非均匀地应力条件下磨损位置对套管应力的影响研究

深井、超深井、大斜度井、大位移井等高难度井逐渐普及，其钻柱工作时间的延长以及井眼轨迹的变化使得套管磨损问题日益突出，而磨损位置的不同会对套管强度降低的程度产生重要影响。为此，文章在充分考虑地应力非均匀性的基础上，建立了磨损后套管应力计算的有限元模型。计算结果表明，当磨损位置处于最小地应力方位时，磨损带来的套管应力增加和地应力非均匀性导致的套管应力非均匀分布得到了叠加，是最危险的情况。由于套管磨损位置带有一定的随机性，因此在设计套管强度时，应以磨损位置处于最小地应力方位为基准才是安全的。

EFFECTS OF WEAR LOCATION ON CASING STRESS UNDER NONUNIFORM IN-SITU STRESS CONDITION

Casing wear is one of the inevitable problems during the drilling process, especially more serious in deep wells, ultra-deep wells, high-angle wells, and extended-reach wells, etc., due to longer working time for drill strings and variations of well trajectories. And the location of casing wear is related with the extent casing strength decreased. Based on the consideration of nonuniform in-situ stresses, the finite element model for stress calculation for worn casing is established. The results show that the induced casing stress from wear and the resulting stress nonuniform distribution from nonuniform in-situ stress have been overlapped when the wear located along the direction of the minimum in-situ stress. So this is the most dangerous situation for the casing safety. Because the wear location is random sometimes, the wear should be supposed to locate at the direction of the minimum in-situ stress to ensure the casing safety in the casing strength design.