Reservoir Characteristics and Control Factor of Feixianguan Formation in Northern Sichuan

Research on oolitic beach reservoir of Feixianguan Formation in northern Sichuan,with a combination of macro and micro methods,shows that the main reservoir rocks are oolitic dolomite and oolitic limestone,reservoir space is dominated by secondary pores and the reservoir property is relatively poor appearing as fracture-pore type and pore-fracture type with low porosity and low permeability.Reservoir of Feixianguan Formation in the study area was formed by eustatic sea level fall.Development and evolution of the reservoir were controlled by deposition and diagenesis.The generation of ancient highland of Permian Changxing reef and Longmenshan island chain provided Feixianguan Formation with high energy sedimentary condition.Relative sea level fall promoted the formation of high-energy beach,and the high energy oolitic beach on platform margin is the advantageous part for reservoir development.On the other hand,secondary pores,which markedly promoted the reservoir properties,were produced by mixing zone dolomitization and burial dissolution.