A decoupled scheme to solve the mass and momentum conservation equations of the improved Darcy-Brinkman-Forchheimer framework in matrix acidization

Matrix acidization simulation is a challenging task in the study of flows in porous media due to the changing porosity in the procedure. The improved Darcy-Brinkman-Forchheimer framework is one model to do this simulation. In this framework, the mass and momentum conservation equations are discretized to form a pressure-velocity linear system. However, the coefficient matrix of the linear system has a large condition number, and solving the linear system belongs to the saddle point problem. As a result of that, convergence is hard to achieve when solving it with iterative solvers. It is well known that the scale of the linear systems in matrix acidization simulation is large, and therefore, the usage of iterative solvers is required. Thus, a decoupled scheme is proposed in this work to decouple the pressure-velocity linear system into two independent linear systems: one is to solve for pressure, and the other one is to solve for velocity. It is emphasized that both of the linear systems are discretized from the elliptical partial differential equations, which guarantees fast convergence can be achieved by iterative solvers. A numerical experiment is carried out to demonstrate the correctness of the decoupled scheme and its higher computing efficiency. After that, the decoupled scheme is applied in investigating the factors that cannot change the optimal injected velocity and the dissolution pattern in matrix acidization.