Bruce was discovered in June 1974 in acreage licensed to BHP in the 4th licensing round. Condensate, a light crude that exists as gas under reservoir conditions, was found 4000 metres below the seabed in a water depth of 121 metres.
Further drilling was largely unsuccessful. However, interest in the prospect was rekindled in early 1981 when BP discovered gas/condensate in an adjacent 5th round block in the centre, followed by a further discovery to the east by Total in 1984.
The field was initially developed using two bridge-linked platforms known as D and PUQ respectively. The transport system comprises: A 6 kilometres long, 32-inch diameter gas export pipeline that joins the 32-inch Total-operated Frigg UK pipeline, taking gas to the St. Fergus Terminal. A 248 kilometres long, 24-inch diameter oil export pipeline to the BP FPS Unity platform and thence into the BP-operated Forties Pipeline System. The PUQ platform, (process/utilities/quarters) and D (drilling) platform are linked by a 47 metre bridge. The PUQ platform comprises a 9400 tonne jacket and three major topside modules. These are:
- 8000 tonne cellar deck
- 7800 tonne production module
- 2500 tonne accommodation module and helipad
The D platform comprises of an 8000 tonne jacket, a 7300 tonne three level integrated deck, drilling derrick and substructure. Oil and gas from the Bruce reservoir is recovered by 20 platform wells and 6 subsea wells. The Bruce field is a complex structure of three reservoirs - Turonian limestone (gas condensate), Bruce sandstone (oil and gas condensate), and Statfjord sandstone (oil and gas condensate). It is a structural trap consisting of several separate accumulations which may need up to 40 wells to produce oil and gas at all reservoir levels. Liquids and gas from the reservoir are produced through two processing trains. In each train, liquids pass through two separation stages at decreasing pressures to the main oil line booster pumps. The hydrocarbon liquid from the two trains is then combined, metered and exported via the Forties Pipeline System. Gas separated from the liquids is cooled, compressed and dried through three turbine-driven compression trains, before being exported via the Frigg UK pipeline to St Fergus. Some of the processed gas is used to power the platform. Gas production in 2004 was an average 600 million cubic feet per day, in total around 7% of the UK's gas requirements. Produced water is cleaned in hydro cyclones to better than 40 parts per million before being re-injected. As part of Phase II Development, a 3rd platform was added to accommodate additional gas compression facilities. This platform, known as the CR platform, is bridge linked to the two original Bruce Field Platforms. First production occurred in 1998, with peak production rates from these facilities, being around 450 million standard cubic feet of gas and 45,000 barrels of hydrocarbon liquids per day.
A major facilities upgrade was completed in 3Q 2000, involving the introduction of a further stage of compression on all three compressor trains. This upgrade allowed a reduction in the wellhead flowing pressure of the wells, maintaining deliverability at plateau flow rates. In 2004 a new module was installed on the CR platform to provide reception facilities for Rhum Field fluids, which are due to commence production in 2005, and an additional stage of gas compression with two Low Pressure Booster Compression trains, which will allow a further reduction in wellhead flowing pressure and will enable an additional 100 billion standard cubic feet of gas to be recovered from Bruce. Bruce field production commenced decline in 2003 and ullage will become available in all parts of the platform facilities over the next few years.