Modeling of gas generation from the Cameo coal zone in the Piceance Basin, Colorado

The gas generative potential of the Cretaceous Cameo coal in the Piceance Basin, northwestern Colorado, was evaluated quantitatively by sealed gold tube pyrolysis. TheH/C andO/C elemental ratios show that pyrolyzed Cameo coal samples follow the Van Krevelen humic coal evolution pathway, reasonably simulating natural coal maturation. Kinetic parameters (activation energy and frequency factor) for gas generation and vitrinite reflectance (Ro) changes were calculated frompyrolysis data. Experimental Ro results from this study are not adequately predicted by published Ro kinetics and indicate the necessity of deriving basin-specific kinetic parameters when building predictive basin models. Using derived kinetics for Ro evolution and gas generation, basin modeling was completed for 57wells across the Piceance Basin, which enabled themapping of coal-rank and coalbed gas potential. Quantities of methane generated at approximately 1.2%Ro are about 300 standard cubic feet per ton (scf/ton) and more than 2500 scf/ton (in-situ dry-ash-free coal) at Ro values reaching 1.9%.Gases generated in both lowandhigh-maturity coals are less wet, whereas thewetter gas is expectedwhere Ro is approximately 1.4–1.5%. As controlled by regional coal rank and net coal thickness, the largest in-place coalbed gas resources are located in the central part of the basin, where predicted volumes exceed 150 bcf/mi, excluding gases in tight sands.