Assessment of undiscovered conventional oil and gas resources of the Western Canada Sedimentary Basin, Canada, 2012

The U.S. Geological Survey mean estimates of undiscovered conventional oil and gas resources from provinces in the Western Canada Sedimentary Basin of central Canada are 1,321 million barrels of oil, 25,386 billion cubic feet of gas, and 604 million barrels of natural gas liquids.

Introduction

The U.S. Geological Survey (USGS) recently completed a geoscience-based assessment of undiscovered oil and gas resources of provinces within the Western Canada Sedimentary Basin (WCSB) (table 1). The WCSB primarily comprises the (1) Alberta Basin Province of Alberta, eastern British Columbia, and the southwestern Northwest Territories; (2) the Williston Basin Province of Saskatchewan, southeastern Alberta, and southern Manitoba; and (3) the Rocky Mountain Deformed Belt Province of western Alberta and eastern British Columbia (fig. 1). This report is part of the USGS World Petroleum Resources Project assessment of priority geologic provinces of the world. The assessment was based on geoscience elements that define a total petroleum system (TPS) and associated assessment unit(s) (AU). These elements include petroleum source rocks (geochemical properties and petroleum generation, migration, and accumulation), reservoir description (reservoir presence, type, and quality), and petroleum traps (trap and seal types, and timing of trap and seal formation relative to petroleum migration). Using this framework, the Elk Point-Woodbend Composite TPS, Exshaw-Fernie-Mannville Composite TPS, and Middle through Upper Cretaceous Composite TPS were defined, and four conventional AUs within the TPSs were quantitatively assessed for undiscovered resources in the WCSB (table 1).

Figure 1. Extent of the Western Canada Sedimentary Basin is approximated by the outer boundaries of the labeled Alberta Basin Province, Williston Basin Province, and Rocky Mountain Deformed Belt Province. Contained are conventional assessment units (AUs) for the (1) Middle and Upper Cretaceous Reservoirs AU of the Middle through Upper Cretaceous Composite Total Petroleum System (TPS); (2) Triassic through Lower Cretaceous Reservoirs AU, and (3) Mississippian through Permian Reservoirs AU, both of the ExshawFernie-Mannville Composite TPS; and (4) Upper Devonian and Older Reservoirs AU of the Elk Point-Woodbend Composite TPS.

Figure 1 shows assessment unit (AU) boundaries for the (1) Middle and Upper Cretaceous Reservoirs AU; (2) Triassic through Lower Cretaceous Reservoirs AU; (3) Mississippian through Permian Reservoirs AU; and (4) Upper Devonian and Older Reservoirs AU. Boundaries of the AUs (fig. 1) encompass the extent of potential conventional petroleum resources within the labeled petroleum provinces. Conventional AUs are defined within three total petroleum systems (fig. 2, table 1) based mainly on results of 1D and 4D petroleum system modeling documented in Roberts and others (2005) and Higley and others (2009). Actual TPS divisions are considerably more complex in the WCSB (Allan and Creaney, 1991), particularly since the petroleum source rock kitchen for the Alberta Basin is proximal to and under the Canadian Rocky Mountains, and the Williston Basin petroleum is sourced from the south.

Resource Summary

The USGS assessed undiscovered conventional oil and gas resources for provinces in the WCSB (table 1). Undiscovered, technically recoverable conventional resources mean totals are 1,321 million barrels of oil (MMBO), 25,386 billion cubic feet of gas (BCFG), and 604 million barrels of natural gas liquids (MMBNGL). Mean undiscovered resources for the (1) Middle and Upper Cretaceous Reservoirs AU are 110 MMBO, 2,530 BCFG, and 69 MMBNGL; (2) Triassic through Lower Cretaceous Reservoirs AU are 571 MMBO, 15,728 BCFG, and 400 MMBNGL; (3) Mississippian through Permian Reservoirs AU include 185 MMBO, 3,210 BCFG, and 42 MMBNGL; and (4) Upper Devonian and Older Reservoirs AU totals are 455 MMBO, 3,918 BCFG, and 93 MMBNGL.

