In recent years, the oolitic shoal gas reservoir in the Feixianguan Formation in fonnortheastern Sichuan basin is an important exploration target. The reservoir rocks include contain oolitic limestone, micritic dolomite and residual oolitic dolomite, of them the residual oolitic dolomite is the best reservoir. The pore space consists of intergranular pore, intergranular dissolvedpore, intragranular dissolved pore, intercrystalline pore, moldic pore and fracture. The gas reservoir is a fractured and porous reservoir with low porosity and low permeability. The development of the reservoir is controlled by sedimentary facies, dolomitization, corrosion and fractures. High grade reservoir is the fringing oolitic beach undergone mixed water dolomitization and burial corrosion(Primary pores produced in the early period of fringing oolitic beach sediment were completely destroyed by compaction and cementation, and lots of secondary pores were produced by the mixed water dolomitization and burial corrosion.