Methodological approaches to evaluation of oil and gas potential of pre-Jurassic sediments in the Southern West Siberia

The Pre-Jurassic oil and gas capacity of the West Siberian sedimentary basin is an actual question of modern petroleum geology when the vector of oil and gas exploration turns away from well-studied and nearly depleted hydrocarbon fields. In the context of reduction of payable hydrocarbon reserves in traditional producing horizons, in particular, the Neocomian sediments of the West Siberian Basin, geological exploration works are increasingly concentrated on less studied and more ancient objects such as the Paleozoic basement. The study of the oil and gas potential of the basement sediments is a strategic task, and its solution can help formulate the fundamental ideas about the formation of hydrocarbon deposits in such sediments, as well as propose a rational complex of geological exploration works and evaluate the prospects of previously unexplored objects due to their complex geological structure and poor study. Within the present research, the occurrence patterns of hydrocarbon reservoirs in the pre-Jurassic sediments of the southern part of the West Siberian basin were determined, as well as the main conditions for the formation of zones of increased reservoir properties in such sediments were characterized. The results obtained can be a framework for a forecast technology and a geological basis for the further study of the Paleozoic basement of West Siberia. Residuum of the Paleozoic sediments containing huge hydrocarbon reserves in the pore space features an increased content of metals. Metasomatic transformations of rocks are associated with tectonic dislocations in basement rock mass, which initiate permeable and loosened zones suitable for fluid seepage. In this manner, formation of metal-bearing residuum can be a factor of extra secondary reservoirs and an indirect sign of oil presence.