Modeling of Matrix-Fracture Interaction for Conventional Fractured Gas Reservoirs.

摘要

Modeling of matrix-fracture transfer function is important in the simulation of fluid flow in fractured porous media using a dual-porosity concept. This transfer function is directly related to the shape factor. One of the main focuses of this study is to find the shape factor for the single-phase flow of compressible fluids in fractured media using the solution of nonlinear gas diffusivity equation. The developed shape factor can be used as an input for modeling flow of compressible fluids in dual-porosity systems. For a compressible fluid, the consequence of a pressure boundary condition on the shape factor has not been investigated in the previous studies. Another major purpose of this study is, therefore, to investigate the effect of the fracture pressure on the shape factor for single-phase flow of a compressible fluid.;Most of the developed models for fractured reservoirs assume ideal matrix block size distribution. This assumption may not be valid in reality for naturally fractured reservoirs and possibly lead to errors in prediction of production from the naturally fractured reservoirs especially during early time production from the matrix blocks. The effect of different matrix block size distributions on the single-phase matrix-fracture fluid transfer is studied using a semi-analytical approach. The proposed model is able to simulate fluid exchange between matrix and fracture for continuous or discrete block size distributions. In the last part of this study we present semi-analytical solutions for release of a single-phase liquid or gas from cylindrical (two dimensional flow) and spherical (three dimensional flow) matrix blocks with various block size distributions and different fracture boundary conditions. This solution can be simplified to model flow of slightly compressible fluids like water or oil in dual-porosity media.;The approximate semi-analytical model for the matrix fracture transfer function presented in this study for different cases is verified using single-porosity, fine-grid, numerical simulations. This model can recover the shape factor of slightly compressible fluids reported in the literature. In the proposed semi-analytical model for all cases the pressure variability of viscosity and isothermal compressibility is considered by solving the nonlinear partial differential equation of compressible fluid flow in the fractured media.