Analysis of Gas Composition Difference and Its Controlling Factors of Yingcheng Formation Volcanic Gas Reservoir in Chaganhua Area, Songliao Basin

Good results have been achieved in volcanic rock exploration in Chaganhua area of Songliao Basin, but there are differences in gas reservoir composition in different zones. Through comparative analysis of the gas genesis, distribution characteristics and differences of the gas reservoirs in the exploration wells in the uplift zone and the depression zone, it is clear that the first-level basement faults and branched second-level faults are the migration channels for mantle-derived gas, while the third-level faults in gentle slope belt are the migration pathways of hydrocarbon gas. Besides, the types of migration faults determine the content of CO₂ and hydrocarbon gas in the gas reservoir. The model of gas migration and accumulation in Chaganhua area was established, which reasonably explains the gas exploration status and complex distribution problems. Finally, it provides a theoretical basis for pre-drilling prediction of CO₂ and hydrocarbon gas.