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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]

Silurian source rocks are among the least studied in the Timan-Pechora basin. This is mainly due to their occurrence at great depths (3.0–4.5 km) and the limited penetration of this stratigraphic interval by wells. Another source of information is the outcrops of the Silurian, which are known in the eastern and northeastern parts of the Timan-Pechora basin. The studied section of the Silurian deposits is exposed on the Padimeityvis River, located on the Chernov swell in the northeastern part of the basin. This article is devoted to the study of Silurian source rocks based on the results of lithological, coal petrographic studies and geochemistry of organic matter. The studied section is composed of carbonate and clay-carbonate deposits formed in shallow-water shelf conditions. Most of the section, composed of microcrystalline and microcrystalline with bioclasts limestones, is characterized by low concentrations of organic matter (Corg is generally less than 0.3 %). Elevated Corg contents (up to 1.16 %) are characteristic of clay-carbonate rock varieties, which make up about 20 % of the section. Sediments with increased concentrations of organic matter were formed in isolated and deepened areas of the bottom of the shallow-water basin as a whole. Assessment of the catagenetic transformation based on Rock-Eval pyrolysis data, coal petrographic studies, and conodont color indices showed that organic matter reached the conditions of the middle-end of the main oil generation zone (gradation MC2‑MC3). The obtained geochemical characteristics (Corg, S2, HI), taking into account a certain level of organic matter maturity, indicate that the Silurian source rocks had an average hydrocarbon potential.

The relevance of the research is caused by the need to expand the resource base in the fields of the Baykit anteclise. Occurrence of two types of oils may be caused by additional source, which increases the prospects of the area. However, variations in the composition of oils may also be associated with high catagenesis and migration effects; therefore, an assessment of the influence of these factors on composition of oils is necessary. The aim of research is to determine the influence of genetic, catagenetic and migration factors on biomarker hydrocarbons in the oils of the Baykit anteclise, to identify areas of preferential influence of each of them. Objects of the research are the oils of the Baykit anteclise. Methods: comparison of the characteristics of biomarker hydrocarbons obtained using gas chromarography-mass spectrometry in saturated and aromatic fractions of oils, assessment of the impact on their composition of the contribution from different source formations, catagenesis and migration, grouping of oils by the predominance of the influence of these factors. Results. The author has characterized biomarker hydrocarbons of saturated and aromatic fractions of the oils from Riphean and Vendian collectors of the Baykit anteclise. Based on the characteristics, which differ from the previously obtained characteristics of the most common and typical ancient oils of the Siberian platform, the author made a conclusion on the impact of the contribution from the Upper Riphean Iremekensky stratum in two oils in the east of the Kuyumbinskoye field, as well as the contribution of probably Vendian oil source formations in oils from Vendian collectors. The main factor in the formation of the composition of most oils of the Kuyumbinskoe field was high catagenesis, enhanced by migration effects towards the enrichment of low molecular weight compounds. Probably, several oils are a mixture of two components with different catagenesis, moreover, more transformed component is enriched with saturated, including cyclic compounds, and less transformed – with aromatic compounds.

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]

Bulk sedimentary nitrogen isotope profiles are often used as proxies for depositional redox conditions, nitrogen cycling, and nutrient uptake in modern and ancient marine systems. The general preference in terms of analysis is that the sediments measured have undergone minimal thermal alteration, as post-depositional processes might have altered the initial δ15N signal, thus complicating the interpretation of these records. Although not a traditional proxy for petroleum evaluation purposes, recently the use of nitrogen isotopes in petroleum systems has been investigated as potential proxies to reconstruct paleoenvironmental conditions such as redox, and for organic matter evaluation. In this paper we review the use of nitrogen isotope data in petroleum systems, their interpretations, and factors that may complicate their use as proxies. We review the evidence for nitrogen isotopic fractionation during diagenesis, catagenesis, and fluid migration as determined by lab experiments, and how these might impact interpretation of δ15N data in petroleum systems. We also analyze the use and interpretation of δ15N data from petroleum-producing reservoir units, including unconventional reservoirs and lacustrine basins. Lastly, we discuss potential applications for nitrogen isotopes in petroleum systems with regards to their use as both geochemical proxies and as tools to evaluate petroleum reservoirs.

