Geochemical Characteristics and Oil Source Correlation of Paleo-Reservoirs in Biluocuo Area, Qiangtang Basin

Qiangtang basin is a large Mesozoic marine sedimentary basin, in which several sets of source rocks are developed, and many paleo⁃reservoirs and hydrocarbon indications are discovered. Determining the oil source of paleo⁃reservoirs is very important for oil and gas exploration. In order to clarify the oil source of the paleo⁃reservoir, geochemical analysis of oil and source rock samples is carried out in this paper. The results show that the paleo⁃reservoirs can be divided into two types: type I paleo⁃reservoirs are in the mature-high mature stage in general with the high content of C24 tetracyclic terpane, the low tricyclic terpane abundance, C29 regular sterane with certain advantages in content, and high C29 hopane content, reflecting the contribution of terrigenous organic matter. Type II paleo⁃reservoir is in the low mature-mature stage in general, with C23 tricyclic terpane as the main peak, low content of C24 tetracyclic terpane and the domination of C27 regular sterane, indicating the precursor was mainly lower aquatic organisms. The oil-source correlation result shows that the two types of paleo⁃reservoirs come from different source rocks. Type I crude oil comes from the source rocks of Zhana Formation of Upper Triassic, and type II crude oil is mainly contributed by the source rocks of Quse Formation of Lower Jurassic. © 2022, Editorial Department of Earth Science. All right reserved.