【作者】 王文昌；

【导师】 狄勤丰；

【作者基本信息】 上海大学 ， 工程力学， 2011， 博士

【摘要】 石油工业中的定向井、水平井的实际井眼轨迹是一条不规则三维空间曲线,具有复杂的空间特征,本文统称其为三维曲井。三维曲井中的抽油杆柱力学行为与常规直井存在很大的差别,主要缘于井眼轨迹的曲率和挠率变化使得具有超细长比的抽油杆柱在井下往复运动时承受轴向拉压、扭转和弯曲的耦合作用,并表现出典型的几何非线性和接触非线性特征,也间接造成了抽油杆柱的偏磨和断脱问题日益严重。而小井眼定向井及稠油水平井的应用更加凸显了这种差别,所以常规的有杆泵抽油系统数值模拟理论不再能够准确适用于定向井。此外,在这一领域还有一个核心的科学问题一直没有得到有效的解决,即目前常用的抽油杆柱力学模型,都采用了抽油杆柱轴线与井眼轴线重合的假设,这样就无法反映抽油杆柱在井筒中的偏心特征。为了能够准确的描述井下抽油杆柱的动态特征和三维构形、分析稳定器数量和位置的影响,开展抽油杆柱三维力学分析新方法探讨就十分必要。本文首先在抽油杆柱微元体三维受力分析的基础上,考虑实际井眼轨迹变化和环空液体阻力的影响,完善了抽油杆柱在实际井眼中的振动模型,并以实测数据为边界条件,用有限差分法对其进行了求解,分析了抽油杆柱的动力学特性,预测了抽油杆柱偏磨严重点位置。其次,针对抽油杆柱动力学特性有限差分法的局限性,利用有限元法建立了抽油杆柱动力学模型。这种方法能够体现在实际井眼约束条件下,抽油杆柱的几何非线性和接触非线性特征,能够反映抽油杆柱的轴向载荷和横向变形、弯曲之间的耦合作用。首次采用结点迭代法和Newmark直接积分法相结合的方式对抽油杆柱的动力学有限元模型进行了求解,利用直接约束法处理杆-管的非线性接触问题,通过循环迭代求解得到了抽油杆柱每一结点在6个自由度方向的受力和变形,描述了抽油杆柱在实际井眼中的动态三维构形及载荷、应力特征。同时,比较了扶正器安装前后及安装方式对抽油杆柱的空间构形和受力的影响,阐明了本文提出的抽油杆柱三维动力学特性有限元分析方法的可靠性和有效性。第三,动态边界条件是计算分析抽油杆柱动力学特性的必要参数。在小井眼定向井中泵的小型化会导致下端动态边界条件的变化,利用经典的经验公式计算的泵功图作为边界条件的准确性已远远不能满足计算分析的需要。为了获得更加准确的计算结果,针对小井眼定向井的特点,首次研制了适合于小井眼定向井的井下测量工具,进行了小井眼定向井抽油杆柱的井下动态参数测试工作,得到了实测的边界条件。第四,通过实测井筒温度数据,研究了克拉玛依油田两口稠油水平井的流体粘度变化特征,确定了杆、管环空中变粘性流体的阻力模型,并对稠油水平井抽油杆柱的动态载荷、应力、变形进行了计算分析。最后,采用本文建立的模型和算法,用MATLAB语言编制了计算程序,通过与已有解析结果的算例进行对比和分析,验证了程序的正确性。通过比较抽油杆柱动态特性的数值分析结果和实测数据,进一步验证了抽油杆柱有限元模型及本文算法的合理性与有效性。更多还原

【Abstract】 The trajectory of directional or horizontal well, which is called three-dimension (3D) curved well in this thesis, is an irregular spatial curve in petroleum industry. Generally, the mechanical behaviors of sucker rod strings in 3D curved well are significant different from that in conventional vertical well. The differences between them are mainly due to the variation of curvature and torsion of wellbore trajectory. It makes the super-thin rod strings with reciprocating motion in wellbore endure the couplings among axial force, torsion and flexure, and the features of geometrical nonlinearity and contact nonlinearity of rod strings are exhibited. Thus the eccentric wear and the break-off of rod strings are induced indirectly and seriously. When slim hole directional well and heavy oil horizontal well were used, this kind of difference is more obviously. Therefore, the numerical simulation method of rod strings dynamics for conventional vertical well and 2D directional well is not applicable to 3D curved well. In addition, a key science problem has not been solved in the dynamic analysis of rod strings, that is, the axis of rod strings is assumed to coaxial with the borehole, then the eccentric characteristics of rod strings in wellbore can not be described clearly. In order to characterize the dynamic properties and the space configuration of rod strings accurately, and to analyze the effection of the position of centralizers on them, a new method for three dimension mechanical analysis of rod strings is need to be studied.First, with the 3D microelement analysis, the vibration model for sucker rod strings was improved by taking into account the influence of actual well trajectory and the fluid resistance. The finite difference method was used to solve the model with the measured data as boundary condition. Then the dynamic properties of rod strings were analyzed, and the eccentric wear position of rod strings was predicted by this method.Second, to overcome the coaxial assumption used in above finite difference method, a new dynamic model of sucker rod strings was established and solved by using finite element method. This new method can embody the features of geometrical nonlinearity and contact nonlinearity, and the couplings among axial force, lateral deformation and flexure of super-thin rod strings in actual 3D curved wellbores. With the time-domain straggling of the kinetic process for sucker rod strings by the Newmark method, the 3D dynamic finite element equation was circularly solved by using the crunode iterative method for the first time. Therefore, the deformation and load in six orientations for each node could be obtained through treating with the dynamic contact between tube and rod strings by means of a direct constraint procedure. Then the 3D spatial configuration of rod strings in wellbore was described in details. In the meantime, the validity and reliability of the finite element method proposed in this thesis were confirmed by comparing the difference of spatial configuration and load of rod strings with various fixation patterns of centralizer and with or without it.Third, the classical empirical formula can not give an reasonable boundary condition when new unconventional rod pumps with small sizes were used in slim hole directional well. In order to obtain more accurate results, a testing tool for slim hole directional well was developed and then used in two wells, and the measured boundary conditions were obtained for the first time.Forth, with the measured temperature data, the oil viscosity in heavy oil horizontal wells of Kelamayi oil field was investigated, and a resistance model related to variable-viscosity annulus fluid was determined. Then the dynamic features of rod strings in heavy oil horizontal wells were calculated and analyzed.Finally, based on the simulation model and numerical methods presented in this thesis, a simulating program was compiled by using MATLAB language. The program was verified by examples with analytic solution, and the validity and rationality of the finite element method proposed in this thesis were confirmed by comparing the numerical results and the measured data.更多还原