Breakthrough multi-string well severance solution used in the Gulf of Mexico

The challenge

Claxton*, a cutting and decommissioning brand in Acteon’s Energy Services division was contracted to provide abrasive cutting services for the severance and removal of a subsea well in 150m. All the work was conducted from an Anchor Handling Tug Supply Vessel, equipped with two ROVs and a 150mT AHC crane. The subsea well removal was the first of its kind to be completed in the Gulf of Mexico region.

The solution

The wellhead system was a Cameron STM15 made up of 16” x 20” internal casings and a 30” Conductor. Claxton utilised the wellhead retrieval tool (WHRT), specially built to lock onto the wellheads 18 ¾” H4 connector. The WHRT is designed to be used in conjunction with the industry leading water abrasive multi-string cutting tool (MSC). Once the severance operation is complete, the 200 tonne WHRT, will recover the severed well back to surface and laid down on the back deck of the offshore vessel.

Claxton drew on their UK based Subject Matter Experts and previous experience cutting subsea wells in the North Sea and Far East. The Cameron STM15 wellhead system had proven challenging to sever in past campaigns. Lessons learned were applied from previous project experiences, including a purpose built, ROV friendly solution for sealing flow by ports. This solution was viewed as critical for the dewatering process and the subsequent success of the multi- string cutting operation.

The result

Despite unanticipated hurdles related to the well make up, the project was completed successfully, meeting all the customer’s requirements. The subsea well severance is viewed as a breakthrough in the Gulf of Mexico region.

*At the time of this project, Proserv FTS was contracted to perform the work. Proserv FTS has since been acquired by Claxton Engineering Services Ltd.