Features of filling reservoirs with hydrocarbons in the territories with a low maturity of the oil and gas parent rocks (a case study of Jurassic hydrocarbon traps in the Uvat district)

Abstract

The article is devoted to the results of an analysis of geological factors that had a great influence on the filling of Jurassic traps with hydrocarbons. Based on the results of paleotectonic analysis, three key stages of reconstructions of the structural plans of sedimentary cover deposits were identified. Each stage was characterized not only by the appearance of new traps in the interval of Jurassic deposits, but also by the sinking of rocks of Bazhenov formation to a certain depth. It is revealed that in most of the territory of the Uvat district, Bazhenov formation didn't have time to fully realize its hydrocarbon-generating potential. In the Central and Eastern regions it entered the main zone of oil formation only in the Paleogene. Since the development of the relief of modern structural plans of Jurassic deposits in this area occurred in several stages, both the formation of traps and the lateral migration of hydrocarbons also occurred in stages. The first stage of migration occurred at the boundary of the lower and upper Cretaceous, the second stage occurred at the beginning of the Paleogene. As a result, the combined influence of lateral migration of hydrocarbons and the gradual formation of local structures in different areas of the Uvat district led to selective filling of Jurassic hydrocarbon traps.