Kristen R. Marra Troy A. Cook Ronald R. Charpentier Donald L. Gautier Debra K. Higley Timothy R. Klett Michael D. Lewan Paul G. Lillis Christopher J. Schenk Marilyn E. Tennyson Katherine J. Whidden Stephanie B. Gaswirth 2013 Using a geology-based assessment methodology, the U.S. Geological Survey estimated mean undiscovered volumes of 7.4 billion barrels of oil, 6.7 trillion cubic feet of associated/dissolved natural gas, and 0.53 billion barrels of natural gas liquids in the Bakken and Three Forks Formations in the Williston Basin Province of Montana, North Dakota, and South Dakota. application/pdf 10.3133/fs20133013 en U.S. Geological Survey Assessment of undiscovered oil resources in the Bakken and Three Forks Formations, Williston Basin Province, Montana, North Dakota, and South Dakota, 2013 reports