【作者】 艾池；

【导师】 翟云芳；

【作者基本信息】 大庆石油学院 ， 油气田开发工程， 2003， 博士

【摘要】 套管井的损坏是一个复杂过程，从钻井到开发，以及石油开采过程中的全部工艺措施都对套损产生影响；套管损坏涉及到了岩石力学、渗流学、管柱力学等学科，以及各学科间的渗透；这些都决定了套管损坏因素和机理的多样性和复杂性。近年来，国内外学者对套管井损坏进行的研究，在套损机理上取得了一定的认识，但目前还没有有效的方法来预防和减缓套管井的损坏，在套管受力计算上还没有提出具体的、有针对性的计算方法。计算并控制套管所受的外挤力是制定防止套管损坏措施的关键：求出在给定开发条件下套管外挤力，确定该载荷下套管的屈服强度，提出满足工程要求套管强度设计。 本文对大庆油田和吉林油田3800多口井和与套损相关因素和资料进行了详尽的统计分析，掌握套管损坏的主要特点和趋势，得出了主要结论：套损层位仍然在泥岩层，泥岩浸水问题是套管发生损坏根本问题，是套管损坏前提条件；油层套损井比例增加，以及油层套损形式和分布揭示了油层内地层滑移机理，油层的套管损坏应作为主要研究对象；上覆地层套管损坏机理是地层纵向变形和水平滑移产生的外载荷作用于套管，在上覆地层套管损坏的形式和井别很好地解释了上覆地层套管损坏机理；注水是引起套管损坏的主要因素，注水压力是套管损坏直接动力；地层倾角起到了加速套管损坏的作用。 对套损地层进行了岩石浸水力学性质的变化、地层浸水方式和浸水速度进行了试验。试验结果表明，泥岩浸水主要沿泥岩层理界面和沿垂直于层理面的裂缝。泥岩浸水速度和浸水距离为注水压力的函数，与注水压力成正比。泥岩层浸水后地层内聚力和内摩擦角随地层水化程度呈线性地降低，而剪切强度成倍地下降。泥岩浸水后力学性质的变化主要受泥岩中粘土含量的影响。 根据套损情况统计分析和泥岩浸水实验结果，确认套管损坏机理分为深部泥岩层蠕变套损机理、上覆地层或浅层滑移套损机理，以及油层局部滑移套损机理，为此，建立套管损坏蠕变力学模型、界面问题混合有限元计算模型和套损流固耦合计算力学模型。提出的界面问题混合有限元法解决了泥岩形成大面积浸水域非光滑接触问题，界面问题混合有限元计算模型可以很好地描述注水压力对地层滑移的作用。模拟计算结果显示地层的最大水平滑移并不发生在注水层，而是发生在注水层上部泥岩层顶部结构弱面。套损流固耦合计算力学模型揭示了注水井套管损坏的机理，注水压力使地层压力区域性不平衡，泥岩层间发生滑移，使套管发生损坏；在模型中引入渗流场，进行了流固耦合，模型中考虑了影响套管损坏因素。应用套损流固耦合位移场计算软件，对影响套损因素进行敏感性分析和实际模拟计算，计算结果与实际套损比较符合率达87.38％。 本文通过套管强度进行了试验研究，提出了套管屈服破坏的力学标准和套管当量强度设计方法。用试验和理论分析的方法，确定套管射孔和水泥环对套管强度的影响。在非均匀载荷作用下，套管屈服椭圆度可以作为套管损坏的力学标准。采用该标准的好处在于：确定套管抗挤毁强度时不需要考虑载荷作用于套管的方式和力的分布，只需知道载荷的大小和套管的椭圆度，使得进行各种载荷下的套管强度设计成为了可能。套管屈服时载荷分布形状在一定程度上可以代表套管的抗挤强度，将套管屈服时的抗挤强度定义为套管的当量抗挤强度。套管射孔对其抗挤强度的影响可用套管强度减弱系数来描述。根据所提出的套管当量强度设计方法，编制了套管当量强度设计软件。软件中建立了套管物理性能数据库，在计算中直接应用地层对套管外挤力来进行套管当量强度设计，套管设计输入数据可直接调入力学模型计算的外挤力数据来进行设计。本软件符合套管柱强度设计最新行业标准《SY/T 5322-2000》。 本文的主要创新包括： (1)将套管井整个使用过程作为套损研究对象。通过套损统计、试验验证、套损机理分析，以及理论计算等手段，确定或计算套管受力方式和大小，并将套管抗挤强度看作是与其受力方式相关的变数，提出套管受力方式与强度转换标准，使得进行非均匀载荷下套管强度设计成为可能。 (2)提出适用于上覆地层大面积滑移非光滑接触的界面问题混合有限元法和套损流固耦合计算力学摘要 模型。套损流固祸合计算力学模型中引入渗流场，并进行了流固祸合，计算结果显示流固祸合 模型用于套损力学问题是适用的。 (3)首次进行泥岩浸水试验研究。泥岩浸水不但沿泥岩层理界面，而且还沿垂直于层理面的裂缝浸 水。泥岩对水的吸附作用会产生网状流。 (4)提出在非均匀载荷作用下套管损坏的力学标准和套管当量抗挤强度。更多还原

