BP said first production from the field came in 1982 and the redevelopment means its life is extended to 2050.
"It is one of BP's most complex field expansion developments and gives Valhall a further 40-year design life with the capacity to handle 120,000 barrels of oil and 143 million cubic feet of gas per day," BP Chief Executive Officer Bob Dudley said in a statement.
Peak production is expected by the middle of this year. No investment figures were given.
Last week, the British government said it expected to see renewed life from its North Sea oil and natural gas fields following years of decline. British Energy Secretary Ed Davey said he expected to approve dozens of new offshore projects.
BP confirmed, in a separate statement, that three of its employees were killed in a terrorist attack at the Ain Amenas natural gas facility in eastern Algeria early this month.