Numerical Simulation Study On Fracture Fluid Flow Characteristics In Rock Rough Fracture Surface

Hydraulic fracturing has become an important technology to exploit unconventional,deep and deep oil and gas reservoirs,playing an irreplaceable role.The process of hydraulic fracturing involves solid mechanics problems such as rock deformation and fracture,and mass transfer problems such as fluid flow in fracture fractures,and these problems are coupled with each other.The artificial fractures formed during hydraulic fracturing are complex in shape,and the artificial fractures formed in brittle rocks are even reticular.The complex shape of the fracture makes the fracture surface irregular,with significant fluctuations,which have a significant impact on the flow of proppant-bearing fracturing fluid.In this paper,fracture surface data are obtained by physical fracturing experiments in the laboratory,and the roughness of fracture surface is calculated by different methods.Secondly,based on the COMSOL software platform,the mechanical model of rock deformation and fracturing fluid filtration that can consider the influence of artificial fracture roughness surface is established.Numerical simulation of multi-factor influence of fluid flow in hydraulic fractures is carried out,and the change of flow law under the influence of various factors is analyzed.The flow characteristics of fracturing fluid in smooth and rough fracture surfaces are studied without considering fluid-solid coupling or fluid-solid coupling.It is found that,without considering the fluid-solid coupling effect,in the steady-state model,the fracture inlet velocity increases with the same roughness,and the maximum pore pressure of rock matrix increases gradually.In the transient model,the increase of fracturing fluid displacement leads to the increase of net pressure and filtration rate in the fracture,while the increase of fracturing fluid viscosity leads to the increase of static pressure and pore pressure in the fracture,while the increase of rock porosity and permeability leads to the decrease of net pressure and pore pressure in the fracture.When fluid-solid coupling is considered,in smooth and rough fracture surfaces,the increase of the pore compressibility leads to the decrease of the maximum net pressure in the fracture and the increase of the permeability.