Analysis of Sensitivity and Influencing Factors of Tight Sandstone Reservoir:A Case Study of Chang 6 Oil Layer in Wangjiawan Southeast Area,Ordos Basin
The Chang 6 reservoir group in the southeastern Wangjiawan area of the Ordos Basin is a tight sandstone reservoir.Reservoir sensitivity evaluation is an important means to study fluid damage to reservoirs and has important guiding significance for later water injection development.Reservoir sensitivity and its influencing factors were studied based on a scanning electron microscope,mercury injection test,and sensitivity test.The results show that the study area is mainly feldspar sandstone with high content of feldspar,quartz and rock debris,and clay minerals are mainly illite,chlorite and illite-montmorillonite mixed layer.The rock is dense,the pore structure is poor,and the pore throat distribution is uneven,which is a low porosity and low permeability reservoir.The sensitivity is characterized by medium-weak velocity sensitivity,medium-weak water sensitivity,medium-strong acid sensitivity,weak-medium-weak alkali sensitivity and medium-weak-weak salt sensitivity.The type and content of clay minerals affect the main factors of reservoir sensitivity.The mixed layer of illite and montmorillonite,illite and chlorite in clay minerals have great influence on salt sensitivity,water sensitivity and acid sensitivity respectively.Therefore,in the process of water injection development,targeted reservoir protection measures should be taken for salt sensitivity,water sensitivity and acid sensitivity.
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