ABSTRACT
A rigorous fully implicit numerical reservoir simulator has been developed to model single phase fluid flow in deformable naturally fractured or carbonate reservoirs. The present formulation represents a great improvement over existing simulators for fractured reservoirs in that many of the limiting assumptions have been removed. The interactions of rock stress, matrix pore pressure, and fracture pressure; bulk rock volumetric expansion effects; unsteady matrix-fracture flow; vug-matrix and vug-fracture flow; and the matrix and fracture anisotropic flow have been rigorously modelled. An interesting comparison in modeling fractured reservoirs is made between the present volume average approach and the deterministic approach where the matrix and fracture geometries are fixed. A parametric study reveals the new finding that the rock-stress interaction effects may modify significantly the compressibility of the fractured rock which would then affect the characteristic behavior of the pressure transients of a fractured reservoir. The stress sensitive permeability effect for the fractures is also determined to be important. It is shown through numerical examples that existing dual porosity models are inadequate to model a vuggy fractured reservoir where the solution vugs are intersected by the fracture network of the reservoir. A field example is used to demonstrate how a detailed geometrical description of the fractured blocks may be obtained by matching the simulated pressure transient behavior of the well test data.
