Thermal maturity of Codell Sandstone-Carlile Shale interval (Cretaceous) in part of Denver basin, Colorado
Based on several geochemical parameters, hydrocarbons in the Codell Sandstone appear to have been derived from the underlying Carlile Shale. Both units are past peak thermal maturity and are at the upper limit of petroleum generation and preservation. The Turonian Codell Sandstone produces oil, gas, and condensate from wells drilled in the northwestern Denver basin. The zone of greatest thermal maturity follows the basin's north-northwest axis. Vitrinite reflectance (R/sub 0/) analyses reveal abundant weathered and reworked particles; R/sub 0/ values are 0.65 to 1.50% for the freshest, least altered particles. Pyrolysis analyses suggest thermal maturities near the upper limit for oil and gas generation and preservation. T/sub max/ values of 400/sup 0/C and bifurcated S/sub 2/ peaks are common. Data plotted on a modified van Krevelen diagram suggest that the Codell contains mainly Type III organic material and the Carlile more Type II material. This Type II organic matter may be the source for the Codell oil and gas. Genetic potential calculations for the Carlile samples support such a possibility. TTI calculations based on Lopatin diagrams predict that the Codell and Carlile lie within the liquid window. These TTI calculations correspond to lower geochemical parameters than those observed, suggesting that both the Codell and Carlile have passed peak thermal maturation.
- Research Organization:
- RPI Pacific, Redwood, City, CA
- OSTI ID:
- 7053931
- Report Number(s):
- CONF-8609129-
- Journal Information:
- Am. Assoc. Pet. Geol., Bull.; (United States), Vol. 70:8; Conference: AAPG Rocky Mountain Section meeting, Casper, WY, USA, 7 Sep 1986
- Country of Publication:
- United States
- Language:
- English
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