Numerical study of three-dimensional rock fracture permeability properties under coupled stress-seepage-dissolution process

Based on lattice Boltzmann method, the evolution of seepage velocity field and solute concentration field was simulated with double distribution functions, and a numerical model was proposed to study the coupling mechanism of stress-seepage-dissolution in three-dimensional rock fracture. The evolution of fracture permeability properties was discussed considering the effect of seepage velocity, normal stress, and dissolution rate. The results show that when the seepage velocity is low, the ions dissolved from the fracture wall cannot be transported in time, which results in a higher concentration and a lower dissolution rate at the outlet , the dissolved fracture is shaped as a "bell mouth". Increasing the normal stress decreases the fracture width and slows down the solute transport rate, which significantly reduces the dissolution at the fracture outlet, limiting the development of its permeability. When the wall dissolution rate is low, the fracture permeability shows a continuous and slow growth. As the dissolution rate increases, the dissolution amount at the outlet is significantly less than that at the inlet, which leads to a slow development of fracture permeability until the wall surface at the outlet occurs significant dissolution, and the fracture permeability shows a rapid growth trend. The results can provide important theoretical support for the quantitative evaluation of rock fracture permeability under acid corrosion.