热洗井空心抽油杆下入深度的计算模型

空心抽油杆应用于油井热洗工艺,可有效解决高含蜡油井定期清蜡问题,克服了常规热洗对油层的污染和产量恢复期长的弊端。但是,通常在确定它的下入深度时只考虑了原油的析蜡点,而忽视了井筒温度场和井下单流阀开启压力的影响。以井筒长度微元为单位,依据井筒能量平衡方程建立了井筒流动与传热数学模型,计算出热洗溶蜡拐点温度,确定空心抽油杆下入深度。然后,考虑热洗泵车施加的开启压力,进行了空心抽油杆的轴向应力校核。现场50余口油井应用表明,建立的模型可靠性高,平均节省空心抽油杆120 m,且抽油机正常运行最大载荷平均下降18.35%,既满足了油井清蜡需要,又节省了油井开发成本。

Calculation Model to the Depth of Hollow Sucker Rod in Hot Wash Well

The problem of regular wax removal in high wax content oil well can be effectively solved with the application of hollow sucker rod in oil well hot wash,which overcomes the disadvantages of conventional thermal washing for oil layer pollution and long recovery period.However,when determining its depth,the wax precipitation point of the crude oil is only taken into account and the influence of the wellbore temperature field and the opening pressure of the downhole single flow valve are ignored.The infinitesimal wellbore length as a unit,wellbore flow and heat transfer mathematical model was established according to the energy balance equation to calculate the hot washing wax dissolving inflection point temperature,determine the hollow sucker rod depth,and then the axial stress of hollow sucker rod was checked considering the opening pressure applied to the hot washing pump.Application in more than 50 oil wells showed that,the reliability of the model is high,120 m hollow sucker rod was saved,and the maximum load of the pumping unit was decreased by 18.35 percentage points.The utility model does not only meet the need of oil well wax removal,but also saved the development cost of oil wells.