定向井有杆抽油泵系统诊断模型的建立

考虑井眼轨迹的井斜角、方位角、油液等对杆柱抽汲运动的影响,从定向井的多级混合杆抽油杆柱上选取微元体,对该微元体做动力学分析.建立反映抽油杆柱动态变化的波动方程,作为有杆抽油泵系统故障诊断的初始动力学模型.对整个杆柱采用变步长取样和多级杆柱的分界面处特殊处理,利用有限差分法求解偏微分方程,得到杆柱上分界面处和均质段任意位置处的位移表达式.确定初始条件和边界条件,经差分和迭代计算获得抽油泵柱塞位移表达式和载荷表达式,完成最终的建模.以油田提供的4口油井的相关数据为例,代入诊断模型得到了泵功图并对其进行故障诊断.结果表明:定向井有杆抽油泵系统诊断模型的建模方法是正确可行的,数学模型应用可靠,能够支持基于知识和基于数据分析的故障诊断方法.

Modeling method for fault diagnosis to sucker rod pumping system in directional well

Considering the influences of deviation angle, azimuth angle and oil on swabbing motion, the infinitesimal was selected from the multistage sucker rod string of directional well. The infinitesimal was analyzed. The wave equation reflecting the rod string's dynamic movement was established and acted as an initial kinetic model for fault diagnosis to sucker rod pumping system. Sampling with variable step method from the whole rod and executing a special treatment at the interface of multistage rod, the finite difference method solves the wave equation to obtain each expressions of displacement at homogeneity and interface positions of multistage rod. Confirming initial and boundary conditions, the expressions of displacement and load on pump plunger can be obtained by the difference and iterative computation to realize final modeling. Inputting the correlation data about 4 oil wells from oilfield into mathematical model, and the indicator diagram of pump working was gotten to make a fault diagnosis. The results show that the modeling method is effective and the reliability of the model was verified. The model could support knowledge-based and data analysis-based fault diagnosis method.