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Three new tools were custom-engineered during a riserless plugging and abandoning job in the Gulf of Mexico.
As the old adage goes, “necessity is the mother of invention,” and that is never more relevant than when working on a unique problem in deep water.
That’s the situation that Wright’s Well Control Services (WWCS) was facing in the Gulf of Mexico (GoM) in June while plugging and abandoning (P&A) a well in more than 300 m (1,000 ft) of water.
This was a riserless operation undertaken from the multiservice vessel HOS Achiever. DOF Subsea USA provided marine and subsea services.
What made the project unusual was the Dril-Quip wellhead, a one-of-a-kind piece of equipment, which would require innovation from start to finish. The wellhead had a subsea annulus monitoring flange at a 35° angle, pointing down. The flange needed to be removed to take returns and monitor the casing annulus during the P&A operation.
WWCS quickly discovered there were no off-the-shelf ROV tools that could perform those functions. The company needed to be able to nipple down on the old flange and nipple up on a newly installed flange – with all the work done subsea.
The concept for a new torque tool was developed, and the tool was designed and built. After the sub-base was removed, WWCS rigged up the new ROV torque tool to nipple down the flange at a 35° angle and nipple up the new flange with a 2-in. hot stab.
The next innovation was under way at the same time, with the company designing a new subsea connector that would allow the Dril-Quip tree-running tool (TRT) to remain subsea for the entire job. This step required a new hydraulic connector that would allow WWCS to engage and disengage a subsea BOP and lubricator – while leaving the TRT subsea – in case problems arose.
WWCS tested the TRT at its Lake Charles, La., facility. It was modified to include an emergency disconnect, a 15,000-psi fail-safe ball valve, and low-torque valves.
The third innovation was the modification of a Dril-Quip tubing-hanger pulling tool so tubing could be pulled using a crane subsea.
With all the tools designed, built, and tested, WWCS was ready to load the equipment on the boat for the P&A operation.
One of the vessel’s two moonpools was used to run the coiled tubing (CT) string and an umbilical, while using the other to pull the tubing and casing to the surface.
During the P&A operation, the company set six cement plugs and three cast-iron bridge plugs as well as cut and pulled 37 joints of 3 1/ 2 -in. tubing, 230 m (750 ft) of 9 5/ 8 -in. casing, 13 5/ 8 -in. casing, and 20-in. by 30-in. casing with a mechanical cutter below mudline.
The entire P&A operation was done in 30 days. In noting the innovation required, WWCS President David Wright, said, “We executed a very challenging subsea P&A utilizing four new subsea tools, including a jumper that we designed and built while on location.”