Guideline for design of flexible pipes against upheaval buckling, Phase II

The project goal is to establish a guideline for safe design of unbonded flexible pipes with due regard to upheaval buckling.

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Background

In 2022, DNV spearheaded a Joint Industry Project (JIP) to address the growing concerns over upheaval buckling (UHB) in flexible pipes in the North Sea oil and gas industry. This initiative came in response to a series of UHB incidents, notably a flexible water injection pipeline failure during pressure testing in January 2019. Unlike rigid pipelines, flexible pipes exhibit different bending stiffness and installation characteristics, influencing their susceptibility to UHB. The JIP's aim is to refine the application of the existing DNV-RP-F110 Global buckling standard to flexible pipes, ensuring safe and reliable designs.

Objective

The JIP Phase II targets enhanced design guidelines that mitigate overly conservative approaches and reduce seabed interventions. The objective is to establish a uniform industry standard for UHB design, improving the consistency of UHB analysis verification and increasing confidence in buried flexible pipes. This phase also intends to extend best practices in the evaluation and verification processes across the industry.

Description

The scope of JIP Phase II includes several pivotal activities:

• Project management and cost control: Oversee project logistics, including workshops and steering committee meetings, emphasizing cost-efficiency and timely execution
• State-of-the-art review of UHB design: This involves re-evaluating existing guidelines based on recent UHB incidents and feedback, aiming to identify and integrate best practices into the new guideline.
• Improving design methodology for irreversible displacements: Focus on enhancing the design approaches and acceptance criteria for scenarios where pipelines exceed initial soil mobilization distances.
• Inclusion of continuous snaking methodology: Develop procedures to introduce controlled lateral buckles, reducing the risk of UHB in pipelines laid in clayey soils.
• Review of survey capabilities: Assess the current survey techniques to ensure accuracy in pipeline laying, which is critical for evaluating UHB risks.

Deliverables

The deliverables of this project are designed to facilitate robust discussion and development of the new guidelines. These include detailed project reports, technical memos, and an updated guideline that aligns with DNV's Recommended Practices, slated for completion and review by December 2025.

Tentative timeline

The project phases are set to unfold over the next year and a half, starting with initial information meetings and partner recruitment from June to September 2024, followed by contract negotiations and culminating in the guideline's completion by the end of 2025.

Budget and funding

The estimated budget for JIP Phase II is NOK 3,000,000. Participation fees vary, with new partners required to contribute additionally towards the costs incurred in Phase I, ensuring all participants are on an equal footing regarding the project's foundational knowledge and resources.