Field Simulation of Naturally Fractured Reservoirs Using Effective Permeabilities Derived From Realistic Fracture Characterization

Abstract

Abstract In this paper, we describe field application of our recently published boundary element and simulation methods to account for flow in naturally fractured reservoirs. We apply our methods to modeling Carter Knox and Rangely Fields, both onshore fractured reservoirs in North America. Carter Knox is a tight-gas reservoir undergoing primary depletion, and Rangely is a mature reservoir undergoing tertiary oil recovery. Our method uses explicit and complex fracture geometries generated for the entire field area of interest. Effective permeability tensors at the grid-block scale are generated by accurately calculating coupled matrix and fracture flow. The effective permeabilities reflect the enhanced and directional flow effects created by the presence of fractures that may not be oriented orthogonally to the simulation grid. A finite-difference reservoir simulator, enhanced to account for tensor permeability input, is used to model field performance. Because the model includes all available geologic and well features (such as natural and induced fractures), ad hoc changes to original geological input during history matching are reduced. Using this improved history-match model allows for improved prediction of reservoir performance. P. 157