Inorganic gases in natural gas as an indicator of subcrustal events in southeastern Colorado

Conference · Thu Aug 01 04:00:00 EDT 1991 · AAPG Bulletin (American Association of Petroleum Geologists); (United States)

OSTI ID:5890006

Nelson, J S; Simmons, E C ^[1]

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1. Colorado School of Mines, Golden (United States)

Helium, nitrogen, and argon are small, chemically unreactive molecules which can diffuse through a gas-field cap rock relatively rapidly compared to hydrocarbons. To maintain the concentration of these species over geologic time spans, the rate of influx of these gases must at least equal their diffusional loss rate. Nitrogen in natural gas is generally believed to result form the thermal degradation of nitrogen-bearing organic compounds. Helium and argon are usually thought to be of crustal radiogenic origin. An alternate source of all three gases may be subcrystal outgassing. Anomalously high concentrations of He, Ar, and N{sub 2} occur in the natural gases of southeastern Colorado. The diffusional flux of He and Ar from gas fields and the generation rate of these through radioactive decay indicate insufficient concentrations of uranium, thorium, and potassium exist within the normal compositional range of the earth's crust. For nitrogen, there is insufficient organic carbon in the sedimentary column to generate the observed volumes of N{sub 2} unless the thermal degradation of organics is a recent event. Anomalous concentrations of He, Ar, and N{sub 2} suggest the presence of a subcrustal outgassing and thermal event under southeastern Colorado. The occurrence of a subcrustal event could correlate with the anomalously high heat flow in eastern Colorado, the recent (less than 5 Ma) epeirogenic uplift of the Great Plains, the thickest continental crust in the Mid-Continent, and recent nearby vulcanism.

• OSTI ID: 5890006
• Report Number(s): CONF-9109239--
• Conference Information: Journal Name: AAPG Bulletin (American Association of Petroleum Geologists); (United States) Journal Volume: 75:8
• Country of Publication: United States
• Language: English

Related Subjects

03 NATURAL GAS
030300* -- Natural Gas-- Drilling
Production
& Processing
ARGON
CHEMICAL COMPOSITION
CHEMISTRY
COLORADO
DEGASSING
DEVELOPED COUNTRIES
DIFFUSION
EARTH CRUST
ELEMENTS
ENERGY SOURCES
FEDERAL REGION VIII
FICK LAWS
FLUIDS
FOSSIL FUELS
FUEL GAS
FUELS
GAS FUELS
GASES
GEOCHEMISTRY
GEOLOGIC DEPOSITS
GEOLOGIC HISTORY
GEOTHERMAL GRADIENTS
HEAT FLOW
HELIUM
MINERAL RESOURCES
NATURAL GAS
NATURAL GAS DEPOSITS
NITROGEN
NONMETALS
NORTH AMERICA
RARE GASES
RESOURCES
TEMPERATURE GRADIENTS
USA