Influence of Permeable Matrix on Non-Darcian Flow in Single Rough-Walled Fracture

Single rough-walled fracture and surrounding rock matrix are the basic units that compose the discrete fracture network,so it is of great significance to study the fluid flow behaviors in it.A series of numerical simulations by directly solving the Navier-Stokes equation were carried out to study the influence of surface roughness,matching degree and matrix permeability on non-Darcian flow in three-dimensional single rough-walled fracture.The results review that the Forchheimer equation can accurately characterize the nonlinear relationship between the flow rate and pressure gradient in single fracture in fracture-matrix model.The increase of surface roughness and the degree of mismatch aggravates the inhomogeneity of aperture distribution,increases the flow resistance of the fracture and facilitates the non-Darcian flow.By contrast,the permeable matrix enhances the flow through the fracture,and the flow rate through the rough single fracture can be increased by up to 14％,which inhibits the non-Darcian flow.The influence level of matrix permeability on the growth of fracture flow capacity is positively correlated with surface roughness and degree of mismatch.