Decommissioning

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Decommissioning

I need a turnkey decommissioning solution to simplify my operations for my project

Claxton and the Acteon group of companies has experience in delivering effective turnkey packages to fit clients’ bespoke needs. Our expert engineers will recommend a tailored solution, based on specific project requirements from our array of rig-based and rigless decommissioning technology and methodology. Options include:

Wellheads and Xmas tree service provision for phase I well intervention and well kill operations
Well control equipment, BOPs, risers and adaptors for plugging and abandonments of wells
Tubing recovery
Regulatory, below mudline – multi-string, well severance services
Combined conductor and casing recovery, sectioning and lay down services for safe disposal
Simultaneous operations (SIMOPS) to safely reduce the critical path timeline.

A Claxton bandsaw being used to cut an offshore conductor

What depth can you cut at?

This is something we get asked regularly. To answer accurately, we need to understand the specific requirements including; what needs to be cut, the configuration of the well, the annuli contents and eccentricity.

As an example, Claxton has successfully performed cuts on platform wells from inside heavy wall casing from 7” out to 30” through fully water filled annuli in up to 125m of water.

As part of our decommissioning technology plan, Claxton’s in-house R&D team have been designing the latest models of our subsea well abandonment equipment with the firm target of 250m cut depth – so watch this space.

HOW DO I OPTIMISE MY DECOMMISSIONING OPERATION?

There are many ways to optimise an abandonment operation, depending on which stage the project is at. To take full advantage of the services provided by Claxton, we advise paying consideration to optimisation during the pre-engineering phase.

The goal is to reduce time and cost, whilst not compromising safety and the quality of the abandonment solution. Claxton can demonstrate this through innovative methodology including; simultaneous operations (SIMOPs), rigless abandonment, tubing abandonment and cheaper deployment of vessels.

Every project will have bespoke aspects and challenges which will steer the optimisation solution. Claxton pioneered many of these techniques and developed proprietary equipment to help fully realise project potential.

What can be done to reduce the cost of a decommissioning campaign?

Claxton will need to gain a clear understanding of the decommissioning programme in question to allow us to design a package and workflow that will safely aim to reduce working days on the project.

From our 25-year experience we are certain that each installation or well group that needs to be decommissioned will present a unique set of criteria and considerations. These need to be carefully reviewed to devise the optimum plan of execution and this calls for close collaboration with the client.

Time and cost savings can be achieved through simultaneous operations (SIMOPs) on a rig-based campaign or by totally removing the need for a rig if possible; Claxton firmly believes in using the right equipment for the job.

For us, this means driving down the utilisation of the high-cost assets and only using a rig when absolutely required. By enabling clients to perform many phases of a decommissioning campaign without the use of a rig, huge efficiency and cost savings can be achieved.

Claxton has an excelled track record of conducting well decommissioning campaigns using a jack-up lift barge (JULB). We have proven that this methodology is ideal for the ageing assets out there, especially those in the North Sea.

Claxton’s rigless well abandonment packages are complemented by our well recovery system, WellRaizer®, with a newly developed mast, which allows us to perform plugging and abandonment (P&A), along with the cutting and retrieval of wells. This offers significant cost savings as opposed to using a rig. Savings are further enhanced through the deployment of our multi-skilled crew, minimising personnel on board (POB).

Our expert view

“Claxton has an excelled track record of conducting well decommissioning campaigns using a jack-up lift barge (JULB). We have proven that this methodology is ideal for the ageing assets out there, especially those in the North Sea.”

Matthew Marcantonio - Head of Decommissioning, Claxton

Can Claxton can supply the services to decommission platform wells?

Yes, we can. As all decommissioning campaigns are unique, it is vital that we understand the full requirement to provide the most efficient solution. We would first investigate if a rig is required or if there is scope for rigless operations. We also need to understand the status of the wells and if there is a P&A plan in place. Claxton recommends that operators engage with us as early as possible to enable us to assist with planning from the offset. We can offer collaborative workshops with our clients to help determine the best solution for their challenge.

To avoid dropped objects, how would you remove a multi-string conductor and casing package if the conductor is corroding and in danger of collapsing?

Corroded conductors and failing connectors are a common problem, therefore we use specialist dropped object protection. Over the years Claxton has developed a variety of methods to mitigate risks associated with ageing conductors and we realise that there is no ‘one size fits all’ answer. Whether it is by means of internal anchors, catch tools, sacrificial strength members or a bespoke solution, rest assured that Claxton has the knowledge and experience to provide the most effective solution for the project.

The installation has a restricted crane capacity

With ageing assets, this is not an uncommon problem and something which Claxton has developed specialist equipment for. All Claxton decommissioning equipment is designed to be modular, with no module weighing more than 11Te. We also have experience in supplying secondary cranes, where space allows, to service deck operations, minimising the utilisation of the platform crane. In critical cases we would suggest the jack-up lift barge (JULB) approach.

The platform has space restrictions, how do I plan an abandonment project?

Space is a common challenge, especially in the southern sector of the North Sea, where assets tend to be small manned or unmanned platforms. However, a lack of space doesn’t not always mean that a rig is required to perform well abandonment.

Where POB (personnel on board) and deck space are at a premium, Claxton can advocate a jack-up lift barge (JULB) approach. These self-propelled units offer valuable additional deck space and accommodation, plus often have excellent crane capabilities.

Over the years Claxton has developed numerous equipment spreads, such as the SABRE™ abrasive severance suite and the light weight recovery deck, to help deliver this cost-effective for our clients.

I have a failed conductor – where do I start?

Failed conductors, caused by corrosion or suspect connections are common place, posing the risks of parted casings and dropped conductors. To combat this, Claxton has developed both downhole and external tooling to provide security where required. Our subsea drilling and pinning inflate anchor/lifting tools plus conductor catch tooling can all ensure confidence during the operation.

The Claxton equipment, in conjunction with using the internal structure of the well or sacrificial string as a strength member, allows the casing string to be locked together and lifted from below. This methodology effectively lifts using compression not tension, reducing the risk of separation.