关于套管所受浮力问题的讨论

Discussion about the Problem of Casing Buoyancy

在水泥浆未固结前,套管在其中受到浮力和重力的双重作用,产生三轴应力状态。传统观点认为浮力是集中作用于套管底面,但这会令套管三轴设计产生安全隐患。通过分析任意截面上套管微元的受力状态,区分所受真实轴向力与有效轴向力的概念,明确所受浮力是分布力还是集中力的问题。针对相关文献上的不准确论述,从材料力学的角度进行了更正和一些细节上的解释说明。最后,利用三轴强度校核理论,特别针对弯曲套管段,推导出新的三轴抗拉强度公式,指出和补充了行业标准的错误和不足。研究结果对套管设计有一定的指导作用。

Before the cement solidification, casing in it will be affected by the dual role of buoyancy and gravity,and then a triaxial stress state is formed. The traditional view is that buoyancy focus on the casing underside, which may cause safety problems on casing design. The concept of the true axial force and the effective axial force are distinguished by the way of analyzing the stress status of Infinitesimal section at any cross section of casing in this article. At the same time, some corrections and explanations are made on the inaccurate relevant literatures using the mechanics of materials theory. At last, a new triaxial tensile strength formula is launched especially for the curved casing section by the use of triaxial strength theory and in which, some mistakes and insuf-ficient in the industry standard are pointed out. This article has a certain guiding role on casing .