海上气井环空带压油套管柱动态安全评价技术

为了有效预测海上气井环空带压油套管柱潜在失效风险及安全管理环空压力，提出1种基于井口压力、温度和液位多参数监测的海上气井环空带压油套管柱动态安全评价技术。首先，结合气井生产状态参数和完井信息，建立气井井筒压力分布计算方法；然后，根据力学知识分析气井环空带压油套管柱应力场特点，进而提出利用环空带压井油套管柱安全系数作为油套管柱失效评价依据；最终，开发海上气井环空带压安全监测系统并开展现场案例井分析。研究结果表明:监测系统能够准确获取环空带压状态参数，通过环空压力状态变化分析阐述“A”环空带压机理为泄漏点处油套管之间压力平衡的保持；结合实际井口环空压力监测数据，井筒安全系数能够实时表征油套管柱安全状态。

Technology of dynamic safety evaluation for tubing and casing strings of offshore gas well with sustained casing pressure

In order to effectively predict the potential failure risk of the tubing and casing strings in the offshore gas wells with sustained casing pressure (SCP) and safely manage the annulus pressure,a dynamic safety evaluation technology for the tubing and casing strings of offshore gas wells with SCP based on the multi parameter monitoring of wellhead pressure,temperature and liquid level was developed.Firstly,a method for calculating the wellbore pressure distribution of gas well was established combining with the production status parameters and completion information of gas well.Then,the stress field characteristics of the tubing and casing string in gas well with SCP were analyzed based on the mechanical knowledge.Furthermore,the safety factor of tubing and casing strings in gas well with SCP was proposed as the basis for the failure evaluation of tubing and casing string.Finally,a SCP monitoring system for the offshore gas wells was developed,and the field case well analysis was conducted.The results showed that the monitoring system could accurately obtain the status parameters of SCP.In addition,the mechanism of SCP in “A” annulus was the maintaining pressure balance between the tubing and casing at the leakage point,which was analyzed and illustrated through the status change of annulus pressure.Combined with the monitoring data of annulus pressure at the actual wellhead,the wellbore safety factor could characterize the safety status of tubing and casing string in real time.