HR: 0800h
AN: H11E-0341    [Abstracts]
TI: Enigmatic Permeability Switching in Fractures Under Net Dissolution
AU: Yasuhara, H
EM: huy103@psu.edu
AF: Pennsylvania State University, The Energy Institute, 204 Academic Activities, University Park, PA 16802 United States
AU: * Polak, A
EM: amirp@techunix.technion.ac.il
AF: Technion, Israel Institute of Technology, Department of Civil Engineering, Haifa, 32000 Israel
AU: Elsworth, D
EM: elsworth@psu.edu
AF: Pennsylvania State University, The Energy Institute, 204 Academic Activities, University Park, PA 16802 United States
AU: Grader, A
EM: grader@pnge.psu.edu
AF: Pennsylvania State University, The Energy Institute, 204 Academic Activities, University Park, PA 16802 United States
AU: Halleck, P
EM: phil@pnge.psu.edu
AF: Pennsylvania State University, The Energy Institute, 204 Academic Activities, University Park, PA 16802 United States
AB: Results are reported for water flow-through experiments conducted on a natural fracture in Arkansas Novaculite at temperatures of 20C, 40C, 80C, and 120C and under ambient confining stress of 1.72 MPa and flow-rates of Q = 1.0 to 0.0625 mL/min. Measurements of fluid and dissolved mass fluxes, and concurrent x-ray CT imaging are used to constrain the progress of dissolution and its effect on transport properties throughout the 3150 hr duration of the experiment. Changes in differential pressure between sample inlet and outlet are recorded and used as a proxy for evolution in fracture aperture (i.e., permeability). Measurements of effluent dissolved mineral mass flux provide an independent measure of aperture changes with time. These measurements of evolving aperture are further constrained through non-destructive imaging by x-ray CT. The hydraulic aperture monotonically decreases from 18 to 7 um during the first 1500 hrs (20C), despite net dissolution of Si. As temperature is incremented to 120C, the fracture switches from net closure to gaping, resulting in a final aperture of 13 um at the end of the 3150 hr duration experiment. Effluent Si concentrations increase with temperature, and imply that precipitation remained inactive within the fracture, and highlighting the potential for the activation of dissolution at fracture void surfaces. The phenomenon of switching from fracture closure to gaping occurred even in the absence of changes in experimental conditions of flow-rate or applied effective stress and is due to a switch in dominant processes; from mineral dissolution dominant at the contacting asperities to free-face dissolution-dominant at the fracture void surfaces.
DE: 5114 Permeability and porosity
DE: 5139 Transport properties
DE: 1829 Groundwater hydrology
SC: Hydrology [H]
MN: 2004 AGU Fall Meeting