地层空隙对套管抗挤强度的影响

采用有限元软件ABAQUS分析了水泥环外的地层空隙对套管抗挤强度的影响。分析结果表明:(1)地层中空隙的存在会降低套管的抗挤强度,空隙周向角度从20°变化到80°,套管内最大Von Mises应力逐渐增大,空隙周向角度从80°变化到180°,套管内最大Von Mises应力逐渐减小;(2)空隙压力的降低,会使套管内最大Von Mises应力增大,当空隙周向尺寸足够大时,空隙压力pv下降会导致空隙内地层边界与水泥环接触,从而减缓套管内最大Von Mises应力增大的幅度。该分析为更精确的套管抗挤强度设计提供了理论依据.

Influence of formation void on the collapsing strength of casing

The influence of formation void outside the cement sheath on the collapsing strength of casing is analyzed by using finite-element software ABAQUS.The result indicates that the occurrence of the formation void reduces the collapsing strength of casing.The maximum Von Mises stress inside the casing will increase gradually when the circumferential angle of the void changes from 20° to 80°,and the maximum Von Mises stress inside the casing will decrease gradually when the circumferential angle of the void changes from 80° to 180°.Secondly,the maximum Von Mises stress inside the casing will increase with the decrease of void pressure.When the circumferential size of the void is big enough,the decrease of the void pressure pv will lead to the contact of formation boundary inside the void with cement sheath,thus alleviating the increase of the maximum Von Mises stress inside the casing.The analysis provides the theoretical basis for designing more accurate collapsing strength of casing.