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Hydrodynamics of Denver Basin; explanation of subnormal fluid pressures

Kenneth R. Belitz and John D. Bredehoeft
Hydrodynamics of Denver Basin; explanation of subnormal fluid pressures
AAPG Bulletin (November 1988) 72 (11): 1334-1359


Anomalously low fluid potential (and hence subnormal fluid pressure) is found in Mesozoic and Paleozoic rocks of the Denver basin. The potentiometric surface for the Dakota and basal Cretaceous sandstones is 2,000-3,000 ft (600-900 m) beneath the land surface in parts of the Denver basin in Colorado and Nebraska. The potentiometric surface for pre-Pennsylvanian carbonate rocks is 1,500 ft (450 m) lower than the potentiometric surface for the Dakota Sandstone in southeastern Colorado and western Kansas. The low fluid potential seems especially anomalous considering the high elevation of the outcrops along the Laramie and Front Ranges and the Black Hills. A quasi-three-dimensional numerical flow model is used to investigate the regional flow system in the Denver basin and adjacent Mid-Continent. The model simulates flow through the entire Phanerozoic sedimentary column and indicates that subnormal pressures are a consequence of hydraulic insulation of the strata within the basin from their recharge zones as compared to their discharge zones. The Dakota Sandstone and underlying hydrostratigraphic units are insulated from the overlying water table by low-permeability shales of Cretaceous age, and from their own high-elevation outcrops by a zone of low permeability coincident with the basin deep. Subnormal pressures in the area of Denver, Colorado, and southward are further enhanced by faulting along the Front Range that isolates the strata within the basin from their outcrops. The results of this study show that (1) subnormal fluid pressures can be explained as a consequence of steady-state regional ground-water flow, (2) shale is an important factor in the regional flow system, and (3) depth is an important control on the distribution of hydraulic conductivity.

ISSN: 0149-1423
EISSN: 1558-9153
Coden: AABUD2
Serial Title: AAPG Bulletin
Serial Volume: 72
Serial Issue: 11
Title: Hydrodynamics of Denver Basin; explanation of subnormal fluid pressures
Affiliation: U. S. Geol. Surv., Menlo Park, CA, United States
Pages: 1334-1359
Published: 198811
Text Language: English
Publisher: American Association of Petroleum Geologists, Tulsa, OK, United States
References: 115
Accession Number: 1988-079712
Categories: Hydrogeology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 3 tables, strat. col., chart, sketch maps
N36°00'00" - N49°00'00", W104°00'00" - W80°30'00"
N40°00'00" - N43°00'00", W104°04'60" - W95°19'60"
N38°04'60" - N42°40'00", W105°19'60" - W102°19'60"
N39°45'00" - N39°45'00", W105°00'00" - W105°00'00"
N37°00'00" - N40°00'00", W102°00'00" - W94°34'60"
N40°55'00" - N41°55'00", W106°25'00" - W105°25'00"
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2019, American Geosciences Institute.
Update Code: 1988
Program Name: USGSOPNon-USGS publications with USGS authors
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