【作者】 谭英杰；

【导师】 唐立强；

【作者基本信息】 哈尔滨工程大学 ， 固体力学， 2005， 博士

【摘要】 岩石是构成地球最基本的材料,研究地球上的诸多现象和过程,都离不开对岩石物理性质的理解和认识。弹性波在岩石中传播特性的研究,为油气勘探提供了有力工具,提供了关于地球岩石圈应力状态的新认识,将成为解释地震和滑坡等自然灾害机理的理论基础,并形成了岩石断裂力学新领域;对泥岩变形进行宏细观力学机理的研究,对石油工业具有重要作用,它影响到钻井、采油等石油勘探开发的许多方面。 油田现场调研表明,油水井套管损坏和钻井工程中的井壁坍塌多发于泥岩层。研究泥岩的物理、化学和力学性质,探讨和研究泥岩吸水、水化宏观与微观过程及此过程中地层水化应力、围岩孔隙压力与岩石力学性能的变化规律及影响因素,研究泥页岩水化机理、膨胀机理。从力学的角度上就是研究力学变形机理和建立泥岩材料的本构关系。 应用本构关系对泥岩所特有的力学性质有全面的理解并对工程问题加以解决,才能更深入地研究地层界面处油水井套管损坏的机理,进而为套管设计、制造、安装和套管损坏防治以及提高井壁稳定性提供理论依据。本构方程的建立将为研究套管的破坏和井壁失稳机理奠定基础,是一个具有理论意义和应用前景的课题。 通过分析和调研,全面地总结油水井套管损坏和井壁失稳机理,指出岩土力学中本构方程理论的重要性,力图用断裂力学和有限变形弹塑性理论方法,揭示泥岩变形的力学机理,并进行了以下工作: 1.深入地研究了泥岩吸水和水化的物理变化过程,进行泥岩吸水和水化的实验,指出体积膨胀非线性变化是泥岩吸水过程物理变化的重要特征,建立了反映这一变化影响的非线性蠕变材料的本构方程。 2.将本构关系与界面断裂力学的理论相结合,应用于泥岩层界面处油水井套管损坏的研究中,建立了地层隆起套管剪切损坏模型的界面裂纹力学模型,即高压注水引起的油藏隆起引起套管剪切损坏的力学模型。通过计算,分析地层倾角对套管剪切损坏的影响,阐明泥岩层界面处油水井套管损坏的力学机理。 3.鉴于泥岩的体积膨胀效应较大,采用有限变形弹塑性理论对其变形机理进行分析是十分必要的。采用有限变形弹塑性理论,建立了压力敏感性材料本构方程。更多还原

【Abstract】 As the basic materials of the earth, rock is studied to understand many phenomenon and processes on the earth. Research on the propagation characteristics of the elastic wave in the rock is beneficial to oil gas exploration and gives further insight into the stress state of the earth’s lithosphere, which forms the theoretical basis on the natural disaster, such as earthquake, landslide. With its help, a new field in the rock fracture mechanics would occur. It is significant for the petroleum industry to investigate on the macroscopic and mesomechanic mechanism of the mudrock deformation, which influences some aspects of petroleum exploration, such as well drilling and oil extraction.The survey of oilfield on site indicates that on the mudrock layer it happens to the oily water well that casing fails and during well drilling well face collapses. In present paper, the physical, chemical and mechanical properties of mudrock are studied, then the macro and microcosmic process of mudrock under water-injection and hydration is analyzed, during which the variation law and influencing factors on hydration stress in the stratum, on the stress in the wall rock pore and mechanical properties of rocks are given. Also the hydration and dilation mechanism of mud shale is investigated. From the point of view of mechanics, the mechanical deformation mechanism and constitutive relation for mudrock material are established.Based on the constitutive relation, the peculiarly mechanical properties of mudrock are understood fully and engineering problems may be solved. Then the mechanism on the casing failure in the oily water well on the stratum interface could be examined further, which provides theoretical basis for the design, manufacture, and assembling of casing, prevention from casing failure and enhancing the stability of well face. Establishment of constitutive equations lays a solid foundation for the research on the casing failure and instability mechanism of well face, which is of great theoretical significance and wide application.After analysis and survey, the mechanism on the casing failure of oily water well and instability of well face is summed up fully. The significance of constitutive relations in geotechnics is given. Fracture mechanics and finite elasto-plastic deformation theory are introduced to reveal the mechanical mechanism of mudrock deformation. The main work is as follows:Firstly, the mechanical property of mudrock under water-injection and hydration is studied. The experiments of water-injection and hydrochemistry ofmudrock were made. It is an important character that nonlinear bulk strain changes under water-injection for mudrock. The nonlinear creeping constitutive equation of mudrock which influences bulk expanding is established.Secondly, with the combination of constitutive relation and interface fracture mechanics, the interface fracture mechanics model is established which is applicable to analysis of strata uplift and casing shearing failure, i.e. high pressure water-injection causes oil pool uplift and casing shearing failure. Upon calculation, the influence of stratum degree of inclination on casing shearing failure is given, and the mechanism on the casing failure in the oily water well on the mudrock interface could be elucidated.Thirdly, seeing that bulking dilatation effect is evident, it is essential that finite elasto-plastic deformation theory be introduced to study the deformation mechanism. Based on the finite elasto-plastic deformation theory, the constitutive equation for pressure-sensitive material is established.Fourthly, with the constitutive equation for pressure-sensitive material, the finite elasto-plastic deformation of pressured spherical cavity (body cell model) is analyzed. Under the assumption of self-similarity, the governing equations for the deformation of pressured spherical cavity are simplified and the differential equations are established with the effective stress as independent variable. The stress and displacement distribution is given, and the impact of material parameter on the bulking dilatation effect is discussed. All these work lays foundation for establishment of the macro constitutive potential and macro failure criterion based on the analysis of body cell.Fifthly, according to the physical circumstances of the oil field on site, with the combination of theory and practical experience, the measures to prevent and treat casing failure in oily water well and instability accident of well face are proposed. The results give a useful theoretical reference for protection and treatment of casing failure in oily water well, design and appraisal of fracture toughness and investigation on the instability mechanism of well face.更多还原