A Numerical and Experimental Procedure to Estimate Grid Based Effective Permeability Tensor for Geothermal Reservoirs

摘要

Natural fractures have strong effect on controlling fluid flow in geothermal reservoirs due to their high permeability compared to the surrounding rock matrix. The challenge in simulation of fractured reservoirs is to efficiently determine the grid based effective permeability tensor distribution. One of the powerful techniques presented to date to simulate fluid flow is the discrete fracture model. In this approach fluid flow is simulated through individual fractures, however, an enormous amount of computation time and resources are needed to solve flow equations for medium to high fracture density reservoirs. In this paper a numerical model to calculate grid based effective permeability for randomly oriented discrete fractured networks using boundary element method is presented. Laplace and Poisson equations are used for calculationof effective permeability tensor for each grid block efficiently. An innovative laboratory procedure was used to verify the numerically derived grid based effective permebaility. Glass bead models with very low matrix permeability and containing single and multiple interconnected fractures are constructed for this purpose. Displacement tests are carried out for single phase flow. Finally the grid based effective permeability tensor model is used to develop a k-tensor map for soultz geothermal reservoir. A range of pressure and production data for a given well orientation (injection and production wells) is presented.