This paper is based on the experience made during the installation of an offshore pipeline recently completed in Indonesia, where a 24” subsea production pipeline (16&nbsp;km long in 70&nbsp;m water depth) was found susceptible during design to lateral buckling. To limit the development of excessive deformation within the acceptance criteria, a mitigation strategy based on interacting planned buckles has been adopted installing three Buckle Initiators (BI) along the pipeline route.Buckling is a well understood phenomenon. However, this project was characterized by major uncertainties mainly focused on soil characterization, soil-pipe interaction and seabed mobility. These uncertainties have played a key role in the in-service buckling design. A lot of engineering efforts have been spent to go through the screening between alternative concepts, the validation of the chosen solution and its detailed engineering phase. This paper discusses the main contributing factors and how the uncertainties have been tackled.The Buckle Initiators are quite large and heavy structures with two main bars: the first ramp has an inclination equal to 30° and the pipeline will be laid on it; a second horizontal ramp was used as sleeper to accommodate the development of the lateral buckle during the operating life. A rotating arm was also used to restrict the pipeline lay corridor on the inclined ramp guaranteeing a combined horizontal and vertical out-of-straightness in the as-laid configuration. The foundation of the Buckle Initiator has a footprint surface of about 60&nbsp;m2 guaranteeing its stability for different soil types. This more complex solution was preferred with respect to a typical sleeper to increase the robustness of the system in terms of buckle mobilization.The design of the Buckle Initiator was a multidisciplinary activity where many novel concepts were developed and many issues were faced (i.e. pipeline laying on an inclined sleeper, anti-scouring system, foundation design, trawl-gear interaction, etc.). &nbsp;The Buckle Initiator design was focused on structural calculations against design loads expected during temporary and operating conditions, geotechnical verifications, installation analysis, pipeline configuration and fatigue assessment.This paper presents all main engineering aspects faced during design and first feedbacks from field after the pipeline installation.

Tangguh Project: Multidisciplinary and Challenging Design of a Novel Concept of Buckle Initiator

Paper Proceedings: https://asmedigitalcollection.asme.org/OMAE/OMAE2021/volume/85116

OMAE 2021

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