Biomarkers and Carbon Isotope of Monomer Hydrocarbon in Application for Oil-Source Correlation and Migration in the Moxizhuang-Yongjin Block, Junggar Basin, NW China.

Abstract

Different opinions on the oil-source correlation and migration of the Moxizhuang-Yongjin block in the Junggar Basin, NW China, have seriously affected oil and gas exploration in this area. This research is based on the results of biomarker analysis and carbon isotope of monomer hydrocarbon on crude oil and source rock samples from different blocks. Two oil families (A1, A2, and B) are classified by cluster analysis on nine typical biomarker ratios. Typically, sub-family A1 oils are distributed in the Zhuang 102 well block of the Moxizhuang block, and their gammacerane index is the highest. The abundance of C24 tetracyclic terpanes is the lowest, the C27 regular steranes are dominant, and the organic matter is mainly input by lower aquatic organisms. Sub-family A2 oils are distributed in the Zheng 1-1 well block of the Moxizhuang block. The gammacerane index of oils is lower than the former, and the abundance of C24 tetracyclic terpanes is higher. In the dual input of lower aquatic organisms and terrestrial higher plants, the input of terrestrial higher plants accounted for a larger proportion. Family B oils are distributed in the Yong 2 well block of the Yongjin block, and their gammacerane index is the lowest. They have a high abundance of C24 tetracyclic terpanes, and C29 regular steranes are dominant, reflecting the characteristics of terrigenous organic matter contribution. Based on the biomarker compound composition, at least two oil charges are indicated: Sub-family A1 oils are likely sourced from the Wuerhe formation, sub-family A2 oils may be a mixture of Wuerhe formation and Badaowan formation, and family B oils are likely sourced from the Badaowan formation. The oil families with typical genetic affinities may indicate two major petroleum systems or multiple oil systems existing in the study area. In addition, the characteristics of hydrocarbon accumulation and migration are also discussed, the oil and gas in the West Sag of Well Pen 1 and Changji Sag are filled from deep to shallow in the vertical direction and migrated from south to north in the horizontal direction, at the same time, with the help of sand bodies and faults, and they migrated to the north and northeast. This work provides a scientific basis for oil and gas exploration in the hinterland of the Junggar Basin.