Section types and oil prospects of the Bazhenov Formation in the Nadym-Ob interfluve

Abstract

The article presents the results of studying the geological structure of the Bazhenov Formation in the Nadym-Ob interfluve of Western Siberia with the aim of predicting the oil content of this black shale stratum. As a result of interpretation of a wide range of well logging represented by electric, radioactive and acoustic logging, with subsequent matching of these results with paleontological definitions of micro- and macrofauna, the distribution of the Salym, Nizhnevartovsky and Tarkosalinsky types of sections of the Bazhenov Formation was clarified, transitional areas between them were identified. It has been established that the Tarkosalinsky type is more widespread in the western direction than was shown earlier and is also distinguished in the Vengayakhinskaya, Yaraynerskaya and other areas. The Nizhnevartovsky type, on the contrary, has a narrower distribution and stands out directly within the same name arc and to the south by the Variegasky-Tagrinsky megahigh. On the basis of geological, geochemical, geophysical criteria and the results of an inflow test in deep wells, a map of the oil potential prospects of the “classical” sections of the Bazhenov Formation has been compiled. Regional prerequisites (high catagenesis of organic matter, significant modern concentrations of organic carbon, etc.) for the discovery of industrial accumulations of oil in the Bazhenov Formation in the southern regions of the Yamalo-Nenets Autonomous Area are identified. The results of the test for the inflow of the Bazhenov Formation in this area in the 70–90s XX century were analyzed; repeated, interval testing of these deposits using modern methods of stimulation of the inflow is recommended. The necessity of laboratory lithological, petrophysical, geochemical study of the core of the Bazhenov Formation in the southern part of the Yamalo-Nenets Autonomous Area is substantiated with the aim of determining its lithological composition, identifying oil source and oil productive intervals, studying the reservoir structure and the nature of saturation of its void space, developing recommendations for calculating oil reserves and creating technology for its cost-effective production.