«OIL AND GAS GEOLOGY» № 1/2017
Geologiya Nefti I Gaza" ("Oil And Gas Geology") is included by the Higher Attestation Commission in the list of leading scientific journals and publications where the main scientific results of dissertations for the degree of candidate and doctor of sciences
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OIL AND GAS POTENTIAL PROSPECTS AND EXPLORATION RESULTS
Geophysical and geochemical indices used for evaluation of oil-gas potential of the Aptian-Cenozoic basins in the East-Siberian Sea are analyzed. Types and thermal maturity of OM showing the oil-gas generation activity are reconstructed for the sediment fill of the basins located in the periphery of the De-Longa uplift and Longa depression. In the acoustic basement rocks the generation potential of OM is sufficiently realized, and in places with mildly deformed sedimentary series the HC generation products could be partly preserved in the form of gas and bitumen accumulations. At present the acoustic basement constitutes a secondary source of HC entering the sedimentary cover of the East-Siberian Sea along the fractures of fault zones.
FORMATION AND LOCATION OF OIL AND GAS POOLS
Grunis E.B., Marakova I.A., Rostovtschikov V.B. Structural features and formation conditions of the Permian terrigenous sequence and stages of non-anticlinal trap formation in the northeastern part of the Timan-Pechora province
Study of the structural features , conditions of formation and oil and gas potential of the Permian-Triassic clastic sediments is very acute in the Timan-Pechora region. Permian terrigenous sequence has been formed at the background of the Urals orogenesis and general sea regres-sion, and non-anticline HC pools were discovered here concurrently with pools associated with conventional traps. Identification of HC pools in these sediments was generally complicated by ambiguity of their well logging characteristics, scarce core data and old seismic materials with low-resolution seismic records. Based on a systematic approach the authors consider various tectonic zones where horizontal and vertical upward movements have affected the formation of the regressive Permian sequence and inherent HC traps. A classification of non-anticline traps based on geological and geophysical data is proposed.
The paper provides essentially new actual data showing universal development of a complex horizontal (multi-leveled) zone of more intensive (micro)fracturing within the Mid-Jurassic - Early Cretaceous rocks throughout the Rakushechno-Shirotnyi swell. The zone includes predominantly macro- and micro-fractures of several recent generations. For the Rakushechno-Shirotnyi swell the authors propose a mechanism of gradual formation of normal fault–slide type - overthrust structures (with small-throw concordant intra-strata overthrust) based on drilling data and taking into account spatial-temporal aspects of the regional geodynamical development of the study area during the most recent phase of geological history.
The article presents the results of combined interpretation of drilling and new seismic data that allowed to describe geological and geodynamical evolution of the region comprising the northeastern part of West-Siberian and the western part of Yenisei-Khatanga basins starting with the Late Permian times. A series of paleo-reconstructions is performed to show the principal stages in evolution of the investigated region and influence of the events in the adjacent regions on this evolution. The Permian -Early Triassic phase of the rifting activity is substantiated. Compression periods responsible for development of inversion structures have been determined, including the mid-Triassic period associated with compression in the Turukhansk-Norilsk area of the Siberian platform, the Jurassic-Cretaceous period contemporaneous with orogenesis in the Verkhoyansk-Chukotka and Mongol-Okhotsk areas and the final Cenozoic compression period, its mechanism, however, still being subject to discussion.
Seismic survey conducted in the recent years has allowed to trace eastwards the earlier assumed North-Kuban Lower Mesozoic-Paleozoic deep. The deep is complicated by tectonic faults of the thrust-overthrust type. Seismic survey within the limits of the Azov swell has confirmed presence of the structural stage comprised of the Lower Mesozoic-Paleozoic sediments. In the Lower Mesozoic-Paleozoic sediments there were discovered uplifts of unquestionable interest from the oil and gas exploration point of view. Considering the Lower Mesozoic-Paleozoic sequence as an oil-and-gas promising object can greatly increase oil and gas potential of the Azov offshore blocks water and significantly enhance investment strategy in the Southern Federal District of Russia.
HYDROCARBON RESOURCES AND RESERVES
The paper presents data on the mean oil recovery factors for oil fields of the central part of the West-Siberian oil-gas province. Variations of neighboring ORF are shown for the entire time period from the start of oil production in the province till present days. Apart from that, the ORF variations are calculated for the Ugra oil fields being developed. In addition, the ORF values have been estimated for the difficult-to-extract reserves (the Achimov and Tyumen suites). Average current ORF is predicted for the time period till 2035.
HARD-TO-EXTRACT AND NON-TRADITIONAL HYDROCARBON SOURCES
The Volga basin is one of the largest and most explored combustible shale basins in the Volga-Pechora province. Oil shales in the basin are associated with the sediments of the Volzhski super-horizon in the Upper Jurassic section. The oil shale in-place resources and reserves of the Volga basin exceed 44 billion ton. The Volga combustible shales are known as a complex energy-technological crude mineral. Innovative technology of the combustible shale production without mining recently developed in Russia permits to produce combustible shales at minimum costs and environmental damage. Combustible shales should be considered as a valuable crude for complex processing to provide a wide range of products, such as: electric power, fuels, chemicals and construction materials. This technology permits to more efficiently process the combustible shales and protect the environments. The use of the innovative production and processing techniques allows to characterize the projects on development of the Volga combustible shale deposits as highly efficient.
Examples of epigenetic mineral associations of hydrothermal origin found in Jurassic deposits of the West Siberian oil-gas basin are shown. The mechanism of secondary porosity development and formation of reservoir rocks in the Jurassic sediments is reconstructed, as well as the suc-cession of hydrothermal formation of minerals, generation of naftides and formation of HC-accumulations. A new method is proposed for detecting secondary reservoir rocks of tectonic-hydrothermal origin based on a combined use of seismic data analysis and tectonic physical modeling.
The experimental study of clay rocks and pore water compositions of the oil Bazhenov formation in Western Siberia are presented in this paper. It was found that the oil reservoir could be formed due to the external influence of the hyperthermal acid fluids as a result of which the secondary minerals were determined in the strong leached clay rocks. Therefore the shales contain the chemically bounded water entered into the composition of sulfate crystallohydrates.
At present the study of gas-hydrates becomes more intensive owing to the gas-hydrate potential significance for power industry, particularly important being investigations of gas hydrate deposits of the sea bottom, as they are most promising for commercial develop-ment. The article is devoted to analysis of factual data on stratigraphic position of the sea-bottom gas hydrates accumulations. This problem still remains unsolved, and the age of the accumulations is assumed as recent or accounting for several ten thousand or million years. Detailed analysis of actual and literature data has permitted to conclude that in the Cenozoic seas the formation of gas hydrates started in the post-Eocene - Early Miocene times. The authors believe that further research combined with determination of relative and absolute age would provide for more accurate evaluation of time, extent and rate of gas hydrate formation in various areas of the World Ocean and direct the investigations to practical development of these nonconventional reserves.