Development of FEM Reservoir Model Equipped with Effective Permeability Tensor and Its Application to Naturally Fractured Reservoirs

摘要

The numerical simulation of naturally fractured reservoirs isrncommonly based on the continuum dual-porosity model.rnHowever, the model needs to assume that the fractures formrnvery regular patterns, different from field observations. In orderrnto overcome this problem, this study proposed a method thatrnconsiders the characteristics of the real fracture system, andrndeveloped a two-phase transient FEM model being able tornimplement effective permeability tensor. For the permeability ofrnnatural fractures assigned to the numerical grid, Darcy’s law inrnmatrix and cubic law in fracture were adopted for consideringrnthe flowing characteristics in discrete fracture network (DFN)rnapproach. The developed model was applied to paludal sandrnreservoir of MWX (multi well experiment) site to demonstraternthe validity and the applicability of the model for the naturallyrnfractured reservoirs. The estimated average permeability in thernMWX is almost identical compared to the results of the welltestrnanalysis. Then the numerical simulation with the FEM modelrnwas performed by using the transient pressure recorded from gasrnwell test on the MWX #1. From the results of BHP and pressurerndistribution within the system, it was noted that the model withrneffective permeability tensor generated almost identical resultsrnagainst DFN model in the aspects of the behavior and therndirection of fluid propagation with pressure decline, andrntherefore, the proposed model is considered to be more efficientrnin terms of the computation time as well as the required storagerncapacity. Also from the upscaling study, it was shown that evenrnwith fewer numbers of gridblocks the developed model canrneffectively describe the directional flow caused by the fracturerncharacteristics such as orientation and density of the fracture.