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A case of collaborative technology

Published by , Deputy Editor
Oilfield Technology,

According to a recent report from the North Sea Transition Authority (NSTA), the oil and gas industry spent £1.6 billion on decommissioning in 2022 alone which is the highest annual spend recorded to date. With a predicted £21 billion of spending forecast for the next decade, this presents significant opportunity for the supply chain.

The UK Continental Shelf is home to some of the most mature fields in the world and with ageing reserves, many operators must begin the complex task of decommissioning infrastructure, including wells. With the industry remaining focused on driving cost efficiencies, decommissioning and the use of efficient Plugging and Abandonment (P&A) technologies are more important than ever.

During a recent North Sea P&A project, Coretrax, and Lee Energy Systems (LES), leaders in wellbore integrity and production optimisation, joined forces to deliver a one-trip solution utilising Coretrax’s CX-2 bridge plug and CX-RTP (retrievable test packer) in conjunction with Lee Energy System’s Gator Hydromechanical Perforator to garner greater efficiencies.

Effective P&A through combined solutions

A major operator was seeking a more efficient solution for remedial annular cementing and plug placement across eight wells, which would be more efficient compared to conventional methods. The company had assessed potential suitable technology, but selected Coretrax and LES’ combined solution given its proven track history.

Within a few weeks, the two companies executed a detailed planning exercise to understand the current casing specifications and mobilised offshore. The one-trip system was run in hole and the CX-2 bridge plug was set in the 9-5/8 in. 53.5# casing to provide a cement base.

Designed to set with a combination of hydraulic pressure and mechanical pull, the system has a built-in setting mechanism, delivering improved efficiency. It is constructed with drillable materials and the tool features a release system which is unique in that it releases with a slick stinger with a large ID, reducing the requirement for a dedicated cementing trip and minimising cement disturbance when pulling out of hole.

Once the CX-2 was successfully set, released and pressure tested, the Gator was subsequently activated to hydromechanically perforate at two depths, creating a circulation path between two sets of Gator perforations.

The tool is an alternative to traditional perforating guns and requires no explosives, delivering a much safer solution. With each activation creating four large perforations delivering a large TFA, and the ability to conduct unlimited activations per run, the system delivers a 360° flow path to the formation or annulus. This allowed an average clean-up rate of 20 bbl a minute at 500 psi.

The CX-RTP was then set, and following confirmed circulation, a drop ball circulation sub was opened to isolate the Gator assembly below. Cement was subsequently pumped and squeezed into the outer annulus through the perforations before the CX-RTP was retrieved. In the final stage of the operation, cement left on top of the CX-2 was successfully tagged and pressure tested to ensure full integrity. Engineering modifications were also implemented to the Gator and CX-2 to ensure the technologies were compatible for use in this single trip application, further reducing rig time.

Reducing costs through improved efficiencies

Across the eight wells, setting depths ranged from 850 ft – 4000 ft with an array of casing sizes and all tools were successfully supplied and refurbished onshore between deployments. During the project, the average time to effectively P&A each well was 15.5 days, compared to the NSTA’s benchmark of 23 days, highlighting a 33% improvement on the industry standard.

With increasing pressures to reduce decommissioning costs, collaboration amongst the supply chain is essential. By deploying combined technologies, operators can actively reduce rig time and deliver more effective environmental barriers.

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