Helical Buckling of Pipe With Connectors

Abstract

Abstract The effect of connectors on pipe buckling is acknowledged, but has received little attention. Lubinski analysed the effect of connectors on pipe in tension in a curved borehole, while Paslay and Cernocky extended this analysis to pipe in compression. These papers indicate that bending stresses are greater due to connector stand-off. However, these papers do not consider a buckled pipe. This paper presents an analytic solution of the beam-column equations in three-dimensions for a helically buckled pipe with connectors. For low axial compression, the solution approximates helically buckled pipe without connectors, however, at higher axial forces, the effects of connectors on contact forces and bending stress becomes significant. Sag between connectors is calculated so that pipe body contact between connectors can be determined. Applications include the analysis of bottom hole assemblies, drill pipe, casing, and tubing. The solutions are simple formulas that are suitable for hand calculations.