Formation Of Hydrocarbon Accumulations Research Articles

About “Paleozoic roots” of the oils of the Eastern Ciscaucasia

The paper considers geochemical data on the biomarker composition of oils from the fields of the Terek-Caspian oil and gas basin. Samples of oils from the fields of the main oil and gas bearing regions of the Eastern Ciscaucasia – Terek-Sunzha zone, Prikumsky swell, Piedmont Dagestan and the Middle Caspian Sea were studied. To determine the “geochemical” age of oils, the ratios of regular steranes in saturated oil fractions were analyzed. It was found that the value of the biomarker parameter St28/St29, which determines the geological age of the original organic matter for oils, varies widely – 0.36–1.47. The most “ancient” age (Devonian-Carboniferous) was determined for the oils of the Prikumsky swell and the water area of the Middle Caspian; in the Terek-Sunzha zone and Piedmont Dagestan, an increase in the proportion of St28 sterane is recorded in oils, which indicates a younger generation age (up to the Paleogene). The data obtained can be used to clarify the history of the formation of hydrocarbon accumulations in this region.

The role of deep faults in the structure formation of the TCFD, the distribution of hydrocarbon accumulations, and thermomineral sources

The work purpose was to assess the prospects of oil and gas potential of the western part of the Tersko-Caspian trough (TCT) concerning the development of deep-sunk areas in the light of modern ideas about the deep-seated formation of hydrocarbons. The main tasks are to analyze the ideas about the formation mechanism of the tectonic structure and formation of hydrocarbon accumulations; to study the relationships between the formation processes, migration, and the areal distribution of hydrocarbon accumulations; to determine the main prerequisites for the deep genesis of oil and gas. The scientific novelty lies in a comprehensive approach to the study of the formation processes of hydrocarbons, migration, the formation of traps, and patterns of placement of hydrocarbon accumulations. The article describes the mechanisms of formation of the Tersk and Sunzha composite anticline as the main zones of oil and gas accumulation. It is suggested that the formation of high-amplitude anticline folds in the upper cretaceous deposits resulted from the vertical migration of high-pressure fluids along deep faults with the breakthrough of their upper horizons of the sedimentary cover into the late-orogenic folding stages. The main prerequisites for the deep genesis of oil and gas are listed as pronounced uneven distribution of hydrocarbon accumulations, AHFP, hydrochemical anomalies, etc.

Basin-filling processes and hydrocarbon source rock prediction of low-exploration degree areas in rift lacustrine basins: a case from the Wenchang Formation in low-exploration degree areas, northern Zhu I Depression, Pearl River Mouth Basin, E China

Hydrocarbon source rocks, as a main geologic factor of petroliferous systems in a sedimentary basin, play a key role in the accumulation of oil and gas and the formation of hydrocarbon accumulations. This study, which focuses on difficulties in prediction of hydrocarbon source rocks in basins or sags with low exploration degree and insufficient hydrocarbon source rock indicators, taking the Wenchang Formation of northern Zhu I Depression, Pearl River Mouth Basin as an example, proposed a hypothesis of “finding lakes and hydrocarbon source rocks”. Detailed steps include, first, determination of the lacustrine basin boundary according to analysis of seismic foreset facies, determination of the depositional area based on the compilation of strata residual thickness maps, determination of the lacustrine basin shape according to deciphering slope break belt system, determination of the fluctuation of paleo-water depth according to biogeochemical indicators of mature exploration areas, determination of the lacustrine basin scale based on analyses of tectonics intensity and accommodation space, which prove the existence of the lacustrine basin and identify the range of semi deep-deep lake; second, further analyses of tectonopalaeogeomorphology, paleo-provenance, palaeoclimate and paleo-water depth to reconstruct the geologic background of the original basin and semi-deep-deep lacustrine facies, to determine the distribution of semi-deep/deep lacustrine sediments in combination with studies of logging facies, core facies, seismic facies and sedimentary facies, and to rank the sags’ potential of developing hydrocarbon source rocks from controlling factors of source-to-sink system development; third, on the basis of regional sedimentary facies analysis, through identification and assessment of seismic facies types of semi-deep/deep lacustrine basins in mature areas, establishing “hydrocarbon source rock facies” in mature areas to instruct the identification and depicting of hydrocarbon source rocks in semi-deep/deep lacustrine basins with low exploration degree; fourth, through systematical summary of hydrocarbon-rich geological factors and lower limit index of hydrocarbon formation of the sags already revealed by drilling wells (e.g., sag area, tectonic subsidence amount, accommodation space, provenance characteristic, mudstone thickness, water body environment, sedimentary facies types of hydrocarbon source rocks), in correlation with corresponding indexes of sags with low exploration degree, then the evaluation and sorting of high-quality source rocks in areas with sparsely distributed or no drilling wells can be conducted with multi-factors and multiple dimensions. It is concluded that LF22 sag, HZ10 sag and HZ8 sag are II-order hydrocarbon rich sags; whereas HZS, HZ11 and HZ24 are the III-order hydrocarbon-generating sags.

