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Parametric Study of Mechanical Stresses within Cement Sheath in Geothermal Wells
Geothermics ( IF 3.9 ) Pub Date : 2021-02-01 , DOI: 10.1016/j.geothermics.2020.102000
Yuxing Wu , Harshkumar Patel , Saeed Salehi

Abstract A cement sheath, placed between the casing and the formation, is an important barrier that establishes a hydraulic seal and provides zonal isolation, preventing fluid communication in the wellbore. In geothermal wells, stress induced by high bottom-hole temperature is one of the major factors triggering failure in the cement sheath. However, the influence of heat flow direction and differential temperature, relative to other design and operating factors, is not well understood. The objective of this paper is to investigate these two important factors. In this study, an analytically verified 2D numerical model was used to perform a parametric study of mechanical stress within a cement sheath. Loading conditions applied to the model included maximum and minimum horizontal formation stresses, wellbore pressures, and temperature differences. Sensitivity analysis was conducted to understand the effect of cement properties, temperature difference between the casing and the formation, and casing pressure on stresses in the cement sheath. Sensitivity response curves demonstrated the relative influence of investigated parameters on radial and hoop stresses. Results showed that heat transfer from the formation to the casing (Ti Tf). When heat flows away from the wellbore, hoop stress in cement is mainly dependent on temperature difference, while radial stress is primarily dependent on temperature difference as well as wellbore pressure. When heat flows toward the wellbore, radial stress in cement is primarily a function of temperature difference and wellbore pressure. Hoop stress, on the other hand, is mainly dependent on temperature difference and the cement’s thermal expansion coefficient.

中文翻译:

地热井水泥护套内机械应力参数化研究

摘要 位于套管和地层之间的水泥环是一种重要的屏障,可建立水力密封并提供区域隔离,防止井筒中的流体连通。在地热井中,高井底温度引起的应力是引发水泥环破坏的主要因素之一。然而,相对于其他设计和操作因素,热流方向和温差的影响尚不清楚。本文的目的是研究这两个重要因素。在本研究中,使用经过分析验证的二维数值模型对水泥环内的机械应力进行参数研究。应用于模型的载荷条件包括最大和最小水平地层应力、井筒压力和温差。进行敏感性分析以了解水泥特性、套管与地层之间的温差以及套管压力对水泥环应力的影响。灵敏度响应曲线证明了研究参数对径向和环向应力的相对影响。结果表明,热量从地层传递到套管 (Ti Tf)。当热量从井筒流出时,水泥中的环向应力主要取决于温差,而径向应力主要取决于温差和井筒压力。当热量流向井筒时,水泥中的径向应力主要是温差和井筒压力的函数。另一方面,箍压力,
更新日期:2021-02-01
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