This workwas supportedby the AssistantSecretaryforConservationandRenewableEnergy,Geothermal

Since their introduction by Barenblatt ct al. (1960), double-porosity models have been widety used for simulating flow in fractured reservoirs. In a dual-porosity sys-tem, the matrix blocks provide most of the storage of the reservoir, whereas the frac-tures provide the global transmissivity. Initially, most work on dual-porosity models emphasized the development of analytical solutions to idealized reservoir problems. Increasingly, the dual-porosity approach is being implemented by numerical reservoir simulators. Accurate numerical simulation of a dual-porosity problem often requires a prohibitively large number of computational cells in order to resolve the transient pres-sure gradients in the matrix blocks. In this paper we discuss a new dual-porosity model that utilizes a nonlinear differential equation to approximate the fracture/matrix interactions, When implemented into a numerical simulator, it eliminates the need to discretize the matrix blocks, and thereby allows more etficient simulation of reservoir problems. When a single-phase, slightly compressible fluid flows through a macroscopically-homogeneous fractured medium, the fluid pressure Pf in the fracture