Segmented vitrinite reflectance profile from the Deep Seam Project, Piceance Creek basin, Colorado - evidence of previous high pore pressure
The mean vitrinite reflectance profile of the REI Deep Seam 32-2 well in the southern Piceance Creek basin has at least three linear segments: a shallow segment extending from the surface to about 3000 ft; an intermediate segment from 3000 to 4900 ft; and a deep segment from 4900 to 5799 ft (total depth). The shallow segment is in Tertiary rocks and is offset from the next-deeper segment. The intermediate segment is steep (low gradient) and intersects the deep, less-steep (high-gradient) segment at a vitrinite reflectance of about 0.80%. By analogy with the model of the origin of abnormal pressures proposed by Law and Dickinson, the gas-bearing subnormal-pressured coal and adjacent strata in the Upper Cretaceous Mesaverde Group have evolved from an earlier overpressured phase. This suggests that during the overpressured phase (stage III of Law and Dickinson), the expulsion of relatively hot pore fluids from the top of abnormally high-pressured rocks into the overlying normal-pressured rocks raised the levels of organic maturation and steepened the vitrinite reflectance profile in the normal-pressured rocks. The bend in the profile at a vitrinite reflectance of about 0.80% represents the top of the earlier overpressured phase. Vitrinite reflectance values of this magnitude are commonly associated with the top of overpressuring in the adjacent Greater Green River basin of Wyoming, Colorado, and Utah.
- Research Organization:
- Geological Survey, Denver, CO
- OSTI ID:
- 6962768
- Report Number(s):
- CONF-8609129-
- Journal Information:
- Am. Assoc. Pet. Geol., Bull.; (United States), Journal Name: Am. Assoc. Pet. Geol., Bull.; (United States) Vol. 70:8; ISSN AAPGB
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
020200* -- Petroleum-- Reserves
Geology
& Exploration
03 NATURAL GAS
030200 -- Natural Gas-- Reserves
Geology
& Exploration
CENOZOIC ERA
COLORADO
CRETACEOUS PERIOD
FEDERAL REGION VIII
GEOLOGIC AGES
GEOLOGIC FORMATIONS
MACERALS
MATURATION
MESOZOIC ERA
NORTH AMERICA
OPTICAL PROPERTIES
PHYSICAL PROPERTIES
PICEANCE CREEK BASIN
RESERVOIR ROCK
SOURCE ROCKS
TERTIARY PERIOD
USA