Method of equilibrium differential equation for analysis of strength of large deflection drill string

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气体钻井中接触非线性问题的数值算法研究

根据动量守恒和钻柱力学的基本理论,建立了气体钻井三维弯曲井眼钻柱动力学模型和钻柱与井壁接触碰撞模型;提出了一种求解钻柱与井壁接触非线性有限元方程的元胞自动机算法。该方法具有编程简单、收敛速度快等优点,以实际工况为例进行仿真模拟,选取有代表性节点的仿真计算结果并加以分析。仿真结果表明:该方法较好地解决了三维弯曲井眼中钻柱与井壁接触碰撞的复杂边界条件问题,在解决气体钻井钻柱与井壁接触非线性问题的研究中具有良好的应用前景。     

Three-Dimensional Nonlinear Analysis of Drill String Structurein Annulus

ＴＨＲＥＥ－ＤＩＭＥＮＳＩＯＮＡＬＮＯＮＬＩＮＥＡＲＡＮＡＬＹＳＩＳＯＦＤＲＩＬＬＳＴＲＩＮＧＳＴＲＵＣＴＵＲＥＩＮＡＮＮＵＩＵＳＬｉｕＹａｎ－ｑｉａｎｇ（刘延强）ＬｕＹｉｎｇ－ｍｉｎ（吕英民）（ＤｅｐａｒｔｍｅｎｔｏｆＥｎｇｉｎｅｅｒｉｎｇｍｅｃｈ...     

隔水管弯曲对钻柱振动影响的计算与分析

海洋油气资源钻探中隔水管的弯曲对钻柱振动以及钻进特性有特别的影响。为得到隔水管弯曲对钻柱振动的影响规律,对南海已钻深水井使用非线性有限元软件建立全井钻井数值计算模型,研究获得了不同垂深时隔水管弯曲对钻柱振动特性的影响规律。研究表明:隔水管弯曲会加剧钻柱的振动,钻柱振动加剧会导致钻井能耗上升、钻头切削能力下降并且会加快钻柱疲劳;当隔水管的弯曲达到某临界值,钻柱与隔水管间的接触力会陡增;井口的钩载越大,隔水管弯曲带来的井口钩载波动量越大;井越深,隔水管弯曲对全井钻柱最大弯矩和钻头切削能力的影响越小。     

复合材料结构力学分析CAE软件现状

复合材料结构分析软件是用以分析、设计复合材料结构的重要工具,常用的复合材料结构分析软件包括基于CAD软件发展而来的复合材料分析工具、通用有限元软件自带复合材料分析工具和以Digimat等为代表的专业化复合材料结构分析软件。本文对常用的复合材料分析软件进行了综述,介绍其主要功能,从学术、应用等多方面探讨相关产品的优点及不足;论述了专业化复合材料结构分析软件的特点及功能;分析了复合材料结构分析软件的现状和发展趋势;探讨了复合材料结构力学分析CAE软件在国产化方面所需进一步解决的问题。     

5-1/2 FH钻杆接头极限承载能力研究

随着超深井、定向井、水平井、大位移井及大斜度井在石油钻井工程中的广泛应用,由井下复杂工况引起的钻杆接头过早失效问题日益突出,导致钻井周期增长,成本增加,成为制约钻井工程效益的主要因素之一.近年来,不少学者对钻杆接头进行了大量研究,多数采用二维轴对称模型,少数采用三维力学模型,但并未同时考虑螺纹升角和井眼弯曲作用等因素的影响,而钻杆接头的极限承载能力研究更是鲜见报道.针对上述问题,基于虚功原理、von Mises屈服原则及接触非线性理论,同时考虑螺纹升角和井眼弯曲作用,建立了钻杆接头的三维数值仿真模型与井眼曲率到加载弯矩的转换模型,研究了钻杆接头的上扣特性、井眼曲率对连接强度和密封性能的影响,考虑预紧力、弯曲载荷及动载安全系数,计算了钻杆接头的极限工作拉力和极限工作扭矩.研究结果表明:上扣扭矩使钻杆接头产生一定的初始接触压力,保证钻杆接头井下作业过程中的连接强度与密封性能;井眼曲率对钻杆接头井下作业过程中的连接强度与密封性能影响极大,常见的某些工况会导致钻杆接头的连接强度和密封性能丧失,考虑服役时的随机振动与冲击,常规的超深井、水平井、定向井、大位移井及大斜度井弯曲段钻杆接头的设计和选型应着重考虑井眼曲率的影响;针对设计的每种钻杆接头,都应考虑常见的井眼曲率和轴向拉伸载荷进行极限工作拉力和极限工作扭矩的精细化数值计算,以确保其安全工作.     

