水驱抽油机井杆管偏磨原因的力学分析

建立了铅垂油井杆管偏磨临界轴向压力的计算公式.杆管偏磨的临界轴向压力只取决于抽油杆直径与轴向分布力;应用波动方程建立了抽油杆柱轴向分布力的模拟方法;建立了供液不足油井液击力的计算公式,改进了柱塞下行阻力的计算方法.系统分析了油井生产条件与生产参数对杆管偏磨的临界轴向压力与柱塞下行阻力的影响.分析结果表明:(1)含水与沉没度对杆管偏磨有显著影响,高含水油井在低沉没度下运行会明显降低杆管偏磨的临界轴向压力;(2)当油井供液不足时,柱塞下冲程时泵内将产生液击,并加大柱塞下行阻力;(3)抽汲参数增加不仅导致抽油杆柱振动加剧,降低了杆管偏磨的临界轴向压力,而且也加大了柱塞下行阻力.当抽油杆柱在上述一个或几个条件共同作用下达到偏磨临界条件时,杆管将产生偏磨.

Mechanical analysis on causes of worn rod string and tubing of rod pumping wells in the water-flooding oilfield

The calculating formula for critical axial load of worn rod string and tubing was set up.The critical axial load only depends on the diameter and axial distributed load of the rod string.The simulating method of axial distributed load of the rod string was given by means of the wave equation of the rod string.The formula for calculating the liquid shock load in the low sinking depth wells was set up,and the formula for the axial load in the down stroke of the plunger was established.The influences of running conditions of the oil wells on the wear of rod string and tubing were systematically analyzed.The bellow conclusions can be obtained:(1) The water content ratio and the low sinking depth have important affect on the wear of rod string and tubing.When the wells run at the low sinking depth,the critical axial load is greatly reduced.(2) When the pump cylinder could not be filled with enough liquid,the liquid shock will occur,and the liquid shock load will make the down stroke axial load of the plunger increase.(3) When the suction parameters of the wells increase,the critical axial load will decrease,and the down stroke axial load of the plunger will increase.When wells run at one or some of the above states,and the practical down stroke axial load of the plunger is greater than the critical axial load,the wear of rod string and tubing will take place.