Project Profile
Value: US$1.17 billion
Total cost of decommissioning: £246 Million (US $327 Million)
Location: North Sea, north-east of Shetland Islands
Blocks: 211/27a and 211/27c
Total estimated reserves: 487 million boe
Recoverable reserves: 126 million boe
Production lifetime: 19 years
Production end: 1st January 2003
The North West Hutton field is located 130km north-east of the Shetland Islands in Block 211/27a in the UK North Sea. It is situated at a water depth of 143m. Discovered in 1975 by the Amoco Group and operated by Amoco (UK) Exploration Company, the field had total estimated reserves of 487 million boe.
The North West Hutton platform is the only integrated oil and gas drilling, production processing and accommodation facility on this field. It includes topsides, jacket, pipelines and drill cutting piles. The oil and gas produced in this field were transported through the 10in gas pipeline (PL 147) and the export oil pipeline (PL 148).
The reservoir sandstones are the Brent Group Sandstones of Middle Jurassic age deposited in a progradational deltaic environment. The Brent Group sandstones vary in thickness from 98-152 m (320-500 ft) over the field.
Decommissioning Programme
The Department of Trade and Industry approved the decommissioning programme for the North West Hutton installations in 2006. The decommissioning involves three separate programmes for the removal of the facilities.
Programme 1: Decommissioning of the platform and associated equipment
• Plugging and abandonment of the wells.
• Topside decommissioning using the reverse installation technique utilising a heavy lift vessel. Modules were then transported ashore.
• Jacket decommissioning: The jacket was cut into sections subsea and then lifted using a heavy lift vessel. The jacket sections were then transported ashore. The footings remain in-situ standing 45m above the seabed in a mean sea water depth of 140m.
Programme 2: Decommissioning PL147 pipeline
PL147 is ~13km in length and when originally laid was trenched to 0.45m and allowed to naturally backfill with sections being rock dumped for stability. Decommissioning included:
• The selective cut and removal of exposed pipeline sections
• The removal of the SSIV and associated spools, umbilicals and concrete mattresses
• The disused welgas spool was included in the Decommissioning Programme 1 but during the subsea work scope this pipeline could not be found and it was concluded that it was not present.
Programme 3: Decommissioning PL148 pipeline
PL 148, the 13 km oil export line between NWH and Cormorant Alpha, originally lay unburied on the seabed.
• During decommissioning this pipeline was trenched and left to backfill naturally
• The pipeline crossings were removed
• The section of PL 148 within the Cormorant Alpha 500m zone was not trenched for safety reasons. The pipeline is disconnected at the riser tie in spool with a 9.7m gap.
Original operators of North-West Hutton, BP, issued close-out report confirming completion of decommissioning works in 2012. DF 22/01/2018
Operators:
Bridge Petroleum: Operator with 100% interest
Contractors:
BMT: Environmental Impact Assessment (EIA) as part of field development work for the large Galapagos Field. (April, 2018)
Diamond Offshore: Drilling contractor owns Ocean Nomad semi-submersible.
Transocean: Drilling contractor owns John Shaw semi-submersible.
Gulfstream Services Inc (GSI): Two decommissioning contracts where GSI tools were used to remove 10” and 20” pipelines from the seabed. GSI’s Hydraulic Shear was an effective engineering solution in the situation due to the quick boat to boat times.
Heerema Marine Contractors: Contract for decommissioning the North West Hutton installations. (October, 2006)
Able UK: To recycle the North West Hutton oil rig. A variety of load in and transportation techniques were specifically designed and executed to facilitate the manoeuvre of the large modular sections. (2008)