Simulation of Matrix/Fracture Interaction in Low-Permeability Fractured Unconventional Reservoirs
Abstract
Unconventional reservoirs, such as shale-gas or tight oil reservoirs, are generally highly fractured (including hydraulic fractures and stimulated and nonstimulated natural fractures of various sizes) and embedded in low-permeability formations. One of the main production mechanisms in unconventional reservoirs is the flow exchange between matrix and fracture media. However, because of extremely low matrix permeability, the matrix/fracture exchange is very slow and the transient flow may last several years to tens of years, or almost the entire production life. The commonly used dual-porosity (DP) modeling approach involves a computation of pseudosteady-state matrix/fracture transfers with homogenized fluid and flow properties within the matrix medium. This kind of model clearly fails to handle the long-lasting matrix/fracture interaction in very-low-permeability reservoirs, especially for multiphase flow with phase-change problems. Moreover, a DP model is not adapted for the simulation of matrix/fracture exchange when fractures are described by a discrete-fracture network (DFN). This paper presents an embedded discrete-fracture model (EDFM) dependent on the multiple-interacting-continua (MINC) proximity function to overcome this insufficiency of the conventional DP model.