基于LuGre摩擦模型的定向井有杆抽油系统动态参数预测

针对定向井有杆抽油系统井下摩擦的非线性特征,提出了一种基于LuGre摩擦模型的有杆抽油系统动态预测方法。介绍了LuGre摩擦模型,并确定了符合工程实际的模型参数。将抽油杆柱的振动视为多级杆的纵向振动,对杆柱单元进行了受力分析,建立了有限元形式的杆柱系统动力学方程。结合泵载荷边界条件,利用状态空间法对系统动力学方程进行了数值求解,获得了悬点载荷随冲程变化的地面示功图。给出了基于LuGre摩擦模型的动态预测实例,并将预测结果与采用经典库仑-黏滞摩擦模型预测所得结果以及实测结果进行了对比。结果表明:LuGre摩擦模型能较好地描述抽油系统井下摩擦状况,基于LuGre摩擦模型的预测结果更接近系统真实值。

Prediction of dynamic parameters of sucker-rod pumping system in directional well based on LuGre friction model

In order to describe the nonlinear friction characteristics of sucker-rod pumping system, a novel method is presented for dynamic prediction of sucker-rod pumping system based on the LuGre friction model. The mechanism of the LuGre friction model was introduced, and six parameters were obtained to satisfy the need of engineering practice according to handbook and computation. The loading analysis of rod element was performed, and the state space method was employed to establish the system dynamic equation with time-varying coefficients. The surface dynamometer card was obtained by means of the numeric solution of the dynamic equation. An example of dynamic prediction based on LuGre friction model was given. The surface dynamometer card of suck-rod pumping system obtained by LuGre friction model was compared with that of classical Coulomb-viscous friction model.The result shows that the prediction result of the LuGre friction model fits the measured result better.