气井带压作业管柱稳定性安全评估方法研究

Safety Evaluation Method of Gas Well Pipe String Stability in Snubbing Operations

为实现气井带压作业管柱安全性的主动控制,防止管柱失稳造成页岩气井喷事故,基于力学分析,考虑作业工况和井内环境参数等复杂因素的影响,建立了管柱轴向压曲力和管柱无支撑长度理论模型,并结合压杆稳定性理论提出了管柱安全无支撑长度理论模型,计算发现,理论计算结果与文献结果相近,验证了模型的可行性。理论模型计算结果表明:管柱下入作业比上提作业更易发生失稳,井内压力越大、井内管柱长度越短、管柱尺寸越小,越易发生失稳安全问题。最后基于安全无支撑长度理论模型和现场管柱起下作业安全准则,提出了失稳区、控制区和稳定区管柱稳定性安全评估方法。研究结果可为气井带压作业管柱稳定性安全智能预警与控制方法设计提供理论依据。

In order to realize the active control of pipe string safety in gas well snubbing operations and prevent the shale gas blowout accidents caused by pipe string instability,based on mechanical analysis and considering the influences of complex factors such as operating conditions and wellbore environmental parameters,a theoretical model of axial compression force and unsupported length of the pipe string was developed.In accordance with the axially-loaded rod stability theory,a theoretical safe unsupported length model was proposed.It is found that the theoretical solutions are in good agreement with the results of previous studies,which verifies the feasibility of the model.The calculation results of the theoretical model show that the running-in operation is more prone to instability than the running-out operation.Instability risks are higher,in cases of larger wellbore pressure,shorter pipe string length and smaller pipe string diameter.Finally,based on the theoretical model of the safe unsupported length and the safety criterion of pipe string tripping field operations,the safety evaluation method of pipe string stability for unstable zone,control zone and stable zone was proposed.The research findings provide a theoretical basis for the design of intelligent alarming and control method for the stability of gas well pipe strings during snubbing operations.