The randomness and fuzziness of geomechanical parameters make it difficult to directly determine the wellbore collapse and fracture pressures, and thus show significant influence on the risk assessment of drilling operations. Therefore, to effectively analyze the risk of wellbore instability in deep formation, this paper develops the evaluation models of wellbore stability for the vertical well drilled through the poroelastic rock formation subjected to borehole stresses under different time domains, including the instantaneous, modified instantaneous, short-time, long-time, and elastic ones. Meanwhile, based on the Monte Carlo method, one compares the difference between Taylor expansion and the Rosenbluth method in quantifying the uncertainty of the evaluation models. One analyzes the risk of wellbore instability under the condition that the geomechanical parameters satisfy the uniform, triangular, and normal distribution characteristics. In addition, different from the single factor sensitivity evaluation in previous uncertainty analysis, one introduces Morris and Sobol methods to conduct the comprehensive analysis of local and global sensitivity of geomechanical parameters. The main results show that the collapse pressure determined by the different cases of borehole stresses presents in descending order of short-time, long-time, and instantaneous. However, the fracture pressure shows in ascending order of long-time, instantaneous, and short-time cases. Besides, the different distribution characteristics of geomechanical parameters lead to the relationship of safe mud weight window in descending order of normal distribution, triangular, uniform distributions, and the uncertainty characteristics caused by the normal distribution of geomechanical parameters can be effectively quantified by Taylor expansion and Rosenbluth method. The strong sensitivity parameters affecting wellbore collapse and fracture are the maximum and the minimum horizontal in situ stresses, respectively. These two parameters present a strong difference in global sensitivity and local sensitivity analysis, which is manifested by the comprehensive effect of global parameters. The influence of the maximum horizontal in-situ stress on borehole collapse is weakened to a certain extent, while wellbore tensile fracturing is strengthened. On the contrary, the minimum horizontal in-situ stress is characterized by enhancing the borehole collapse whereas weakening the tensile fracturing. Besides, the influence degree increases with the increasing of parameter uncertainty.

中文翻译：

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考虑地质力学参数不确定性的多孔弹性介质井筒失稳定量风险分析及参数敏感性评价

地质力学参数的随机性和模糊性使得难以直接确定井壁塌陷和破裂压力，从而对钻井作业风险评估产生重大影响。因此，为了有效分析深部地层井壁失稳风险，本文建立了穿越多孔弹性岩层的直井在不同时域下受井眼应力作用的井壁稳定性评价模型，包括瞬时、修正瞬时、短时域等。 -时间长、时间长、有弹性。同时，基于蒙特卡罗方法，比较了泰勒展开式与Rosenbluth方法在量化评价模型不确定性方面的差异。分析了地质力学参数满足均匀分布、三角分布、正态分布特征的情况下井壁失稳的风险。此外，与以往不确定性分析中的单因素敏感性评价不同，引入Morris和Sobol方法对地质力学参数的局部和整体敏感性进行综合分析。主要结果表明，不同情况下的钻孔应力所决定的塌陷压力呈现出短时、长时、瞬时的递减趋势。然而，破裂压力按长时、瞬时和短时情况的升序显示。此外，地质力学参数的不同分布特征导致安全泥浆比重窗口的关系依次为正态分布、三角分布、均匀分布，并且通过泰勒展开式可以有效量化地质力学参数正态分布带来的不确定性特征。罗森布鲁斯方法。影响井壁塌陷和破裂的强敏感参数分别是最大和最小水平地应力。这两个参数在全局敏感性和局部敏感性分析中呈现出很强的差异，这通过全局参数的综合效应来体现。最大水平地应力对井壁塌陷的影响在一定程度上减弱，而井壁拉伸压裂的影响则增强。相反，最小水平地应力则表现为增强井眼塌陷、减弱拉力破裂。此外，影响程度随着参数不确定性的增加而增加。