GEOCHEMICAL CHARACTERISTICS OF CRUDE OIL IN CHANG 3 MEMBER OF TRIASSIC YANCHANG FORMATION, SOUTHWESTERN ORDOS BASIN.

The oil reservoir of the Chang 3 Member of the Triassic Yanchang Formation is the main oil-producing reservoir in the southwest of Ordos Basin. In recent years, with the deepening of exploration in this area, a major breakthrough has been made in the exploration of the Chang 3 member, Yanchang Formation, and several industrial oil flow Wells have been discovered in this area. Based on the detailed analysis and comparison of the molecular geochemical characteristics of the extracts from crude oil and oil-bearing sandstones, this paper conducts a comparative study on the source rocks of different strata of the Triassic Yanchang Formation according to the combination characteristics of biomarkers and carbon isotope characteristics. Furthermore, the source of crude oil in the Chang 3 Member is discussed. The results show that the oil of the Chang 3 Member and the source rocks of the Chang 6 and 7 Members in the southwest Ordos Basin have similar characteristics in terms of parent properties, sedimentary environment and maturity. At the same time, regional unconformity surface and fracture became the migration channel connecting the Chang 3 reservoir with the Chang 6 and Chang 7 oil sources. The crude oil of the Chang 3 Member of the Yanchang Formation is mainly derived from the source rocks of the Chang 6 and Chang 7 Members. [ABSTRACT FROM AUTHOR]