Abstract: Through studying the characteristics of sedimentary,petrology,reser voir physical property,and pore structure and analyzing the effect factors on reservoir physical property of Chang 2 reservoir in Yanchang formation of the Zhaike area,Zhidan oil field,the authors hold that the Chang 2 sedim entation of this area is a delta-plain sub-facies,with the plain distributary channel microfacies and the sand bodies being well developed.After reservoir was deposited,it ex perienceda strong epigenesis,compaction pressure solution,filling authig enic minerals,and the secondary enlargement of and feldspar and quartz, making the reser voir decrease in porosity and become poor in physical property.Mean while,authigenic chlorite film of the debr is surface prevented filling authigenic mineral during the diagenetic process,enable more primary inter granular pores to be preserved,and strong dissolution also improved reser voir physical property.Therefore,compared with Yanchang formation of the other areas of northern shaanxi,the physical property of Yanchang formation Chang 2 member in the research area is better,that is the key cause of highersingle well production,better stable yield.It is these factors that makes it a "small-and- rich" oil field in north Shannxi.