Elm Coulee Oil Field

Oil production from Montana and Elm Coulee Oil Field through 2005

Map of Williston Basin oil fields with reservoirs in Bakken Formation

Elm Coulee Oil Field was discovered in the Williston Basin in Richland County, eastern Montana, in 2000. It produces oil from the Bakken Formation and, as of 2007, is the "highest-producing onshore field found in the lower 48 states in the past 56 years." By 2007, the field had become one of the 20 largest oil fields in the United States.

The field exploits horizontal drilling technology by perforating the productive rocks parallel to the beds, rather than through a vertical well perpendicular to the relatively thin Bakken Formation. At Elm Coulee Field, the Bakken is only about 45 feet (15 m) thick and lies at depths of 8,500 to 10,500 feet (2,600–3,200 m), but horizontal wells penetrate 3,000 to 5,000 feet (900–1,500 m) of the reservoir rock, a porous dolomite of Devonian age that probably originated as a large carbonate bank on the western flank of the basin. The field is a stratigraphic trap.

In 2006, Elm Coulee was producing about 53,000 barrels (8,400 m³) of oil per day from more than 350 wells. Ultimate production is expected to exceed 270 million barrels (43,000,000 m³), with some estimates as high as 500 million barrels (79,000,000 m³). Production at Elm Coulee has more than doubled the oil output of the state of Montana, from around 40,000 barrels per day (6,400 m³/d) in 2000 to almost 100,000 barrels per day (16,000 m³/d) in 2006. However, Montana production fell again starting in 2007, down to some 70,000 barrels per day (11,000 m³/d) in mid 2009.