Occurrence and geochemistry of natural gases, Piceance basin, northwestern Colorado

Conference · Wed Mar 01 04:00:00 EST 1989 · AAPG (Am. Assoc. Pet. Geol.) Bull.; (United States)

OSTI ID:6128402

Rice, D D; Johnson, R C

The Piceance basin is a hydrocarbon-rich province that has major resources of natural gas in coal beds and tight sandstone reservoirs of Cretaceous age. In general, gases from all producing intervals are of thermal origin and become isotopically heavier (/delta//sup 13/C/sub 1/ values = /minus/51.3 to -29.1 ppt) and chemically drier (C/sub 1//C/sub 1-5/ values = 0.41 to 1.00) with increasing level of thermal maturity (R/sub 0/ values = 0.45 to 2.4%) over a depth range of 1100 to 11,702 ft. Maturity increases to the south because of higher paleotemperatures. Based on chemical and isotopic composition, three types of gases can be distinguished: those generated from (1) mixed types II and III kerogens, (2) dispersed type III kerogen, and (3) coal, shown in series from chemically wettest to driest and isotopically lightest to heaviest at equivalent levels of thermal maturity. Type 1 gases are produced from marine sandstones, such as those of the Mancos B and Iles formations, and are associated with oil. Type 2 gases are in nonmarine sandstones of the Williams Fork Formation, are nonassociated at all levels of maturity, and contain large amounts of carbon dioxide (as much as 22%) derived from thermal decomposition of type III kerogen. Methane-rich type 3 gases are produced by devolatilization of humic coal and are contained in coal beds of the Cameo-Fairfield zone of the Williams Fork Formation. They have not migrated into adjacent sandstone reservoirs. Gases in immature Tertiary reservoirs are similar in chemical and isotopic composition to those of underlying reservoirs. They are interpreted to have migrated from deeper, more mature Cretaceous source rocks.

• Research Organization: Geological Survey, Denver, CO (USA)
• OSTI ID: 6128402
• Report Number(s): CONF-890404-
• Conference Information: Journal Name: AAPG (Am. Assoc. Pet. Geol.) Bull.; (United States) Journal Volume: 73:3
• Country of Publication: United States
• Language: English

Related Subjects

03 NATURAL GAS
030200* -- Natural Gas-- Reserves
Geology
& Exploration
BITUMINOUS MATERIALS
CARBON 13
CARBON ISOTOPES
CARBONACEOUS MATERIALS
CENOZOIC ERA
CHEMISTRY
COAL DEPOSITS
COAL SEAMS
COLORADO
CRETACEOUS PERIOD
EVEN-ODD NUCLEI
FEDERAL REGION VIII
GEOCHEMISTRY
GEOLOGIC AGES
GEOLOGIC DEPOSITS
ISOTOPES
KEROGEN
LIGHT NUCLEI
MATERIALS
MATURATION
MESOZOIC ERA
MINERAL RESOURCES
NATURAL GAS DEPOSITS
NORTH AMERICA
NUCLEI
ORGANIC MATTER
ORIGIN
PICEANCE CREEK BASIN
RESERVOIR ROCK
RESOURCES
ROCKS
SANDSTONES
SEDIMENTARY ROCKS
SOURCE ROCKS
STABLE ISOTOPES
TERTIARY PERIOD
USA