Crude Oil Geochemical Characteristics and Source Analysis of the Northern Structural Belt, Kuqa Depression

Although the Northern Structural Belt is an important successor area for oil and gas exploration in the Kuqa Depression, only sporadic oil reservoirs have been discovered. Previous studies have mainly focused on the structural deformation, reservoir characteristics, and the overall oil and gas reservoir formation system of the Kuqa Depression. The oil and gas sources and characteristics of potential hydrocarbon source rocks in the Northern Structural belt have received relatively little research attention. The insufficient understanding of the origin and source of crude oil sources and hydrocarbon generation potential of the source rocks in this region severely hinders further exploration and development. In this study, we meticulously analyzed the geochemical characteristics of both crude oil and the potential source rocks in the Northern Structural Belt. The results suggest that the source of the crude oil parent material in the Northern Structural Belt was predominantly derived from aquatic organisms of low to moderate productivity and was deposited under a reducing environment. The average total organic carbon (TOC) content of the Huangshanjie Formation source rocks is 0.88%, with the organic matter being mainly types II1 and II2 (highly mature). The average TOC of the Chakmak Formation source rocks is 0.82%, and the organic matter type is II2 (mature). Oil-source correlation and inclusion temperature measurements revealed that the crude oil and oil seepages in the study area are mainly derived from the source rocks of the Huangshanjie Formation, and the main filling period of the crude oil is 2–5 Ma.