US-based TDW Offshore Services has concluded a subsea pipeline pressure isolation operation in the Gulf of Mexico.

TDW carried out the operation at a depth of 70ft (113 m) against 870 psig to enable the safe and effective tie-in of a piggable wye to the Mississippi Canyon Gas Pipeline and the Venice Gas Plant in Louisiana.

"The isolation project has utilised two remote-controlled 30-inch SmartPlug dual module pressure isolation tools to isolate 45 miles of pipeline."

The Mississippi Canyon Gas Pipeline, owned by Enbridge, is a 30-inch natural gas line running between the West Delta 143 platform which forms a hub facility for deepwater oil and gas production.

The isolation project has utilised two remote-controlled 30-inch SmartPlug dual module pressure isolation tools to isolate 45 miles of pipeline.

Commenting on the operation, TDW project manager Bjørn-Olav Gilje said: "The SmartPlug® isolation tool is certified to ‘Safety Class High’ in accordance with OS-F101 for submarine pipeline systems and is uniquely suited for use in connection with diving operations."

Technicians at TDW on board the Norman Commander vessel constantly monitored the locations of the SmartPlug tools during the operation to subsea set destinations, using the SmartTrack system.

The SmartTrack system, which is a tracking and pressure monitoring system, uses two-way, through-wall, electromagnetic communication between a transponder and a receiver to track tool progress.

The first module on the second tool provided a hydraulic locked barrier of the high pressure side, for the divers installing the wye, while the second module was used to perform a leak test to verify the integrity of the new wye after installation.

One of the tools, both of which contain two plug modules and two pigging modules, has provided double block isolation on the high pressure side of the tie-in location. After setting the tools, it roughly took about two and a half weeks for the isolation, the company said.

"TDW worked with the client and their contractors over several months to ensure that associated risks were evaluated and mitigated," Gilje added.

"This thorough up-front planning resulted in a successful tie-in operation for our client."

TDW Offshore Services is a subsidiary of T.D. Williamson, which provides products and services to construct and maintain pipelines.