A combination of geochemical methods were used to study organic matter from Permian rocks in the central part of the Vilyui syneclise (East Siberia) penetrated by the Srednevilyuiskaya-27 ultra-deep well in the depth range of 3370-6458 m. This study discusses variations in the pyrolysis indices (HI, Tmax), hydrocarbon type content (hydrocarbons-resins-asphaltenes), vitrinite reflectance (R0vt, %), organic carbon content (Corg), as well as some trends in the saturated and aromatic hydrocarbon compositions of bitumen extracts from the Upper Paleozoic rocks. Below a depth of about 4.5 km (late mesocatagenesis), the hydrocarbon type composition is characterized by a sharp decrease in the content of asphaltenes from < 30 % (at 4.5-5.0 km) to < 15 % (at 5.0-5.5 km), which are not detected at greater depth. In turn, the resins became the dominant constituent (~ 50-70 %), whereas hydrocarbons account for < 20 % at depths down to 5 km and < 40 % at greater depth. These depths are also characterized by a predominance of saturated hydrocarbons over aromatic compounds with a decrease in the relative contents of high molecular weight compounds in both fractions, as indicated by mass chromatograms. The hydrocarbon index (HI) of organic matter decreases to the first tens from the depth of 4.9 km and to the bottomhole (6519 m); the temperature of the maximum hydrocarbon yield (Tmax) varies between 570-580 °C, showing a slightly increasing trend. Our results show that the generative potential of organic matter from the rocks within the studied depth range (4.9-6.5 km) has been exhausted and that the terrestrial organic matter undergoes significant changes under severe temperature and pressure conditions at great depths.

Оbject. The article presents the results of studies of secondary mineral formation in the lower Cretaceous sediments of the Bolshekhetskaya depression, which contain highly promising oil and gas deposits, with established industrial performance at Pyakyakhinskoye, Khalmerpayutinskoye and South-Messoyakhskoye fields. The objects under consideration are located in the most submerged part of the Nadym-Taz syneclise in the zone, where the Taz and Urengoy facies regions meet.Materials and methods. Main types of postsedimentary changes of reservoir rocks selected on the basis of study of core material Pokurskaya, Angelovskaya, Sortymskaya and Megionskaya fms. Petrography and Mineralogy of the rocks under consideration were studied on the basis of stage analysis using optical and electron microscopy, and X-ray diffraction study at the Center of core and reservoir fluids research of “LUKOIL-Engineering’s KogalymNIPIneft branch In Tyumen” (Kogalym). Determination of the mineral type of zeolite was performed by X-ray phase analysis at the Institute of Geology and Geochemistry UrO RAS (Ekaterinburg).Resuts. It was found that for rocks Pokurskaya, Angelovskaya, Sortymskaya and Megionskaya fms characteristic a diverse range of secondary minerals and structures, evidence of the background stage catagenesis and the superimposed processes. The most important among them is the regeneration of quartz, the transformation of feldspar, violation of the crystal structure of biotite, the formation of various clay minerals, crystallization of zeolites and calcite.Conclusions. Studies show that the upper part of the section of the lower Cretaceous deposits of Bolshekhetskaya depression corresponds to the area of the middle catagenesis (gradation MK2), the bottom – changed to the stage of deep catagenesis (gradation MK3). In this case, the epigenetic process proceeded unevenly, pulsation, due to changing tectonic conditions. Particular attention is paid to the origin of zeolites, which is still debatable. It is assumed that their formation is associated with the transformation of “camouflage pyroclastic” in particular, feldspar clastics.

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.

