射孔水泥环损伤评价及压裂裂缝扩展规律

Damage Evaluation of Perforated Cement Sheath and Study on Fracture Propagation Law

为了进一步提高储层段水泥环在射孔作业、压裂充填完井或水力压裂作业过程中的力学完整性,满足后期增产作业对固井质量的需求。以射孔作用下的水泥环损伤响应为研究对象,在模拟地层温度和压力工况条件下分别采用大孔径和深穿透2种射孔弹开展射孔实验,分析射孔水泥环损伤与射孔弹及水泥环性能的关系。结合射孔弹结构,建立射孔动态冲击载荷作用下的水泥环伤响应数值模型,提出以累计塑性应变率和最大偏应力为关键指标,形成射孔水泥环冲击损伤量化评价技术。基于流固耦合理论和压裂裂缝扩展力学理论,建立非均值特性水泥环压裂裂缝延展数值分析模型,针对射孔水泥环初始裂纹的4种状态,开展了压裂过程中的水泥环损伤及裂缝延展规律研究。研究结论可指导优化固井设计、优化射孔方案和优化压裂完井方案,对保障井筒安全具有重要意义。

In order to further improve the mechanical integrity of cement sheath in the process of perforation,fracturing and filling completion or hydraulic fracturing,and meet the requirements of completion and stimulation operation for cement sheath integrity.Aiming at the damage of cement sheath under perforating impact,perforation shooting test is carried out,and the relationship between perforation cement sheath damage and perforator and cement sheath performance under simulated temperature and pressure conditions is analyzed.Combined with the structure of perforating charge,the numerical model of cement sheath damage under perforating impact load is established.The cumulative plastic strain rate and maximum deviator stress are taken as the key indexes to form the quantitative evaluation technology of perforating cement sheath impact damage.Based on the fluid solid coupling theory and fracture propagation mechanics theory,a numerical analysis model for fracture propagation of cement sheath with non-mean characteristics is established.The damage of cement sheath and fracture propagation law during fracturing are studied according to the four states of initial crack of perforated cement sheath.The research conclusion can provide feedback guidance for perforation parameter optimization,cementing design optimization and fracturing completion operation optimization,and improve the mechanical integrity of cement sheath in reservoir perforation section,which is of great significance to ensure wellbore safety and prolong the life of oil and gas wells.