坚硬顶板定向射孔群同步压裂裂缝扩展规律研究OA

Aiming at the technical challenges of complex and variable formation lithology,significant differences in mechanical properties and in-situ stress conditions,the hydraulic fracturing directional roof cutting and pressure relief technology faces core is-sues of complex propagation morphology and unclear extension laws of hydraulic fractures in applying in hard rock formations.To address these problems,we conducted laboratory true triaxial fracturing seepage physical tests using self-designed opposite double-pipe cast concrete fracturing specimens,and combined with the extended finite element method(XFEM)on the ABAQUS platform for numerical simulation.The fracture propagation laws of simultaneous fracturing under different fracturing fluid types and direc-tional perforation spacing conditions were systematically investigated,and the wellbore injection pressure curves and acoustic emis-sion dynamic response characteristics were analyzed.The test results show that:clean water fracturing forms a single fracture with limited propagation scale,while guar gum fracturing can induce multiple complex fractures with significantly larger propagation scale,confirming that guar gum fracturing has better fracture propagation effect.Compared with clean water fracturing,the average wellbore initiation pressure of guar gum fracturing increases by 17.09%,the initiation time extends by 83.54%,and the acoustic emission energy increases by 28.33%.Within a certain range,with the increase of opposite perforation spacing,the specimen surface fracture development diagram and acoustic emission three-dimensional positioning results indicate that the fractures formed by sim-ultaneous fracturing exhibit the characteristic of coordinated transverse and longitudinal propagation along the perforations inside the specimen.Secondary fractures develop during the propagation of the main fracture,showing various propagation modes such as ter-mination,intersection,and deflection,and the overall propagation morphology is asymmetric.The numerical simulation results re-veal that during the simultaneous injection fracturing process,the adjacent areas of the two propagating fractures undergo in-situ stress superposition effect.The superimposed stress significantly promotes the connection of fractures between perforations,and the fracture propagation presents the characteristic of extending first to the middle area and then expanding to both sides.The fracture width exhibits a phased evolution law of"slow growth-constant rate rise-stabilization"during the propagation process.