The regularities were determined for changes in the lithological and geochemical composition of rocks of the Bazhenov Formation (BF) characterized by various degrees of transformation of organic matter (OM). From the M to MK2 stages (140–170–195°C), trends are seen toward (a) an increase of the quantity of limestone–dolomitic interlayers along with the dolomite content; (b) a decrease of the OM content over the entire section; (c) a decrease of the OM and sulfide sulfur concentrations in the pyrite–kerogen band of the roof of the BF; (d) a decrease of the C/S ratio; and (e) an increase of the thickness of the pyrite layer in the transition zone between the BF and overlying sediments along with the growth of the pyrite content. It was concluded that the interval between the M and MK2 stages experienced OM transformation, the migration of transformation products, dolomitization of the rocks, and pyritization of low-carbon rocks in the BF-overlying Podachimovo strata. [ABSTRACT FROM AUTHOR]

The petrographic, lithogeochemical and U-Pb (LA-ICP-MS) geochronological studies were carried out to investigate the terrigenous rocks sampled from the lower part of the Ipsit suite of the Karagass series (Sayan segment of the Sayan-Baikal-Patom belt). These rocks include sandstones, aleurite sandstones and aleurolites, and their mineral compositions are close to that of arkose. Most of the studied rock samples show petrographic features typical of the epigenetic changes at the stage of catagenesis: regeneration of quartz clastic grains, pelitization of potassium-feldspar clastic grains, occurrence of clay-hydromica aggregate, sericitization of plagioclase, chloritization of biotite, and silicification of dolomite pieces, and occurrence of authigenous tourmaline. The above was confirmed by the analysis of the concentrations of petrogenic elements in the studied rocks from the lower part of the Ipsit suite. The analysis results show that the concentrations of K2O are elevated, while the concentrations of Na2O are relatively very low, which may be due to the redistribution of these elements during epigenetic transformations. According to the classification by genetic types on the basis of the system of petrochemical modules, the rocks of the lower part of the Ipsa suite are of the petrogenic nature. The acidic igneous rocks are dominant in the source area, as evidenced by the presence of granitoid and quartzite fragments in the clastogenic component, as well as the set of accessory minerals typical of the igneous rocks of the acidic composition, and the distribution pattern of rare and trace elements. According to the U-Pb (LA-ICP-MS) dating of detrital zircons from the aleurite sandstone sampled from the lower part of the Ipsit suite, the zircons are exclusively of the Archean-Early Proterozoic ages. Such ages correlate with the age of the granitoids of the Sayan complex and the felsic volcanites from the Maltsev layer of the Elash series (Biryusa block). Furthermore, the detrital-zircon age spectra of the aleurite sandstone of the lower part of the Ipsit suite are identical to the detrital-zircon age spectra of the terrigenous rocks from the underlying strata of the Shangulezh and Tagul suites of the Karagass series. This study suggests that sedimentation of the Ipsit suite of the Karagass series took place due to the influx of detrital material from the southern part of the Siberian craton into the sedimentation basin, and the acidic igneous rocks of the Biryusa block were one of the main sources of detrital material.

A combination of modern analytical methods was used to study terrestrial organic matter from upper Paleozoic rocks in the central part of the Vulyui hemisyneclise (East Siberia) sampled from the depth interval 3370-6458 m penetrated in the Srednevilyuiskaya- 27 superdeep well. In this study, we used 71 core samples to trace depth variations in the geochemical characteristics of organicmatter during middle-late mesocatagenesis and apocatagenesis: organic carbon content (Corg), Rock-Eval pyrolysis parameters (HI, max), carbon isotope composition, thermal maturity (Ro Vt, %), hydrocarbon type composition (hydrocarbons, resins, and asphaltenes), distributions of n-alkanes (TIC), steranes (m/z 217), and terpanes (m/z 191), and standard biomarker indices with increasing degree of thermal maturity. It is shown that during late mesocatagenesis and apocatagenesis, the pyrolysis parameters and biomarker indicators are no longer effective as indicators of organic-matter maturity and genesis. [ABSTRACT FROM AUTHOR]

