Simulation of hydraulic-mechanical-chemical coupled acid fracturing of rock with lattice bonds.

The acid fracturing is a very important stimulation technique for carbonate reservoir. The hydraulic-mechanical-chemical effect is tightly coupled in this fracture process. In this paper, the discretized virtual internal bond is extended to simulate this coupling process in which the rock matrix is considered to consist of many discrete bond cells with finite number of bonds. Each bond is taken as transport channel of acid fluid, the reaction site of chemical dissolution and the mechanical linkage. When acid fluid flows through a bond, the bond will be dissolved. As result, both the bond porosity and permeability are increased, and the mechanical properties are weakened. By this method, the hydraulic, mechanical and chemical fields are coupled together on the micro bond. The acidization, the chemical-induced mechanical weakening and the fracture propagation can be well reproduced. This method transforms the complicated 3D multi-physical coupling problem into the 1D bond problem, which significantly simplifies the simulation of multi-field coupling process. It provides a feasible approach to simulate the HMC coupled acid fracturing process.