Relation of natural gas composition to thermal maturity and source rock type in San Juan Basin, northwestern New Mexico and southwestern Colorado

Journal Article · Mon Aug 01 04:00:00 EDT 1983 · Am. Assoc. Pet. Geol., Bull.; (United States)

OSTI ID:5493330

Rice, D D

San Juan basin is a roughly circular, asymmetric structural depression located in northwestern New Mexico and southwestern Colorado. Ultimate recoverable reserves of predominantly nonassociated gas (23 tcf, 0.65 X 10/sup 12/ m/sup 3/) are present in the structurally low part of the central basin. The major producing intervals are low-permeability sandstone reservoirs in the Upper Cretaceous Dakota Sandstone, Mesaverde Group, and Pictured Cliffs Sandstone. Lesser amounts of oil and/or gas are produced from Pennsylvanian, Jurassic, and Cretaceous rocks along the southern and western flanks of the basin. The gases display a trend of becoming isotopically heavier (delta/sup 13/C/sub 1/ values range from -48.7 to -31.4%.) and chemically drier (C/sub 1//C/sub 1-5/ values range from 0.75 to 0.99) with increasing depth. The gases also become isotopically heavier and chemically drier to the northeast, following the trend of increasing maturity of all units in that direction. Lack of oil in the central basin is believed to be the result of two factors. First, gas in reservoirs such as the Dakota Sandstone may have resulted from thermal cracking of oil generated from marine source rocks during late mature (wet gas-condensate) and post-mature (dry gas) stages of hydrocarbon generation. Second, gas in reservoirs such as Mesaverde Group and Pictured Cliffs Sandstone is nonassociated and probably was generated from nonmarine (coaly) organic matter during the mature and post-mature stages. Minor amounts of condensate, instead of oil, may have been generated from nonmarine source rocks during the mature stage. (JMT)

• Research Organization: Geological Survey, Denver, CO
• OSTI ID: 5493330
• Journal Information: Am. Assoc. Pet. Geol., Bull.; (United States), Journal Name: Am. Assoc. Pet. Geol., Bull.; (United States) Vol. 67:8; ISSN AAPGB
• Country of Publication: United States
• Language: English

Related Subjects

03 NATURAL GAS
030200* -- Natural Gas-- Reserves
Geology
& Exploration
CHEMICAL COMPOSITION
COLORADO
CRETACEOUS PERIOD
ENERGY SOURCES
FEDERAL REGION VI
FEDERAL REGION VIII
FLUIDS
FOSSIL FUELS
FUEL GAS
FUELS
GAS FUELS
GASES
GEOLOGIC AGES
GEOLOGIC DEPOSITS
GEOLOGIC STRUCTURES
GEOLOGY
JURASSIC PERIOD
MESOZOIC ERA
MINERAL RESOURCES
NATURAL GAS
NATURAL GAS DEPOSITS
NEW MEXICO
NORTH AMERICA
ORIGIN
PALEOZOIC ERA
PENNSYLVANIAN PERIOD
PETROLEUM GEOLOGY
RESERVOIR ROCK
RESOURCES
ROCKS
SANDSTONES
SEDIMENTARY BASINS
SEDIMENTARY ROCKS
SOURCE ROCKS
USA