钻柱卡点预测实验

卡点预测是处理卡钻事故的关键。利用管柱扭转变形的特性,设计了无钻杆接头的单一管柱和有钻杆接头的组合管柱,并分别建立了卡点预测计算公式。利用管柱力学实验平台、四分量传感器、数据无线传输系统、HP数据采集系统和相关数据处理软件,对两种管柱进行了扭转实验。本次实验结果为:对于单一管柱,相对误差为-1.88%;对于组合管柱,当不考虑钻柱接头的影响时,相对误差为-3.8%,考虑钻柱接头的影响时,相对误差为-1.02%。实验结果表明:扭转法可用于直井中钻柱卡点预测,钻杆接头和钻柱加厚部分对卡点计算的影响较大,用带有修正系数的计算公式预测精度较高。     

PROGRESS IN MEASUREMENT TECHNOLOGY FOR DRILL STRING VIBRATION

随着深井、超深井数量的快速增加, 钻柱振动导致的钻具失效问题更加突出. 针对钻柱振动的研究可分为理论与数值模拟、测量分析两种方法. 由于钻柱振动具有复杂的非线性特征, 使得理论与数值模拟研究受到了很大限制, 因此井下振动测量技术的研究显得尤为重要. 本文比较全面和系统地介绍了国内外钻柱振动测量技术研究现状和进展情况, 并对几个应用较为成熟的国外测量系统的工作原理、分析方法及应用技术进行了详细的综述. 所得结论可为我国井下振动测量技术的发展提供重要参考.     

有限差分法模拟单位冲激函数声波在钻柱中传播

为实现声波为载波,钻柱为信道传输井下信息的目的,了解声波在钻柱中的传输规律是必要的. 将钻柱简化为理想周期性管结构,利用有限差分方法,对单位冲激函数声信号在钻柱中传播进行了模拟,分析接收信号时域及频域分布得出：响应信号持续时间较长,信号随时间增长衰减,且最大幅值较输入信号小;钻柱结构的信道为梳状滤波器结构;通带存在谐振尖峰,尖峰数量与钻杆及接头数量有关. 模拟结果与同类研究成果有较好的一致性.     

Controlling torsional vibrations of drill strings via decomposition of traveling waves

Torsional vibrations in drill strings, especially stick-slip vibrations, are detrimental to the drilling process as they slow down the rate of penetration and may lead to failure of the drilling equipment. We present a method for controlling these vibrations by exactly decomposing the drill string dynamics into two traveling waves traveling in the direction of the top drive and in the direction of the drill bit. The decomposition is derived from the wave equation governing the string vibrations and is achieved with only two sensors that can be placed directly at the top drive and at a short distance below the top drive (e.g., 5 m). Therefore, downhole measurements along the string and at the bit are not necessary, which is a major advantage compared to other control concepts for drill string dynamics. The velocity of the top drive is then controlled in order to absorb the wave traveling in the direction of the top drive, thus achieving a reflection coefficient of zero for the frequency range of the undesired torsional vibrations. The proposed algorithm is implemented for both a numerical example and an experimental setup; results show that the control concept works very effectively.     

