Reliability of offshore pipelines subject to upheaval buckling

Abstract

Offshore pipelines are used to transport oil and gas in different areas of the world. The economic importance of offshore pipelines has increased in recent years with the development of oil and gas transportation systems. Hydrocarbons are transported in the pipelines at high temperature and pressure in order to facilitate the flow of oil and to prevent its “solidification”. However, these high temperatures and pressures may force the pipeline to buckle either in the horizontal (lateral) or in the vertical direction (upheaval). The latter buckling mode may lead to pipeline failure which could cause massive oil leakage and severe environmental damages. Several experimental studies have investigated the uplift resistance of buried pipelines with different soil cover depths, while other studies have proposed analytical and empirical methods that aim at predicting the response of a pipeline that is subjected to upheaval. The objective of this paper is to investigate the effectiveness of some of these methods by assembling a database of published model tests conducted on pipelines that were subjected to uplift. By comparing measured and predicted uplift forces, a quantification of the model uncertainty could be accomplished. A reliability analysis was then conducted to quantify the probability of failure and reliability index for pipelines designed using different factors of safety and cover heights.