Characterization and numerical simulation of nonlinear flow mechanism in offshore low-permeability reservoir
Compared to onshore low-permeability reservoirs,offshore low-permeability reservoirs have larger well spacing,which results in a wider range of low-pressure gradient areas and thus more significant non-Darcy flow phenomena in matrix.For another,the fracturing scales of offshore low-permeability reservoirs are relatively smaller,and fracture stress sensitivity has a greater impact on production capacity.This paper establishes a non-Darcy flow model for matrix which considers the effect of residual boundary layers and a fracture stress sensitivity model considering proppant parameters.The models are then applied to the embedded discrete fracture model that can finely depict the morphology of fracturing fractures.The study investigates the impact of nonlinear flow on the flow field and development indicators of low-permeability fractured oil reservoirs.The results show that non-Darcy flow in matrix significantly reduces the peak annual oil production and cumulative oil production of oil wells under depletion development.The effect of dimensionless initial boundary layer thickness is more prominent than that of residual boundary layer thickness.Fracture stress sensitivity has a more significant effect on the peak annual oil production than on the cumulative oil production.The proppant sand concentration has a great impact on the cumulative oil production,while the proppant diameter has a small impact on the cumulative oil production.Nonlinear flow has a significant effect in reducing the swept area and delaying the water breakthrough time in the water flooding development of fractured wells.If nonlinear flow is not considered,the water cut rises faster after water breakthrough.The method in this paper provides an efficient tool for productivity prediction and development optimization of offshore low-permeability reservoirs.
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