Influence of the Emeishan basalt eruption on hydrocarbon generation and expulsion characteristics of Sinian (Ediacaran) algal dolomite in Sichuan Basin

Abstract

Deep marine carbonate oil and gas resources in the Sichuan Basin are currently key exploration areas. As an important tectonic thermal event, the Emeishan mantle plume has an important influence on the source rocks under the Middle-Lower Permian in the Sichuan Basin. Therefore, the better understanding of the effect of Emeishan basalt eruption on source rock is vital for the exploration of marine oil and gas resources. On the basis of the thermal history study of the Sichuan Basin, this study restored the thermal maturity of the algal dolomite of the Sinian (Ediacaran) Dengying Formation in the Sichuan Basin in normal evolution. Using the hydrocarbon generation potential variation method, the hydrocarbon generation and expulsion characteristics of normally evolved algal dolomite and algal dolomite affected by basalt eruption were calculated. Through comparison, the influence of the Emeishan mantle plume on the algal dolomite of the Sinian Dengying Formation is analyzed. The research indicates that the thermal effect of the Emeishan mantle plume promotes the maturation of algal dolomite, which leads to the shortening of the oil generation period and the early arrival of the gas generation peak. The main hydrocarbon expulsion period of the normally evolved algal dolomite should be from the end of the Triassic to the end of the Jurassic, while the main hydrocarbon expulsion period of the algal dolomite affected by basalt eruption was advanced to the end of Silurian to the end of Triassic. In the current period, due to the high maturity of algal dolomite, the Emeishan mantle plume has little impact on the total resources.