Geochemistry and catagenetic transformation of kerogen from the bazhenov horizon

Abstract

A representative suite of 276 samples was used to study the isotopic and element geochemistry of kerogens from the Bazhenov horizon (Bazhenov Formation and its time equivalents) of the West Siberian sedimentary basin and to construct maps reflecting changes in the elemental composition of kerogen. The elemental composition of kerogen was used to determine the types of organic matter (H and C contents), the initial components of the living matter, the sources of kerogen (H and N contents), diagenetic history of organic matter (S content), the level of catagenetic transformation (C and O contents). Kerogen from the central, western and southern regions of the West Siberian basin toward the boundary of the Bazhenov horizon pinch-out shows strong enrichment in hydrogen (up to 8–9%) and 12С (δ13С‰ from -35 to -29), suggesting its derivation from the polymer lipids of aquatic origin. Kerogen from the Bazhenov horizon (catagenetic grade MC1) in the northeast of the basin contains much lower hydrogen concentrations (2–4%). A map of organic matter types in the Bazhenov horizon was constructed.