基于不确定性分析的钻井工程风险定量评价方法

A quantitative evaluation method of drilling risks based on uncertainty analysis theory

为建立一套适用于复杂地质环境的钻井工程风险定量评价方法,首先分析地层压力和钻井液循环当量密度的不确定性,得到地层压力和钻井液循环当量密度的概率分布;在此基础上,基于广义应力与强度干涉理论,将广义应力定义为致险因子,即钻井液循环当量密度;将广义强度定义为安全因子,即地层压力;将功能函数定义为井下复杂与事故的风险函数;最终推导建立钻井工程风险概率计算公式,运用该方法可以定量计算钻井作业中危险井段发生风险的概率值。实例分析结果表明风险评价结果与实际发生风险相吻合。

In order to establish a quantitative evaluation method of drilling risks, firstly, the uncertainty of the formation pressure and the equivalent circulation density of drilling fluids were analyzed and the probability distributions of formation pressure and equivalent circulation density of drilling fluids were obtained. Then based on the theory of generalized stress and strength interference, a quantitative evaluation method of drilling risks was established. In this method, the generalized stress is defined as the risk factor, which is the equivalent circulation density of drilling fluid. The generalized intensity is defined as the safety factor, which is the formation pressure. A risk function is also defined. The results of case studies indicate that this method can be used to predict the probability of the drilling risks, which were in good agreement with the actual drilling scenarios.