The article reflects the study results of oil and gas bearing rocks of the North-Taz Basin. The interconnection of oil seismology and hydrothermal processes is pointed by the example of local and integral seismic effects. We determined that the fluidization processes are associated with the activation of abdominal faults and are secondary to the previously formed classical zones of epigenesis. Based on paragenetic mineral associations and epigenetic changes in the rocks of the study area, new types of hydrothermal-metasomatic formations are identified - mudstones and fluidisites. The lithogeochemical anomalies of potassium, phosphorus, iron, fluorine, and arsenic confirm the presence of vertical migration and are linked to the morphological features of the reflecting horizons of the study area. The results of determining the petrochemical modules for the Turonian-Maastrian reserves confirm that the lithogeochemical anomalies of the selected group of elements are associated with the Late Cretaceous stage of activation of deep-seated processes. According to the results of X-ray diffraction analysis, three main complexes of clay minerals of the sedimentary section were identified: montmorillonite-kaolinite, hydromicaceous-chlorite, hydromicaceous-chlorite-zeolite. It was established that the presence of montmorillonite is a distinctive feature of these reserves and its presence leads both to high reliability of tires and to a significant deterioration in the reservoir properties of sand varieties. Zeolites are defined as indicators of diagenetic transformation of rocks. For micaceous mineral, the most common polytypic varieties were identified, characterizing the presence of a hydrothermal process. According to electron microscopic studies of the composition of the rocks, their pore space, and the analysis of the geological characteristics of the study area, six types of integral fluidization zones and three local levels were established. The mineral composition of the fluidization zones was characterized as a result of hydrothermal-metasomatic transformations of the corresponding rock complexes. Assumptions are made about the forms of bodies of hydrothermally transformed rocks, defined in the field of seismic waves, as the results of the development of fluid zones of a certain mineral type and similar to primary halos of ore reserves. The characteristics of the zones of colmatation of two types are given that affect the flow rate of wells and form a new type of metasomatic traps for oil and gas reserves. [ABSTRACT FROM AUTHOR]

The paper is devoted to modeling of the processes of oil and gas deposits formation of the Vuktyl thrust development area, to which the largest in the Timan-Pechora oil and gas province is associated with the same oil and gas condensate deposit. Oil and gas of deeply buried formations of the autochthon of the overthrust region remains poorly studied. Therefore, application of modern methods of basin modeling is relevant for oil and gas content estimation. In order to simulate the section, Schlumberger PetroMod software package was used. The package allows to determine the history of generation of hydrocarbons on the geological time scale, migration paths, amount and type of oil and gas accumulations in both surface and reservoir conditions. Using the 1D and 2D modeling of the Vuktylskaya-58 parametric well and the overthrust region models were obtained. The models reflect the modern geological section, its evolution during the geological time. The processes of formation of oil and gas were studied. As a result, it was shown that the parent rocks of the allochthonous section part could not participate in the formation of the main gas-condensate deposit of the Vuktyl deposit because they entered only the main oil formation zone. In deeply buried deposits of the autochthon starting from the Permian and Triassic formation of the Vuktylsky gas-condensate field and possibly the deposits in poorly studied deep formations could be caused by processes of generation of gases and gas condensates. That is proved by the discovery of a large number of gas emergences beyond the 4-5 km in a section of the only well drilled beyond the 6 km such as Vuktylskaya-58. Generation and accumulation of gas hydrocarbons occurred mainly after the appearance of thrust dislocations, when the main traps were formed both at ordinary and high depths.

Fossil resins and amber are a product of lithogenesis of resinous substances of higher plants – resinite. These components of plants, like other lipoid ingredients (suberins, coutines, sporinins, natural rubbers) are resistant to microbial action, so they are well preserved in bacterial processing of organic matter in the stages of sedimento- and diagenesis, and are well diagnosed in microscopic studies. They occur in a rather wide age range of sedimentary rocks. The amber of the Baltic region of the Eocene age is most fully studied. The article presents the results of a study of the collection of fossil resins and amber from various regions of the world. Samples were studied microscopically; carbon isotope analysis, infrared spectroscopy (IR spectroscopy) were performed. The most informative analysis of high-molecular polymeric compounds is IR spectroscopy. It was found that in the analyzed samples of fossil resins of different ages, aromatic compounds are not observed, most of which are first volatilized in fossilization processes. The possibility of influencing the group composition of amber and amber-like resins for sedimentation, diagenesis and catagenesis is discussed. The IR spectra of fossil and modern resin conifers are compared. Using the IR spectroscopy method, an attempt was made to identify the botanical origin of fossil resins.

