TESTS OF LABORATORY RETORTING ON DEVONIAN BLACK SHALES

Outcrop samples of Cleveland Shale, Marcellus Shale were tested using a storing method to evaluate the potential gas production. Samples of organic-rich shales include immature to over-mature in thermal maturation. One core sample of gas producing Woodford Shale and another sample of organic poor shale were also tested to provide contrast. Shale size fraction of approximately 100µ (mesh #60 to #140) was heated in vacuum to 300°C, 500°C and 700°C for 60 to 90 minutes with or without a dry ice cold trap. The released gas was measured by the pressure change in the vacuum line. Major types of gas released, as identified by IR, include water, hydrocarbons and CO₂. All shales released water during the heating from at 0.5% to 2% by weight. Water was filtered out by using the cold trap. CO₂ is mainly released by shale which contains carbonates, and it was released only in the 700°C tests The abundance of hydrocarbons released at 300°C was approximately 0.1% by weight while when heated to 500°C was 1% by weight. The gas producing core sample of Woodford Shale yielded the highest amount of both water and hydrocarbons. The non-producing organic-rich Cleveland Shale, and the thermally over-matured shale yielded more hydrocarbons than the outcrop samples of Marcellus Shale in both the 500°C test and the 300°C test. This study strongly suggests that the retorting of organic rich shale is able to yield significant amounts of hydrocarbon gases at 500°C. The amount of hydrocarbon gas yielded is about 1% of the sample weight, or 15,000 liters of methane equivalent per 1000 kg of shale. This is equivalent to 530 scf/ton and is higher than the estimation of gas in place (GIP) of the Woodford Shale.