Abstract: The authors summarized the process and history that natural gas was obtained by drilling in well Ba 3 in Fei 1 member at Shiyougou, east Sichuan in 1963, and then Feixianguan Formation gas reservoirs were discovered in Fuchengzhai, Bandong and Huangcaoxia structure successively, in well Du 1 at Dukouhe structure, poroustype dolomite was found and natural gas current was gained, a number of whole package oolitic shoal gas reservoirs in Feixianguan Formation at Luojiazhai, Tieshanpo and Jinzhuping were explored. Based on the exploration data, source rocks, reservoirs, cap condition of the reservoirs in northeast Sichuan are analyzed, meanwhile, it indicates that crude cracked gas is dominated in Feixianguan Formation gas and source rocks in Permian. The types of reservoir rocks mainly are oolite dolomite and dissolved porous oolite limestone. Through the formation evaluation, the favorite area of reservoir development can be predicted. By analysis of the process of gas reservoir forming, it is considered the process is classified into three phases: paleooil reservoir, large scale reservoir and paleo gas reservoir reforming. Finally, based on geologic structure, sedimentary facies distribution and trap factors, the forming mechanism and the reservoir characteristics in Feixianguan Formation oolitic shoal reservoirs in Luojiazhai structure are analyzed.

Key words: Feixianguan Formation, oolitic shoal reservoir, gas reservoir characteristics, analysis of gas reservoir forming, Sichuan Basin