Maersk Oil – Engineering a unique solution

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Submitted by Maersk Oil

Impact

Replacing the buoyancy modules on a live riser system has never successfully been completed before. The Maersk Oil team met this challenge head on and developed an innovative solution, avoiding the need to replace the riser completely. The project only took around two and a half weeks and cost around 16% of the average fee of replacing a riser. Throughout, there was no production loss and no need for diving personnel, reducing the risk to human life.

Description of Best Practice

Replacing the buoyancy modules on a live riser system has never successfully been completed before. The Maersk Oil team met this challenge head on.

Rather than replacing the whole riser, an extremely time consuming, expensive and risky operation, the team sought an alternative way to correct the slippage. A rough concept was put to the supply chain: we wanted to fix the problem in a targeted manner using an ROV, allowing us to move away from conducting saturation diving operations for repair or replacement. This also allowed the team to engineer a solution which could be implemented whilst in operation.

In collaboration with SubC Partner, inventor and owner of the technical solution, a bespoke tool was created over six months which connected to a ROV. As EPCI contractor, SUBC Partner’s was responsible for: conceptual/detailed engineering; construction of subsea and support tools; supply of vessel/ROV; supply of manpower and project management.

The tool had to be specially developed for the task because there were a number of specific requirements: it had to work underwater whilst connected to the ROV, dock onto the riser and remove the old buoyancy module and inner clamp from the riser. Then bring the old parts to the surface, pick up the new clamp and module and go back down to the riser to install the new parts. Furthermore, the new clamp was installed with rubber compliant pads to stop future slippage; a technique already effectively used by Maersk Oil.

In the end, the team found an innovative solution to a complex issue, avoiding the need to replace the whole riser, the only other viable option: the project only took around 2 and a half weeks and cost around 16% of the average fee of replacing a riser. Throughout, there was no production loss and no need for diving personnel, reducing risk to human life.

Contact: Danielle O’Donnell
danielle.odonnell@maerskoil.com

Centrica – Rose well abandonment

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Submitted by Centrica

Impact

The job was executed in 9.5 days vs the estimated 6.5 days due to slight issues which arose. Although the completion was delayed by 3 days it was still completed in half the time that option 1 would have taken.  By adopting this new method, the project was completed in less time and with reduced risks of increased costs occurring due to complications occurring.  By looking for new innovative processes available we have improved our efficiency by plugging the well using less time and less costs.

Description of Best Practice

Whilst preparing to decommission the Rose field in the Southern North Sea, it was identified there was a challenge to isolate the over pressured Plattendolomit formation.  Due to tops of cement and casing configuration within the well, there were only limited options available for setting the abandonment plug.  Three options were considered, reviewed and the best approach selected.

The option Centrica chose to go ahead with was to perforate and wash 200ft interval using Hydrawell’s Hydrahemera System.  The Hydrahemera operation was new technology originating from Norway.  It is the first dual string abandonment application in the UK and during the review process was found to have a good track record and extensive onshore testing.  By using this method the process was estimated to take 6.5 days as opposed to 18 days for option 1 (to cut and pull then pilot mill 1000ft of 9-5/8 casing).

The Hydrahemera system allows for a well to be plugged across multiple annuli without performing a section milling operation.  The well is washed down from top to bottom perf and then back up from bottom perf to top perf to clean thoroughly behind multiple perforated casings.  Cement is then pumped into the well and the well barrier is established.

Contact: Jonathon Lilley, Centrica