Fluid Seepage Characteristics under Influence of Surface Composite Topography of Single Fracture
The fracture surfaces of natural reservoir often show the mismatched feature at a certain scale,and the resul-ting non-uniform distribution of apertures significantly influences the fluid flow behavior.Therefore,it is crucial for the accurate evaluation of oil and gas productivity to clarify the controlling effects of the composite topography of fractures on penetrating quality.Firstly,combined with the composite topography,the two effects that hinder fluid flow in rough fractures were deter-mined by analytical derivation,i.e.,surface roughness effect and aperture roughness effect.Then,on the basis of the two-di-mensional characterization of the mismatched behavior between surfaces by using the weight algorithm,the transport processes of fluid in mismatched rough fractures were simulated by lattice Boltzmann method at pore scale,and the influence characteris-tics of fluid flow were analyzed.The results indicate that,due to the influence of aperture non-uniform distribution,the permea-bility estimated by triple-effect model is overestimated,and the prediction error depends on the degree of surface mismatch.Mo-reover,the aperture non-uniform distribution hinders the effective migration of fluid to some extent,and weakens the penetrating quality of fractures indirectly,which is controlled by aperture relative roughness.
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