composition and structure of asphaltenes in different types of organic matter (OM) of sediments and rocks at different lithogenesis stages were studied. Insight into the main steps and processes controlling the transformation of OM asphaltenes in different steps of thermal maturation was gained, and new opportunities for using parameters of the asphaltene structure for constructing geochemical models were revealed. The following trend in variation of bitumen asphaltene parameters in the course of catagenesis was revealed for both genetic forms of OM: directional carbonization of asphaltenes, accompanied by a decrease in the content of hydrogen and an increase in the relative content of aromatic (including condensed) structures and by a decrease in the role of aliphatic substituents. Linear relationship was revealed between the parameters of the composition and structure in the course of thermocatalytic transformations. Three successive stages of thermal maturation of asphaltenes were distinguished. [ABSTRACT FROM AUTHOR]

One of the widely used methods of assessing the maturity of organic matter based on aromatic compounds uses indexes reflecting changes in the relative concentrations of phenanthrene and its methyl-substituted derivates. A set of ratios now widely used in national and international practice (MPHI, MPI-1, MPI-1mod., PP-1, and PHI) is analyzed based on data on these compounds in terrestrial organic matter (OM) recovered by Srednevilyuskaya-27 superdeep well. Equations are derived for calculating synthetic values of vitrinite reflectance based on phenanthrene maturity indexes at meso- and apocatagenesis. Data are presented on typical changes in the relative phenanthrene concentrations and its methyl-substituted derivates under high P–T parameters: the more stable behavior of 2-, 3-, and 1-methylphenanthrene than 9-methylphenanthrene. The relative concentrations of phenanthrene itself are demonstrated to broadly vary at apocatagenesis, and this factor deteriorates the maturity indexes of the phenanthrene ratios. It is necessary to select proper equations for various hydrocarbon systems and determine the boundaries of the transition from positive correlations between phenanthrene indexes with the vitrinite reflectance to negative ones. The obtained results are compared with the classic understanding of the problem. [ABSTRACT FROM AUTHOR]

Tracing interactions during burial-induced organic maturation and associated clay-material alteration is of prime importance for understanding both the individual and combined mineral and organic processes. In the present study the light elements B, Li, O, and H of a sample from oil-prone Eocene Kreyenhagen Shale from San Joaquin Basin (California) were examined. The natural burial-induced temperature increase was simulated by pyrolysis experiments at progressively increasing temperatures (270–365°C) and for varied durations (72–216 h) applied to the whole rock and its <2 μm fraction. The illite structure as well as the K-rich interlayers of the illite-smectite mixed layers were not affected by the pyrolysis experiments and the smectite-rich interlayers did not collapse, while the soluble minerals and the organic matter were altered. The distribution pattern of the rare-earth elements (REEs) from untreated whole rock and of its pyrolyzed equivalents are within analytical uncertainty, which confirms that the changes induced by pyrolysis experiments were minimal in the bulk sample. Conversely, the REEs from the <2 μm fractions were modified significantly, suggesting that the whole rocks and the <2 μm fractions may contain different types of organic materials. Also, only the carbonates, oxides, chlorides, and organic matter were affected together with the smectite-rich interlayers of the illite-smectite structure. Bitumen coating of the smectite interlayers probably increased the amount of B of organic origin in their sites. The δ11B and δ7Li of the successively expelled hydrocarbon phases changed with increasing pyrolysis temperatures, together with the B and Li contents of the hydrocarbon-related fluids. On the basis of the δ11B and δ7Li from pyrolyzed clay fractions, the B released successively was not isotopically homogeneous, probably depending on how the type of organic matter decomposed during the successive pyrolysis steps, and on which components were released. The δ11B of organic-B increased progressively from –2‰ at low experimental temperature up to +9‰ at the highest temperature. The calculated δ7Li that was released also increased relative to the value of the outcropping sample used as a reference, but it remained almost constant from –7‰ at 310°C for 72 h to –8‰ at 365°C for 216 h. The δ18O values of the <2 μm size fractions decreased significantly during pyrolysis above 300°C, but the δD changes were rather modest. The total organic carbon (TOC) remained statistically constant after pyrolysis to 300°C, as did the δ7Li values. The pyrolysis experiments in the present study suggest the presence of bitumen-coated smectite interlayers that could have been misidentified as dehydrated smectite in the literature. Together with abnormal illite K-Ar ages, the occurrence of such bitumen-coated illite-smectite interlayers occurring in source and reservoir rocks could indicate the timing of hydrocarbon maturation relative to illitization. [ABSTRACT FROM AUTHOR]

