Bakken and Three Forks Formations, Williston Basin, North Dakota and Montana
By Kristen Marra, U.S. Geological Survey, Central Energy Resources Science Center, Denver, CO, USA
The Bakken Petroleum System of the Williston Basin (North Dakota and Montana, USA) consists of the Late Devonian to Early Mississippian Bakken Formation, the underlying Three Forks Formation, and the overlying lower Lodgepole Formation (Early Mississippian). The Bakken Formation is composed of 4 distinct informal members: 1) the Pronghorn member (formerly defined as the “Sanish sand”, e.g. LeFever et al., 2011), 2) lower shale member, 3) middle Bakken member, and 4) upper shale member. The source rocks of the system are the organic-rich upper and lower shales of the Bakken, which average approximately 11% total organic carbon (TOC) and contain Type II kerogen. The primary reservoir targets are the low porosity and low permeability members of the middle Bakken and upper Three Forks, with continued exploration into the middle and lower intervals of the Three Forks Formation and the Pronghorn member. Bakken-sourced oil is also found in Lodgepole Formation limestones (Gaswirth and Marra, 2015; Sonnenberg, 2017).
Oil production in the Bakken and Three Forks Formations began in the early 1950s at Antelope Field (North Dakota). Drilling later shifted to the Billings Nose area (North Dakota), where the upper Bakken shale was exploited. The first horizontal Bakken well was drilled in this region in 1987. Major sweet spot discoveries include Elm Coulee Field in 2000 and Parshall Field in 2005-2006. Since that time, exploration and production has expanded across the basin, resulting in over 11,000 productive wells in the Bakken Formation to date. Successful horizontal tests in the underlying Three Forks Formation were completed in Divide County (North Dakota) in 2005-2006. Drilling into the Three Forks Formation has expanded north and south along the main structure of the Nesson anticline, along with expansion into the central Williston Basin (North Dakota) and eastward into the region of Parshall Field. More than 5,000 Three Forks wells had been drilled by the end of 2020. Although the upper Three Forks interval is the primary target due to proximity to the organic-rich lower Bakken shale member, drilling and exploration of the middle and lower Three Forks continues across the basin (Sonnenberg and Pramudito, 2009; Gaswirth and Marra, 2015; Nesheim, 2019; IHS Markit®, 2021).
The Bakken and Three Forks Formations were assessed by the U.S. Geological Survey (USGS) in 2013, resulting in undiscovered, technically recoverable mean resource estimates of 3.65 billion barrels of oil (BBO) for the Bakken Formation and 3.73 BBO for the Three Forks Formation (total mean resource estimate of 7.38 BBO; Gaswirth and Marra, 2015). The USGS is currently conducting a revised resource assessment of the Bakken and Three Forks Formations.
Additional recent assessments of the Bakken and Three Forks Formations include: • Platte River Associates (Theloy et al., 2017): 3.4-4.0 BBO technically recoverable in the Bakken and Three Forks Formations (North Dakota region only) • BEG (Gherabati et al., 2019): 262 BBO total oil in place in the Bakken, Three Forks, Pronghorn, and Scallion units • Saputra et al. (2019): 8 BBO technically recoverable (plus the addition of 5 BBO from existing wells) in the Bakken and Three Forks Formations • U.S. Energy Information Association (EIA, 2021): 17.6 BBO technically recoverable in the Bakken and Three Forks Formations (10.9 BBO attributed to the Bakken Formation and 6.7 BBO attributed to the Three Forks Formation) (It is important to note, however, that the methodologies used by various publications and reporting groups vary. The reader is directed to the individual reference for each reported value for further clarification).
Since 2010, production in the Bakken has generally increased, with various declines beginning in 2014 due to a drop in oil prices and in mid-2020 due to the decrease in demand during in the ongoing COVID-19 pandemic (Figures 1 and 2). Due to the drop in well completions, production growth may not rebound until 2022 (Tobben, 2020). Overall, oil production has remained high, and North Dakota continues to be the second largest oil producing state in the country.
References
Gaswirth, S.B. and K.R. Marra, 2015, U.S. Geological Survey 2013 assessment of undiscovered resources in the Bakken and Three Forks Formations of the U.S. Williston Basin Province: AAPG Bulletin, v. 99, no. 4, pp. 639-660.
Gherabati, S.A., Hamlin, H.S., Smye, K.M., Eastwood, R.L., Male, F.R., and McDaid, G., 2019, Evaluating hydrocarbon-in-place and recovery factor in a hybrid petroleum system: Case of the Bakken and Three Forks in North Dakota: Interpretation, v. 7, no. 3, https://doi.org/10.1190/INT-2018-0213.1
IHS Markit®, 2021, Enerdeq™ US well history and production database: Englewood, Colo., IHS Markit. http://www.ihsenergy.com, accessed February, 2021.
Le Fever, J. A., Le Fever, R.D., and Nordeng, S.H., 2011, Revised nomenclature for the Bakken Formation (Mississippian-Devonian), North Dakota, in Robinson, J.W., LeFever, J.A., and Gaswirth, S.B., eds., The Bakken-Three Forks Petroleum System in the Williston Basin: Denver, Colo., Rocky Mountain Association of Geologists, p. 11–26.
Nesheim, T.O., 2019, Examination of downward hydrocarbon charge within the Bakken-Three Forks petroleum system – Williston Basin, North America: Marine and Petroleum Geology, v. 104, pp. 346-360.
Saputra, W., Kirati, W., and Patzek, T., 2019, Generalized extreme value statistics, physical scaling and forecasts of oil production in the Bakken Shale: Energies, v. 12, no. 19, https://doi.org/10.3390/en12193641.
Sonnenberg, S.A., 2017, Sequence Stratigraphy of the Bakken and Three Forks Formations, Williston Basin, USA, in Sequence Stratigraphy: The Future Defined, Bruce Hart, Norman C. Rosen, Dorene West, Anthony D’Agostino, Carlo Messina, Michael Hoffman, Richard Wild.
Sonnenberg, S.A. and A. Pramudito, 2009, Petroleum geology of the giant Elm Coulee field, Williston Basin: AAPG Bulletin, v. 93, no. 9, pp. 1127-1153.
Theloy, C., Leonard, J.E., Leonard, C.O., and Ganster, P.W., 2017, Using an uncertainty assessment approach for estimating recoverable reserves from the Bakken Petroleum System in North Dakota: Search and Discovery Article #10918, posted March 6, 2017.
Tobben, S., 2020, North Dakota regulator sees Bakken shale growth stalled until 2022: World Oil News, https://www.worldoil.com/news/2020/12/15/north-dakota-regulator-sees-bakken-shale-growth-stalled-until-2022, accessed June 2021.
U.S. Energy Information Association (EIA), 2021, Assumptions to the Annual Energy Outlook 2021: Oil and Gas Supply Module, https://www.eia.gov/outlooks/aeo/assumptions/pdf/oilgas.pdf, accessed June 2021.