Elm Coulee Oil Field
Overview
 
Elm Coulee Oil Field was discovered in the Williston Basin
Williston Basin
The Williston Basin is a large intracratonic sedimentary basin in eastern Montana, western North and South Dakota, and southern Saskatchewan known for its rich deposits of petroleum and potash. The basin is a geologic structural basin but not a topographic depression; it is transected by the...

 in Richland County
Richland County, Montana
-Demographics:As of the census of 2000, there were 9,667 people, 3,878 households, and 2,652 families residing in the county. The population density was 5 people per square mile . There were 4,557 housing units at an average density of 2 per square mile...

, eastern Montana
Montana
Montana is a state in the Western United States. The western third of Montana contains numerous mountain ranges. Smaller, "island ranges" are found in the central third of the state, for a total of 77 named ranges of the Rocky Mountains. This geographical fact is reflected in the state's name,...

, in 2000. It produces oil from the Bakken Formation
Bakken Formation
The Bakken formation, initially described by geologist J.W. Nordquist in 1953,is a rock unit from the Late Devonian to Early Mississippian age occupying about of the subsurface of the Williston Basin, underlying parts of Montana, North Dakota, and Saskatchewan...

 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
Directional drilling
Directional drilling is the practice of drilling non-vertical wells. It can be broken down into three main groups: Oilfield Directional Drilling, Utility Installation Directional Drilling Directional drilling (or slant drilling) is the practice of drilling non-vertical wells. It can be broken down...

 by perforating the productive rocks parallel to the beds, rather than through a vertical well perpendicular to the relatively thin Bakken Formation.
 
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