Riverstone Holdings LLC, a private equity firm that focuses on energy and power sectors, said it would sell U.S.-based oil and gas explorer Rock Oil Holdings LLC to SM Energy Co (SM.N) for $980 million in cash.

SM Energy said the deal would increase its assets in the Midland Basin in Texas to 46,750 acres and add net production of 4,900 barrels of oil per day (boepd).

Rock Oil, founded in 2014, has about 24,783 acres in the Permian Basin in Texas.

Riverstone Holdings’ British unit, Riverstone Energy Ltd, (RSER.L) said it would realize cash proceeds of $237 million from the sale.

SM Energy’s shares were slightly up in early trading on the New York Stock Exchange after being down 5.1 percent before the opening bell on Monday. Riverstone Energy’s shares were up 2.7 percent at 1068 pence on the London Stock Exchange at 1255 GMT.

Since July last year, at least seven deals have been struck by public oil and gas companies in Texas’ Permian Basin, one of the biggest U.S. shale oil fields, as oil prices have remained weak.

Jefferies is advising Rock Oil and Riverstone Holdings LLC. Latham & Watkins LLP is Rock Oil and Riverstone’s legal adviser.