ВПЛИВ СТИСКАЛЬНИХ НАПРУГ У ПІВДЕННО-КАСПІЙСЬКІЙ МЕГАЗАПАДИНІ НА РОЗВИТОК І НАФТОГАЗОНОСНІСТЬ ЛОКАЛЬНИХ ПІДНЯТТІВ

The following structural elements in the South Caspian megadepression (SCMD) have been considered: the interfluve of the Kura and Gabirri, the Absheron and Baku archipelagoes, the Lower Kur depression (LKD) and the Godin massif, that stand out geodynamically, from point of view of structural and tectonic evolution and oil and gas content. To solve this problem, the geodynamic environment of the SCMD has been analyzed based on the geodynamic chart of the Central segment of the Mediterranean folding belt compiled by the author, as well as the orientation chart of compressional stresses in the SCD and the methodology, developed for the first time ever, for their qualitative assessment within the structural elements by means of compiling isomorphic maps. The latter make it possible to determine the intensity and nature of the propagation of compressional stresses, the specifics of their impact on folding, oil and gas generation and formation of hydrocarbon accumulations. The Kur-Gabirri interfluve is situated in the west of the SCMD between the closely located Greater and Lesser Caucasian collisions. It is characterized by oil and gas bearing and potential sublatitudinally oriented linear folds, complicated by faulting and mud volcanism. The values of isolines of the isomorphic map and their density are indicative of high intensity of the north-west oriented compressional stresses here. The Absheron archipelago is a western element of the Absheron-Balkhan residual subduction. According to the isomorphic map with a dense network of isolines of sublatitudinal orientation, the archipelago is complicated by linear folding, as well as thrusts, transverse strike-slip faults, mud volcanism, oil and gas content, and oil and gas manifestations indicating the build-up of intense compressional stresses here. Evolution of folds within the Baku archipelago and the Lower Kur depression took place under the stresses of longitudinal and transverse bending. The faintly pronounced linearity of the compressional stresses is apparently associated with the formation of the Western Board of the SCD in the form of a regional submeridianal uplift. It developed under the impact of compressional stresses arising from the effect of the northeastern projection of the Arabian plate on the Iranian one. LKD is an onshore extension of the Baku archipelago. Its anticline zones, regional faults, mud volcanism and oil and gas content continue in the latter. The Godin Massif is the easternmost structural element of those considered with a faintly pronounced reflected folding of unknown prospects. Isolines of the isomorphic map are not directly associated with local uplifts, which is indicative of the absence of clearly pronounced compressional stresses here. The analysis made it possible to determine the degree of development of compressional stresses, their impact upon formation of the sedimentary section, folding, mud volcanism and oil and gas content of the considered structural elements.

Формування та критерії нафтогазоносності вуглеводневих скупчень Західного нафтогазоносного регіону України

In the paper we have analysed hydrocarbon deposits of the Western region according to their belonging to the tectonic zones, stratigraphic complexes, types and depths of occurrence. The law-governed nature of alteration in physical-chemical properties of oil and gas, hydrogeological and geochemical peculiarities of productive thickness were studied, haloes of the distribution of gas of hydrocarbon and non-hydrocarbon composition outcrops of fluids were mapped. Problems of the formation of hydrocarbon accumulations were considered. According to the results of integrated analysis of different geological factors, besides the main factors of oil and gas presence – structure, reservoir, cover – additional criteria were proposed. In the direction to the deposit, the nitric-methane gases are changed into sufficiently methane and hydrocarbon-methane ones, and values of saturation pressure are comparable to the formation pressure. Indication of oil-gas presence are water-soluble organic matters of oil origin: bitumen, phenols, hydrocarbons, naphthenic acids as well as the presence of condensation waters or their mixture with formational waters. Probable indicators of hydrocarbon accumulations are sulfides of zinc, lead, copper in rocks. For the existence of the deposits the hydrogeological closing of the bowels is necessary: small velocities of the formational waters, their high mineralization, metamorphism intensity, chlorine-calcium type of waters. Natural oil-gas showings as a reflection of deposits that occur at a depth serve as criterion for estimation of prospects of the oil-gas presence in the open territories. The example of substation of prospecting objects is given according to criteria of the oil-gas presence in the platform autochthone under the overthrust of Pokuttia-Bukovyna Carpathians.

