The majority of the deepwater pipelines operating in the Gulf of Mexico (GoM) carry hydrocarbons at ahigh pressure and temperature resulting in the system’s thermal expansion. In order to relieve the highstresses due to thermal expansion, these pipelines are designed to use buckle triggers in order to bucklelaterally at pre-determined locations. Since these assets are expected to last a few decades, it is imperativethat a robust long-term integrity management program is in place to effectively operate these pipelines,monitor their long term performance, verify design assumptions and thus, reduce any potential risks.As a part of BP’s comprehensive In Water Integrity Management (IWIM) program, three pipelineswere surveyed during a 2012 Multi-Beam Echosounder (MBES) survey campaign. The surveys checkedfor buckle initiation, buckle locations and obtained accurate buckle shapes to allow subsequent integrityassessments to be performed. Ten out of ten planned buckles formed across the three operationalpipelines; a mixture of sleepers and buoyancy modules initiated these buckles at pre-determined locations.Smaller buckles were also observed at unplanned locations in the pipeline system. These pipelinesterminate at subsea structures situated at the ends of the pipelines. In order to track the pipeline’slong-term global movement; the end displacements at these structures were recorded as well.During its operation, a pipeline system will be shut-down and re-started multiple times, thus creatinga series of thermal cyclic loadings. In order to ascertain the long-term performance of the pipelines undersuch sustained thermal loading cycles, a Finite Element (FE) model is built using the pipeline data, seabedbathymetry and other environmental conditions. The FE model is calibrated using the recorded 2012MBES survey in-service pipeline lateral buckling profiles. The calibrated FE model generates axial stressranges at critical locations (buckle crown); these stress ranges are subsequently used to perform fatigueanalyses. The estimated fatigue damage is used to forecast the pipelines’ long-term fatigue performance,which will determine the future inspection and monitoring plans.This paper presents an overview of the 2012 MBES Survey conducted on three of BP’s operationalpipelines as well as the subsequent FE and fatigue analyses performed to assess the long-term integritywithin lateral buckles.
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