The Reservoir Evaluation Of The Chang 6 Member Of The Yanchang Formation In Wangwazi Area Of Wuqi Oil Field

Wangwazi area of Wuqi oil field is located in the west of Wuqi County, shaanxi province.It’s tectonic location is the western edge of the Yishan slope, Ordos Basin. The Chang-6 member of the Yanchang formation is the main bed producing oil.According to characters of lithology, electricity and oiliness,the Chang-2 member of the Yanchang formation is subdivided into 4 types: Chang-61, Chang-62, Chang-63, Chang-64, and established the unified stratigraphic framework on the basis of contrasting the stratum.The structure of Chang-6 member of the Yanchang formation is a gently west-dipped monocline, and developing small nose-like structures.Based on the analysis of sedimentary background, the distribution pattern of the sandstone in plane, the type of rock and the logging curve in this area, the analysis of the facies shows that the Chang-6 member of the Yanchang formation of Wangwazi is a delta front subfacies and it’s further divided into 4 kinds of sedimentary micro facies: underwater distributary channel, underwater interdistributary estuary, mouth bar and frontal sheet sand. And further analysises the type of sedimentary microfacies and the sand distribution pattern of each sub-bed in Chang-61, Chang-62, Chang-63 and Chang-64 member of Yanchang formation. Chang 61 is the main reservoir, so Chang 61 reservoir should take detailed analysis and evaluation.Based on all the research of core observation, indoor microscopic identification and sample tests of rock slice show that the reservoir sandstone of Chang-61 member, the Yanchang formation in Wangwazi, is mainly feldspar sandstone and lithic feldspar sandstone, intergranular porosity is the main pore types, the reservoir sandstone has reached the late stage of middle diagenesis A period and the early stage of middle diagenesis B period in the study area.Chang-61 member of the Yanchang formtion is the reservoir with poor physical property and especially low pore and super-low permeability. It has a strong anisotropism. Comprehensive analysis of these study show that type Ⅳa and type Ⅳb are the main reservoir, according to the reservoir classification standard.