Formation Mechanism of Volcanic Gas Reservoir and Favorable Areas Predication in Xujiaweizi Fault Depression

The discovery of large volcanic gas reservoir in Xujiaweizi fault depression has promoted the exploration of volcanic gas pools in China.Based on data from drillings formation mechanism of the volcanic gas reservoirs is researched in Xujiaweizi fault depression by means of geological,geophysical and geochemical method.The results show that source rock is the first controlling factor for the reservoir,in that it is the material basis on one hand and controls distribution of gas reservoirs on the other hand.Basement faults control distribution of the volcanic centers and can provide pathway for the natural gas migration.Volcanic lithofacies and cycles influence formation processes of the reservoirs.In general,good reservoirs are well developed on top of the volcanic cycles.Distribution of regional and local caprock controls the preservation of volcanic gas reservoirs.According to all about these,it is thought that eastern of Anda sag,Xudong furrow zone,Xuxi slopes and Songzhan uplift are the most favorable exploration areas for the further exploration.