Quantitatively investigate the effect of fracture roughness on hydraulic and electrical transport properties evolution induced by mineral dissolution

Abstract

Monitoring the mineral dissolution process in rock fractures is very important at many subsurface systems, such as geothermal and carbon dioxide capture and storage projects. And transport properties of fractures are useful parameters to evaluate the underground reservoirs. Because the rock fracture is natural roughness, hence, understanding the role of roughness on the dissolution process is vital in geoengineering developments. However, the influence of roughness degree on transport properties evolution is rare quantitatively studied. To fill the research gap, herein, an adjusted-segment method is used to generate five artificial fracture models with various roughness, and the roughness degree is modeled by tortuosity. We applied a lattice Boltzmann method with dual multiple-relaxation-time (MRT) distribution functions to simulate the hydraulic transport property evolution in the mineral dissolution process in a wide range of Péclet (Pe) and Damköhler (Da) numbers. And the finite element method is employed to calculate the electrical conductivities of fracture models. The simulation results show that, under identical Pe and Da conditions, the transport properties evolution is sensitive to the roughness degree; and in the same fracture model, the hydraulic transport evolution cannot be quantified by an empirical formula. Finally, we proposed a model to predict the permeability from the electrical conductivity involving the roughness degree for a monitoring purpose.