Digital oil and gas complex of Russia

Digital and technological modernization of the oil and gas industry through the use of innovative technologies and platform solutions, intelligent control systems, domestic “end-to-end” digital technologies will help strengthen Russia’s position in the global oil and gas market. One of the megascience projects being developed at the Institute of Oil and Gas Research Institute of the Russian Academy of Sciences is the creation of a Geosphere Observatory. The Geosphere Observatory is focused on studying the influence of fundamental geological processes (crustal waveguides, fracture centers, etc.) in the mantle and crust of the Earth on the formation of hydrocarbon accumulations and management of field development in real time based on the introduction of advanced technologies in the field of ultra-deep drilling, fiber optics and laser physics, processing large volumes of geo-information (BigGeoData) and the theory of reconfigurable active-passive sensor networks (AntennaGrid).

Особенности распределения нефтяных и газовых месторождений в земной коре

Hydrocarbon deposits within oil and gas-bearing territories are distributed very unevenly both in area and in the section of sedimentary deposits, which is the main geological feature of oil and gas placement in the subsurface. The formation of hydrocarbon accumulations in the sedimentary cover is due to a set of genetic factors, which ultimately determines the patterns of placement of oil and gas accumulations along the section and area of the sedimentary cover. The study of the factors determining the zonation of oil and gas accumulation and genetically her condition, zoning of oil and gas formation, contributes not only to expanding our knowledge on the fundamental problems of petroleum geology, but also improve the efficiency of exploration.

Analysis of Water–Gas System Equilibria in Jurassic–Cretaceous Reservoirs (by the Example of the Yamal-Kara Depression)

Abstract —The paper presents results of the pioneering study of equilibria in the water–gas system by the example of Jurassic–Cretaceous deposits of the Yamal–Kara depression located within northern West Siberia and its Arctic regions. Numerical modeling of physicochemical equilibria and evasion–invasion processes in the water–gas system allowed determination of the degree of groundwater saturation with gases and the nature of diffusive redistribution of gases in the media that form at the hydrocarbon deposit–groundwater contact. According to the degree of water saturation with gases (Kg), aquifers with poorly (<0.2) to ultimately (0.8–1.0) gas-saturated waters have been established. The revealed increase in the degree of groundwater saturation with gases in sinking producing reservoirs reflects its dependence on their total gas saturation. All waters with a total gas saturation of more than 1.8 L/L become ultimately saturated with gases (Kg = 1.0), thus theoretically predetermining the formation of hydrocarbon accumulations. Major gas condensate deposits are confined to the zone of gas-saturated waters with Kg from 0.8 to 1.0, while oil accumulations, to waters with lower gas saturation. Based on the established nature of water–gas, we can argue that oil and gas accumulations in Jurassic–Cretaceous reservoirs act as a conservative element of the lithosphere, i.e., its geologic and geochemical “relics”. The surrounding subsurface waters, as a more active constituent of the system, have largely anticipated its geochemical development, which is manifested in the differentiation of the fugacity ratios of individual gases in groundwater and hydrocarbon accumulations. The composition of the latter is therefore subjected to slow directional changes while the equilibrium is established, to usher in the qualitatively new state of the geochemical water–gas system.

Geofluid dynamic concept of prospecting for hudrocarbon accumulations in the earth crust

In our paper we produce new evidence of the tectonosphere and hydrosphere structure of oil and gas sedimentary basins and confirm significant influence of geofluid-dynamic processes on formation of hydrocarbon accumulations in the crust at the great depths. In our opinion the theory based on obsolete views on the tectonosphere structure lessen the importance the sedimentary migration theory of hydrocarbon generation. We prognosticate a particular stagnant type of post-elysionic water-drive systems in the crust at the great depths in conditions of increased hydrodynamic isolation. Absence of regionally sustained vertical and lateral drainage layers characterizes geological environment where stagnant type developed, and, corollary, fluids outflow into external environment is practically unfeasible. The subsalt filling complexes of the epicontinental deepwater basins are included into the post-elysionic water-drive systems. These complexes occur at the great depths and possibility of striking unique and large oil and gas fields there is inherent. We propose a system of fluid-dynamic conditions for preserving hydrocarbon accumulations in the lower crust as a result of developing sedimentary-migration theory for oil and gas formation. We consider the refinement of methods for prospecting and exploration large deposits at the great depths will pave the way for expanded reproduction of hydrocarbon reserves in the “old” oil and gas producing regions in our country.

