非均匀地应力下套管偏心对抗挤强度的影响

在常规地层条件下,套管的强度具有足够的富余量,因而一般对套管的偏心影响考虑较少.但在深井及盐膏层地层中,套管偏心的影响不可忽略.针对塔里木油田英买力区块钻进过程中出现的技术套管受挤变形问题,建立有限元模型,分析套管偏心对套管抗挤强度的影响规律,绘制套管偏心与套管最大应力的对应关系图,回归套管偏心与套管最大应力关系的计算公式.研究结果表明,非均匀地应力下,在最大地应力方向,套管偏心距越大,套管抵抗非均匀载荷能力越强;在最小地应力方向,套管偏心距越大,套管越容易挤毁.最后,利用研究结果确定了该区块的最低钻井液密度,从而有效地解决了套管变形问题。

Effects of Eccentricity of Casing on Collapse Resistance in Non-uniform In-situ Stresses

In conventional stratum,the casing strength is sufficient,and therefore the influence of casing eccentricity is generally less considered.However,in a deep well or in carbonate formations,the influence cannot be ignored.Considering eccentricity of casing in a circular hole,a finite element model is established and the effect of casing eccentricity on collapse resistance of casing analyzed.A contour map showing relationship between collapse resistance of casing and eccentricity is drawn,and a regression formula for eccentricity and the maximum casing stress is obtained.Simulation results show that,under non-uniform in-situ stress,the larger the casing eccentricity in hole,the greater the ability of casing resisting non-uniform loading in the maximum in-situ stress direction;and the larger the casing eccentricity in hole,the easier the casing damage becomes.