Effect simulation of horizontal well fracturing through strata based on coal seam permeability anisotropy test

The independently-developed true-triaxial permeameter was applied to test the triaxial permeabilities of coal samples, roof and floor rock samples. Based on experiment results, finite element 3D numerical simulation method was adopted to study the influences of permeability anisotropy on the horizon-crossing fracturing fracture propagation of horizontal wells at deep coal seam roof. The simulation results have indicated that: (1) The true-triaxial permeameter can realize triaxial differential stress loading, thus breaking through the bottleneck of conventional triaxial permeameter unable to load maximum and minimum primary horizontal stress respectively, and making experimental conditions be more consistent with formation conditions. (2) The true-triaxial permeability test results of high-rank anthracite and roof siltstone present significant anisotropy characteristics. Both permeabilities in the direction perpendicular to beddings are smaller than those in the direction parallel to beddings. For anthracite, significant differences also exist in the permeability in the direction parallel to beddings, while the permeability in cleat direction at vertical end is greater than that on vertical plane. (3) Compared with homogeneous model, failure pressure and operation pressure are increased during the fracturing simulation process of permeability anisotropy model, as well as the superposition degree of pore pressure; the overall fracture morphology is shorter and wider with fracture height increasing at the termination of simulation. ©, 2015, Science Press. All right reserved.