SOME ASPECTS OF OIL AND GAS CARBONACEOUS DEPOSITIONS FORMATION ON THE TERRITORY OF RUSSIA

Abstract

The article discusses the conditions of sedimentation of carbonaceous depositions and the formation of reservoir properties in them on the example of the Domanik and Bazhenov formations, as the most promising potentially oil and gas objects in Russia. It is shown that in the passive Paleozoic along the eastern periphery of the Russian platform, there was a passive continental margin that developed in the French-Tournaisian time as an uncompensated depression. Typical domanik sections are unconventional reservoir confined to the tracts of high sea level and are localized in the axial parts of the depressions. Here they are represented by siliceous, carbonatesiliceous lithotypes enriched in humus-sapropel material. Bazhenov depositions were formed in the syneclyse basin, which arose under the influence of early Triassic rifting. Submergence and uncompensated development of the bazhenov sea occurred in the volga period. Despite belonging to different geodynamic types of basins, carbonaceous strata are characterized by a common feature - they are part of the riftdepressive complexes of the transgressive stages of the sedimentation cycles, which predetermined a stable non-compensated crust submersion and ensured the formation, accumulation and preservation of large volumes of organic matter. It is established that the distribution of organic matter in the basins is subject to areal zoning and vertical cyclicity: the maximal concentrations of organic matter are confined to the axial ones, and the minimal to onboard relatively elevated areas. A regular stratified sequence of enriched and depleted organic matter layers in the section is noted, which may be due to periodic changes in bioproductivity or physico-chemical conditions of sedimentation. An important role in the formation of an unconventional reservoir of interrelated processes of external and internal dynamics, including submersion lithogenesis, tectonic activation and the accompanying temperature, pressure and fluid dynamic changes of organic matter, is shown. The decisive role of catagenetic transformations in the hydrophobization of the matrix and the formation of the abnormally high pressure zones, as well as geodynamic factors that contribute to the formation of reservoir properties, which should be taken into account when carrying out exploration and oil field development, is emphasized.