Hydrothermal liquefaction (HTL) of sewage sludge is considered in the article as an analogue of the natural processes of oil formation (catagenesis). A comparison of the physicochemical composition of primary and secondary sludge with type II kerogen (natural precursor of oil) showed their similarity. Both types of sludge have a slightly higher level of oxygen and nitrogen. The study tested the hypothesis that the elements included in the inorganic part of the oil source rocks can have a catalytic effect on the oil formation processes. For the conducted studies of sludge HTL, the catalysts containing cations and substances found in oil source rocks were chosen: as homogeneous catalysts (KOH, NaOH, NH4Fe(SO4)2, CoCl6, NiSO4, CuSO4, ZnSO4, MoO3) and as heterogeneous catalysts (MgO, Zeolite, Al2O3). The effectiveness of catalysts containing metal ions, zeolite and aluminum oxide has been proven. The highest biocrude yield was achieved in a process with NiSO4 as the catalyst in a dose 2 g per 10 g of sludge: oil yield increased by 34.9% and 63.4% in the processing of primary and secondary sludge, respectively. The use of catalysts provided an increase in fuel HHV by 10.8–12.5%, which is associated with a decrease in oxygen content (by 10.8–43.2%) with a simultaneous increase in carbon (by 7.9–10.9%) and hydrogen (by 6.5–18.7%) content.

[Display omitted] • Hydrous pyrolysis experiments were conducted under diagenetic to catagenetic conditions. • Half-lives of organic acids were between 8.88 × 1010 and 2.81 × 10-3 years (80–200 °C, 20 MPa). • Pyrolytic organic acid generation might result in millimolar in situ concentrations in pore water. • Reaction rates allow the prediction of expected concentrations of LMWOA in pore water at elevated temperatures by geochemical modelling. Increasing temperature in claystone formations accelerates geochemical reactions between organic matter, water and mineral phases, promoting the generation and decomposition of organic compounds such as low-molecular-weight organic acids (LMWOA). LMWOA presence in claystone formations can enhance mineral dissolution, stimulate gas generation through thermal decomposition reactions, affect metal-ion complexation, alter sorption processes, and provide feedstock for microbial life. Hydrous pyrolysis experiments (80–200 °C and 20 MPa) using Dickson-type flexible gold-titanium reaction cells were conducted to investigate the thermal generation and decomposition of LMWOA in organic matter poor (0.64 wt%) Opalinus Clay. Maximum concentrations of dominant species were 44 µmol/kg clay formate (120 °C), 310 µmol/kg clay acetate (200 °C), and 74 µmol/kg clay oxalate (120 °C). Calculated half-live ranges of the dominant compounds were between 8.88 × 1010 and 2.81 × 10−3 years for the experimental conditions. Comparison of observed and calculated reaction rates suggests that the thermal generation and decomposition of LMWOA proceed simultaneously. Therefore, the observed generation rates in these and other previously published experiments are minimum estimates that need to be corrected for parallel decomposition reactions. The new quantitative reaction rate data presented here facilitate modelling of production/decomposition and local pore water concentrations of LMWOA by the extrapolation of kinetic data to temperatures encountered, for example, in natural heating during subsidence or by thermal intrusions. [ABSTRACT FROM AUTHOR]

