Origin and distribution of fractures in Tertiary and Cretaceous rocks, Piceance Basin, Colorado, and their relation to hydrocarbon occurrence
Gas production in the lower Tertiary Wasatch Formation and Upper Cretaceous Mesaverde Group, Piceance basin, Colorado, is controlled by a network of open and partly mineralized natural fractures. These fractures formed in response to high pore-fluid pressures that developed during hydrocarbon generation, and to widespread tectonic stress associated with periods of uplift and erosion that occurred during the late Tertiary. Sandstone beds commonly contian vertical extension fractures that are cemented with fine to coarsely crystalline calcite and locally with quartz, barite, and dickite. These minerals cut detrital grains, authegenic cements, and secondary pores, indicating that fracture mineralization occurred during later stages of diagenesis. Isotopic compositions for fracture-fill calcite in the Wasatch vary from - 5.0 0/00 to -11.6 0/00 for sigma/sup 13/C and from -9.5 0/00 to -14.9 0/00 for sigma/sup 18/O. In the Measverde, calcite ranges from -0.7 0/00 to -10.4 0/00 for sigma/sup 13/C and from -13.3 0/00 to -17.7 0/00 for sigma/sup 18/O. These isotopic data indicate that fractures were mineralized during burial by fluids of meteoric origin, with temperatures that remained fairly constant, or by fluids of meteoric origin, with temperatures that remained fairly constant, or by fluids that circulated at a rate that prohibited significant cooling. The wide range in sigma/sup 13/C compositions reflects mixtures of organically derived carbon and dissolved marine carbonate. In reservoir rocks that are extensively fractured, gas generated in situ from carbonaceous and coaly shales and tongues of lacustrine rock may have migrated locally along open faults and fractures.
- Research Organization:
- Geological Surveys, Denver, CO
- OSTI ID:
- 5992793
- Report Number(s):
- CONF-8506201-
- Journal Information:
- Am. Assoc. Pet. Geol., Bull.; (United States), Vol. 69:5; Conference: AAPG Rocky Mountain Section meeting, Denver, CO, USA, 2 Jun 1985
- Country of Publication:
- United States
- Language:
- English
Similar Records
Reservoir characterisation of the (M/T) Thamama structure (offshore Abu Dhabi) based on petrography and geochemical analysis
Diagenesis of the Machar Field (British North Sea) chalk: Evidence for decoupling of diagenesis in fractures and the host rock
Related Subjects
03 NATURAL GAS
NATURAL GAS DEPOSITS
SOURCE ROCKS
PETROLEUM DEPOSITS
PICEANCE CREEK BASIN
FRACTURES
PERMEABILITY
POROSITY
CARBON 13
COLORADO
GEOLOGIC FORMATIONS
ISOTOPE RATIO
TERTIARY PERIOD
CARBON ISOTOPES
CENOZOIC ERA
EVEN-ODD NUCLEI
FAILURES
FEDERAL REGION VIII
GEOLOGIC AGES
GEOLOGIC DEPOSITS
ISOTOPES
LIGHT NUCLEI
MINERAL RESOURCES
NORTH AMERICA
NUCLEI
RESOURCES
STABLE ISOTOPES
USA
020200* - Petroleum- Reserves
Geology
& Exploration
030200 - Natural Gas- Reserves
Geology
& Exploration