Gas Shale Resources—Role of Organic Matter

S. Ramos
University of British Columbia, Department of Earth and Ocean Sciences, Vancouver, British Columbia, Canada

Natural gas in organic-rich fractured shale is stored as free gas in fractures and as sorbed gas on organic matter. Measuring sorption isotherms account for the adsorbed component for gas-in-place calculations (production per unit volume of reservoir rock). Adsorption isotherms of methane and possibly carbon dioxide will be measured at 30 degrees C on selected Western Canadian shale samples such as the Nordegg, Exshaw, Bakken, and Colorado White Specks shales. The selected shale samples range in thermal maturity and total organic carbon content. Reflected light and UV fluorescence microscopy will characterize maceral composition and reflectance measurements will be used to establish the degree of organic maturation.

Rock-Eval pyrolysis will be used to determine total organic carbon content and kerogen type. Inorganic fraction will be quantified by xray diffraction analysis and contributions to the isotherm will be determined. The diffusivity of the shales will be determined from adsorption and desorption rates. The extent and nature of fracturing of the shales will be evaluated visually and by well logs.

The gas shale resource potential the organic-rich shales will be estimated by integrating the fracture data (free gas data) with the sorption data. By looking at a variety of shale lithologies, a better understanding will be gained of the relationship of gas storage to kerogen type, degree of organic maturation, and mineralogy. This research project will assist the oil and gas industry to evaluate potential gas shales in Canada.

AAPG Search and Discovery Article #90902©2001 AAPG Foundation Grants-in-Aid