Oil-source Correlation Study in the Kelasu Tectonic Belt of Kuqa Depression, Tarim Basin

The research area is the Kelasu tectonic belt, which is an east-west thrust belt located at the middle-west part of the Kuqa Depression of northern Tarim Basin. In this research, 13 Paleogene and Cretaceous oil sand samples from 6 wells were collected from the research area, and the saturated hydrocarbons were analyzed by gas chromatography and gas chromatography-mass spectrometry. There are two types of source rocks in the research area: lacustrine source rock from Triassic Huangshanjie Formation (Th) and coal-measure source rock from Jurassic Yangxia Formation (Jy). The oil in the Kelasu tectonic belt can be divided into two types. The Type 1 oil has abundant tricyclic diterpanes, high ratios of steranes/hopanes and ααα-20R C27/C29 steranes, indicating lower organisms input. Low ratio of Pr/Ph means higher reducing environment. The Type 2 oil has high ratios of tricyclic diterpanes C19/C23 and C24 tetracyclic diterpane/C26 tricyclic diterpane, low ααα-20R C27/C29 steranes ratio, indicating higher plants input. Higher ratio of Pr/Ph and gammacerane/C30 hopane means weak reducing and weak oxidizing environments. The Type 1 oil comes from Th source rock, the Type 2 oil is generated from both Th and Jy source rocks, and more from Th source rock.