【作者】 吴恩成；

【导师】 闫铁； 刘合；

【作者基本信息】 大庆石油学院 ， 油气井工程， 2007， 博士

【摘要】 封隔器是油田开发中常用的工具,其质量的优劣及可靠性将直接影响油田的开发成本。封隔器分掰式卡瓦是封隔器重要部件之一,其工作性能直接影响封隔器的性能,因此,对封隔器卡瓦进行力学理论分析与实验研究,降低其生产成本,提高其工作效率及可靠性,已经成为世界各国油田公司竞相研究的热点。随着我国主力油田已陆续进入中、高含水阶段以及深井、超深井油气田的发现,油气田开发活动对封隔器及其配套工具的性能和技术指标提出了新的、更高的要求。即耐温、耐压、下入深度等性能需要相应的提高。而在实际应用过程中,经常出现坐封不稳、卡瓦易损坏及套管受损等问题。这些问题发生的主要原因是卡瓦的结构设计不尽合理,因此迫切需要对封隔器卡瓦进行力学分析及结构优化设计,研究封隔器卡瓦和套管的应力分布规律,并优化出封隔器卡瓦的最佳结构。本文将基础理论研究、实验研究和应用技术研究有机地结合起来,建立了一种封隔器卡瓦优化设计的新方法,这对提高封隔器的设计水平、促进相关学科发展具有一定的理论意义。本文涉及到弹性力学、塑性力学、实验力学、光弹理论、相似理论及非线性有限元分析,同时还需研究金属的本构关系等多种学科,是材料非线性、接触非线性和瞬态动力学多重耦合的问题。本文通过力学分析,建立了封隔器卡瓦的力学模型及有限元模型。运用动量定理和动力学原理建立了封隔器卡瓦在有限变形范围内的守恒方程和瞬态动力学平衡方程。根据封隔器卡瓦的结构参数和运动条件推导了接触界面不可侵彻度量方程,并根据变分原理和完全的Lagrange格式推导了平衡方程的弱形式。采用增广Lagrange乘子法建立封隔器卡瓦与套管的界面动量方程。采用有限元方法,运用载荷增量法、增广Lagrange乘子法、Newmark法计算封隔器卡瓦在多重耦合情况下的受力和变形状态。通过受力分析和实验研究,明确了卡瓦与套管的受力状况及咬合力分布规律,为卡瓦的优化设计奠定了基础。在卡瓦的优化设计中,首先确定了卡瓦每个相关结构参数变化时,计算结果的变化规律。然后比较每个结构参数所对应结果,如卡瓦和套管的当量摩擦系数、最大Von Miese应力、接触径向压力等,找出每个结构参数最佳值。最后将需要优化结构参数通过正交设计方法进行组合,确定出卡瓦的最优结构参数组合。这为优化封隔器及类似的工具提供了新的思路、新的方法。虽然数值计算方法的功能越来越强,计算结果的精度对于工程解也是可靠的,但是对于模型的建立以及边界条件的确定,单靠数值计算是不够的,还需要通过实验应力分析技术来进行必要的验证。为了检验计算结果的正确性,本文采用光弹性实验模拟封隔器构件模型。将实验结果与计算结果相对比后,两模型中卡瓦和套管的应力分布规律比较一致,且在计算模型中,若卡瓦与套管的摩擦系数等于0.28时,两组结果符合的相对好。本文所提出的优化方法对油田目前出现的新问题具有较强的针对性,所得出的结果为封隔器的设计提供了理论基础。为保证封隔器的正常作业、延长作业周期、提高原油产量和降低生产成本提供了保证,对提高油田经济效益具有一定的现实意义和实用价值。更多还原

【Abstract】 Packers are commonly used tools in the oilfield development. Their qualities and reliability will directly affect the oilfield development’s cost. The slips are very important parts in the packers, whose working performance directly influences the packers’performance. Therefore, the packer slips’mechanical analysis and experimental research can effectively reduce the production cost, increase the working efficiency, and enhance the working reliability. The studies on the packer slips have become the research focus of many oilfield companies in the world.With the main reservoirs in China have entered into the medium or high water cut period and the discovery of many oilfields with deep wells and super deep wells, the packer’s performance and its accessories needs to have new and higher requirements---that is temperature resistance, pressure resistance and running depth need to be improved. During the field operation, some problems usually take places, such as packers’unstable setting, slips easily broken and casing damage. The reasons are mainly due to the unreasonable design on the packer slips. As a result, it is urgent to do the mechanical analysis and optimum design for the slips and to study the stress distribution laws of packer slips and casing. Consequently, the best structure for packers can be optimized. This paper combines basic theory studies with experimental research with application technologies. A new design way for optimizing the packers’structure has been constructed, which can improve the packers’design level and promote the relevant subjects development.The paper is involved in many subjects, for instance, elastic mechanics, plastic mechanics, experimental mechanics, photo-elastic theory, similar theory, and non-linear FEA. At the same time, it includes many disciplines about metal structure relation, such as multiple coupling problems about material non-linearity, contact non-linearity and transient dynamics. By the mechanical analysis, mechanical model and finite element model of packer’s slip are set up in this paper. Conservation equation and transient dynamics balance equation of packer’s slip are set up by using momentum theorem and dynamics principle in the scope of finite distortion. Non-embed measurement equation of contact surface is derived from the slip’s structure parameters and movement condition. The weak style of balance equation is derived from variation principle and updated Lagrange format. Adopting augmented Lagrange multiplier method sets up the interface’s momentum equation between slips and casing. At last, the force and deformation state of packers are calculated on the conditions of multiple coupling by using FEA (finite element analysis) method, load increment method, augmented Lagrange multiplier method, and Newmark method.The force of packers and casing and the occlusive force distribution laws are found out by force analysis and experimental research, which establish the theory basis for optimizing slips. In the process of optimizing slips, the computing results should be confirmed firstly with the change of slips’each relative parameter. Then by comparing each structure parameter, such as the equivalent friction coefficient between slips and casing, the maximum Von Mises stress, contacting radial stress and so on, the each slip’s optimum structure parameters are determined. At last, the optimum structure parameters of slips are confirmed by orthogonalizing each parameter. All of those studies provide new ideas and methods for optimizing packers and similar tools.Although the function of numerical calculation method becomes stronger and the precision of computing results are reliable, the numerical calculation is not enough for setting up the model and the boundary condition, which also need to be confirmed by the experimental stress analysis technology. Photo-elasticity experiment is adopted to simulate the packers’component model in order to verify the correctness of results. The stress distributing law of slips and casing in computing model is comparatively consistent with that in experimental model after comparing the experimental results with the computing results. Moreover, the two model results are coincident when the frictional coefficient in computing model is equal to 0.28.The optimum methods put forward in the paper are good guidance for the new problems arising from the oilfield development. The achieved results provide the theoretical basis in designing packers, which guarantee packers’working operation, prolonging duty cycle, increasing production rate and reducing production costs. The significance of increasing oilfield economic benefits is quite clearly.更多还原