Table 1. Western Canada Sedimentary Basin conventional resource assessment results. [MMBO, million barrels of oil. BCFG, billion cubic feet of gas. MMBNGL, million barrels of natural gas liquids. Results shown are fully risked estimates. For gas fields, all liquids are included under the NGL (natural gas liquids) category. Undiscovered gas resources are the sum of nonassociated and associated gas. F95

Sources of Data

The primary source of well history and production data used in this assessment was the IHS Energy Enerdeq™ Desktop Canada database (2011). Other data sources are documented in Higley and others (2005, 2009). The Energy Resources Conservation Board (Energy Resources Conservation Board, 2011) contains pertinent geoscience and energy-reserves information accessed for this study.

Assessment Team

Western Canada Sedimentary Basin Assessment Team: Debra K. Higley (Task Leader; higley@usgs.gov) and Review Committee: Ronald R. Charpentier, Troy A. Cook, Timothy R. Klett, Richard M. Pollastro, Christopher J. Schenk (Project Leader), Marilyn E. Tennyson, and Craig J. Wandrey. Further information on this and other World Petroleum Resources Project basins can be accessed at http://energy.usgs.gov/OilGas/AssessmentsData/WorldPetroleumAssessment.aspx.

Figure 2. Generalized stratigraphic section of mainly the Alberta portion of the Western Canada Sedimentary Basin showing age ranges of the Middle through Upper Cretaceous Composite TPS (yellow), Exshaw-Fernie-Mannville Composite TPS (pink), and Elk Point-Woodbend Composite TPS (blue). Lithologies include primarily shale or marl (gray), sandstone (stipple), carbonates (white), and coal (black). Mossop and Shetsen (1994) was the primary source for lithofacies types. Modified from Higley and others (2009). (Fm(s), Formation(s); Gp., Group; Mem., Member; Perm., Permian; Penn., Pennsylvanian.)

References Cited

Allan, J., and Creaney, S., 1991, Oil families of the Western Canada Basin: Bulletin of Canadian Petroleum Geology, v. 39, no. 2, p. 107–122.

Energy Resources Conservation Board, 2011, Alberta’s energy reserves 2010 and supply/demand outlook 2011–2020: Calgary, Alberta, Energy Resources Conservation Board ST98-2011, 263 p.

Higley, D.K., Henry, M.E., and Roberts, L.N.R., 2005, Petroleum system modeling of the Western Canada Sedimentary Basin—Isopach grid files: U.S. Geological Survey Open-File Report 2005–1421, 14 p. (Also available at http://pubs.usgs.gov/of/2005/1421.)

Higley, D.K., Lewan, M.D., Roberts, L.N.R., and Henry, M.E., 2009, Timing and petroleum sources for the Lower Cretaceous Mannville Group oil sands of northern Alberta based on 4-D modeling: American Association of Petroleum Geologists Bulletin, v. 93 no. 2, p. 203–230.

IHS Energy, 2011, IHS Energy Enerdeq™ Desktop Canada database: Unpublished database available from IHS Energy, 15 Inverness Way East, Englewood, Colo., 80112.

Mossop, G., and Shetsen, I., comps., 1994, Geological atlas of the Western Canada Sedimentary Basin: Calgary, Alberta, Canadian Society of Petroleum Geologists and Alberta Research Council, accessed June 1, 2012, at http://www.ags.gov.ab.ca/publications/wcsb_atlas/atlas.html.

Roberts, L.N.R., Higley, D.K., and Henry, M.E., 2005, Input data used to generate one-dimensional burial history models, central Alberta, Canada: U.S. Geological Survey Open-File Report 2005–1412, 14 p. (Also available at http://pubs.usgs.gov/of/2005/1412/.)

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