中文摘要：

采用螺旋射孔完井时,准确模拟不同孔眼周围裂缝的起裂形态能够有效指导射孔参数的优化。基于渗流-应力耦合方法建立螺旋射孔井有限元数值模型,引入损伤变量描述岩体破坏后的弹性参数、强度和渗透率随损伤的变化规律,进一步追踪模拟岩体损伤裂隙的演变过程,借此预测近井筒周围的水力裂缝起裂和扩展形态。模拟结果表明：采用耦合损伤变量的有限元模型能够模拟出沿井筒面和射孔方向扩展的两种水力裂缝的起裂及其随液压加载的扩展趋势;针对不同井筒方向条件可模拟出不同孔眼处水力裂缝的起裂差异,以此评估孔眼间水力连接性,并预测近井筒裂缝形态。室内物理模拟实验与数值模拟结果一致,表明建立的有限元数值模型可用于分析近井筒裂缝起裂的复杂性问题,对现场射孔压裂优化设计具有指导意义。

英文摘要：

The accurate simulation of the fracture initiation around perforation channels can help guide the optimization of perforation design when spiral perforation is used. A finite element model（FEM）has been developed based on the flow-stress coupling theory to simulate the fracture initiation around perforation channels. A damage variable was employed in the model to describe the changes in stiffness, strength and permeability of the rock material, in order to track the initiation and propagation of the hydraulic fractures from the perforation channels and the wellbore. The simulation result shows that two patterns of the hydraulic fractures can be observed to occur successively with the increasing bottom-hole pressure（BHP）with the damage-coupled FEM model（D-FEM）, which are the fractures propagating along the borehole wall and those propagating along the perforation axis. In addition, the initial hydraulic fractures of perforation channels for various wellbore orientations have also been investigated based on the D-FEM. By analyzing the hydraulic communication possibility and propagation trends of different initial fractures, the pattern of near-wellbore hydraulic fractures can be predicted. A set of physical simulation experiments has been performed, proving the validity of the D-FEM model. This model can be used to analyze the hydraulic fracture complexity in the near-wellbore region and provide guidance to field operations.