The assets include a 25.5% interest in the Pikka Unit and adjacent exploration acreage and a 37.5% interest in the Horseshoe Block.
Oil Search said that the leases contain approximately 500 million barrel (gross) in the Nanushuk and satellite oil fields.
The Nanushuk field is said to one of the largest conventional oil fields discovered in more than 30 years in the US.
Oil Search expects the assets to complement its existing gas assets in Papua New Guinea and balance its gas portfolio.
Additionally, Oil Search has an option to purchase all of Armstrong and GMT's remaining interest in the Pikka Unit and the Horseshoe Block as well as 25.5% interest in the adjacent exploration acreage and 37.5% in the Hue Shale for $450m.
Oil Search managing director Peter Botten said:"For some time, Oil Search has been seeking to acquire oil interests to complement our PNG gas assets, to create a more balanced portfolio that is less exposed to one single commodity and one country.
“The key challenge has been to achieve this without diluting the Company’s world class, high returning PNG assets.
“Utilising our existing relationships, this Alaska North Slope opportunity has been proactively pursued and an agreement structured to the benefit of all parties.”
The acquisition, which is planned to be completed in the first quarter of 2018, is subject to standard US regulatory approvals, including approval by the Committee on Foreign Investment in the US (CFIUS).
