Structural factors controlling gas invasion as revealed by physical and geochemical indicators: A case study of Tazhong area, Tarim Basin

Abstract

Significant progress has been made in oil and gas exploration in the Tarim Basin, particularly in the Tazhong area. Exploration practices have shown that gas invasion influences the distribution of petroleum resources. This study uses geochemical analysis methods to investigate the distribution of physical properties, biomarkers, light hydrocarbon compositions, and carbon isotopic ratios in oil and gas reservoirs across different well blocks. The results reveal strong gas invasion in the crude oil in the TZ83 wellblock, while the ZG43 well block experiences weaker gas invasion. The study suggests that the intensity of gas invasion is influenced by the structural positions of the well blocks. The TZ83 well block, located in the high-position structural zone at the intersection of the Tazhong I fault slope fold belt and the strike-slip fault, is strongly affected by gas from underlying sources, resulting in condensate oil. In contrast, the ZG43 well block, situated on the platform zone of the Tazhong 10 fault belt, has fewer deep and large fault systems, leading to weaker gas invasion and waxy oil formation. Additionally, reservoirs with shallow structural positions may contain undiscovered condensate oil accumulations. Future exploration should focus on areas near fault zones to enhance energy reserves.