Identification of multi-source hydrocarbon genesis: a case study of Baijiahai Uplift, Junggar Basin, China

There are multiple hydrocarbon-generating sags on the peripheral plane of Baijiahai Uplift, and there are multiple layers of source rocks in the vertical direction. How to identify which sags and source rocks are the sources of oil and gas in Baijiahai Uplift is the focus of oil and gas exploration. In this paper, based on the geochemical characteristics of oil and gas, the genesis of multi-source oil and gas is identified and summarizes the law of oil and gas enrichment. The results show that the carbon isotope of crude oil in this area is -26.73‰ to -29.51‰, Pr/nC17 and Ph/nC18 are low, sterane and light hydrocarbon parameters indicating that crude oil is a mixture of Permian and Jurassic source rocks. Using the formula: (δ13Coil) = (δ13Coil)C46 X + (δ13Coil)C1 (1-X). It is concluded that the mixed source oil and gas mainly come from Jurassic source rocks, and there is a small amount of mixture of Permian source rocks. The dry coefficient of natural gas in Baijiahai Uplift is between 0.92 and 0.98, most of which are dry gas. The average carbon isotope of ethane is about -26‰, which is similar to natural gas in Kelameili gasfield, and both are derived from Carboniferous source rocks in Dongdaohaizi Sag. The distribution of faults has a certain control effect on the migration and accumulation of oil and gas. Oil and gas are mainly distributed in Dongdaohaizi fault zone and Baijiahai fault zone. The next exploration direction should be close to the faulted structural belt of the hydrocarbon-generating sag.