抽油机斜直井杆管接触与磨损力学模型

Mechanical model of rod-tubing eccentric wear for pumping unit in slant and vertical well

斜直井中抽油杆在上下往复运动过程中,轴向力周期性地拉压变化:受拉时,抽油杆在扶正器限制下被拉直,不与油管发生接触;受压时,当抽油杆所受的压力大于临界压力值,将发生失稳,失稳过大会与油管接触并伴有接触力。接触力的存在对抽油杆柱与油管的安全生产极为不利,特别是高含水油井,抽油杆与油管间发生水性研磨,将增加抽油杆的断脱几率或加快油管磨穿速度。从杆管接触理论关系出发,利用力矩原理,计算杆管接触力的大小;结合现场井下作业油管创口形态,建立理论示功图条件下的油管柱创口模型,预测油管磨穿时间,并利用缝隙流理论预测了漏失量。通过该方法计算得到的油管磨损理论创口形态与现场实际较为接近,针对复杂示功图可用近似标准示功图代替。

The axial force of rod changes periodically when the rod moves back and forth in slant and vertical well. Rod-tubing eccentric wear does not happen when rod was stretched and confined by centralisers and tubing. Rod destabilizing effect emerges when the axial pressure of compressional rod is greater than the critical pressure. Rod-tubing contact force generates because of severe destabilizing, which is harmful to the safe production, especially for the oil producing well with high water cut. High water cut makes rod break or tubing punch a fracture ahead of time owing to high water cut and abrading in water. This paper calculates the contact force of tubing and rod based on moment principle and establishes the geometric model of tubing and rod wound according to the contact mechanics and picture about injure tubing, and calculates the broken time of rod or tubing and predicts the leakage based on gap hydromechanics. The theoretical wound shape of tubing calculated in this way is similar with the one in site and there is a way of proximate process to theoretical indicator diagram for the complex curve.