Abstract
This paper brings together several buckling and pipe deformation analysis themes. Clearly, connectors should have an effect on the loading of pipe. For non-buckled pipe, Lubinski analyzed the effect of connectors on pipe in tension in a curved borehole and Paslay and Cernocky extended this analysis to pipe in compression. Connectors have an effect on the buckling of pipe, but the effect of connectors has only recently received attention. Three-dimensional helical buckling of pipes with connectors were analyzed by Mitchell, presented at SPE/AIDC 1999. Laterally buckled pipe with connectors was presented at SPE/AIDC 2000. In these papers, analytic solutions of the beam-column equations were developed in three-dimensions, and critical loads for buckling initiation were determined. Conditions for positive contact forces were determined and compared to previous buckling criteria, such as Paslay-Dawson.
In this paper, the wellbore curvature effects studied by Lubinski, Paslay, and Cernocky are included in the buckling effects studied by Mitchell. The modifications necessary to the analysis of lateral buckling are made for a curved wellbore. The resulting model gives a buckling criterion similar to He and Killingstad's results for pipe without connectors. The buckling model is integrated with the Paslay-Cernocky analysis to resolve some of the odd bending stress results developed by their model. Pipe deflections, contact loads, and bending stresses are determined with explicit formulas. Sag between connectors is calculated so that pipe body contact with the wellbore between connectors can be determined. Conditions for positive contact forces are determined and compared to previous buckling criteria, such as Paslay-Dawson and He-Kyllingstad.
Applications include the analysis of bottom hole assemblies, drill pipe, casing, and tubing. The solutions are simple formulas that are suitable for hand calculations.
