Lateral buckling of pipe with connectors in curved wellbores

Connectors should clearly have an effect on pipe loading. For nonbuckled 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. Recently, helically buckled and laterally buckled pipes with connectors have been analyzed. In these papers, analytic solutions of the beam-column equations were developed in 3D, and critical loads were determined for buckling initiation. Conditions for positive contact forces were determined and compared to previous buckling criteria, such as Dawson-Paslay. In this paper, the wellbore curvature effects studied by Lubinski, Paslay, and Cemocky are included in the buckling effects. The modifications necessary to analyze lateral buckling are made for a curved wellbore. The resulting model gives a buckling criterion similar to He and Kyllingstad'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 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 bottomhole assemblies (BHAs), drillpipe, casing, and tubing. The solutions are simple formulas that are suitable for hand calculations.