T.D. Williamson (TDW) carried out a subsea pipeline pressure isolation that protected divers during a wye installation in the Gulf of Mexico.
The installation was of a piggable wye to tie-in a new deepwater oil and gas system in the GoM. The first phase of the program included isolating pressure in a riser so that the wye could be safely installed. Any delays in the first phase would cause delayed plans to bring the new oil and gas system on-stream and produce “first oil” from the field. The pressure needed to be isolated to make certain that the divers, who would be working 228m subsea near the open end of the line, would be safe.
TDW used its SmartPlug tool to isolate pressure in specific sections of pipelines and risers so that repairs or interventions could be carried out safely. Operated by remote control, the SmartPlug tool is certified to “safety class high” in accordance with OS-F101 for submarine pipeline systems. It is also certified and type-approved by Det Norske Veritas (DNV) to execute independent double-block isolation to provide a safe environment for divers while working near a pressurized gas pipeline.
TDW developed a custom solution that provided the dive specialist with a safe, reliable method of isolating the riser and platform from the section that was to be prepared for the wye installation.
TDW conducted a piggability and pipeline stress simulation study by bi-directionally running a modified gauge pig, similar to the SmartPlug tool, to simulate the exact path of the isolation tool during the forthcoming operation. The study confirmed that the SmartPlug tool would successfully traverse the piping and reach its target destination.
Working from the platform, TDW launched the SmartPlug tool into the riser. As the tool travelled through the riser, the TDW team onboard the support vessel used its remote-controlled SmartTrack tracking and monitoring system -which uses two-way, through-wall electromagnetic communication between a transponder and a receiver - to track the tool’s progress, control its speed, and monitor conditions in real-time. When it reached its subsea set location of 228m the tool was set into position where it remained for three and a half days, isolating the riser against a pressure of 914 psi.
Throughout the operation, divers worked near the open-ended line with only the SmartPlug tool preventing the gas pressure from escaping. The wye spool was installed, and the SmartPlug tool was retrieved through a valve fitted with a temporary receiver. The procedure was completed on schedule, without incident.
Image from TDW.
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