A novel thermal-hydro-mechanical-chemical coupled pore-scale model for the fracture propagation process

Abstract

Fracturing is one of the primary engineering techniques for improving the connectivity in enhanced geothermal systems (EGS), in which the entire process is a classical thermal-hydro-mechanical-chemical (THMC) process. Numerical simulation is an important way to investigate its mechanism. This paper develops a pore-scale THMC coupled model combined with the lattice Boltzmann method (LBM) and the discrete element method (DEM). Comprehensive THMC coupled phenomena in pore-scale are considered, including fracture dependent fluid conductivity, conjugate heat transfer, hydrodynamic force, thermal strain, acid dissolution, convection-diffusion of heat and solute, chemical damage, etc. The main features of the proposed model are that it can accurately calculate fluid flow and solute transport in fractures and the heat transfer in both fractures and DEM particles, and the influence of fracture wall dissolution on fracture propagation is also considered. After validations, the THMC coupled fracture propagation under different Damkohler numbers and Peclect numbers are discussed. The simulation results show that fracture geometry complexity is relatively sensitive to Peclect numbers, while the area of the fracture process zone is relatively sensitive to Damkohler numbers.