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
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