Study on the characteristics of hydrocarbon source rocks and evolution history in Zhahaquan depression

Kunbei, Wunan and other large quantity of hydrocarbon reservoir along Zhahaquan depression have been discovered, but its oil source layer and depression source rocks generation capacity is unclear. According to the study on source rocks distribution, organic matter abundance, type and maturity, it is pointed out that Zhahaquan depression source rocks distributed from E1+2 to N12 with the eastward movement and northward movement features. A content level in organic carbon and chloroform bitumen is higher in E13 and E23 source rocks, which reached good source rocks standards in accordance with the classification criteria of Qinhai oilfield. Organic carbon content in N1 and N12 source rocks is lower with lower generation capacity.Source rocks kerogen maceral are mainly sapropelinite, which is more than 90%, organic matter is type I. Based on the one-dimensional numerical simulation, E13 and E23 source rocks reached maturity, N1 and N12 source rock are in the non or low mature period. The study indicated that E13 and E23 source rock have better hydrocarbon generation capacity and can provide rich oil and gas.