Liberty Resources II LLC is buying oil and gas assets for $455 million.

The company is picking up about 53,000 acres in North Dakota’s Williston Basin.

Denver-based Liberty is an oil and gas company that is backed by private equity firm Riverstone Holdings LLC. Riverstone, in partnership with Oakmont Corp., invested about $350 million in Liberty in November.

Riverstone had previously partnered with the management of Liberty Resources II on Liberty Resources LLC, an oil and gas company that focuses on the Bakken Shale of North Dakota.

New York-based Riverstone is an energy-focused private equity firm that has raised about $27 billion in capital. Riverstone Energy invests in the energy industry.  

There has been a steady flow of M&A from the oil and gas sector. Recent deals include American Midstream Partners LP’s (NYSE: AMID) deal for a natural gas gathering system, and Fieldwood Energy LLC’s acquisition of SandRidge Energy Inc.’s (NYSE: SD) Gulf of Mexico and Gulf Coast business.