Centralisers

Whilst centralisers may appear simple, they must withstand severe conditions at the critical interface between the platform structure and the well. Our centralisers feature a rugged, fit–for-purpose design that saves operational time and cost in every situation from harsh North Sea environments to low-load applications in the Far East.

Our extensive knowledge and integrated approach mean that our centralisers deliver the performance needed to protect the conductor throughout the lifecycle of the asset.

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When the maximum allowable clearance is less than a fixed-blade design can achieve, an adjustable mechanism is required to reduce the clearance after installation.

Adjustable centralisers are typically fitted at the splash-zone level, where lateral loads are higher and tighter tolerances are required.

There are two main types of adjustable centralisers:

• Shim-type adjustable centralisers are hinged designs constructed in two halves with two bolting flanges and two sets of blades per half. The blades are adjustable by rope-access personnel and are kept to the required extension by installing nylon shims behind the blades.
• Remotely adjustable centralisers are similar to shim-type centralisers, but the blades are activated by a deployment ring that uses hydraulic cylinders to activate the adjusting mechanism. The adjustment is carried out remotely, enhancing operational safety.

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Structural internal centralisers are run on internal strings where there are concerns over the structural integrity of the inner strings and riser and completion analysis indicates a risk of buckling, so a standard cementing (bow-type) centraliser is inadequate.

Our internal centralisers are constructed in two halves, with two joining flanges on each half for easy installation around the plain casing.

The design considers the effect of test pressure in the inner casing as well as the medium that the centralisers will be exposed to throughout their life.

Internal centralisers are commonly designed for radial loads of 5–10 tonnes but can also be designed for high lateral loads of over 20 tonnes.

The annulus medium is also considered when specifying the fasteners and coating to be used for the design.

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We have designed, built and installed thousands of centralisers, including many for complex projects to address even the most unique centralisation challenges.

We have developed new designs and methodologies for centralising conductors for new developments as well as for retrofitting or replacing centralisers on old platforms.

The installation of bespoke centralisers can present a variety of challenges, on top of already-complex drilling programmes or the upkeep of ageing platforms and conductors. We help to simplify these operations by providing centralisers that will be fit for purpose while considering installation methods and schedules.

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Fixed-blade centralisers are used at various levels of a conductor to provide stability from the splash zone to the seabed. They are installed within the subsea guides of a platform and/or at splash-zone level when riser analysis indicates a need for lateral support and a standard range of clearance tolerances.

Fixed-blade centralisers feature a hinged design in two halves with two bolting flanges. The design can include bumpers to prevent metal-to-metal contact. These bumpers are steel inserts coated with a polyurethane elastomer that is durable, abrasion-resistant and impervious to UV and ozone.

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Centralisation is easily neglected during the planning process for new wells, and ever-changing drilling schedules may demand a rapid response.

Additionally, as platforms exceed their anticipated lifespan, equipment needs to be upgraded or replaced. Retrofit centralisers can be fitted with minimal disruption to standard operations.

Retrofit centralisers are fitted between the conductor and the guide after the conductor is already in place. They can also be used between existing pre-installed centralisers that are not performing. They can be fitted at the splash-zone level and on subsea guides.

We have provided several retrofit centralisers in a range of designs to clients all around the globe. We have extensive experience of modifying and retrofitting centralisers and can offer a broad range of proven designs.

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