Comparison of thermal analysis between Devonian shale and Green River oil shale

Results are presented of a comparison between Green River oil shale and Devonian shale by the use of the differential scanning calorimetry (DSC) and the thermogravimetric analysis. The effect of demineralization of shales upon heats of reaction is also reported. Results show that Devonian raw shale contains 2 to 3% (by weight) of pyrite. Pyrite is strongly associated with kerogen matrices in Devonian shales. It is extremely difficult to separate it from the shale organic material. The DSC curves of Devonian shale kerogen, pyrite mineral, and pyrite reduced kerogen are compared diagrammatically. The major DSC peak of pyrite centered around 550 to 560/sup 0/C had been eliminated in the pyrite reduced kerogen. The heat of pyrite decomposition from Devonian shale kerogen was estimated to be 67.6 cal/g. Though transition temperatures of decomposition for both kerogen concentrates are identical (at 500/sup 0/C), Devonian shale kerogen is much older in geological age and has higher aromaticity than Green River shale kerogen. The higher activation energy obtained from Devonian shale kerogen (64.9 kcal/g-mole vs 50 kcal/g-mole) could be due to a major reflection of aromatic bond breaking rather than a rupture of saturated aliphatic bond. This provides some internal information on structural differencemore » between the kerogens. The thermal properties of Devonian shale are quite different from those of Green River oil shale. The associated pyrite in kerogen concentrate may contribute greatly to the effect on thermal degradation of Devonian gas-bearing shale. For the first time the differential scanning calorimetry was applied to determining thermal properties of Devonian shale as well as Green River oil shale. Results have been compared with published data on Green River oil shale.« less