Organic geochemical characteristics of the Permian source rocks in Mahu Depression, Junggar Basin: depositional environment significance

In recent years, several oil-bearing areas have been discovered in the Mahu Depression of Junggar Basin, with great potential for oil and gas resources. However, few studies have dealt with the lacustrine basin evolution in this area, which seriously restricts exploration deployment. In this study, we analyzed the characteristics and genesis of Permian source rocks inferred from Rock-Eval pyrolysis parameters, biomarker compositions, and vitrinite reflectance data. The biomarker compounds show that the source rocks of Jiamuhe Formation (P 1 j) developed in an open reducing mixed input, mixed depositional environment, has gas generation potential, and the Tmax values and HI-Tmax diagrams are indicative of high thermal maturity and type III kerogen, respectively. The source rocks of Fengcheng Formation (P 1 f) are developed in a saline reducing inland lake basin mainly fed by terrestrial organisms. The organic content has a type II kerogen, which is in the mature stage and has a good oil generation potential. The source rocks of Lower Wu’erhe Formation (P 2 w) are developed in a freshwater oxidized fluvial environment, and the kerogen type is III, which is in the low mature stage.