In 2013, the U.S. Geological Survey (USGS) assessed the technically recoverable oil and gas resources of the Bakken and Three Forks Formations of the U.S. portion of the Williston Basin (Gaswirth and others, 2013). The Bakken and Three Forks Formations were assessed as continuous and hypothetical conventional oil accumulations using a methodology similar to that used in the assessment of other continuous- and conventional-type assessment units (AUs) throughout the United States. The purpose of this report is to provide supplemental documentation and information used in the Bakken-Three Forks assessment.