射孔侵彻过程固井水泥环损伤影响因素分析

射孔是连通油层与井筒的主要手段之一,射孔起爆产生的聚能射流在侵彻过程中会破坏水泥环的完整性,影响油井安全。为了分析射孔过程水泥环的损伤程度及其影响因素,建立了水泥环损伤分析数值模型。采用ALE算法描述射孔弹药型罩,模拟高速金属射流的非线性大变形; 采用Lagrange算法描述套管-水泥环-地层,模拟动态冲击载荷作用下水泥环的力学响应; 获得了评价水泥环损伤程度的塑性应变等关键数据。通过室内物理试验,验证了模型的有效性,并在此基础上,基于正交试验方法设计数值模拟方案,定量分析了水泥环损伤的影响因素及其影响规律。研究结果表明,水泥环材料参数及射孔弹装药量是影响水泥环损伤程度的主控因素,水泥环强度影响权重最大,水泥环厚度与射孔弹装药量次之; 聚能射孔侵彻过程中,水泥环表现出明显的脆性特征,随着影响参数的变化,损伤程度非线性变化。研究结果对合理选择射孔参数,完善水泥环抗损措施具有一定参考。

Influencing Factors of Cement Sheath Damage During Perforation Penetration

Perforation is one of the main means to connect reservoir and wellbore. The shaped charge jet generated by perforation explosion will damage the integrity of cement sheath and affect the safety of oil wells. In order to analyze the damage degree of cement sheath and the influence rule of parameters during perforation penetration, a numerical model for damage analysis of cement sheath was developed. The ALE algorithm was used to describe the ammunition liner and the Lagrange algorithm was employed to describe the structure of casing-cement sheath-formation in presented model. The non-linear large deformation of shaped charge jet and the dynamic response of cement sheath were simulated by the presented model. Meanwhile, the key data such as plastic strain to evaluate the damage degree of cement sheath were obtained. The validity of the model was verified by laboratory experiments. A numerical simulation scheme was designed based on the orthogonal experimental method and the influence of parameters on the damage of cement sheath was analyzed. The results show that, the material parameters of cement sheath and explosive charge of perforating are the main controlling factors affecting the damage degree of cement sheath, and the strength of cement sheath has the greatest weight, followed by the thickness of cement sheath and the charge of perforating. During the penetration process of shaped charge perforation, the cement sheath shows obvious brittleness characteristics. With the change of influence parameters, the damage degree varies nonlinearly. The results provide a reference for choosing perforation parameters reasonably and improving the anti-damage measures of cement sheath.