The main risk during the construction of oil wells is the possibility of uncontrolled hydrocarbon flow occurring from the well to the environment, commonly known as a blowout. After the Macondo accident, in the Gulf of Mexico, in 2010, there has been, in recent years, a significant increase in researches related to both well integrity and operational safety. A possible approach is to seek tools that can predict disastrous scenarios and support the decision making process. In this context, this work evaluates the reliability of the weakest rock in an open hole section, which is the formation immediately below the last settled casing shoe. Reliability, in this case, refers to the likelihood that the rock does not fracture during a possible kick or during drilling fluid circulation without a kick. The formulation of this problem involves addressing the inherent uncertainties, which may cause the failure of the “rock” barrier element. Modeling was performed by assigning probabilistic distributions to the parameters carrying uncertainties and by proposing two solutions. If all the uncertainties can be modeled using the normal distribution, it is possible to calculate the reliability analytically; meanwhile, if the variables are modeled using more than one type of distribution, an analytical solution may be hard to achieve and Monte Carlo simulations are preferred to obtain a numerical solution. The numerical solution does not require mean values and standard deviations of the output variables and becomes particularly useful when these characteristics are unknown. Therefore, this methodology evaluates the competence of the rock as a barrier element, enhancing operational safety and maintaining well integrity. The calculated reliability values can be used to assist in real-time drilling monitoring, from a rock integrity standpoint. The results of this methodology include the rock reliability as a function of the well depth, based on the current drilling phase. This includes the two aforementioned scenarios, with and without a kick.

油井建设过程中的主要风险是可能发生不受控制的碳氢化合物从油井流向环境的现象，通常称为井喷。在Macondo事故之后，2010年在墨西哥湾，近年来，与井眼完整性和操作安全性相关的研究显着增加。一种可能的方法是寻找可以预测灾难性情况并支持决策过程的工具。在这种情况下，这项工作评估了裸眼部分中最弱岩石的可靠性，该部分是最后沉降的套管靴正下方的地层。在这种情况下，可靠性是指岩石在可能的一脚踢或没有脚踢的钻井液循环过程中不会破裂的可能性。这个问题的表达涉及解决固有的不确定性，这可能会导致“岩石”屏障元件失效。通过将概率分布分配给带有不确定性的参数并提出两个解决方案来进行建模。如果可以使用正态分布对所有不确定性进行建模，则可以通过分析来计算可靠性；同时，如果使用多于一种类型的分布对变量进行建模，则解析解决方案可能难以实现，因此最好使用Monte Carlo仿真来获得数值解。数值解不需要输出变量的平均值和标准偏差，当这些特性未知时，它变得特别有用。因此，这种方法评估了岩石作为屏障元素的能力，从而提高了操作安全性并保持了井的完整性。从岩石完整性的角度来看，计算得出的可靠性值可用于协助实时钻井监控。该方法的结果包括基于当前钻探阶段的岩石可靠性与井深的关系。这包括上述两种情况，有无踢。