Torsional vibration analysis of push-the-bit rotary steerable drilling system

Ordinary drillstring torsional vibration is a very common phenomenon that has been attracted great interesting. Through Measurement data, a series of studies and analysis of torsional vibration characteristics of the bottom hole assembly (BHA) have been developed. However, for rotary steerable system (RSS), especially push-the-bit mode, its drill torsional vibration phenomenon will demonstrate the new properties, because that the underground implementing agencies will generate cycle torque and drag to the BHA in the orientation process. This process is completely different to the previous. A set of “strap-down” measurement system was developed in this paper, and the triaxial accelerometer and triaxial fluxgate were installed near the bit. Proposed a method of solver drill bit rotation speed using real-time downhole measurement data (sampling frequency 100 Hz), and the torsional vibration mathematical model of push-the-bit RSS was established. We found that the torsional vibration phenomenon of push-the-bit RSS is more serious than the ordinary drilling system by downhole measurement data analysis, even in most cases manifested as stick-slip. The torsional vibration was divided into five different modes, which showing different statistical regularities. Corresponding analysis of the angular displacement and speed, we found that the drill bit always appears low-speed in the position of oriented. This is a strong proof of that the RSS implementing agencies pushing the BHA caused the drill bit torsional vibration more serious. This work is supplemented and development of the drill string torsional vibration studies. Contribute to the better understanding of the dynamics of the push-the-bit RSS. Put forward a new way of analysis the rotary steerable drillstring fatigue damage predicted, steering ability and the torsional vibration control.     

Vibration analysis of rotating twisted and open conical shells

Based on a non-linear strain–displacement relationship of a non-rotating twisted and open conical shell on thin shell theory, a numerical method for free vibration of a rotating twisted and open conical shell is presented by the energy method, where the effect of rotation is considered as initial deformation and initial stress resultants which are obtained by the principle of virtual work for steady deformation due to rotation, then an energy equilibrium of equation for vibration of a twisted and open conical shell with the initial conditions is also given by the principle of virtual work. In the two numerical processes, the Rayleigh–Ritz procedure is used and the two in-plane and a transverse displacement functions are assumed to be algebraic polynomials in two elements. The effects of characteristic parameters with respect to rotation and geometry such as an angular velocity and a radius of rotating disc, a setting angle, a twist angle, curvature and a tapered ratio of cross-section on vibration performance of rotating twisted and open conical shells are studied by the present method.     

AN EXPERIMENTAL STUDY ON POST-BUCKLING BEHAVIOR OF SLENDER COLUMN WITH FIBER REINFORCED COMPOSITE MATERIAL

Equilibrium paths of post-buckling are measured for large slenderness column specimensmade of the fiber reinforced composite material. The influence of the initial curvature is investigatedexperimentally and compared with the result of the initial post-buckling theory. Both the theoreticaland experimental results reveal that the column with the initial curvature has stable post-buckling be-haviors and is not sensitive to the imperfection in the form of initial curvature. The experimental re-sults show that when the lateral buckling displacement is less than 20 percent of the column length, theexperimental results agree with the results from the theory of initial post-buckling quite well, whilethey agree with the results from the large deflection theory in a quite large range.     

Analytical solution for bending beam subject to lateral force with different modulus

A bending beam, subjected to state of plane stress, was chosen to investigate. The determination of the neutral surface of the structure was made, and the calculating formulas of neutral axis, normal stress, shear stress and displacement were derived. It is concluded that, for the elastic bending beam with different tension-compression modulus in the condition of complex stress, the position of the neutral axis is not related with the shear stress, and the analytical solution can be derived by normal stress used as a criterion,improving the multiple cyclic method which determines the position of neutral point by the principal stress. Meanwhile, a comparison is made between the results of the analytical solution and those calculated from the classic mechanics theory, assuming the tension modulus is equal to the compression modulus, and those from the finite element method (FEM) numerical solution. The comparison shows that the analytical solution considers well the effects caused by the condition of different tension and compression modulus. Finally, a calculation correction of the structure with different modulus is proposed to optimize the structure.     

