The discovery was announced as BP returned to the black with net profits of pounds 615m for last year against a pounds 458m loss in 1992, when it was forced to take a pounds 1bn restructuring charge and halve the dividend.
The oilfield is about 15 kilometres from a similar sized find made by BP last year. Together they represent the biggest discoveries in British waters for more than five years and open up an entirely new oil province.
BP and its partner Shell plan to drill up to six wells in the next year to appraise the area's potential. The two groups are considering early development of the fields and could initially use a floating platform to generate about 100,000 barrels of oil a day within the next few years.
The results reflected the benefits of a pounds 500m cost-saving across the group and a pounds 135m windfall from changes to petroleum revenue tax.
Although BP is on target to achieve underlying net profits of about dollars 2bn, David Simon, chief executive, has set a new goal to boost its performance by a further dollars 1bn in the next three years.
The improvements were expected to come from higher production and sales volumes and a new efficiency drive, but no further job cuts were planned, he said.
The group raised about dollars 3bn from asset disposals last year, dollars 1bn more than planned, and another dollars 1.5m worth of disposals are expected this year. Capital spending fell from pounds 3.5bn to pounds 2.8bn. Net debts were cut by pounds 1.9bn to pounds 8.4bn.
The results included pounds 200m exceptional costs relating to the closure of a loss-making chemicals plant in South Wales.
Earnings per share amounted to 11.3p against a loss of 8.5p in 1992. But the quarterly dividend is held at 2.1p, reducing the year's total from 10.5p to 8.4p.
Nick Clayton, of Nomura Research, said: 'The company has made good progress in improving its performance given the difficult economic environment.' The broker is forecasting net profits to improve to about pounds 1.1bn this year and a full year dividend of 8.8p.
BP shares fell 4.5p to 386p after hitting a five-year peak at 405p. They have come up from about 180p since June 1992, when Bob Horton was forced to resign as chairman and chief executive.
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