Forecasting the quality of fluid seals and reservoirs for the Upper Jurassic deposits in the southeastern part of the West Siberian oil and gas province

Abstract

Background. Upper Jurassic natural reservoirs are the main deposits containing 65–75% of recoverable hydrocarbon reserves in the Tomsk Region. They are overlapped by the fluid seals of the Bazhenov–Georgievsk complex, the quality of which deteriorates in the easterly direction. Therefore, to predict new promising areas, it is necessary to determine the quality and thickness of the Upper Jurassic seals and natural reservoirs. Objective. The need to forecast the quality of the Upper Jurassic fluid seals and reservoirs of the “Yu group” in the southeastern part of the West Siberian oil and gas province (Tomsk Region). Materials and methods. The paper uses regional and local studies of different years, materials and methods for interpreting geophysical well studies and seismic data from 2D reflection and core studies, databases of geological and geophysical information, methods of mathematical modeling of sedimentary basins and an original methodological approach proposed by the authors. Results. The time of the beginning of the lithification of the Bazhenov–Georgievsk rocks of the Upper Jurassic–Early Cretaceous (Aptian–Albian) was determined, and a regional model of the Georgievsk horizon distribution was constructed. The porosity of the Upper Jurassic natural reservoirs and the thickness of the Bazhenov fluid seal at the selected fields were calculated. Conclusions. The assessment of the quality of fluid seals and natural reservoirs made it possible to determine more promising areas for geological exploration using the oil and gas exploration criterion determined on the basis of the analysis of the thickness of the Georgievsk horizon (Kontorovich criterion). The efficiency of the proposed method is described using the example of the Upper Jurassic oil and gas fields in the Tomsk Region (Western Siberia).