TDW Services Completes Deepwater Pipeline Isolation
TDW Offshore Services L.L.C. (TDW) has announced that it successfully completed a pipeline pressure isolation operation in the Gulf of Mexico for a major operator. The operation made it possible for the operator to safely replace a faulty shut down valve (SDV) located above the riser on a platform situated off the coast of Louisiana. The riser leads to a pipeline that plays a central role in transporting gas through a key transportation system.
When it became apparent that an SDV on this line would have to be replaced, the operator examined the situation closely. The engineers concluded that they were not confident that the two downstream valves would be capable of isolating the pressure while the faulty valve was replaced.
‘Double-Block’ Isolation
To ensure that the SDV would be safely replaced, TDW was retained to provide a field-proven solution. TDW would perform a “double-block” isolation against the gas pressure in the designated riser using two SmartPlug isolation plug modules linked together. TDW would monitor the location of the SmartPlug modules continuously as they traveled along the pigging route using its remotely-operated SmartTrack tracking and pressure-monitoring system, providing further assurance that pressure in the riser would remain properly isolated during installation of the new SDV.
“By using this method, the operator would not only create a safe working environment for the valve replacement operation, its in situ gas inventory would be maintained at working pressure,” said Mike Benjamin, Vice President of Offshore Pipeline Solutions for TDW. “The operation would be achieved without venting or flooding the line, which would disrupt flow and cause downtime on neighboring developments.”
Safely Replaced
In keeping with new U.S. safety, environmental and risk mitigation regulations, TDW and the operator prepared for the operation by carrying out extensive hazard identification exercises and equipment testing. Extraordinary levels of on-site operational redundancy were incorporated in preparation for the operation.
Working from the platform, TDW launched the SmartPlug modules, using the SmartTrack system to monitor pressure and track them. The modules were pigged in for 80-ft – traveling under a flow rate of 30 – 40 gallons per minute at approximately 131 bar (1900 psi) – until reaching their destination near the top of the riser. TDW set the downstream SmartPlug module and bled the topside pressure to approximately half of the riser pressure. With data communicated by the SmartTrack system confirming the integrity of the downstream seal, TDW technicians set the upstream SmartPlug module and monitored the pressure between modules until they were confident that the module was holding pressure. The SDV could be safely replaced.