| In order to further study the propagation mechanism and law of hydraulic fractures in shale reservoirs,it is urgent to combine fracture mechanics and damage mechanics theory to simulate hydraulic fracturing which is more suitable to the actual situation.The stress-seepage-damage coupled two-dimensional hydraulic fracturing process of shale was numerically simulated by the secondary development of ABAQUS general finite element analysis software.Based on the extended finite element method,the initiation and propagation characteristics of a single hydraulic fracture in an intact rock mass and its influencing factors are understood in more detail;The comprehensive criterion for the complex mode of fracture intersecting is summarized,and based on the cohesive element method,the propagation modes and failure modes of hydraulic cracks when they meet natural cracks under different working conditions are analyzed,and 10 propagation modes are summarized;The control law of hydraulic fracture height in stratified strata is analyzed.According to the failure modes and influencing factors obtained from the numerical simulation,a new mathematical model of hydraulic fracture propagation that can predict the evolution of three-dimensional geometry of fractures is proposed and its accuracy is verified.Finally,a quantitative description of hydraulic fracture propagation law is realized.A systematic understanding of the three-dimensional dynamic growth law of hydraulic fractures is realized by using the method of two-dimensional local simulation,and a new mathematical model is proposed,which can provide important guiding significance for the design of hydraulic fracturing.The paper has 78 figures,17 tables and 78 references. |
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