BILLINGS, Mont. (AP) — A Montana oil and gas company say it is acquiring an Australian company's U.S. subsidiary to increase production in the Bakken oil patch in a cash and stock deal worth an estimated $40 million.

The deal combines Billings-based Voyager Oil and Gas, Inc. with a subsidiary of Emerald Oil and Gas NL of Australia.

The new company, Emerald Oil, will be based in Denver, Colo. It holds leases in Montana, North Dakota, Wyoming and Colorado.

Company executives said Tuesday they will start drilling next year with a single rig in the North Dakota Bakken, one of the most productive oil fields in the country.

Emerald chairman McAndrew Rudisill will be president of the new company. He says it will double Voyager's current production to 2,000 barrels of oil a day.