ZONING OF OIL-GAS POTENTIAL OF PRE-JURASSIC RESERVOIRS IN NYUROL'KA MEGADEPRESSION (USING PALEOTEMPERATURE MODELING AND DRILLING)

The relevance of the research consists in the necessity of assessing a search strategy (search criteria, conceptual technological scheme) of bodies in the pre-Jurassic petroleum play of Western Siberia (hard to recover reserves). The aim of the study is to identify the primary research areas of hydrocarbon reservoirs in pre-Jurassic basement by the example of the Nurol'ka megadepression and its framing structures which are located on the main oil- field regions of Tomsk, on the left bank of the Ob River. Object of research is the drilled reservoirs of weathering crust and Paleozoic basement. The weathering crust reservoirs are formed on clay and siliceous, carbonate and acid volcanic rocks, for which the Lower-Jurassic clay is fluid seal. The reservoirs of bedrock are associated with secondary reservoirs formed by limestones, granites, rhyolites and ultrabasites under certain conditions. Fluid seals in this reservoir are day formations of weathering crust or impermeable rocks within the basement. The main oil source formation is the Lower Jurassic Togur formation. The research is carried out based on the concept of vertical migration. The research area is located in boundaries of the oil source formation. The research methods include the analysis of mapping results of the source kitchen of Togur oil by the geotemperature criterion and predicting mapping of the weathering crust and the Paleozoic basement reservoirs according to the data of deep drilling, oil geological zoning and perspective area's ranking. As a result of the research, the perspective research areas for the weathering crust and the Paleozoic basement reservoirs have been selected and ranked within the source Togur formation. The priority areas for research of hydrocarbon reservoirs in the weathering crust are the south beads of Kulan-lgay, Tamrad basins and its adjacent areas (about 1100 km(2)). The priority areas for research and development of Paleozoic basement reservoirs are the south beads of Kulan-lgay basin and adjacent zone of Tamrad basin which partly overlap with the perspective areas of the weathering crust, with some decrease in area (up to 900 km(2)), as well as the lands of the south-eastern beads of Nurol'ka megadepression and the adjacent lands of Chuzik-Chizhap mesosaddle (about 1200 km(2)). The consistency of the forecast and the identified oil-and-gas potential of pre-Jurassic rocks prove the accepted migration concept of hydrocarbons feeding reservoirs, and the previously stated resource-efficient and technology strategy of exploration for oil deposits in the pre-Jurassic basement of Western Siberia.