Riverton, WY-based U.S. Energy Corp. (USEC) said Monday it has acquired producing assets in the Bakken and Three Forks shale plays in North Dakota for $2.5 million, giving the small exploration and production (E&P) company minority interests in up to 23 drilling units with an estimated 307,000 boe in proved oil reserves.

The transaction’s effective date is July 1, 2012.

USEC holds other drilling interests in North Dakota’s Williston Basin, along with interests in Louisiana and Texas fields. Its latest purchase and sale agreement was with an undisclosed seller for producing wells spread over McKenzie, Williams and Mountrail counties in the midst of the state’s richest shale plays.

The publicly held E&P acquired working interests in drilling units averaging 1.45% and ranging from less than 1% to nearly 5%. There are currently 27 gross producing wells in the acreage, a USEC spokesperson said.

Twenty-five of the producing wells are in the Bakken; two are in Three Forks. There are about 400 net acres in the acquisition, said USEC, noting that it will be getting about 47 boe/d net from its interests.

In the future “there is the potential for USEC to participate in an additional 135 gross wells from the Bakken and Three Forks formations combined, and the company will be heads up for its proportionate interests on all new wells drilled within the units,” the spokesperson said.

For the past three years, USEC has entered a drilling participation agreement (DPA) with a subsidiary of Brigham Exploration Co. to jointly explore for oil and gas in up to 19,200 gross acres in a portion of Brigham’s Rough Rider prospect in Williams and McKenzie counties, ND.

“Under the DPA, we earned working interests, out of Brigham’s interests, in 15 1,280-acre spacing units in Brigham’s Rough Rider area by participating in the drilling of one initial well on each unit of acreage,” the spokesperson said. “Accordingly, we have earned the rights to drill up to 30 gross wells in the Bakken formation and an additional 30 gross wells in the Three Forks formation, based on current North Dakota spacing rules. If the spacing is ultimately increased to four wells per 1,280-acre spacing unit, the potential number of drilling locations could increase to 120 gross wells.”

CEO Keith Larsen said the additional drilling interests have “increased our proved reserves [in North Dakota] significantly at accretive value.”