Gas evolution during pyrolysis of various Colorado oil shales

Rates of evolution of C0₂, CO, H₂, CH₄ and the C₂ and C₃ hydrocarbons during the pyrolysis of seven Colorado oil shales have been measured. These shales, which are from various depths at two different sites, yield 34–255 ¦ of oil per tonne raw shale (9–61 US gal of oil per short ton raw shale) and linear heating at a rate of 2°C min⁻¹ was used for the retorting of all samples. The objective of the study is to monitor variations in gas evolution from shales of different organic content and from various stratigraphic and areal locations. Comparisons between shales from each site are made together with correlations with data from Fischer assays. A kerogen concentrate (mineral fraction removed by HCl-HF treatment) and retorted shale from a Fischer assay are also included. The ability of a kinetic model due to Campbell et al. to predict gas evolution is tested and it is found necessary to modify slightly some of the stoichiometric coefficients to obtain good agreement. The resultant kinetic model should adequately describe the gas and oil evolution behaviour of shale from the upper portion of the Green River formation.