Numerical modeling of the organic matter transformation in the sedimentary rocks of the northeastern Sakhalin shelf

Abstract

A basin modeling system was used to numerically reconstruct the burial, thermal, and catagenesis histories of the rocks in the sedimentary sections of four boreholes in the Kaigan-Vasyukan part of the Sakhalin-5 area on the northeastern shelf of Sakhalin. The sedimentary section of the basin includes the Late Cretaceous complex in addition to the Cenozoic one. The region of the shelf considered here is located within the Okhotsk block margin near to the East Sakhalin accretion complex in the region subjected to active fault tectonics. Consequently, two limiting versions of the basin’s development are analyzed in this paper: the first with the local-isostatic response of the basin’s lithosphere during the basin’s entire history and the second with the isostatic behavior of the lithosphere beginning from the time of the Kuril Island Arc’s formation (about 34 Ma BP). The modeling suggests a rather high thermal mode of the basin at intensive sedimentation during the last 10 Ma. The rocks of the upper half of the Late Cretaceous formation; the Eocene, Machigar, and Daekhurin formations; and the lower half of the Uinin complex could generate oil up to the present time. In contrast, the rocks of the upper half of the Uinin complex and the Dagi, Okobykai, and Lower and Upper Nutov formations are interesting only as the reservoir and cap rocks for the hydrocarbons generated in the lower levels.