基因芯片纳米挠度和表面应力的解析预测

本文利用能量法解析分析了无标记生物检测中基因芯片的纳米力学行为.首先,考虑微悬臂梁机械能和基因层静电能、水合能和构型熵,建立了基因芯片能量模型,并采用泰勒级数展开法.获得了能量势的一阶近似式.其次,利用能量最小原理,得到了芯片稳态弯曲的曲率半径、纳米挠度和表面应力的解析表达式,从而克服了求解多极值能量泛函数值解的困难.最后,预测了DNA的链长和种植密度对芯片纳米力学行为的影响,同时将表面应力的解析预测结果与有关实验数据进行了比较,证明了本文方法的可靠性.     

Dynamics of rotating conveying mud drill string subjected to torque and longitudinal thrust

In the view of fluid-structure interactions and rotor dynamics, this paper models the lateral vibration of a vertical downward rotating elastic drill string conveying mud subjected to supporting stabilizers, bit torque and longitudinal thrust. The dynamic model involves the rotational inertia of the drill string tube cross section, the gyroscopic effect caused by rotation, the damping due to friction with the surrounding fluid, the gravity force and mud buoyancy. Damped natural frequency, stability and resonance of the drill string system are determined by quadratic eigenvalue problem and investigated at influences of the stabilizer, rotational angular speed, mud flowing velocity, bit torque and thrust. As a result, the drill string can lose stability both at simultaneous and separate influences of the mud conveying, bit torque and thrust, whereas the rotation, stabilizer and gravity of the drill string can improve system stability; the rotational angular speed causing system resonance decreases with the increase of the mud flowing velocity, bit torque and thrust.     

结构力学分析方法在南海水平井钻进预测中的应用

本文探讨了结构力学分析方法-非线性有限元性在预测水平井钻进中的工程应用,在钻探水平井尤其是大位移水平井中,事先较准确地预测出钻柱的钻进扭矩及钻头前进的方向,是取得水平井成功的关键条件之一。利用非线性有限元理论,着重分析了水平井实际钻进中的钻柱大变形非线性及钻柱与井壁的接触非线性问题,并导出了一套非线性有限元钻柱力学模式,在此基础上编制了一套非线性力学计算程序软件,并在海洋石油南海西部石油公司一个钻井平台水平井钻井进行了五口井的实际验证,获得了一些有启迪性的结论。     

考虑尺寸效应的双材料轴对称界面端应力奇异性

提出了一种分析双材料轴对称界面端的应力奇异行为的特征值法.基于弹性力学空间轴对称问题的基本方程和一阶近似假设,利用分离变量形式的位移函数和无网格算法,导出了关于应力奇异性指数的离散形式的奇异性特征方程.由奇异性特征方程的特征值和特征向量,即可确定应力奇异性指数、位移角函数和应力角函数.数值求解了纤维/基体轴对称界面端模型的奇异性特征方程, 结果表明:尺寸效应参数δ(奇异点与轴对称轴的距离和应力奇异性支配区域大小的比值)影响着应力奇异性的强弱与阶次, 准一阶近似解析解只是δ>>1时的一个特例.      

Critical states of drill strings in the channels of inclined boreholes

The problem of determining the critical states and the postbuckling deformation of drill strings in the cavities of curvilinear boreholes is posed. The process of elastic bending of the drill string is associated with the motion of its axial line along the corresponding channel surface. On the basis of the theory of flexible curvilinear rods, a specially chosen moving system of axes is used to construct nonlinear ordinary differential equations describing the contact interaction between the drill string tube and the borehole wall. Themoving reference system allows us to separate the desired variables and decrease the order of the resolving equations. As an example, we solve the problem of stability of drill strings lying at the bottom of a cylindrical cavity in a rectilinear inclined borehole. The critical values of the axial forces are determined and the buckling modes are constructed. It is also shown that they have the form of edge effects typical of singularly perturbed equations. The developedmethods can be used in design of a curvilinear borehole and its possible driving conditions to determine the admissible values of the axial force and the torque at the point of the drill string suspension so as to prevent its bifurcation buckling.