A coupled seepage and dissolution model of rough rock fractures considering surface reaction based on lattice Boltzmann method

To study the seepage and dissolution coupling mechanisms of rough rock fractures, the pricewise linear method is adopted to generate the fracture surface and the fractal dimension is utilized to characterize the roughness. A lattice Boltzmann model, applying the double distribution function to respectively simulate the evolutions of velocity field and concentration field and assuming that the dissolution at the fracture surface satisfies the first-order dynamic reaction model, is proposed to simulate the coupling mechanism considering the effect of surface reaction. The validity of the proposed model is verified by two classical examples, and the effects of the fractal dimension, Pe number and Da number on the seepage and dissolution coupling mechanism of rough fractures are discussed. The results show that the larger the fractal dimension is, the slower the solute transport is, which results in a slower dissolution rate at the fracture surface. The dissolution occurs preferentially at the raised position of fractures, which makes the surface smooth gradually. When the Pe number is larger, the seepage velocity is relatively higher, which promotes the solute transport and the dissolution reaction, causes the surface geometry flattening and increases the permeability. The larger the Da number is, the faster the dissolution rate at the entrance is, which leads to more undissolved parts accumulated at the end of the fracture when the porosity is the same and affects the permeability of the fracture. © 2019, Science Press. All right reserved.