Oil and gas operator Apache North Sea has started production at a new field after investing nearly £40million in the project.
Apache said Tonto was producing more than 10,000 barrels of oil a day, which was way above the 3,000 it predicted previously that the development would yield.
It has estimated that Tonto, which was drilled through the operator’s Forties Bravo platform, holds 2.5million barrels of recoverable reserves.
The company holds a 100% stake in the field 110 miles north-east of Aberdeen and expects to continue producing from it until 2019.
Apache North Sea vice-president Jim House said new seismic techniques revealed the full scale of Tonto and encouraged the company to push ahead with the project.
The US firm is also planning another development well in the area before the end of this year.
Apache said earlier this year that it had turned its attention to Tonto following its success at Maule, another smaller find brought online through Forties Alpha in 2010.
The operator said Maule – which it had estimated to hold up to 4.4million recoverable barrels of oil – was still producing about 1,200 barrels daily. Apache’s Bacchus development, which produces about 12,900 barrels of oil a day, is also tied back to Forties Alpha.