The largest onshore US oil discovery in 30 years has been made in Alaska.
Oil and gas firms Repsol and Armstrong Energy drilled the Horseshoe-1 and Horseshoe-1A wells in the winter of 2016-2017, which confirmed the Nanushuk play on the North Slope could amount to approximately 1.2 billion barrels of recoverable light oil.
The Horseshoe wells extend an existing play known as Pikka by around 20 miles.
Successive campaigns in the area have added significant new potential to what was previously viewed as a mature basin.
Repsol previously drilled 13 other exploration and appraisal wells, which led to multiple reservoir discoveries currently included in the Pikka Unit.
Repsol holds a 25% working interest in the Horseshoe discovery and a 49% working interest in the Pikka Unit, with Armstrong holding the remaining share and serving as the operator.
First production at Pikka is expected in 2021, with a potential output of 120,000 barrels of oil per day.
Oil and gas service firms Amec Foster Wheeler and Wood Group have announced they will merge into a single £5 billion business.