水泥环性质对套管抗挤强度影响的有限元分析

套管常在油层和泥岩部位严重损坏，分析认为这是生产过程中地应力发生了变化，导致油层孔隙压力或泥岩力学性质改变，造成地应力重新分布的结果。因此，水泥环的质量对套管的影响较大。建立了二维平面轴对称和平面应变有限元模型，利用Ansys有限元软件分析了套管在水泥环影响下的变形特征。分析表明，最大应力在套管内壁产生，均匀我荷下套管抗挤强度是非均匀载荷的5～7倍，而且栽荷椭圆度越大，套管内壁应力越大。增大水泥环弹性模量可以有效减小套管最大应力，因此，均匀我荷下应适当提高水泥环弹性模量，以达到提高套管抗挤强度的目的。

Finite Element Analysis of Effect of Cement Sheath Property on Casing Collapsing Strength

Casings are always damaged heavily in sandstone and mudstone formations. The analysis indicates that the change of the formation stress during production caused the change of the formation pore pressure or the mechanical properties of mud and caused the redistribution of the formation stress. The quality of the cement sheath has very important impacts on casings. Thereafter, a 2D plane axisymmetry and strain finite element model was created. The characteristics of casing deformation under the impact of cement sheath were analyzed using the Ansys finite element software. The analysis indicates that the maxi mum stress is located in the inner casing; the Casing Collapsing Strength of casing under uniform load is 5 -7 times higher than that in non-uniform load; and the higher the load ellipticity, the larger the inner casing stress is. Increasing the cement sheath elasticity modulus can effectively reduce the casing maximum stress; therefore, appropriately increasing the cement sheath elasticity modulus under uniform load can increase the casing collapsing strength.