Skip to content

Four key North Sea well abandonment projects

LEMAN A1

The failed conductor and a Claxton tension ring – part of the novel package we developed to recover the conductor.

The abandonment of Leman A1 by Claxton opened the door to rigless platform well abandonment.

Well A1 in the field had suffered corrosion fatigue failure of the 20 inch conductor, 6 metres below sea level. Partial fracturing and wear to the caisson were also observed. The well was immediately shut in and, due to concerns about the integrity of the conductor, a full abandonment operations needed to be carried out before winter weather set in.

Claxton were called to devise a strategy for the P&A of the well, and  to provide project management through the operational phase as well as the recovery of multiple casing tubulars and abrasive cutting services.

The package of equipment Claxton developed ensured the first rigless well abandonment was completed safely and since the project, rigless decommissioning and slot recovery operations have become increasingly common.

SAVING APACHE £1.5M VIA RIGLESS TUBING RECOVERY

Left: Claxton’s offshore crew recovering the tubing. Right: Part of Claxton’s bandsaw fleet cutting a conductor on another project.

After being tasked with recovering 5,000 metres of tubing from five wells, Apache chose Claxton to provide technicians and implement a bespoke recovery system. The in-house design team created a recovery system to interface with the client’s platform and enable tubing to be pulled through. This was then cut by Claxton’s cutting fleet including bandsaws and abrasive jet cutting technology.

The results of the methodology meant cost and time were saved from recovering the tubing to the tune of £1.5 million.

This was completed by 12 service technicians working on a 24-hour basis to recover the 1,000 metre length of tubing, with an average string weight of 27,000kg, from each of the five wells.

TYRA EAST FIELD

One of Claxton’s 300te tension rings was used to secure the conductor during the slot recovery operation – holding the conductor in place while it was drilled, pinned and recovered in sections. 

Claxton took away a significant operating headache for MAERSK in 2013, completing a rigless slot recovery and, in the process, performing the first-ever rigless retrieval of a stuck bottom hole assembly (BHA).

Originally drilled in the 1980s, the well during its construction saw the BHA had become stuck, preventing the well from being completed and contributing to the gas production.

Claxton provided the cutting and recovery equipment needed on the project – which included cutting and recovering the BHA in sections – and devised a unique whipstock which would allow a new conductor to be kicked off in any direction.

Although safety and missing deadlines are two major concerns in slot recoveries, this operation and the rigless approach, saved substantial rig time in fact, despite time spent waiting on weather, the operation was completed four days ahead of schedule.

BUILDING ON EXPERIENCE

As the decommissioning industry continues to grow in scale it is increasingly important for operators to engage with the supply chain to develop new strategies and approaches to the issues posed.

The above projects demonstrate the well-proven adage that there’s no substitute for the oil and gas industry ‘learning by doing’. As the volume of decommissioning work continues to ramp up, the experience of companies like Claxton will be key in ensuring safe, reliable and cost-efficient abandonment operations.

Decom case study pack
E-book download

Decommissioning Case Study Pack

The Claxton offshore decommissioning case study pack showcases our vast experience of delivering successful decommissioning projects.

Download