• During soaking pyrolysis C 2 to C 5 gases decreased with increase in pyrolysis temperature. • For hydrous pyrolysis C 4 and C 5 gases increased with increase in pyrolysis temperature. • MW of compounds in oil from soaking and hydrous pyrolysis ranged from 86 to 376 g/mol. • The yield of the organic acids appeared to be higher in the presence of DI water. In the present study, soaking and hydrous pyrolysis experiments were performed on Indian oil shale in the presence of de-ionized (DI) water and brine solution under isothermal conditions of 300, 350, and 400 °C, and residence time of 72 h to simulate the effect of underground aquifers on the expulsion and composition of hydrocarbons from source rocks. During soaking pyrolysis, the oil yield increased minutely with the increase in soaking time from 1 to 4 weeks but was not influenced by the presence of brine solution (8.82 wt/wt%) or DI water (8.46 wt/wt%). A similar trend in the generation of oil yield was observed during hydrous pyrolysis in both DI water and brine solution. GC analysis of the gas samples showed methane (CH 4) as the prominent gas produced during soaking and hydrous pyrolysis. During soaking pyrolysis, the concentration of C 2 to C 5 gases decreased with increased pyrolysis temperature. However, during hydrous pyrolysis, the concentration of C 4 and C 5 gases increased with an increase in pyrolysis temperature. GC-SimDist analysis of the oil samples obtained from soaking pyrolysis at 400 °C showed the compounds ranged from C 8 to C 38 in brine solution and from C 6 to C 34 in DI water. Nevertheless, during hydrous pyrolysis in both DI water and brine solution, the carbon number distribution of the oil samples was observed to be in the range of C 8 to C 38. GC–MS analysis of the oil samples obtained from the soaking and hydrous pyrolysis experiments showed that the molecular weight of the identified compounds ranged from 86 to 380 g/mol. GC–MS, ATR, and 1H NMR analyses showed that the oil samples obtained from soaking and hydrous pyrolysis experiments were rich in aliphatic compounds. The organic acids content appeared to be higher in the presence of DI water as compared to the brine solution. [ABSTRACT FROM AUTHOR]

Coal-bearing deposits of the Tunas Formation suggest the existence of potential gas-prone source rocks in the Claromecó Basin, south of Buenos Aires province, Argentina. Two wells, PANG 0001 and PANG 0003, containing Permian rocks assigned to the Tunas Formation were studied through core observation, X-Ray diffraction, petrographic description, geochemical analysis, and organic petrography to investigate the hydrocarbon potential of the Claromecó Basin and define horizons with source rock potential. The analyzed sedimentary successions are composed of medium- to fine-grained sandstones interbedded with tuffs, mudrocks, carbonaceous mudrocks, and coal. Two main horizons with potential source rocks were determined: an upper horizon, at the top of the succession (300–400 m) and a lower one, at the base (740–850 m). These layers are mainly composed of mudrocks, carbonaceous mudrocks, and coal beds up to 4.50 m in cumulative thickness. Total organic carbon (TOC%) content is high, with most samples ranging from 0.5 to 2% in organic-rich mudrocks, and from 26 to 53.9% in carbonaceous mudrocks and coals, characterizing the coal-bearing layers as good-quality source rocks. The organic matter is of terrigenous origin as indicated by the abundance of woody plant debris. Predominant organic matter constituents belong to vitrinite group (type III kerogen), with a low abundance of the inertinite group macerals. Vitrinite reflectance (Ro) values in carbonaceous mudrocks and coals ranged from 1.3 to 1.6% for the upper horizon to 1.9–2.4% at the lower one, reflecting a catagenesis to late catagenesis stage within the wet to dry gas window. The organic matter quantity, type, and maturity in Tunas Formation coal-bearing deposits suggest that this unit has a good potential as gas-prone source rocks. • The hydrocarbon source rock potential of Tunas Formation coal-bearing deposits were evaluated. • Total organic carbon (TOC%) content is high, with an average of 2.69%. • Predominant organic matter is terrestrial (type III kerogen). • Vitrinite reflectance values range from 1.3 to 2.4%, indicating a mature to over mature stage within the wet to dry gas window. • The Tunas Formation coal-bearing deposits have a good potential as gas source rocks. [ABSTRACT FROM AUTHOR]