New results of research of sulfur from rocks and organic matter (OM) for the Kuonamka complex of the Lower and Middle Cambrian in the eastern Siberian platform have been demonstrated. It has been shown that in the rocks enriched in organic matter the amount of organic carbon controls not only the total content of sulfur and sulfide sulfur, but also the content of sulphate sulfur. It has been revealed that the sulfur content in bitumen extracts of Cambrian black shales in the northeastern Siberian platform decreases with increasing carbon and hydrogen. It was hypothesized that during diagenesis the introduction of sulfur in the OM structure led to dehydrogenation and decarboxylation. The intensity of these processes is associated neither with the mineral composition of the sediment nor with its enrichment in OM. The paper discusses the structure and patterns of distribution of OM sulfur compounds in the rocks of the Kuonamka complex in the sections of the northern and southeastern Siberian platform.

This is a pioneering study on lateral zoning of groundwater chemistry and authigenic mineralogy in the Oxfordian regional reservoir of the Nadym-Taz interfluve. According to thermodynamic calculations, the nonequilibrium-equilibrium water-rock system lacks equilibrium with primary magmatic minerals, such as albite, anorthite, and microcline, though the water is moderately saline (up to 63.3 g/L) and has been in interaction with rocks for ~165 million years. Authigenic minerals form continuously and successively (kaolinite-montmorillonite-illite-micas-chlorite-albite-microcline) from waters that have certain pH and contents of SiO2, Al, Na, K, Ca, and Mg. The equilibrium of groundwater with primary aluminosilicate minerals impinges on a carbonate barrier, and almost all rocks are more or less strongly carbonatized. Authigenic mineral assemblages from the southern Nadym-Taz interfluve include kaolinite unlike those from the northern part of the region, where albitization is more common. Authigenesis generally decays in the eastern direction. [ABSTRACT FROM AUTHOR]

The zoning of catagenic OM transformation of sediments of the Bazhenovskaya highly carbonaceous formation is analyzed with respect to evolution of pore capacity system in its OM. The regional prospecting criteria of oil beds of the reservoirs related to OM porosity in the formation are formulated on the basis of our studies. [ABSTRACT FROM AUTHOR]

