套管磨损及地应力对深井套管柱强度的影响分析

油田开发过程中,采油套管损坏给油田造成了巨大的经济损失。采用弹性力学解析及有限元方法,给出了考虑磨损时套管剩余抗挤强度、抗内压强度,以及非均匀地应力作用下套管外壁等效外挤载荷的计算方法,分析了非均匀地应力作用下不同套管磨损量对套管强度,以及不同地层性质对套管地应力外挤力的影响。研究表明,当磨损度为10%时,套管的剩余抗外挤强度、剩余抗内压强度降低约30%;套管内壁的M ises应力和套管外壁地应力外挤力随地层弹性模量的增大均明显减小,说明地层越硬,套管将偏于安全。

Effects of Casing Wear and Geologic Stress on Casing Strength in Deep Wells

During the oilfield development,production casing damage will cause tremendous economic loss.Through using elasticity and finite element method,residual collapsing strength and residual internal pressure strength of worn casing and equivalent external pressure of casing outer wall under non-uniform geologic stress were derived.Effects of casing wear degree on residual strength of casing and stratum constants on equivalent external pressure of casing were analyzed.It is shown that residual collapsing strength and residual internal pressure strength of worn casing decrease about thirty percent when casing wear degree is ten percent.With the increment of stratum elastic modulus,Mises stress and equivalent external pressure of casing decrease greatly,which shows that casing is safe when stratum is hard.