HR: 14:10h
AN: H33M-03    [Abstracts]
TI: Characterization of Fractured Reservoirs Using a Combination of Pressure and Self-potential Transient Data
AU: * Ishido, T
EM: ishido-t@aist.go.jp
AF: Geological Survey of Japan, AIST, Central 7, 1-1-1 Higashi, Tsukuba, 305-8567, Japan
AU: Nishi, Y
EM: y.nishi@aist.go.jp
AF: Geological Survey of Japan, AIST, Central 7, 1-1-1 Higashi, Tsukuba, 305-8567, Japan
AU: Pritchett, J W
EM: John.W.Pritchett@saic.com
AF: SAIC, 10260 Campus Point Drive, San Diego, CA 92121, United States
AB: Fractured geothermal reservoirs are often represented computationally as "MINC" double-porosity media. In such reservoir descriptions, global mass exchange between adjacent macroscopic computational grid blocks takes place mainly through the "fracture zone". Inter-block flow through the "matrix region" is relatively unimportant and is usually neglected in most MINC treatments. But this approximation is inappropriate when calculating the global "drag current" caused by electric charges moving with the flowing fluid due to electrokinetic coupling. Since the magnitude of the drag current density is proportional not to the permeability but to the porosity of the medium, the contribution of the drag current through the matrix region to the total global current between adjacent macroscopic grid blocks is not negligible, and in fact usually predominates under steady-state conditions. This property of the drag current brings about much more pronounced differences in the "self-potential transients" between competing "fractured/MINC" and "porous-medium" descriptions of the same reservoir than is the case for pressure transients. Combining continuous pressure and self-potential measurements may therefore provide a means for better characterizing fractured reservoirs. Probable methods to measure the transients of "macroscopic" electric potential, which reflects the contribution of the drag current through the matrix region, will also be discussed.
DE: 0925 Magnetic and electrical methods (5109)
DE: 1829 Groundwater hydrology
DE: 1847 Modeling
DE: 3914 Electrical properties
DE: 5104 Fracture and flow
SC: Hydrology [H]
MN: 2007 Fall Meeting