Integrated Methodological Approach to Assessing Petroleum Systems of Complex Geological Objects in West Siberian Oil and Gas Province

Successful exploration in mature, geologically complex regions like the West Siberian province requires advanced predictive modeling to reduce the risk prospects. This paper presents an integrated methodology for evaluating generation-accumulation petroleum systems, combining detailed lithofacies, structural, and geochemical analysis with paleo-reconstructions and 3D basin modeling. Special attention is given to the construction of a robust geological framework, incorporating fault mapping, pseudo-3D seismic interpretation for delineating sedimentary bodies, and the calibration of the thermal history using vitrinite reflectance and biomarker data. The results show that the primary source rocks, including the Bazhen Formation, have entered the early stage of the main oil generation phase, with a realized transformation ratio of up to 20% in the most mature sediments. The model quantifies a substantial volume of in-place unconventional resources within the Bazhen source rock (664 Mt of oil) and identifies the most prospective conventional traps in the AS8 and AS9 reservoirs, which are controlled by lithofacies and hold combined estimated resources of 84.78 million tons of oil. The analysis successfully delineates hydrocarbon migration pathways, highlighting areas of vertical migration through compromised seals. This comprehensive assessment provides a robust predictive tool for reducing exploration uncertainty and guiding future drilling campaigns toward both high-potential conventional traps and unconventional shale plays.