THE BEHAVIORS OF THERMAL DEGASSING OF MARCELLUS SHALE

Outcrop samples of Marcellus Shale and stratigraphic equivalents across the Appalachian Basin are compared on their thermal degassing behavior based on data obtained from TGA, DSC and Bomb Calorimetry. Thermal degassing tests are done on shale size fractions ranged from 2000µ to 50µ in diameter, and are degassed with various heating rate and heating time. The purpose is to understand the behavior of shale degassing and to estimate the potential of hydrocarbon generation at a higher level of resolution. Carbonate is decomposed at 650°C. Both the decomposition of kerogen and the dehydroxylation of illitic clay take place between 350°C and 550°C. It is significant to notice that water and light hydrocarbon, about 1% of sample weight, are continuously degassed in the temperature range 100°C and 350°C. The water is interpreted as that been kept in micron size and sub-micron size pore spaces. The hydrocarbon could also be gas held in micropores, but it is more likely to be the gas derived from the decomposition of kerogen in that range of temperature. Less mature organic shale released noticeably higher weight percentage of gas during the 100°C to 350°C temperature range than more mature organic shale did. A smaller rate of heating achieved the same outgassing effect at the lower temperatures than a larger rate of heating did.