New methodology to explore gas-bearing volcanic reservoir in Xujiaweizi Fault Depression of the northern Songliao Basin

Many gas-bearing volcanic reservoirs were discovered in Xujiaweizi Fault Depression of northern Songliao Basin,especially in Yingcheng ⅠFormation.The lithology of the volcanic rock is mainly dominated by the spatial overriding of multi-eruption facies and effusion facies.Early exploration shows that the widely distributed natural gas reservoirs was greatly controlled by developed paleo-craters and areal structure.Eruption facies and effusion facies around volcanic vent,relative high position of local structure and areas near fracture were thought to be prospective exploration areas.The physical properties of volcanic rock were not controlled by the burial depth.Water layer appearing in every gas bearing reservoir at different sea-level elevation,which means the gas reservoir boundary is controlled by lithology.Comprehensive analysis results indicate that the gas reservoir type belongs to litho-structural reservoir.Since the exploration work focusing on volcanic rock is very hard,little could be referred from the rarely reported effective and mature methods both at home and in abroad.Combining with the exploration process to the gas bearing volcanic reservoirs of the Yingcheng ⅠFormation in Xujiaweizi Fault Depression,northern Songliao Basin,the authors proposed a volcanic reservoir exploration method,which enriches the volcanic exploration theory and offers analytical references to the further volcanic reservoir exploration work.