水泥环力学变形规律及其对结构完整性的影响

发布时间：2018-12-14 06:41

【摘要】：油气井、储气库注采井等生产过程中,井筒的完整性,尤其是水泥环的结构完整性对于保障生产安全占有至关重要的地位。论文在研究水泥环变形规律的基础上,建立三轴压缩条件下水泥环的理想弹塑性模型、线性硬化模型、非线性弹塑性变形模型三种力学本构方程,针对蠕变非均匀地应力条件,利用套管-水泥环-地层组合体力学模型,分析了不同变形规律的水泥环的在加载、卸载过程中对组合体力学完整性的影响;为合理评价组合体力学完整性、选择水泥环力学参数、指导水泥浆体系的设计提供了基础。研究结果表明,水泥环的理想弹塑性、线性硬化以及非线性弹塑性变形三种本构关系对水泥环界面应力有不同的影响。在相同参数条件下,在水泥环未屈服时,三种本构关系的水泥环的应力基本相同,而在水泥环屈服后,加载时非线性弹塑性变形本构关系的水泥环界面接触应力、Mises应力、周向应力和剪切应力最高,容易发生压缩、拉伸和剪切破坏;压力卸载后,理弹塑性本构关系的水泥环界面各项应力最小,容易发生界面撕裂。因此在较深的井下,应该尽量不使用理想弹塑性模型或线性硬化模型来简化计算三轴应力下的水泥环的变形规律对组合体完整性的影响;但在低地应力的井口位置,可以用理想弹塑性本构方程或线性硬化本构方程来简化计算水泥环的变形规律来判断水泥环胶结界面的完整情况。
[Abstract]:In the production process of oil and gas wells and gas storage wells, the integrity of wellbore, especially the structural integrity of cement ring, plays an important role in ensuring production safety. On the basis of studying the deformation law of cement ring, three kinds of constitutive equations of cement ring under triaxial compression are established, such as ideal elastoplastic model, linear hardening model and nonlinear elastoplastic deformation model. Based on the mechanical model of casing cement ring-stratum combination, the influence of different deformation laws on the mechanical integrity of the composite during loading and unloading is analyzed. It provides a basis for evaluating the mechanical integrity of the composite reasonably selecting the mechanical parameters of cement ring and guiding the design of cement slurry system. The results show that the three constitutive relationships of ideal elastoplasticity linear hardening and nonlinear elastoplastic deformation have different effects on the interfacial stress of cement ring. Under the same parameters, the stress of the cement ring with three constitutive relations is basically the same when the cement ring is not yielding, but the contact stress and Mises stress at the interface of the cement ring under the nonlinear elastoplastic deformation constitutive relationship after the loading of the cement ring yield. The circumferential stress and shear stress are the highest, which are prone to compression, tensile and shear failure. After unloading under pressure, the stress at the interface of the cement ring is the smallest, and the interface tear is easy to occur. Therefore, the ideal elastic-plastic model or linear hardening model should not be used as far as possible to simplify the calculation of the influence of deformation law of cement ring under triaxial stress on the integrity of the composite. However, at the wellhead of low ground stress, ideal elastoplastic constitutive equation or linear hardening constitutive equation can be used to simplify the calculation of deformation law of cement ring to judge the integrity of cement ring cementing interface.
【学位授予单位】：东北石油大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TE256

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