Bittern Oil and Gas Field, North Sea, UK

The Bittern oil and gas field, situated in the Central North Sea of the UK, commenced production in April 2000.

The partners in the field include Serica Energy (64.63%), Dana Petroleum (32.95%), which serves as the operator, and Waldorf (2.42%).

A four-well programme is slated to begin in 2024 with the Bittern B1z sidetrack, now designated as the B6 well, which has been drilled successfully. The plan is to complete the well and commence testing in August 2024, following the scheduled Triton summer shutdown.

Additionally, a new 22km-long water injection pipeline with a diameter of 12in will be installed. The management and engineering works are scheduled to commence in Aberdeen in June 2024 while the offshore activities are scheduled for the third quarter of 2025.

Bittern oil and gas project location

The Bittern oil and gas field is located in Blocks 29/1a and 29/1b within the production licence P361. It lies approximately 190km east of Aberdeen in the UK Central North Sea, at a water depth of 90m.

The field is part of the larger Triton area, which encompasses eight producing oil fields, all developed through a shared infrastructure in the UK Central North Sea. It is situated around 22km south-east of the Triton floating production storage and offloading (FPSO) unit.

The other oil and gas fields within the Triton area include Evelyn, Guillemot West, Guillemot Northwest, Gannet E, Clapham, Pict, and Saxon.

Bittern oil and gas field details

The Bittern field was discovered in 1995 and was developed with five production wells and two water injection wells, employing a subsea tie-back system to the Triton FPSO.

Infrastructure at the Bittern field includes two seven-slot manifolds, four 10in production wells, a 12in water injection pipeline, and a 4in gas lift pipeline. The water injection pipeline (PL1650) and the gas lift pipeline (PL1649) were trenched and buried upon installation.

The two pipelines connect the Triton FPSO injection riser base in the UKCS block 21/30 to the Bittern field’s Drill Centre B manifold (DCB) in block 29/1, over a distance of around 20km.

The Bittern oil and gas field underwent several well interventions and a sidetrack of the B2 well between 2019 and 2022.

Oil transportation capabilities

Oil from the Triton FPSO is exported via a shuttle tanker, while gas is conveyed through the Shell Esso Gas and Associated Liquids (SEGAL) pipeline network.

The SEGAL system comprises two wet gas transportation pipelines, the St Fergus gas terminal, the Fife NGL terminal, and the Braefoot Bay tanker loading facility.

Wet gas is transported from the Northern North Sea via the Far North Liquids and Associated Gas System (FLAGS) pipeline to St. Fergus, and from the Central North Sea via the Fulmar Gas Line (FGL).

Triton FPSO details

The Triton FPSO is situated in Block 21/30 of the Central North Sea, approximately 193km east of Aberdeen. It extracts oil and gas from the Bittern, Clapham, Pict, Saxon, Guillemot West, and North West fields, all linked to Triton through subsea infrastructure.

The FPSO spans 244m in length, has a moulded breadth of 42m, and a moulded depth of 21.3m. With a deadweight of 105,000t, it operates in a water depth of 90m. It has a 42MW power generation system via two LM6000 dual-fuel gas turbines.

The storage capacity of the FPSO is 630,000 barrels, and it has processing capabilities of 105,000bpd of oil, 140 million cubic feet per day of gas, and 125,000bpd of water injection.

The FPSO boasts a mooring / riser system with a passive design incorporating an internal bow turret with a diameter of 4.4m, engineered by Bluewater. The mooring configuration comprises three groups of three lines, each 1,250m long, arranged in a chain / wire / chain formation.

The riser assembly consists of nine flexible risers and four umbilicals, with a capacity for 15 riser slots to accommodate future expansions.

Contractors involved

Subsea7, a subsea engineering, construction and services company, was awarded a contract valued between $50m and $150m by Dana Petroleum for the Bittern development in June 2024.

The contract’s scope included project management, engineering procurement construction, and installation (EPCI) of the new water injection pipeline, along with associated subsea structures and tie-ins at both the Triton FPSO and the Bittern field.