彩南油田抽油杆偏磨机理和防治研究

MECHANISM ANALYSIS AND COUNTERMEASURES ON PARTIAL WEAR OF SUCKER ROD IN CAINAN OILFIELD

一般认为影响抽油杆偏磨主要有三大因素:一是井斜;二是柱塞下行阻力;三是底部油管屈曲。通过应用摩擦强度的概念对这三大因素的分析发现,井眼轨迹的弯曲、底部油管屈曲是抽油杆偏磨的主要因素,井斜、柱塞的下行阻力所引起的偏磨并不严重。对彩南油田抽油杆偏磨情况分析后,得到如下主要结论:在弯曲井段,全角变化率越大,杆管摩擦强度越严重。在斜直井段,当井斜角大于4度时,需要考虑安放抽油杆扶正器;在大间隙柱塞副、低粘度井液、小泵径的油井工况下,柱塞的下行阻力并非是抽油杆偏磨的主要原因;上冲程在柱塞拉动下,底部油管发生屈曲,由此形成的杆管之间的摩擦强度较为严重。

It is known that usually there are three factors affecting the eccentric wear of the sucker rod,and they are:hole deviation,resistance force on running-in plunger,and the bulking of the bottom tubing.The analysis on these factors reveals that the curvature of wellbore trajectory and the bulking of bottom tubing are the main factors and the eccentric wear caused by hole deviation and resistance force on running-in plunger are not relatively serious.The term(or concept) of frictional strength is introduced in analysis to compare frictional behavior of rod in various hole and operating conditions.The following conclusions can be drawn by evaluating the effect of wellbore trajectory,resistance force on running-in plunger and the bulking of the bottom tubing on eccentric wear of rod.1) Dogleg severity Kp is adopted to evaluate the frictional strength of bending rod in curved portion.It is apparently founded that the larger dogleg severity of hole section is,the more severe frictional strength of rod becomes.It is needed to install centralizers for rod in slant hole section when the deviation angle is above 4 degree.2) The resistance force on running-in plunger is not the key reason which gives rise to eccentric wear of rod if there are larger plunger,lower viscous fluid and small diameter pump in the well.3) Upstroke of the plunger drag can cause bottom tubing to bulk,which will generates higher frictional strength between rod and tubing.