Comparative Study of Changes in the Composition of Organic Matter of Rocks from Different Sampling-Depth Intervals of Domanik and Domankoid Deposits of the Romashkino Oilfield

Abstract

This paper presents the results of a comparative study of rock samples from depth intervals of 1705–1728 m of Semilukian–Mendymian (domanik) deposits of the Berezovskaya area and 1379–1394 m of carbonate (domanikoid) deposits of the Dankovian–Lebedyanian horizon of the Zelenogorskaya area of the Romashkino oilfield. It has been shown that rocks with different mineral compositions differ in the content and composition of organic matter (OM), including kerogen, and its resistance to thermal impacts. The yield of extracts from the rocks and the differences in their group, structural-group, and hydrocarbon-group compositions have been determined. According to the molecular-mass distribution of normal and isoprenoid alkanes, the extracts from the rocks are oils of types A¹ and A². Peculiarities in the distribution of higher biomarkers have been revealed, indicating that the hydrocarbons of the examined samples of domanik and domanikoid rocks are genetically uniform in nature, but differ in the geochemical environment of the transformation of the original OM and, possibly, in the effect of migration processes.