稠油热采井套管柱应变设计方法

Strain design method for casing strings in heavy oil thermal recovery well

为解决稠油热采井不断出现的套管损坏现象,改变传统的管柱强度设计方法。基于弹塑性力学理论,在满足套管柱强度设计的基础上建立套管柱应变计算模型;通过对比套管材料应变与结构应变,借助Rambery-Osgood模型得到应变安全系数最小值,提出套管柱应变设计的理论判据,形成套管柱应变设计方法。结果表明,该设计方法在西部油田8口稠油热采井Φ177.8 mm×8.05 mm TG80H特殊螺纹套管柱设计中得到应用,生产4轮次后套管柱未出现变形和泄漏现象,经过14轮次后,套管服役性能依然良好,新热采井套管柱应变设计方法允许套管在可控范围内变形,可有效延长套管使用寿命,降低套损率。

Considering the fact that casing damage becomes more and more serious in steam injection wells,the traditional string strength design method needs to be changed.According to the elasto-plastic mechanics theory,the strain calculation model of the casing string was established on the basis of casing strength design.The minimum value of the strain safety factor was given by comparing the casing material strain and structural strain in use of the Ramberg-Osgood model,and the theoretical criterion of strain design on casing strings was then proposed.The result shows that,when this design method was applied in Φ177.8 mm×8.05 mm TG80 H premium thread casing strings,the leakage and deformation phenomena did not appear after 4 rounds steam stimulation.Moreover,the performance of the casing strings kept very well even after 14 rounds.The new strain design method on casing strings in the thermal recovery well admits their deformation in a controllable range,and it can effectively extend the lifetime and lower the damage probability of casing strings.