Characteristics and Oil Control Effect of Chang 81 Tight Reservoir in W105 Area of Nanliang Oilfield, Ordos Basin

The research on the main controlling factors of tight oil has always been the core content of unconventional oil and gas geology theory.Taking the tight oil of Chang 81 reservoir group in W105 area of Nanliang Oilfield in Ordos Basin as the research object, the characteristics of reservoir sand body thickness, lithology, reservoir space and physical properties were analyzed by using logging, mud logging, core and oil test data.The type of Chang 81 reservoir was clarified, and the control effect of reservoir properties on Chang 81 tight oil was revealed.The results show that the average thickness of Chang 81 sand body in W105 area of Nanliang oilfield is 3.2 m.The reservoir lithology is mainly composed of fine-grained lithic feldspar sandstone and feldspar lithic sandstone.The reservoir space types of Chang 81 are mainly intergranular pores and feldspar dissolved pores.The average porosity of the reservoir is 8.7%, and the average permeability is 0.28 mD, which belongs to the tight reservoir.Chang 81 reservoir type is lithologic reservoir.Summary: When the sand body thickness of Chang 81 tight oil is greater than 5 m and the shale content is less than 15%, it is a fine sandstone with good physical properties, which is conducive to the formation of tight oil enrichment and high yield.