深水井控STAMP/STPA安全性分析

Safety analysis of deepwater well control based on STAMP/STPA

传统安全分析方法无法解决复杂系统部件之间异常交互作用的评价问题。针对深水井控的复杂性和动态性特点,将井控系统在钻井过程中的安全性问题作为系统控制和反馈问题,基于系统理论的事故模型和过程(STAMP)模型,采用STPA系统性安全评估方法,构建井控系统在深水钻井过程中的控制关联模型和反馈回路,通过识别系统安全风险与约束、定义安全控制结构、分析不安全控制行为及关键因素等进行深水井控安全性分析。以STAMP/STPA作为分析准则,结合全动态多相流模拟软件OLGA,建立深水井控工艺流程,以井涌后没有提供控制行为以及关井和压井等控制行为发生延迟为例,对井控作业的安全性进行动力学分析。结果表明:运用STAMP/STPA方法可从控制和约束角度为深水井控的安全系统性分析提供指导,通过对溢流、关井和压井过程模拟,可量化施加安全控制与约束行为以免事故发生与升级的时间裕量;该方法作为指导准则用于深水井控复杂系统安全性分析可行且有效。

Traditional methods of safety analysis cannot solve the evaluation problem of the abnormal interactions among elements of complex systems. In view of the complex and dynamic characteristics of deeper well control, the safety analysis of deepwater well control during the drilling process is regarded as a system control and feedback problem in this study. Based on the accident model on the system theory, and the STAMP model, we use the STPA safety evaluation method to establish the control interaction model and feedback control loop of the well control system. In the model, the system safety risks and restrictions are identified. Then the control structure of the safety-related is defined, and the key factors which contribute to unsafe control behaviors are analyzed. Using the dynamic multiphase simulation software OLGA, and adopting the STAMP/STPA as the criterion, we analyze the process of well control and simulate the unsafe control behaviors during the deepwater drilling. The dynamics analysis of the well control safety is performed, where the case without control after well kill and the delay of control from shut in to well kill are taken as examples. The results show that the STAMP/STPA method is an effective solution to evaluate the safety of deep water well control from the perspective of control and feedback. The rational control can prevent accidents occurrence and escalating, which ensured the system safety in the certain time horizon, by modeling the process of well kick, shut in and well kill. The results also demonstrate that the method is available and useful for the safety analysis of deepwater well control.