INTRUDED COALS OF THE RATON BASIN: EVALUATION OF METAMORPHIC EFFECTS ON COAL SEAMS

Oil and gas exploration typically employs a variety of methods including vitrinite reflectance and Rock-Eval analysis. These parameters are effective tools for determining source-rock potential and the level of maturation in organic-rich source rocks. The current research focuses on the changes in vitrinite reflectance and Rock-Eval parameters as a function of distance from intrusions in both the Viejo and Raton coal formations within the Raton Basin. Several factors contribute to the maturation level of coals and carbonaceous shales. The primary factor in organic maturation is temperature, but time and pressure may also play an important role. Contact metamorphism (i.e., that associated with metamorphic intrusions) may result is different maturation pathways than that associated with burial maturation. Within the Raton Basin, several examples of intruded coals have been reported in the literature. In the settings studied in this project, vitrinite reflectance (a primary indicator of rank) increases significantly towards the intrusions; reflectance levels typically exceed those associated with anthracite rank adjacent to the intrusion, with values exceeded 5% next to the intrusion. Carbon content increases towards the intrusion, whereas volatile matter, hydrogen, oxygen, and nitrogen show a decrease. Kerogen quality and organic maturation plots reveal the importance of igneous intrusions in areas such as the Raton Basin with respect to maturation of source rocks and possibly coal-bed methane generation. Organic petrology, coal geochemistry (including isotopic geochemistry), and Rock-Eval pyrolysis analyses for two suites of intruded coals will be evaluated in terms of coal maturation and source-rock potential.