Pore-scale study on the permeability characteristics of fractured rock under hydraulic-chemical coupling

The permeability characteristics of fractured rock significantly influence the efficient development of subsurface energy resources. Under subsurface environmental conditions, the evolution of fractured rock permeability is affected by both fluid flow and chemical reactions. Traditional models like the Kozeny-Carman model are no longer suitable for accurately predicting the permeability under hydraulic-chemical coupling. In this study, a two-dimensional fractured rock model is constructed and combined with the lattice Boltzmann method, a pore-scale hydraulic-chemical coupling model is developed to explore the evolution characteristics of the pore structure and permeability of fractured rocks under different conditions. The results show that due to the comprehensive influence of seepage flow and chemical reactions, the distribution characteristics of pore structure in fractured rocks are different during the evolution process, including diffusion-controlled, convection-controlled, and reaction-controlled. Additionally, pore structure variations result in permeability differences among fractured rock with identical porosity. Finally, an efficient model is proposed to predict the porosity–permeability relationships of fractured rocks under hydraulic-chemical coupling. The relative error between the predicted value and the value calculated using the formula falls within the range of ± 15%.