Shearwater

Location and Geology

• The Shearwater gas field is situated approximately 200km east of Aberdeen, in the Central Graben area of the central North Sea, at a water depth of about 90 meters (995 feet).

Ownership and Operation

• The field is owned by Neo Energy Group and Shell UK. Shell UK operates the field.

Drilling and Wells

• The project involves five high-pressure/high-temperature (HP/HT) development wells, which were drilled using the jack-up rig Maersk Endurer. Each well is over three miles long and contains over 1,000 tons of heavy wall, high-tensile steel and chrome tubes to withstand the harsh conditions, including the presence of hydrogen sulphide, carbon dioxide, and concentrated salt solutions.

Infrastructure

• The wellhead platform (WHP) is connected to a central processing facility (CPF) via a bridge. The CPF is responsible for processing the reservoir fluids, which are produced at temperatures of 248-284°F. The topsides of the wellhead platform are supported by a 5,900-ton steel jacket designed to withstand severe weather conditions and accidental events. The jacket is fixed to the seabed by eight 2.75-meter-diameter piles.

Processing and Separation

• The wellstream is separated into gas, condensate, and water on the CPF. The primary separator operates at 90 bar, and gas sweetening is carried out by an amine plant to remove hydrogen sulphide and carbon dioxide. The regeneration tail gas is disposed of through incineration, converting hydrogen sulphide into sulphur dioxide, which is then mixed with seawater to form sulphate ions that can be safely returned to the sea.

Export

• Separated condensate is transported ashore via an 8km (five-mile) spur pipeline to connect with the Elgin/Franklin fluids export system. It then travels to Cruden Bay via the BP Unity Platform in the Forties Pipeline System (FPS). The gas is exported through the new 34-inch-diameter, 463km (290-mile) SEAL gas pipeline, which connects to the Shell/Esso gas-reception terminal at Bacton.

Contractors and Construction

• Key contractors involved in the project include AMEC for the process, utilities, and quarters (PUQ) facilities, and Heerema’s Hartlepool yard for the wellhead topsides, bridge, flare, main jacket, and piles. Other contractors include Subsea 7, John Wood Group, Prosafe, James Fisher and Sons, and Keppel.

Production History and Future

• The Shearwater conventional gas field reached peak production in 2004 and has recovered 93.89% of its total recoverable reserves. Based on economic assumptions, production is expected to continue until the field reaches its economic limit in 2031. The field currently accounts for approximately 1% of the UK's daily gas output.

Expansion

• An expansion project, known as the Shearwater Expansion, is currently in the construction stage.