Geofluid Dynamic Concept of Prospecting for Hydrocarbon Accumulations in the Earth Crust

In our paper we produce new evidence of the tectonosphere and hydrosphere structure of oil and gas sedimentary basins and confirm significant influence of geofluid-dynamic processes on formation of hydrocarbon accumulations in the crust at the great depths. In our opinion the theory based on obsolete views on the tectonosphere structure lessen the importance the sedimentary migration theory of hydrocarbon generation. We prognosticate a particular stagnant type of post-elysionic water-drive systems in the crust at the great depths in conditions of increased hydrodynamic isolation. Absence of regionally sustained vertical and lateral drainage layers characterizes geological environment where stagnant type developed, and, corollary, fluids outflow into external environment is practically unfeasible. The subsalt filling complexes of the epicontinental deepwater basins are included into the post-elysionic water-drive systems. These complexes occur at the great depths and possibility of striking unique and large oil and gas fields there is inherent. We propose a system of fluid-dynamic conditions for preserving hydrocarbon accumulations in the lower crust as a result of developing sedimentary-migration theory for oil and gas formation. We consider the refinement of methods for prospecting and exploration large deposits at the great depths will pave the way for expanded reproduction of hydrocarbon reserves in the “old” oil and gas producing regions in our country.

Geochemical conditions of hydrocarbon accumulation in low-permeability shale sequences

The report is devoted to the study of conditions for the formation of organic porosity–void spaces of organic origin formed during transformation of the organic matter into hydrocarbons, and their role in the formation of hydrocarbon accumulation in low-permeability shale strata. The experience of studying and developing known shale formations of the world testifies to the fact that such strata are hybrid phenomena, that is, they are both oiland gas-bearing strata containing traditional and non-traditional accumulations of hydrocarbons. Based on the results of the programmed pyrolysis by the Rock-Eval-6 method, an estimate has been performed to quantify organic (kerogen) porosity. This estimate allows for determining the forecast retention volume of HCs generated during catagenesis.

The experiment of integrated mobile technologies used for deep hydrocarbon accumulation prospecting and geophysical mapping at the West Antarctic bottom structures

The data obtained confirm earlier assumption about possible existence of large accumulations of oil and gas hydrates in this part of the West Antarctica. Their formation in the structures of passive continental margin of the Antarctic Peninsula occurred as a result of repeated intrusions of deep geo-fluids into the earth crust different horizons during regional reactivation of paleo-fractures and attenuated zones. Materials of geophysical studies in the region have shown the presence of complicated system of local structures, considered as typical for passive continental margins. Shared feature for these structures of continental margin of Antarctica as well as for other similar structures of the great ocean is sufficiently close regional, and possibly genetic connection of mud volcanoes with explored areas of BSR-reflections and the places of formation of gas and gas hydrates accumulations. The data obtained attest the considerable role of deep fluids in formation of hydrocarbon accumulations in different horizons of the Earth’s crust of the passive margins of West Antarctica.

The evolution of hydrocarbon systems in the North Kara sea: Evidence from 2D modeling

This work presents the results of the two-dimensional (2D) modeling of hydrocarbon systems along a regional seismic profile that crosses the sedimentary basins of the North Kara Sea, St. Anna Basin, Priseverozemelsky Trough, etc. Based on the geochemical data that were obtained on adjacent land areas, potential source strata were identified. In addition, four types of models were developed: reconstruction of the subsidence history, a warming model, oil-and-gas generation, and migration of hydrocarbons. Based on the model results, we analyzed the possibility of the formation of hydrocarbon accumulations within the North Kara Sea, their sources, and migration paths.

