2009 Portland GSA Annual Meeting (18-21 October 2009)

Paper No. 6
Presentation Time: 9:00 AM-6:00 PM

CARBON SEQUESTRATION IN COAL: PREDICTING THE BEHAVIOR OF ORGANIC CONSTITUENTS DURING CO2 SEQUESTRATION


THOMAS, Burt, NRP, USGS, 345 Middlefield Rd, MS 420, Menlo Park, CA 94025, ROSENBAUER, Robert, Coastal and Marine Geology, U.S. Geological Survey, 345 Middlefield Road, MS-999, Menlo Park, CA 94025 and KHARAKA, Yousif K., U. S. Geological Survey, 345 Middlefield Road, Menlo Park, CA 94025, burt_thomas@usgs.gov

Flooding coals with carbon dioxide (CO2) is expected to produce an acidic aqueous phase in addition to the supercritical water-saturated CO2 phase. At low pH, organic acids within porewater and within the organic-rich rock matrix preferentially exist in neutral form and are soluble in the supercritical phase. Here we describe the experimental interaction between supercritical CO2, saline water, and thermally immature coal at 60°C and 100 bars. We also describe a protocol to sample both supercritical and aqueous phases for the chemical analyses of dissolved organic acids and volatile aromatic compounds. Short chain monocarboxylic acids are measured by HPLC, whereas longer chain mono and dicarboxylic acids are analyzed as n-propyl esters via conventional gas chromatography and mass spectroscopy. Carbon dioxide-induced liberation of organic acids from natural earth materials could affect mechanisms of mineral surface reactivity. This process could also provide an important, unintended source of labile carbon to the deep biosphere.