考虑尖端塑性的垂直裂缝延伸计算

基于断裂力学、弹塑性力学,对水力压裂裂缝延伸过程中的尖端塑性区进行了研究,给出了裂缝尖端塑性区的定量表达式,推导了缝尖塑性区影响下的缝高扩展方程,建立了考虑缝尖塑性屈服的裂缝三维延伸数学模型,模拟分析了缝尖塑性屈服对水力裂缝扩展的影响.研究表明,在缝尖塑性屈服影响下,缝长延伸略有增加,缝高延伸得到比较明显的遏制;缝尖塑性屈服导致裂缝扩展所需作业压力增加,作业压力增加的同时会导致缝宽方向扩展的增加,越靠近裂缝端部,缝尖塑性屈服对作业压力及缝宽扩展的影响越明显.

Extension calculation of vertical fracture considering fracture tip plasticity

Based on the fracture mechanics and elastic - plastic mechanics, the plastic area in vicinity of the fracture tip in hydraulic fracture extension is studied. The dimension of the plastic area around the fracture tip is quantitatively presented, the fracture height equation considering the fracture tip plasticity is derived, and 3D extension model is established with respect to the plastic yielding. Then the effect of the plastic yielding on the hydraulic facture extension is simulated and analyzed. The study results demonstrate that, extension of fracture length increases a little, and the vertical extension of fractures is restrained apparently under the influence of fracture tip plasticity. Moreover, the fracture tip plasticity results in the increase of operation pressure, at the same time the increase of operation pressure causes the increase of fracture width. The more adjacent to the fracture tip, the more sensitive for the influence of fracture tip plasticity on the operation pressure and fracture width is observed.