Avaliação do potencial gerador de petróleo da seção Aptiana-Albiana da Bacia de Sergipe, integrando análises palinofaciológicas e dados de geoquímica orgânica

Data presented in this investigation refer to studies integrating palynofacies and organic geochemistry analyses that were performed on 51 samples of PEC-41-SE-9 well, located in the Sergipe Basin, Eastern Brazilian continental margin. It was evaluated the potential for oil generation, identifying the type and degree of maturation of the organic matter. Optical analyzes show that the organic matter is composed in greater proportion by amorphous organic matter in good preservation, with high fluorescence. It also presents a 67% average concerning the total composition of the kerogen. The phytoclasts usually are well preserved in almost all the section. The palynomorphs are composed of an association, predominantly, of spores and pollen grains of genus Classopollis, featuring a predominantly arid to semi-arid climate environment at deposition time. Presence of the dinoflagellate in the upper section displays the first marine ingressions that happened in the end of Aptian. Based on the qualitative and quantitative results of kerogen, it was possible to characterize three distinct palynofacies, in which the palynofacies I had the best features for quality and preservation of organic matter. The results show total organic carbon values up to 6.39% and Rock-Eval pyrolysis data pointed to the type II kerogen rich in organic matter suitable for the formation of hydrocarbon accumulations. The hydrogen index is found between 200 and 550 mg HC/g of total organic carbon, which shows good potential for oil and gas generation. Spore color index data conclude that the organic matter is found predominantly on the immature maturation phase, with SCI values of 4.0 to 4.5, corroborating with data of maximum temperature, of up to 432°C.

The petroleum potential and a geodynamic model for the formation of hydrocarbon accumulations on the southern shelf of Cuba

The petroleum potential and a geodynamic model for the formation of hydrocarbon accumulations on the southern shelf of Cuba

Formation and accumulation of oil and gas in marine carbonate sequences in Chinese sedimentary basins

Advances in studies of formation and accumulation mechanisms of oil and gas in marine carbonate sequences have led to continuing breakthroughs of petroleum exploration in marine carbonate sequences in Chinese sedimentary basins in recent years. The recently discovered giant Tahe Oil Field and Puguang Gas Field have provided geological entities for further studies of the formation and accumulation of oil and gas in marine carbonate sequences. Marine carbonate sequences in China are characterized by old age, multiple structural deformation, differential thermal evolution of source rocks, various reservoir types (i.e. reef-bank complex and paleo-weathered crust karst reservoir), uneven development of caprocks, especially gypsum seal, and multi-episodes of hydrocarbon accumulation and readjustment. As a result, the formation of hydrocarbon accumulations in the Chinese marine carbonate sequences has the following features: (i) the high-quality marine source rocks of shale and calcareous mudstone are often associated with siliceous rocks or calcareous rocks and were deposited in slope environments. They are rich in organic matter, have a higher hydrocarbon generation potential, but experienced variable thermal evolutions in different basins or different areas of the same basin. (ii) High quality reservoirs are controlled by both primary depositional environments and later modifications including diagenetic modifications, structural deformations, and fluid effects. (iii) Development of high-quality caprocks, especially gypsum seals, is the key to the formation of large- and medium-sized oil and gas fields in marine carbonate sequences. Gypsum often constitutes the caprock for most of large sized gas fields. Given that Chinese marine carbonate sequences are of old age and subject to multiple episodes of structural deformation and superposition, oil and gas tend to accumulate in the slopes and structural hinge zones, since the slopes favor the development of effective assemblage of source-reservoir-caprock, high quality source rocks, good reservoirs such as reef-bank complex, and various caprocks. As the structural hinge zones lay in the focus area of petroleum migration and experienced little structural deformation, they are also favorable places for hydrocarbon accumulation and preservation.

New views on the formation of hydrocarbon accumulations in the northern Indian Ocean

New views on the formation of hydrocarbon accumulations in the northern Indian Ocean

A review and technical summary of the AAPG Hedberg Research Conference on “Origin of petroleum—Biogenic and/or abiogenic and its significance in hydrocarbon exploration and production”

A research conference originally scheduled as a Hedberg Research Conference examining the origins of oil and gas was held in Calgary, June 2005. This report summarizes the 14 presentations made at the conference, which discussed data and evidence regarding the abiogenic and biogenic origins of petroleum. In addition, the postpresentation discussion is summarized. Multiple concepts for the abiogenic formation of petroleum were presented. These concepts fell mostly into two broad families: mantle degassing associated with the polymerization of low molecular weight compounds and serpentization in association with Fischer-Tropsch reactions. The Fischer-Tropsch reactions are catalyzed reactions in which carbon monoxide and hydrogen are converted into hydrocarbons. The presentations on the biogenic origin presented a uniform model in which sedimentary organic matter is thermally converted to oil and gas. Little common ground was found to exist between the abiogenic and biogenic schools of petroleum formation, with the possible exception of the importance of fluid flow in controlling the formation of hydrocarbon accumulations. Although few, if any, conference participants changed their perspectives, most concluded that the meeting was informative and a useful exercise.