Multi-string well severance

Gulf of Mexico

Background

Client: Apache Corporation

Location: Mississippi Canyon 357

Equipment: 15k multi-string abrasive cutting system, internal pipe cutting tool

 

The first of its kind subsea well removal  to be completed in the Gulf of Mexico region.

Proserv was contracted to provide abrasive cutting services for the severance and removal of a subsea well in 450 fsw.  All of the work was conducted from an anchor handling tug supply vessel, equipped with two ROV’s and a 150mT AHC crane.

Scope

The wellhead system was a Cameron STM15 made up of 16” x 20” internal casings and a 30” conductor. Proserv 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 (MSCT).  Once the severance operation is complete, the WHRT is rated for a 100 ton pull to recover the severed well back to surface and lay it down on the deck of the offshore vessel.

Proserv drew on their UK based subject matter experts with previous experience cutting subsea wells in the North Sea and Far East.  The Cameron STM15 wellhead system had proven to be challenging to sever in past campaigns.  Lessons learned were applied, which included a purpose built, ROV friendly solution for sealing flow by ports.  That solution was viewed as critical for the dewatering process and the subsequent success of the multi-string cutting operation.

Conclusion

Despite unanticipated hurdles related to the well make-up, the project was completed successfully, meeting all of the client’s requirements.  The subsea well severance is viewed as a major breakthrough in the Gulf of Mexico region.   The project could not have been completed without the tooling and technical support from multiple Proserv business units, as well as meticulous planning led by Apache Corporation.  As a fully integrated services provider with a global presence, Proserv is well positioned to provide an unrivalled scope of decommissioning solutions.

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