Project Profile
Value: US$600 million - US$700 million
Location: Blocks 9/14a and 9/14b, North Sea, approx. 220 miles northeast of Aberdeen and 15 miles north of Kerr-McGee\'s Gryphon development, UK
Reserves: 120 MMboe - 170 MMboe
Production: 45,000bpd
Water Depth: 113 metres (370 ft)
Leadon is located in blocks 9/14a and 9/14b in the North Sea, approximately 220 miles north-east of Aberdeen and 15 miles north of Kerr-McGee\'s Gryphon development. The field was discovered in 1979 by the British National Oil Company, but it was considered sub-economic until an an appraisal well was drilled by Kerr-McGee in 1998. Using modern geophysical tools, this suggested that a northern extension would be oil bearing. The decision to develop the field was made in association with the development of two satellite fields: Birse stretching across blocks 9/14b, 9/14a; and Glassel in block 9/14a. These are located about 5 miles from Leadon. A number of acquisitions during 1998/99 resulted in Kerr-McGee gaining a 100% stake in the development. The Leadon development cost is projected at US$600 million to US$700 million, depending upon the size of the finished field size. The field came on-stream in late 2001, less than two years after the field discovery and less than one year after government approval of the field’s development. It represents the largest net investment in Kerr-McGee history, as well as the largest development in the UK sector of the North Sea by any company in 2001.
Projected Oil Production:
Combined reserves are estimated at 120 million to 170 million barrels of oil equivalent and the life of the field is put at over 16 years. The initial production rate was approximately 10,000bpd, and is expected to ramp up to peak production in excess of 45,000bpd. Because the Leadon, Birse and Glassel fields lie in a water depth of 370ft, they were developed using subsea horizontal wells tied back to a floating production, storage and offloading (FPSO) facility. The FPSO was christened as the Kerr-McGee Global Producer III.
Kerr-McGee acquired the Mitsui F-601 hull from Mitsui Engineering. The topsides processing facilities were constructed by Swan Hunter on Tyneside. Halliburton - Brown & Root provided detailed engineering from Aberdeen. Rockwater were involved in the fabrication of the pipeline bundles at Wick, with Baker Hughes supplying the produced water package from the Midlands. Over 75 companies, spread throughout the UK, have also benefited from their involvement in this project. Inmarsat\'s subsidiary Inset was awarded the upgrading and modification contract by the offshore operator Kerr-McGee, to provide an array of enhanced telecommunication services for the FPSO. DNV has been assigned to provide verification services in accordance with UK Legislation for the design, construction, hook-up and commissioning phases of the project.
Decommissioning Phase:
In 2006 the FPSO and mooring system were disconnected and relocated to the Donan field; in accordance with an agreement with DECC. Back in 2007 the Risers were removed and shipped onshore.
The decommissioning programme comprises safe removal of wellheads, towheads, the midline structure and riser bases. Supporting infrastructure such as concrete mattresses and grout bags will also be removed as part of the plan. Flowlines, connectors and pipeline bundle will be completely removed and transported onshore for recycling or disposal. The subsea wells will be plugged and abandoned. As part of the plan, large structures such as towheads will be cut into manageable lifts and will be recovered using heavy lift vessels. The wells will be plugged and abandoned in continuation to minimise the relocation cost of the drilling rig and conduct the operation more efficiently.
The pipeline bundle consists of two sections and is planned to be decommissioned in-situ with towheads and midline structure being removed and cut ends rock placed over the area to make the bundles over-trawlable. The bundles will be recovered in the future and will be inspected and monitored regularly.
The flowline PL1895 will be partially covered from Leadon\'s midline section to the Beryl 500m zone with plans to recover the remaining section at a later date. Grout bags and mattresses used for stabilising the remaining section of PL1895 will be removed later along with the remaining section of the flowline whereas spools, mattresses, grout bags and control jumpers will be removed and sent onshore.
**Leadon decommissioning programme approved by BEIS and under way:
Phase 1: execution and strategy awards due to have been performed by end-2017.
Phase 2: Subsea scope 1: Spools, riser bases, mattresses, due between end-2017 and Q2 2018. (Contractor Petrex Limited conducting recovery study for riser bases).
Phase 3: wells decommissioning, completion due between Q2 2019 and end-2020.
Phase 4: Subsea scope 2: cut and recover Leadon structures, rock dump bundles, ends and trawlability trials: due between end-2018 and Q2 2020.
Phase 5: Post decommissioning Survey due between Q2 2020 and end-2020.
Projected Phase 1-5 costs disclosed to UK Department of Business and Energy (BEIS) but not yet publicly released. DF, 01/01/2018**
Operators:
Kerr-McGee: Operator with 100% interest
Contractors:
Baker Hughes: Supply of the produced water package from the Midlands
DNV: Provide verification services for the design, construction, hook-up and commissioning phases of the project
Framo Engineering: Supply the swivel stack for Leadon
Inset: Upgrading and modification contract by the offshore operator Kerr-McGee, to provide an array of enhanced telecommunication services for the FPSO
Harkand: Conduct subsea inspection
Halliburton - Brown & Root: Provided detailed engineering
Rockwater: Fabrication of the pipeline bundles
Swan Hunter: Topsides processing facilities
Petrex Developments: Contract from Maersk Oil North Sea (UK) to provide support to the Leadon decommissioning programme. (March, 2016)
Maersk Drilling: A contract for the jack-up rig Maersk Gallant to plug and abandon the Leadon and James subsea fields. (September, 2016)
Maersk Supply Service: Managing the scope of the subsea decommissioning.