水泥环参数和套管形状参数对套管强度的影响

The influencing of cement sheath parameters and casing shape parameters on casing strength

目前,国内外均面临着严重的套管损坏问题,因此研究套管强度的影响因素是必要的。通过建立套管和水泥环的三维有限元模型,并利用Ansys有限元分析软件研究了水泥环参数、套管偏心率和椭圆度对套管强度的影响。模拟结果表明,只有水泥环的弹性模量超过一定值,增加水泥环的厚度、弹性模量才能提高套管的强度,否则还会增加套管内壁的等效应力,并且得出了水泥环对套管强度的增幅效果是套管径厚比的函数;此外套管的强度随着套管偏心率和椭圆度的增加而大幅度降低,容易引起套管屈服破坏。

At present,both at home and abroad are facing serious casing damage problems,so it is necessary to study the influencing factors of casing strength.By establishing a three⁃dimensional finite element model of casing and cement sheath,and using Ansys finite element analysis software to study the influence of cement sheath parameters,casing eccentricity and ovality on casing strength.The simulation results show that only when the elastic modulus of the cement sheath exceeds a certain value,increasing the thickness and elastic modulus of the cement sheath can improve the strength of the casing,otherwise the equivalent stress of the inner wall of the casing will be increased,and the effect of the cement ring on the strength of the casing is a function of the diameter⁃thickness ratio of the casing.In addition,the strength of the casing decreases significantly with the increase of the eccentricity and ellipticity of the casing,which can easily cause yield failure of the casing.