Clay subfractions (SFs) with particles size of 2–5, 0.6–2.0, 0.3–0.6, 0.2–0.3, and 0.1–0.2 μm of two shale samples (Upper Riphean Inzer Formation, South Urals) are studied using transmission electron microscopy, X-ray diffractometry (XRD), and U–Pb, Sm–Nd, Rb–Sr, and K–Ar methods. The SFs are composed of low-temperature 1Md illite; quartz, chlorite, and 2M1 illite are observed only in some coarse SFs. Irrespective of the size, the clay particles are equant. The standardized illite crystallinity indices (CIS) of all SFs are typical of the dia(cata)genesis zone. The CIS value increases, the I002/I001 ratio of XRD patterns decreases, and the K content and K/Rb ratio increase with decreasing particle size of the SFs from 2–5 to 0.1–0.2 μm. Leaching with 1N HCl and 1N NH4OAc and U–Pb, Sm–Nd, and Rb–Sr analysis of untreated SFs, leachate, and residue allowed us to study the isotope systematic of mixing in mobile and silicate material of shales. The 208U/204Pb and 87Rb/86Sr ratios of leachates are lower and the 147Sm/144Nd ratio is higher than those of residues. The leachates are also characterized by less radiogenic Pb and Sr and more radiogenic Nd relative to residues. With decreasing size of SF particles, the U, Pb, Sm, Nd, and Sr contents of leachates gently decrease and the Rb content increases. The 87Rb/86Sr and 87Sr/86Sr ratios of leachates of fine SFs are significantly higher, whereas their 238U/204Pb ratio is lower in comparison with coarse SFs. What is more, the data points of residues of various SFs occur along the mixing lines in the 87Rb/86Sr‒87Sr/86Sr and 1/86Sr‒87Sr/86Sr plots. The data points of corresponding leachates also form linear trends in 238U/204Pb‒206Pb/204Pb, 206Pb/204Pb‒207Pb/204Pb, 147Sm/144Nd‒143Nd/144Nd, and 87Rb/86Sr‒87Sr/86Sr coordinates. Apparent Rb–Sr ages calculated from slopes of "inner isochrons" ("leachochrons") as well as K-Ar ages gradually decrease from 835–836 and 721–773 Ma, respectively, for SFs of 2–5 μm and to 572‒580 and 555‒580 Ma, respectively, for SFs of 0.1–0.2 μm. Thus, the XRD and isotopic data indicate that both clay and mobile shale constituents are mixtures at least of two components, and the silicate phase contains authigenic illites of various ages. First-generation illite abundant in the coarse SFs of 2–5 μm and 0.6–2.0 μm was formed immediately after the deposition of the Inzer sediments and its age of 803–836 Ma is consistent with stratigraphic age of the Inzer Formation. The formation of this illite was facilitated either by lithostatic burial or intense horizontal fluid flow caused by tectonic inversion in the eastern regions of the Uralian paleobasin. The age of the second-generation illite is 572–580 Ma; it was formed as a result of vertical movements or renovation of the composition of the pore fluids during deformations and metamorphism of the South Urals related to the evolution of the Beloretsk metamorphic complex. [ABSTRACT FROM AUTHOR]

Abstract The compositional and bulk isotopic signatures of hydrocarbon compounds are routinely characterized to constrain the origin of oils and natural gases in sedimentary basins. Recent developments in clumped isotope geochemistry have given rise to a suite of measurements that provide new information on the thermal history of low molecular weight hydrocarbon gases. However, to date no study has linked these compositional, bulk and clumped isotope constraints to any mechanistic understanding of how these signatures develop and evolve. In this study, we developed a kinetic Monte Carlo method to predict consistent and simultaneous molecular distributions, bulk isotopic content, and detailed (multiply substituted and site-specific) isotopic structures of hydrocarbons from a cracking model. The detailed isotopic structure of the source (initially modeled as long alkanes), the intermediates, and the product molecules is followed as a function of the level of conversion due to cracking reactions. The bulk 13C content of gaseous alkane products generated via the model is shown to follow the linear natural gas plot at low conversion, but to deviate at high conversions. As examples of the information generated, the populations of center vs. terminal 13C-substituted propane are reported as a function of the starting alkane chain length and conversion and the population of doubly-13C-substituted ethane is described as a function of conversion and for different 13C substitution patterns in the source. The results are compared to experiment where possible and highlight the possibility of constraining hydrocarbon source isotopic structure and the nature of the generation processes leading to the formation of natural hydrocarbon deposits. [ABSTRACT FROM AUTHOR]

The article deals with the chemical structure of kerogen and its transformation in catagenesis of shale formations by the example of the Middle Volga shale formations and the Domanic carbonaceous deposits of the East European Platform. The studies allowed identifying the main distinctive features in the structure of individual structural components of these types of kerogen and refining the models of the fragment of their chemical structure. Some of the oxygen-containing structures are found to be present in the Middle Volga kerogen as carbohydrate moieties and algaenan components, the alkyl chains in which are interlinked by ether bonds, and the structure of the sulfur-containing components can be represented as sulfide (polysulfide) bound n-alkyl structures, in pyrolysis of which low-molecular and high-molecular alkyl-substituted thiophenes, thienyl- and phenylthiophenes are formed. The average S/C value exceeding 0.04 classifies the Upper Jurassic kerogen as Type II-S. The predominant components constituent in the composition of kerogen of Domanic rocks are lipid components, however, its lower aliphaticity is probably due to the higher maturity of organic matter (OM) and to the low ratio of n-alkyl structures to polyaromatic moieties, the formation of which is connected with the rearrangement of polyene and heteroatomic structures in catagenesis. [ABSTRACT FROM AUTHOR]