【Abstract】 Failure prosess of casing well is complicate. Technique and practice used in drilling, production and development program all affect casing failure, which involves some subjects, such as rock mechanics, percolation flow mechanics, pipe string mechanics. All these decide the factors that affect casing failure are variety and complexity. In recent years, many scholars have studied the causes and mechanism of casing failure. Some mechanisms of casing failure are recognized, but there are not effective measures to prevent or retard casing failure, and methods to calculate stress aced on casing by formation in view of specific situations. Calculating and controlling stress acted on well casing is the key to take reasonable measures to stop or slow down casing failure, which are to calculate stress on casing in a given development condition, to determine casing strength with the stress and to promote casing string design meeting requirements of petroleum engineering.In this paper, information of 3800 wells with casing failure in Daqing and Jilin Oilfields and the factors affecting the well failure are analyzed statistically. The main characters and the trends of casing failure are grasped, and some conclusions are gotten: most locations of casing failure is in mud shale rock; and water encroachment in mud shale is a precondition of casing failure; the increase of well number with casing failure in oil reservoir and forms of casing failure and the well distribution bring to light the mechanism of casing failure in oil reservoir, which is bedding slip between shale layers in oil reservoir; the mechanism of casing failure in overlying formations is slip between layers caused by deformation in the direction of perpendicular to the layers; water injection pressure is direct dynamic force to drive formation moving that casing failure results from, and formation dip speeds up casing failure.The tests of mud shale properties by water encroachment, and the way and velocity water advanced in mud shale are taken. The result of the tests indicates that water advanced along bending interfaces and fractures vertical to the beddings. The velocity and distance water advances in mud shale is the function of and direct proportion to water injection pressure. Cohesion force and internal friction angle of mud shale are linearly decreased and shearing strength is’decreased rapidly with hydrated level of the shale. Alternations of mud shale properties are affected by clay content in the shale.According to result of statistical analysis and the tests, casing failure causes and mechanism are determined, which are casing damage by creep deformation of shale in deep formation, by shear slip in overlying formations, and by local slip in oil reservoir. Based on the mechanism of casing failure, the model of creep deformation, the model of combination finite element for bed interface problem, and the model of fluid-solid coupling, are developed. The model of combination finite element solves the contact problem of non-smooth interface of large-scale water encroachment area in mud shale. From the result of numerical simulation with the model, bedding glide does not occur in injection interval, but at hydrated weak plane in overlying formation above the injection interval. The coupling model reveals the mechanism of casing failure of water injection wells, which is pressure inequilibrium in local area results in casing damage. Percolation flow pressure field in oil reservoir is lead into the model, and coupled with reservoir. Sensitivity analysis of the factors affecting casing failure and numerical calculation are carried out with the model. 87.38% of Calculated casing failure wells conforms to the reality of casing failure in the simulated area.Based on the collapsing tests of casing, mechanical standard of casing yield failure and design method of casing equivalent strength are given. Effect of casing perforation and cement sheath on casing strength are tested and analyzed with mechanical test and theory, and their influence coeffi更多还原