磨损对套管抗挤强度影响的有限元分析

FINITE ELEMENT ANALYSIS ON EFFECT OF WEAR ON CASING COLLAPSING STRENGTH

随着石油工业的不断发展 ,深井、超深井、水平井和大位移井越来越多 ,而这类井由于其自身的特殊性 ,在钻井过程中钻具在井中旋转及起下钻对套管内壁造成磨损 ,导致其抗挤强度、抗内压强度等使用性能降低 ,对油气井的安全构成威胁 ,因此 ,套管设计时应当考虑磨损对抗挤强度的降低问题。APIBul 5C3挤毁压力公式没有考虑磨损对套管抗挤强度的影响。文章主要通过有限元法并辅以理论分析 ,深入研究套管内壁磨损对其抗挤毁性能的影响规律 ,分别详细比较“月牙形”磨损模型与偏心筒近似磨损模型、最小壁厚均匀磨损模型之间的差异 。

With the development of petroleum industry, there are more and more deep well, ultra-deep well, horizontal well and extended-reach well. Due to their particularities, the wear caused by drill string inside casing wall during drilling makes casing strength decrease. Thus, the effect of the wear on casing collapsing strength should be considered while casing design. But the effect was not considered among the collapse-pressure equations given in API Bulletin 5C3. In this paper, the effect is lucubrated by both finite element method and theoretical analysis. The difference between crescent-shape wear model and eccentric cylinder approximation wear model, and that between crescent-shape wear model and minimun wall thickness uniform wear model are discussed respectively in details. At the same time, the mechanisms leading to the differences among the three wear models are also discussed.