CHARACTERISTICS AND HYDROCARBON GENERATION EVOLUTION OF PINGLIANG FORMATION SOURCE ROCKS, SOUTHERN ORDOS BASIN

Combining organic geochemistry together with organic petrology, the source rocks of the Pingliang Formation of the Middle Ordovician in the southern Ordos Basin have been systematically studied in this paper. Controlled by sedimentary facies, the thickness of hydrocarbon source rocks of the Pingliang Formation was characterized by horizontal distribution of thick in the south but thin in the north. The abundance of organic matter was characterized by longitudinal distribution of high in the below but low in the upper area. The types of organic matter were identified by type index of carbon isotope and the result reflected that there was mainly sapropelic kerogen. The marine vitrinite reflectance showed that maturity was higher in the east than in the west and it was mainly during the late-mature and the high-mature stage. The hydrocarbon source rocks of the Pingliang Formation worked as effective source rocks. Using the PetroMod software, combined with the hydrocarbon generation simulation experiments, it had been concluded that, source rocks of the Pingliang Formation began to generate oil in the Late Triassic, reached oil generation peak in the Middle Jurassic and generated gas in large scale in the Early Cretaceous. The muddy hydrocarbon source rocks of the Pingliang Formation have some natural gas potential in the southern Ordos Basin.