膨胀套管中的残余应力问题

为探求套管径向扩张膨胀后的残余应力大小、产生原因及对套管性能的影响,进行了套管的实物膨胀试验,用切环法对膨胀后套管的横向残余应力进行了测量分析,发现套管膨胀后具有高的环向收缩残余应力,这种残余应力削弱了套管的抗挤强度。分析了套管膨胀后残余应力较高的原因,认为套管膨胀过程中的不均匀变形是套管膨胀后残余应力大的主要原因。介绍了衡量套管不均匀变形程度的指标-截面形状变化指数,并用试验数据对该指标的应用进行了检验。最后从制管工艺及膨胀工艺2方面提出了减弱套管膨胀后残余应力的措施。

Question of Residual Stress in Expansion Casing

In order to find the magnitude and the cause of residual stress after the casing radial expansion and its effect to the casing performance, we conduct the casing expansion test. The hoop residual stress of the expansion is measured and analyzed by loop cutting method. We find that the hoop shrinkage residual stress is high, and the residual stress can weaken the casing collapsing strength. The reason that casing has quite high residual stress after expansion is analyzed, and indicates that non-uniform deformation is the main reason. The section form variation coefficient which is the judgment of non-uniform deformation degree index of casing is introduced. And the application of the index is examined by the test data. Finally, we provide the measurement that can weaken the residual stress by both manufacture and expansion technology.