Abstract
Capacity to repair subsea oil and gas pipelines have become not only an economic important issue but also a strategic position in today's global energy security. The 2022 sabotage actions to gas pipelines in Baltic Sea changed the context of pipeline repair preparedness.
"Prepared for the unplanned" suddenly got a meaning beyond the technical level, and the Norwegian based Pipeline Repair and Subsea Intervention (PRSI) Pool showed to be an even more strategic asset than in the past 30 years.
The PRSI Pool operated by Equinor on behalf of 24 operators have for more than 3 decades developed technology and performed both planned pipeline tie-ins as well as pipeline repairs using both hyperbaric welding and mechanical connectors. This paper presents the technology and applications; remote controlled hyperbaric welding used for hot taps and tie-in and repair of large diameter pipelines, how technology was qualified, the offshore track record since introduction and how it may be expanded to water depths of 3000 meter and new material combinations.
The fully diverless, remote controlled robotic hyperbaric welding operation is performed in an inert, dry gas atmosphere in a subsea installed habitat. The pipeline joint is using a novel engineered weld profile, Gas Metal Arc Welding and process monitoring as input to the quality control of the weld. Welds are considered "golden welds" in accordance with DNV which makes time consuming hydrostatic testing to be omitted.
After four successful subsea tie-ins the system is now well proven and demonstrate the capacity both for planned tie-ins and emergency pipeline repairs. Next development step is to extend depth capacity from todays 1300 meter to 3000 meter and to qualify repair of bi-metallic pipelines (metal clad or lined pipelines).
