Study on the testing productivity prediction method in ultra-low permeability sandstone reservoir

The layers of slump turbidite fans in HQ area are influenced by various period sedimentation, diagenesis and tectonic, which result in complex pore structure including high porosity low permeability, medium porosity low permeability and low porosity low permeability formation, and ultra-low permeability flow unit. There are lots of factors affecting reservoir seepage and production capacity. The testing oil capacity was comprehensively estimated from the aspects of reasonable productivity parameters, quality indexes, flow unit indexes, storage parameters, effective thickness of layers, permeability, energy thickness of single permeable sand layer, oil saturation and shale content based on the relationship of porosity and permeability in ultra-low permeability reservoir quality and seepage structure. The reservoir quality, seepage and capacity date were weighted and selected according to the grey theory of oil and gas test analysis method and evaluation criteria for oil production prediction, and it also considers the accuracy and resolution of productivity evaluation parameters and classification parameter. There are 44 well among 51 oil-testing intervals in HQ area carried out production prediction and 38 well with 45 evaluation and prediction results coincide with the actual oil testing production results. The prediction coincidence rate reached up to 88.2%. This method effectively overcomes the mistakes resulting from seepage mechanism opposing Darcy capacity equation and local parameters not fitting with complex seepage characteristics. Meanwhile, it promotes the quantitative evaluation ability furthest for ultra-low permeability reservoir productivity prediction, providing effective information and analysis method for extra-low and ultra-low reservoirs production prediction.