聚合物驱井内流体作用于抽油杆的侧向力解析

为了分析采出液中聚合物溶液的黏弹性效应对聚合物驱机采井杆管偏磨的影响,基于流体内部的应力状态分析,推导出了井筒内流体作用于抽油杆上侧向力的计算公式。以Maxwell模型作为聚合物采出液的本构关系,建立了采出液在偏心环空内流动时的数学模型。采用数值方法得到了环空内的速度场,并以此为基础计算了环空内的侧向力。分析结果表明,杆管环空的偏心和采出液中聚合物的弹性是产生侧向力的原因。侧向力随抽油杆的往复运动呈现出周期性的变化规律,滞后于抽油杆运动约1/4周期相位。在上、下冲程中沿杆长均匀分布有侧向力,极易超过使抽油杆发生弯曲变形所需的最小载荷而产生偏磨,且其偏磨现象比水驱井严重。

Analysis on lateral force of produced fluid acting on the sucker rod in polymer flooding wells

In order to analyze the influence of visco elastic effect of polymer solution in produced fluid on the eccentric wear of sucker rod in polymer flooding wells, a mathematical formula of the lateral force acting on the surface of sucker rod was derived by analyzing the stress state of fluid. Taking Maxwell model as the constitutive equation for produced fluid containing polymer, the mathematical models for the produced fluid flowing in eccentric annular were set up. The velocity field was obtained by using the numerical method. The lateral force was calculated on the basis of the velocity field. The analysis results showed that the lateral force was caused by the eccentric of the rod in annular and the elasticity of the fluid. Lateral force changed periodically with the reciprocating movement of the sucker rod and lagged behind the rod for about one quarter cycle. There are lateral forces along the rod equably acting on the rods during the upstroke and the down stroke. The lateral force can exceed the minimum load easily and result in the distortion of the rods and the eccentric wear between the rods and tubes. The eccentric wear of sucker rod in polymer flooding wells was more serious than that in water flooding wells.