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Quick approximate elastoplastic solutions of wellbore stability problems based on numerical simulation and statistical analysis
Gas Science and Engineering ( IF 5.285 ) Pub Date : 2018-03-01 , DOI: 10.1016/j.jngse.2018.01.005
Chang Huang , Babak Akbari , Shengli Chen

Abstract Wellbore instability has been a chronic issue for well operators over several decades in petroleum industry. Traditional linear elastic models may sometimes fail to provide a proper mud weight window for drilling engineers. Elastoplastic models can better represent the rock behavior and, therefore, more accurately evaluate the risk of wellbore instability. However, elastoplastic models have failed to gain popularity in the industry because of the model complexity and computation cost. This work proposes an approximating method in a novel manner, incorporating both the validity of the elastoplastic constitutive model and the rapidity of the linear elastic model to predict wellbore behavior. The non-associative strain hardening Drucker-Prager elastoplastic model is used. The relationship between the yielded zone area calculated by the elastoplastic model and the pseudo-yielded zone area calibrated by the linear elastic model is statistically investigated. It is found that the two can be correlated with high confidence based on a set of common input parameters, like in-situ stresses, wellbore pressure, Young's Modulus, etc. Three correlation equations are provided according to the value range of the predicting terms and an application example is addressed at the end. In conclusion, this approach will help engineers make reliable wellbore stability decisions without resorting to sophisticated elastoplastic models. The equations can be directly used in simple spreadsheet functions or real-time data processing schemes to make faster and more efficient decision.

中文翻译:

基于数值模拟和统计分析的井筒稳定性问题弹塑性快速近似解

摘要 几十年来,井筒不稳定一直是石油工业井运营商面临的一个长期问题。传统的线弹性模型有时可能无法为钻井工程师提供合适的泥浆重量窗口。弹塑性模型可以更好地代表岩石行为,因此可以更准确地评估井眼不稳定的风险。然而,弹塑性模型由于模型复杂性和计算成本而未能在行业中普及。这项工作以一种新颖的方式提出了一种近似方法,结合了弹塑性本构模型的有效性和线弹性模型的快速性来预测井眼行为。使用非关联应变硬化 Drucker-Prager 弹塑性模型。统计研究了弹塑性模型计算的屈服区面积与线弹性模型标定的伪屈服区面积之间的关系。发现基于一组常见的输入参数,如地应力、井筒压力、杨氏模量等,两者可以高置信度相关。 根据预测项的取值范围提供三个相关方程,最后给出了一个应用示例。总之,这种方法将帮助工程师做出可靠的井筒稳定性决策,而无需求助于复杂的弹塑性模型。这些方程可以直接用于简单的电子表格函数或实时数据处理方案,以做出更快、更有效的决策。
更新日期:2018-03-01
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