A statistic analysis of lithology，thin section，SEM observation and mercury injection data reveals the physical properties and pore structures of the reservoirs in the study area.It suggests that the Putaohua reservoir is characterized bymedium porosity and m iddle-to-high permeability.Its pore types include normal intergranular pores，reduced intergranular pores and intragranular dissolved pores.The reservoir also features in low displace-ment pressure，low median capillary pressure，well-developed m icroscopic pore structure，and medium-to-large pore throat.Five parameters，namely the porosity，permeability，displacement pressure，mean pore throat radius and mercuryˉinjection saturation，are used to classify the reservoirs in the area into four types.TypeⅠhas large pore and wide throat;typeⅡhasmedium pore and medium throat;typeⅢhasmedium to small pore and small throat;and typeⅣhas small pore andm icro throat.They are supreme，good，fair and poor reservoirs respectively.The reservoir qualities are controlled by sedimentation，compaction and cementation，amongwhich sedimentation is predom inant.Reservoir quality of underwater distributary channel sand is the best.