STATS Group were contracted by a major operator to supply high pressure isolation plugs to provide a double block and bleed isolation barrier for the safe tie-in of a replacement section of the main 24-inch oil export line from the Platform. Located in the Central North Sea the isolation needed to be completed without having to de-oil the entire 80km pipeline.
To facilitate the double block isolation and enable a reinstatement leak test in accordance with the pipeline design code, STATS provided two remotely controlled Tecno Plugs™. The first Tecno Plug™ provided a proven double block isolation from pipeline pressure. The second Tecno Plug™ provided a local leak test boundary. Using two plugs in this manner maintains a safe isolation until the leak test is completed and prevents pressurising the entire pipeline up to leak test pressure.
An expert isolation committee of a subsea engineering and construction company, which included their global technical risk experts, assessed the suitability of the high pressure remote isolation plug as a double block barrier for diver breaking containment activities. The critical operational areas of concern were scrutinised and the Tecno Plug™ was deemed to provide an acceptable isolation barrier for the required work scope.
Prior to award of the isolation work scope STATS conducted a detailed engineering and piggability study to confirm the fitness for purpose of the Tecno Plug™. Further reassurance of piggability and reduction of risk was achieved by deploying a geometry proving pig and a high resolution Inline calliper survey tool.
The primary project objectives of safety and efficiency were delivered to ensure a minimal shut down period was achieved. Excellent project management, intercompany team working and appropriate use of isolation technology resulted in a successful pipeline replacement that was completed in a timely manner.
Dale Millward, STATS Group director of EPRS and subsea services, commented on the successful project: “Although not our first subsea isolation, this project is a milestone subsea isolation project that shows how far we and our technology have progressed since the introduction of STATS remote isolation plug technology 10 years ago.”