Numerical investigation of flow conductivity of propping agent in hydraulic fracture under in-situ stresses

The current research on the migration of the proppants in hydraulic fractures and the corresponding flow conductivity are mainly carried out by indoor experiments, though the entirely computer-based research is the tread, yet rare now.In this paper, based on our previous DEM results of proppants in hydraulic fractures, the digital models of the propping agent under different stresses are obtained using digital reconstruction method.Subsequently, based on the digital reconstruction models, the single phase fluid flows through proppants are simulated numerically by utilizing the lattice Boltzmann method, and the absolute permeability values for different proppants and stresses are derived accordingly.Moreover, the numerical permeability coefficients are in good agreement with the empirical Kozeny-Carman formula.The study shows that the higher stresses imply the smaller crack apertures, the tighter proppant packing and the more embedment of proppant.With the increase of stress, the specific surface area increases, and the porosity and permeability reduce accordingly.Under the same stress level, the larger proppant corresponds to the smaller porosity and specific surface area, the easier to embed, and the larger permeability reduction though generally higher than the smaller proppant size.