Genetic types and source correlation of natural gases in volcanic reservoir of the Xujiaweizi Fault-Depression,Songliao Basin

The natural gas of volcanic reservoir in the Xujiaweizi Fault-Depression, Songliao Basin, was mainly stored in Members 1 and 3, Yingcheng Formation in age of Early Cretaceous. Three nearly N-S fractures and two W-E uplifts divided the depression into five blocks, and characters of natural gas had some differences in each block. Bounded by the Shengping Uplift,the Member 3, Yingcheng Formation developed to the north of the uplift, while the member 1 of the formation occurred to the south of the uplift. The total thickness of the volcanic formation of the two members was 50 to 1500 meters, with an average thickness being 600 meters. Natural gas reserve mainly(about 79.5%) came from the volcanic formation of Yingcheng Formation. The charateristics, genetic types, source and distribution of natural gas were studied in the paper. Most of natural gas in the volcanic reservoir was hydrocarbon gas, with a genetic type being coal-type gas. The hydrocarbon gas was controlled by the source rocks, while the carbon dioxid