摘要
///The Chang 81 reservoir is one of the oil stratigraphic horizons with great exploration potentiality in jiyuan region of the Ordos basin. This reservoir is investigated by analysis of lithology,thin sections,SEM and core properties. It is showed that the types of pore are mainly intergranular pores with minor secondary solution pores, and the reservoir is characterized by low porosity and permeability with average porosity of 7.81%, average permeability of 0.26×10-3 μm2. Sedimentary condition is the basis for the formation of original mineral compositions and rock texture, which plays some control action on reservoir physical property and creates the differences among original reservoir physical property of distributary channel, underwater distributary channel,mouth bar and distal bar. Diagenesis was the key factor affecting reservoir physical property.