More than 1500 measurements of vitrinite reflectance (R° t ), along with mathematical modeling and computing, have been used to map the uppermost Middle Jurassic sediments of the West Siberian basin according to thermal maturity (catagenesis). The thermal maturity varies within the grades PC 3 to AC 2 . Sediments are the least mature along the margins of the basin, and the maturity grade increases progressively toward its central and northern parts (grades MC 1 -MC 2 ). It reaches a maximum in the north (AC 2 ), where the sediments which subsided to large depths became exposed to high temperatures and pressures. The maturity zones of Jurassic sediments in the West Siberian basin form a typical pattern of regional catagenesis. [ABSTRACT FROM AUTHOR]

Samples of Triassic sediments were collected from cores of parametric boreholes drilled on the Admiralteiskii Rise, Franz Josef Land Archipelago, and Fersman structure in the northeastern part of the Barents Sea sedimentary basin. The composition and distribution of hydrocarbon biomarkers ( n -alkanes, isoprenoids, cyclic alkanes, and polyaromatic hydrocarbons) were studied using the GC-MS method and provided information about the genesis, facies conditions of sedimentation, and catagenetic maturity stage of dispersed organic matter (DOM). The Late Mesozoic-Cenozoic uplifting of the region and active magmatic processes significantly influenced the thermal transformation of sediments. The revealed trend is best observed in the sediment section of the Franz Josef Land Archipelago, where the thermal effects led to a radical increase in DOM transformation, up to the AC 1 stage. [ABSTRACT FROM AUTHOR]

This study provides geochemical, mineralogical, and isotope data for rocks and ores from Lower Proterozoic black shale formations of the Kodar-Udokan structural and formational zone, which host the Khadatkanda gold-uranium deposit. The results indicate that the uranium and gold mineralizations were formed at different times in relation to different geodynamic settings. The gold mineralization is associated with the inception of the Syulban fault and has a juvenile source. The later Th-U mineralization originated during tectonic rejuvenation of the Syulban fault zone, while the sources of radioactive elements were presumably the underlying sediments of the Kodar Group, which are widespread throughout the area of the Baikal mountain region (BMR). Based on the above results, the Au-U mineralization in the study area can be recognized as unconformity-type deposits, analogous to the well-known deposits of Australia and Canada. In this connection, the Baikal mountain region has a good potential for the discovery of Au-U deposits. [ABSTRACT FROM AUTHOR]

With the development of electron microscopy-based porosity measurement techniques, it is possible to devise new oil and gas reservoir rock classification schemes that would take the geometrical features of the pore space into account. This is associated with the fact that the structure of the pore space of reservoir rocks has a significant effect on the recovery of hydrocarbons upon reservoir processing. For several years, we have carried out microstructural studies of rocks from the productive strata of various fields using cathodoluminescence scanning electron microscopy (SEM) and porometric software for the analysis of SEM images. The investigations show that it is possible to classify reservoirs by the connectivity of pores and pore channels in reservoir rocks. [ABSTRACT FROM AUTHOR]

The article discusses the geochemical features of mature hydrocarbon (HC) systems and their recognition. It mentions that the composition of HC systems in sedimentary sequence is transformed from immature at shallow depths to degraded mature and ultramature oils and condensates at large depths and shows pressure, temperature gradients and a particular type of initial organics. It discusses the isomerization parameters needed to evaluate HC systems.

The peculiarities of the processes of postsedimentary lithification and their dynamics in various geostructural areas (cratons, young platforms, and orogens) are considered. The direct and indirect impacts of geodynamic factors on these processes are substantiated. [ABSTRACT FROM AUTHOR]

[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]