The Criterion of Lateral Buckling and Axial Walking for HPHT Offshore Pipelines

Abstract

Offshore pipelines that deliver raw fluids usually work under high temperature/high pressure (HPHT) conditions to ease the flow and prevent the solidification of wax fractions. Under HPHT conditions, lateral buckling and axial pipeline walking can occur. Existing studies have shown that axial walking is prone to occur in short pipelines and lateral buckling tends to occur in long pipelines. However, there is no clear definition for distinguishing between short and long pipelines, nor are there criteria to determine the occurrence of these two behaviors under certain conditions. In this study, the relationship between the length of a pipeline and lateral buckling critical temperature was derived based on an analytical solution, considering the influence of tension forces and seabed slope angle. A theoretical analytical solution of axial walking was reviewed and summarized. The two solutions for axial walking and lateral buckling were combined, and a criterion based on critical pipeline length was proposed to estimate the possibility and priority of these two behaviors for a given pipeline under certain conditions. The influence of seabed slope and axial and lateral friction factors on the two behaviors was explored by carrying out parameter analysis, and the influence regularity of these factors on critical pipeline length and critical temperature was obtained.