Abstract: Chishui sag is one of the regions with relativelylow degree of exploration.On the basis of regional petroleum geology study,the strata and depositional features are analyzed,and the conditions of gas accumulation and prospection potential of shallowmid clastic strata in Chishui depression and its adjacent areas are discussed in detail from the view point of gas source rocks,reservoir beds,seal,their combination and factors of accumulation in this paper.It is concluded that although in the Xujiahe formation in lower Jurassic and upper Triassic system there is some potential of hydrocarbon generation,the Silurian Longmaxi formation and the Permian Longtan formation are the main gas source,the gas reservoirs in the second and the forth members of Xujiahe formation and lower Shaximiao formation exhibit polyphase migration and accumulation and are adjusted and modified,finally formed in Himalia stage,the gas was from continental and marine facies and generated in older and lower strata but stored up in later and upper strata,the favorable gas accumulation belts lie in the GuanduTiantangba and BaoyuanXuebaiping regions,and are also the favorable belts of a whole body including upper and lower strata,continental and marine facies together considered,and spatial exploration in Chishui and its adjacent area.

Key words: condition of gas accumulation, exploration potential, middleshallow beds, Chishui area