Carboniferous-Permian sedimentary formation and hydrocarbon generation conditions in Ejin Banner and its vicinities, western Inner Mongolia: a study of Carboniferous-Permian petroleum geological conditions (part 1)

Based on a study of the characteristics of Carboniferous-Permian basin basement structure, lithostratigraphy, sedimentary evolution and planar sedimentary facies, the authors consider that the Carboniferous-Permian basin of Ejin Banner and its vicinities is a uniform rift basin: there existed onlap sedimentation from north to south during Early Carboniferous-early Early Permian period and onlap sedimentation from south to north at the middle stage of Early Permian- Early Permian period, and the basin evolution reached its climax in Amushan stage of Late Carboniferous- Early Permian period, with the sediments being mainly of shallow sea shelf facies. Based on a study of the distribution of hydrocarbon source rocks, organic matter abundance, kerogen type and hydrocarbon source rock evolution, it is considered that widespread shallow sea- continental shelf argillutite has good conditions for hydrocarbon generation. There are several sets of hydrocarbon source rocks characterized by large thickness, middle-higher content of TOC and II type kerogen. The evolution has mainly been affected by burial history, and the hydrocarbon source rocks are of the mature-high mature stage. Controlled by thermal contact of Yanshanian intrusive rock and tectonic dynamometamorphism in the strongly tectonic reworking belt, the hydrocarbon source rocks of the northern study area was once reached the mature stage.