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The AAPG/Datapages Combined Publications Database

Williston Basin Symposium

Abstract

MTGS-AAPG

Seventh International Williston Basin Symposium, July 23, 1995 (SP12)

Pages 323 - 339

Assessment of Undiscovered Resources in Petroleum Plays: U.S. Portion of Williston Basin and North-Central Montana

T. S. Dyman
J. A. Peterson
J. W. Schmoker
C. W. Spencer
D. D. Rice
K. W. Porter
D. A. Lopez
T. J. Heck
W. R. Beeman

ABSTRACT

Assessment of conventional and unconventional petroleum resources for the U.S. Geological Survey 1995 National Petroleum Assessment is based on analysis of confirmed and hypothetical plays using field-size distributions, discovery process models, and statistical estimation procedures that yield probabilistic estimates for undiscovered accumulations. Unconventional resources in continuous-type accumulations, for which the concept of discrete fields has little meaning, are independently assessed based on quantitative methodologies that treat the play as a collection of hydrocarbon-containing cells. Work done in consultation with the Montana Bureau of Mines and Geology, North Dakota Geological Survey, and the petroleum exploration community, includes identification, description, and correlation of petroleum plays. Resource estimates presented in this report were prepared by the U.S. Geological Survey which is solely responsible for them.

The U.S. portion of the Williston Basin petroleum province is bounded on the east and southeast by the Canadian shield and Sioux uplift, on the west and southwest by the Black Hills uplift, Miles City arch, Porcupine dome, and Bowdoin dome, and on the north by the Canadian border. More than 400 accumulations greater than 6 BCF or 1 MMBO ultimate recoverable production have been discovered in the province as of 1993. Six confirmed or hypothetical conventional plays are listed here with their identification number from the National petroleum assessment: Madison (Mississippian) (3101), Red River (Ordovician) (3102), Middle and Upper Devonian (Pre-Bakken—Post-Prairie Salt) (3103), Pre-Prairie Middle Devonian and Silurian (3105), Post-Madison through Triassic elastics (3106), and Pre-Red River Gas (3107). Continuous-type unconventional plays include three fractured Bakken shale plays (Bakken Fairway-3110, Bakken lntermediate-3111, and Bakken Outlying-3112) and the Southern Williston Basin Margin Niobrara Shallow Biogenic Gas Play (3113) which extends beyond the borders of the Williston Basin. Three other biogenic gas plays were assessed as part of the North-Central Montana province. The Williston Basin province contains an estimated mean value of 650 MMBO and 1.69 TCFG from undiscovered resources in conventional plays. Resources attributed to reserve additions to known accumulations are considered substantial but are not available at the play or province level.

The North-Central Montana petroleum province extends from the eastern margin of the Montana disturbed belt eastward to the western boundary of the Williston Basin and southward to the Crazy Mountains and Powder River Basins. More than 50 accumulations greater than 6 BCF or 1 MMBO ultimate recoverable production have been discovered in the province as of 1993. Conventional or unconventional and confirmed or hypothetical plays are listed here with their identification number from the National petroleum assessment: Proterozoic (2801), Cambrian-Ordovician Sandstones (2802), Red River Carbonates (2803), Bakken Shale Fracture Systems (2804), Devonian-Mississippian Carbonates (2805), Tyler Sandstone (2806), Fractured-Faulted Carbonates in Anticlines (2807), Jurassic-Lower Cretaceous Sandstones (2808), and Shallow Cretaceous Biogenic Gas (2809). Unconventional gas plays include the Northern Great Plains Biogenic Gas High Potential (2810), Moderate Potential (2811), and Low Potential (2812) Plays. The province contains an estimated mean value of 270 MMBO and 840 BCFG from undiscovered resources in conventional plays. The entire region (Williston Basin, North-Central Montana, and areas extending beyond the borders of both provinces) contains an estimated mean value of 167.4 MMBO and 43.4 TCFG from unconventional oil and gas plays. Resources attributed to reserve additions from known accumulations are considered substantial but are not available at the play or province level.

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