Denver Basin Geology
Denver Basin Geology
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The Denver Basin is an asymmetrical Laramide-age basin that covers more than 180,000 square km (70,000 square mi) in parts of Colorado, Wyoming, South Dakota, Kansas, and Nebraska. The bulk of the basin is in Colorado. The basin is often termed the Denver-Julesburg Basin or the Denver-Julesburg-Wattenburg Basin. The Wyoming portion of the Denver Basin is in the southeastern corner of the state, and is bounded on the west by the Laramie Range and on the north by the Hartville Uplift.
The Denver Basin has typical foreland basin-style geometry with a north- south-trending basin axis. The strata on the western side of the basin dip steeply toward the east, while the strata in the eastern Denver Basin gently slope to the west. The basin is more than 3,962 m (13,000 ft) deep, as defined by the 1.6-billion-year-old Precambrian basement. The bulk of the strata preserved in the Denver Basin were deposited during the Cretaceous in the Sevier foreland basin, and later separated from similar strata in other Wyoming basins by the Laramide orogeny. Surface outcrops in the Denver Basin are generally Tertiary in age.
The Silo field, discovered in 1981 (Sonnenberg, 2011), is the most productive oil and (associated) natural gas field in the basin. Production in the Silo field is primarily from the self-sourced Cretaceous Niobrara Formation, which is predominantly fractured chalk (reservoir) encased in tight shales and mudstones (seal). This unconventional reservoir is conducive to horizontal drilling and hydraulic fracturing, which significantly enhance production.
In addition to the Niobrara Formation, other possible source rocks in the Denver Basin include the Cretaceous Belle Fourche (Graneros), Mowry, and Carlile shales, as well as the Greenhorn Formation. Oil generation in these formations began during the Laramide orogeny and continued through the Miocene (Higley and Cox, 2007).
Production
Production
Oil and gas was first discovered in the Denver Basin in 1901, and it now includes approximately 1,500 hydrocarbon fields spanning several states (Higley and Cox, 2007). The Wyoming portion of the Denver Basin has 33 named oil and gas fields, 12 of which are currently producing oil or gas (WSGS oil and gas map). Production from these 12 fields and numerous wildcat wells steadily increased by more than an order of magnitude since 2009, thanks in part to some of Wyoming’s most productive oil wells. Each year since 2017, the Denver Basin has accounted for 10% of the state’s total oil production (WOGCC, 2024).
Future Development
Future Development
Although production efforts in the Denver Basin have historically focused on the Niobrara Formation, operators are beginning to explore other unconventional plays in the basin. Horizontal drilling and hydraulic fracturing have increased recent production from the tight sand formations of the Upper Cretaceous Muddy "J" Sandstone and the Codell Sandstone Member of the Carlile Shale. As drilling techniques and reservoir characterization in the Denver Basin are refined and improved, there is the potential for increased production from unconventional reservoirs.
Tertiary White River and Arikee formations on the Goshen Hole Rim. [Credit: WSGS]
References
References
Higley, D.K., and Cox, D.O., 2007, Oil and gas exploration and development along the Front Range in the Denver Basin of Colorado, Nebraska, and Wyoming, in Higley, D.K., comp., Petroleum systems and assessment of undiscovered oil and gas in the Denver Basin Province, Colorado, Kansas, Nebraska, South Dakota, and Wyoming—USGS Province 39: U.S. Geological Survey Digital Data Series DDS-69-P, chap. 2, 41 p.
Sonnenberg, S.A., 2011, Silo field summary, in Estes-Jackson, J.E., and Anderson, D.S., eds., Revisiting and revitalizing the Niobrara in the central Rockies: Denver, Colo., Rocky Mountain Association of Geologists, p. 494–497.
WOGCC, 2024, Wyoming Oil and Gas Conservation Commission website, accessed March 2024, at http://pipeline.wyo.gov/legacywogcce.cfm.
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