EVALUATION OF THE CHATTANOOGA SHALE IN KANSAS AS A SHALE GAS RESOURCE

The Devonian-Mississippian Chattanooga Shale in eastern and central Kansas has the potential to produce shale gas. Initial desorption testing of the Chattanooga showed an initial rapid release and then an abrupt stop. The sudden stop differs from typical gradual release of gas in more common and less-mature Pennsylvanian shale of the area. A possible cause for the sudden termination of the gas production could be heavier-molecular-weight hydrocarbons blocking the micropores in the shale, effectively inhibiting further release of the shale gas. To test this hypothesis, additional shale cuttings were collected from an actively drilling well in southeastern Kansas and desorption rates were measured. Wellsite, laboratory, and mathematical techniques were used to determine the gas content from the shale cuttings. The cuttings were collected from three distinct lithologic horizons within the formation: A dark gray with some green fragments, a dark black that smelled strongly of hydrocarbons, and a light gray. The gray samples released little or no gas. The black sample produced 90 cm3 before terminating. After initial gases were desorbed over a two-week period, the black sample was decanistered, cleaned, dried, and weighed. The sample was separated and sieved into four size fractions (0.0197, 0.0394, 0.0555, and 0.0787 inches.) Non-generating particles were removed and the samples were weighed again to determine the percentage of shale in each size fraction which was, 95%, 96%, 95%, and 05%, respectively. The sieved cuttings and a portion of the remaining cuttings from sample two were combined and 14% of the original sample was crushed in a ball mill to promote the further release of gases that may be trapped in the micropores of the shale. The milled sample released an additional 59 cm3 of gas. The sample has been submitted for mole % compositional analysis to determine percentages of low-molecular weight gases and analysis of the total organic carbon content to provide an estimate for the shale’s overall potential for gas generation. Additional sampling is planned to determine the potential for shale gas production in southeastern Kansas.