Ithaca Energy has submitted draft plans for the decommissioning of subsea infrastructure at the Fionn and Causeway fields as part of a joint campaign.
Draft plans for the fields were submitted to the Offshore Petroleum Regulator for Environment and Decommissioning (OPRED) on 17 November.
The Ithaca Energy-operated Causeway and Fionn facilities lie across in Blocks 211/23, 211/22 and 211/21 in the East Shetland Basin in the northern North Sea.
Causeway, first discovered in 1983, is tied back to the TAQA-operated North Cormorant platform which lies around 10 miles to the west.
Its facilities comprise a production pipeline, control umbilical and a water injection pipeline connected to one producing and one water injecting well, all of which are slated for decommissioning.
Fionn was discovered in 2007 as part of the Causeway field appraisal programme. Having been confirmed as a separate oil accumulation, it was agreed the prospect should be developed as a separate field, subsequently re-named Fionn.
Facilities at Fionn comprise a production pipeline tied into the Causeway pipeline, as well as one control umbilical which support a single production well. The control umbilical is also tied into North Cormorant.
Production at the fields ceased in 2018.
Ithaca holds sole interest in Fionn, and a majority stake in Causeway (64.5%) alongside NEO Energy (35.5%).
Ithaca acquired the field through its takeover of Valiant Petroleum in 2013 as part of a £203 million deal.
Under the plans, production infrastructure and Xmas trees at both fields will be removed by a drill rig and transported onshore for recycling, with removed weight totalling around 150 tonnes. Pipelines and umbilicals will be disconnected with ends cut and buried, before they are left in situ, while spools will be recovered to shore for recycling.
216 mattresses will also be recovered to shore from Causeway, and 155 from Fionn, while others will be assed for individually for abandonment in situ.
Per submitted proposals, well decommissioning is expected to begin in 2023, while subsea removals and seabed reinstatement are earmarked for completion by the end of 2027.