Genetic types of shallow gas in the south of Songliao basin and its favorable target areas

The shallow natural gas in the south of Songliao basin mainly occurs in the late Cretaceous strata.Based on the analysis and study of the measured gas composition and isotopic geochemical data in the southern part of Songliao basin,the genetic types of natural gas are classified,and the distribution,genetic types and main controlling factors of shallow gas accumulation in the southern part of Songliao basin are studied.The results show that there are three sets of source rocks in the south of Songliao basin,which provide gas sources for shallow gas accumulation of different genetic types;traps provide favorable places for natural gas accumulation,and there are four types of traps;mudstone of Qingshankou formation and Nenjiang formation provide good caprock conditions;multiple tectonic movements and fault reactivation provide shallow gas migration channels and barriers.On the basis mentioned above,four favorable target areas of shallow gas are selected,which is of guiding significance for the exploration of shallow gas in the south of Songliao basin.