HR: 0800h
AN: H41B-0406 INVITED     [Abstracts]
TI: Constrained Observations of Stress- and Chemistry-Mediated Changes in the Transport Properties of Fractured Rocks via Physical and Chemical Signals Supplemented by X-ray CT
AU: * Elsworth, D
EM: elsworth@psu.edu
AF: Energy and Geo-Environmental Engineering, Penn State University, University Park, PA 16802 United States
AU: Yasuhara, H
H41B-0406 AF: Energy and Geo-Environmental Engineering, Penn State University, University Park, PA 16802 United States
AU: Liu, J
H41B-0406 AF: Centre for Oil and Gas Engineering, University of Western Australia, Perth, WA 6009 Australia
AU: Polak, A
H41B-0406 AF: Civil and Environmental Engineering, The Technion, Haifa, 32000 Israel
AU: Grader, A
H41B-0406 AF: Energy and Geo-Environmental Engineering, Penn State University, University Park, PA 16802 United States
AU: Halleck, P
H41B-0406 AF: Energy and Geo-Environmental Engineering, Penn State University, University Park, PA 16802 United States
AB: Anomalous changes in permeability are observed in fractures circulated by water. Flow through experiments monitor the evolution in fracture impedance and effluent chemistry, with time, with intermittent imaging by X-ray CT. Where resolution permits, these measurements provide three independent constraints on the redistribution of mineral mass within the fracture. Surprisingly, under net dissolution and net removal of mineral mass, fractures may alternately gape or seal, depending on the prevailing mechanical and chemical conditions. The influence on transport properties is observed to be large, rapid, and irreversible: permeabilities reduce one-hundredfold in a month, and the direction of permeability change may switch spontaneously, with no change in environmental forcing. These behaviours are apparent in both silicate and carbonate rocks, at both low temperatures and stresses. The observed response carries many of the characteristics expected of pressure solution, but is activated at surprisingly low temperatures. Lumped parameter and distributed parameter models are developed to represent this behaviour, and to partially replicate stress- and chemistry-mediated effects, although some aspects remain enigmatic.
DE: 5114 Permeability and porosity
SC: Hydrology [H]
MN: Fall Meeting 2005