The paper presents how Dolphin Energy's Emergency Pipeline Repair System'ASSIST'(AdvancedSubsea Intervention Support & Technology)has addressed the challenges of being ready to decommissionand recommission a large diameter high pressure gas pipeline during a pipeline repair in the shortestpossible time,while also protecting onshore assets.The challenges in temporary decommissioning andrecommissioning of a large size high pressure gas pipeline are demanding,due to the complex technicalrequirements and the need to intervene quickly.This case study shows how Dolphin Energy has tackled thistechnical challenge by developing bespoke subsea tooling not available from the market.At the same time,the company has balanced its commercial responsibilities by ensuring third parties provide other tools andresources required during an intervention.This means Dolphin Energy can study available resources fromcontactors'over the long term,ensuring resources are available as and when needed.To address this challenging technical requirement,ASSIST has implemented the following threesolutions:1.Development of a unique subsea launcher & receiver covering Dolphin Energy's 48"and 36"subsea pipelines;this allows the pipe to be decommissioned and isolated on the seabed,thusenabling the repair to proceed in a dry condition without the need to recover the inventory of aflooded pipe at one of the terminals.The subsea tool does not require extensive subsea preparations 2.Procedures and processes to allow decommissioning to start in the shortest possible time have beendeveloped 3.An on-call LTSA Provider,capable of providing equipment and personnel to meet the demandingrequirements of decommissioning and recommissioning large gas pipelines.This includes regularmonitoring of market capabilities and availability of equipment and personnel By implementing these three steps,we ensure that decommissioning and recommissioning of the pipelinedoes not become'bottle necked'.The impact on asset integrity has also been minimized.
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