The investment in the Eastern Trough Area Project (ETAP) would secure the future of the field until 2030 and beyond, BP said in a statement.

"These are challenging times for the industry and we are having to make hard choices," BP said in a statement.

"Nonetheless, we remain committed to improving the competitiveness of the North Sea and to maximizing economic recovery from our fields."

ETAP is an integrated development of nine different fields, of which six are operated by BP and the other three by Royal Dutch Shell . Production, which started in 1998, is at around 120,000 barrels per day, according to BP's website.

The North Sea has struggled in recent years to attract investment due to high operating costs, an unattractive tax regime and decreasing output in the basin, whose production peaked in the late 1990s. Many companies are seeking to exit the region, further pressured by the halving of oil prices to $50 a barrel over the past year.

Trade body Oil & Gas UK welcomed the investment.

"Given the harsh business environment upstream oil and gas companies currently face...industry as a whole is putting a great deal of effort into improving the performance of its assets," Oil & Gas UK Chief Executive Deirdre Michie said in a statement.

(Reporting by Ron Bousso; additional reporting by Claire Milhench; editing by Susan Thomas)