US independent Devon Energy is expanding its position in the Williston basin with an agreement to buy RimRock Oil & Gas’ assets in the play for $865 million.

Devon described the addition of 38,000 net contiguous acres as a “bolt-on” acquisition, which increases the company’s position in the basin to approximately 123,000 net acres.

The RimRock assets are currently producing about 15,000 barrels of oil equivalent per day, with 78% of that amount being oil.