Stratigraphic column of the Spearfish Formation and bounding units, modified by Murphy et al. (2009).
Stratigraphic Overview
The Spearfish Formation was deposited in the Permian and Triassic and consists of, in ascending order, the Belfield Member, Pine Member and Saude Member. The lowermost Belfield Member was deposited during the Permian and is comprised of reddish-orange shale (Dow, 1967). The middle Pine member, also deposited in the Permian, contains interbedded salts and red and gray shale. The uppermost Saude Member was deposited in the Triassic. The Saude Member consists of red, interbedded shales and fine- to coarse-grain sandstone and siltstone (Ziegler, 1955). The Saude Member contains four informal sandy intervals that have been productive hydrocarbon reservoirs in Bottineau County, North Dakota. In ascending order: they are the A, B, C, and Basal sand.
The depositional environment of the Saude Member has been debated over the years. Dow (1967) first suggested a non-marine environment. LeFever and LeFever (1991) argued for both marine and non-marine deposition. In contrast, Sebade (2014) concluded that the depositional environment was exclusively marine despite a complete lack of marine fossils in the Saude Member. As there is little evidence in core of marine deposition, a non-marine depositional environment similar to that of McIlroy et al. (2019) best describes these continental red beds.
Extent map of the Spearfish Formation (red) within North Dakota (Spearfish extent from Carlson, 1993). The extent of the Pine Salt is displayed in blue (Stolldorf, 2022). Productive Spearfish oil and gas wells are displayed by black dots. View Production Map Area
Hydrocarbon Targets and Play Concepts
Wells were first drilled and completed in the Spearfish in 1954. Development has continued intermittently from the 1950s through present day in North Dakota. Play concepts within the Spearfish have evolved over the years and can be separated by target interval. The first attempts to recover oil from Spearfish reservoirs came from vertical wells with perforations in both the basal sand of the Spearfish and the underlying Madison Group. The second play concept targets the Spearfish’s upper sands (A sand & B sand). The final play concept targeted the Basal sand of the Spearfish. The Basal sand is often the cleanest sand and was first developed as a stand-alone play in the Russell field with the Carl Kersten 1 (API: 330090076700), which was completed in 1963.
Hydrocarbon Production Overview
Spearfish production consists of primarily commingled Spearfish and underlying Madison reservoirs. Spearfish pool production, which consists of commingled and stand-alone production, has generated 64 million barrels (MMBLS) of oil, 3.8 million cubic feet (MMCF) of gas and 134 MMBLS of water. Stand-alone production from the Spearfish Formation has produced 5.8 MMBLS of oil, 2.2 MMCF of gas and 16.4 MMBLS of water. All production numbers are as of Q3 2022. Updated production numbers are available from the North Dakota Industrial Commission (https://www.dmr.nd.gov/oilgas/).
Barchyn, D., 1982, Geology and hydrocarbon potential of the Lower Amaranth Formation, Waskada-Pierson are, Southwestern Manitoba, Manitoba Energy and Mines, Geological Report GR 82-6, p. 30.
Butcher, G.S., Kendall, A.C., Boyce, A.J., Millar, I.L., Andrews, J.E., & Dennis, P.E., 2012, Age determination of the Lower Watrous red-beds of the Williston Basin, Saskatchewan, Canada. Bulletin of Canadian Petroleum Geology, 60 (4), p. 227-238.
Carlson, C.G., 1993, Permian to Jurassic redbeds of the Williston Basin: North Dakota Geological Survey, Miscellaneous Series No. 78, 27 p.
Cumming, A.D., 1956, the Watrous strata in Saskatchewan: 1st International Williston Basin Symposium, Conrad Publishing Co., Bismarck, North Dakota, p 165-169.
Dow, W.G., 1967, The Spearfish Formation in western North Dakota, 3rd International Williston Basin Symposium, p. 127-131.
Husain, M., 1991, regional geology and petroleum potential of the Lower Amaranth, Coulter-Pierson area, southwestern Manitoba. 6th International Williston Basin Symposium, p. 151-160.
LeFever, R.D., and LeFever, J.A., 1991, Newburg and south Westhope Fields – USA, Williston Basin, North Dakota, including N.H. Foster and E.A. Beaumont, compilers, Stratigraphic traps II: American Association of Petroleum Geologists Treatise of Petroleum Geology Atlas of Oil and Gas Fields, p. 161-187.
Milroy, P., Wright, V.P., and Simms, M.J., 2019, Dryland continental mudstones: Deciphering environmental changes in problematic mudstones from the Upper Triassic (Carnian to Norian) Mercia Mudstone Group, south-west Britain, Sedimentology, Volume 66, Issue 7, P. 2557-2589.
Murphy, E.C., Nordeng, S.H., Juenker, B.J., and Hoganson, J.W., 2009, North Dakota Stratigraphic Column, North Dakota Geological Survey, MS-91, 1p.
Musial, R., 1995, An overview of the Lower Watrous Manor Pool in southeast Saskatchewan. 7th International Williston Basin Symposium, p. 219-231.
North Dakota Industrial Commission, Department of Mineral Resources, Oil and Gas Statistics, https://www.dmr.nd.gov/oilgas/
Oglesby, C.A., and Fischer, D.W., 1991, Sedimentology and petroleum geology of a Triassic Spearfish sandstone reservoir, South Starbuck Field, Bottineau County, North Dakota, 6th International Williston Basin Symposium, p. 161-164.
Sebade, M.J., 2014, The depositional environment and diagenetic effects on sand bodies within the unconventional resource play of the Spearfish Formation (Triassic) in north-central North Dakota, unpublished M.Sc. thesis, University of North Dakota, 131 p.
Stolldorf, T.D., 2022, Pine Salt Extent and Thickness, Williston Basin, North Dakota: North Dakota Geological Survey, Geological Investigations No. 264, 4 pl.
Zieglar, D.L., 1955, Pre-Piper post Minnekahta “red beds” in the Williston Basin: North Dakota Geologic Society, 1955 Field Conference Guidebook, p. 49-55.
Last Updated: 01/12/2024.