Origin of heavy crude oil in the northern segment of the Zhangbei fault-bundling belt, eastern Junggar Basin, China

Abstract

ABSTRACT Junggar Basin is rich in hydrocarbon resources. After decades of exploration, numerous hydrocarbon resources have been found in Junggar Basin, among them, the reserve of heavy oil dominated above one-second of the total amount of heavy oil resources in China. In the world, heavy oil is a hot and difficult point for scholars to study, and the research on the origin of heavy oil is the basis of exploration and development. Heavy oil resource abundance in Junggar Basin, but the inherent laws and chemical molecular characteristics of crude oil are diverse in different regions. The origin and understanding of heavy oil in Pingdiquan Formation of Permian system in the eastern of Junggar Basin are not clear, which severely strain further prospecting and planning. In view of the understanding of inherent laws of heavy oil, combined with its carbon isotope and saturated hydrocarbon chromatography, this paper comprehensively analyzed the origin, source and accumulation pattern of heavy oil in Pingdiquan Formation of Permian. The results show that Pr/Ph of heavy oil is between 1.08 and 1.6 in this area. Its carbon isotope distribution ranges from −30.1‰ to −34.6‰. Sterane maturity parameter C29ββ/(αα+ββ) ranges from 0.24 to 0.41. Heavy oil in this area should be the product of source rock of Pingdiquan Formation of Permian. The maturity of crude oil in Huobei area is basically the same as the evolution of its source rocks, which should provide hydrocarbons for in-situ source rocks. Low density crude oil of mature stage exists in the Huoshaoshan area, which indicates that there are many stages of crude oil mixing in this area.