Print this pageAbstract: Methane in Green River Oil Shale
John R. Dyni, Rex D. Cole, G. J. Daub
Methane occurs at depths of about 430 to 550 meters in the lacustrine Green River Formation of Eocene age in north-central Piceance Creek basin, western Colorado. The methane occurs in an evaporite facies containing high-grade oil shale and sodium carbonate minerals and halite. Several hundred gas desorption tests of sealed drill cores of oil shale found gas concentrations ranging from 0 to 3.2 cm3/gm of rock. The composition of the gas averages 77.2% CH4, 17.3% CO2, 4.3% N2, and 0.3% 02. The total gas resource in the evaporite facies is estimated at 1.5 × 1011 m3 (5.3 × 1012 ft3).
Plots of the vertical distribution of gas in core holes suggest that some gas has migrated up-section, possibly through fractures formed during low-temperature thermal decomposition of the organic matter, and has accumulated below impermeable beds of halite and nahcolite. Because the permeability of the methane-bearing oil shales is nil, economic recovery of the gas will depend largely upon fracture porosity and permeability.
Additional gas resources are also indicated in core holes drilled into the Mahogany oil-shale zone in the southern part of the basin. In addition, enormous quantities of synthetic gas may be producible from the oil shale by new innovative technologies using borehole heaters to convert the organic matter to gas.
AAPG Search and Discovery Article #90986©1994 AAPG Annual Convention, Denver, Colorado, June 12-15, 1994