关键词: 套管强度, 双向应力椭圆理论, 套管设计, 轴向力, 计算公式

Abstract: The basic theory of a previous researcher was analyzed by using the reduction to absurdity.The problems existing in his deduction were discussed.It is proved that there is no contradiction between biaxial stress ellipse theory and practical loading condition.The monotone property of multivariate function proved that the maximum stress strength point exists on the inner surface of casing under the triaxial stress conditions.The formula for calculating the axial stress of casing was discussed with theoretic deduction and calculation methods.The calculation case shows that the result of collapse strength calculated by using the triaxial stress circle theory is bigger than that by other theories.

Key words: casing strength, biaxial stress ellipse theory, casing design, axial stress, calculation formula