Abrasive severance and recovery solution for gas fields in the Celtic Sea

PROJECT OVERVIEW

An energy operator required services for the severance and recovery of subsea wellheads and subsea cutting and recovery of two Xmas tree piles and the recovery of 36 severed Xmas tree legs on two gas fields situated in the Celtic Sea, off the south coast of Ireland. The subsea wellhead scope consisted of 10 production wellheads, four exploration, and appraisal wellheads, and recovery of wellhead guide bases where applicable.

Claxton, a Cutting and Decommissioning brand in Acteon’s Energy Services division was contracted to provide expert decommissioning services and personnel to perform the decommissioning activities over four weeks during the Spring of 2022.

THE CHALLENGE

Due to the age and unknown condition of some of the wells, a dynamic assessment of each wellhead was required, and equipment would need to be configured accordingly to ensure successful severance. With several differing wellhead configurations in place, an adaptable solution would be applied to each type to enable successfully cut and recovery using the Claxton JetCut spread and associated recovery tooling.

CUSTOMER GOAL

The operator needed to sever and recover the wellheads 10ft below the mudline whilst mitigating any potential issues associated with the integrity of the aging wells using a proven full-service solution. Due to the fixed-price nature of the project, all wellheads and Xmas trees needed to be completed within the scheduled timeframe to avoid additional costs.

OUR SOLUTION AND ITS COMMERCIAL BENEFITS TO THE PROJECT

Develop market leading services and integrated solutions

• Claxton provided equipment for each aspect of the scope as one complete package to severe and recover wellheads below the mudline by integrating solutions for internal and external cutting scenarios; including a diamond wire saw for the severance of the Xmas tree legs.
• An internal wellbore lifting, and recovery method was utilised for the wells which had a guide base installed.
• Integration of newly acquired Oceaneering seal assembly successfully sealed the wells for cutting.
• Of the 14 wellheads, ten were abrasively severed and recovered and three were recovered as per the pre-agreed contingency plan, where abrasive severance was not possible.
• Claxton dynamically assessed each wellhead and configured equipment accordingly to overcome the challenges associated with lack of well data and ensure successful severance.

Work at scale with a proven track record for delivery

• The experience gained from Claxton’s track record for abrasive cutting and recovery of wellheads was applied during the project to provide an effective solution to cut and recover the aging infrastructure.

Optimise the project to increase commercial value

• The work scope was completed on schedule to ensure that the customer did not encounter any additional vessel time.

Minimise the environmental impact

• Severing wells at or below mudline removed the environmental impact of having wellhead stick-ups on the seabed.

PRODUCTS USED

• Jetcut Spread
• Multi-Wellhead Recovery Tool
• MSC 2.0
• Diamond Wire Saw (06-48)
• Internal Lifting Tool
• Subsea Grab

SUPPORTING INFORMATION

“The age and condition of the wells was the key challenge on the project. Claxton worked closely with the customer to plan the project carefully before the offshore phase and evaluate the risks. The management of risk combined with Claxton’s leading technology and expertise supported a successful conclusion and on time delivery,” said David Anderson, Claxton Regional Manager.

Download a copy of this case study