Lorne, Benoit and Perrier, Frédéric and Avouac, Jean-Philippe (1999) Streaming potential measurements 2. Relationship between electrical and hydraulic flow patterns from rock samples during deformation. Journal of Geophysical Research B, 104 (B8). pp. 17879-17896. ISSN 0148-0227 http://resolver.caltech.edu/CaltechAUTHORS:20120914-082754709
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Streaming potential and resistivity measurements have been performed on Fontainebleau sandstone and Villejust quartzite samples in a triaxial device during compaction, uniaxial compression, and rupture. Measurements on individual samples do not show any clear intrinsic dependence of the streaming potential coefficient with permeability. An apparent dependence of the streaming potential coefficient with permeability is, however, observed during deformation. The effect of surface conductivity is taken into account and is small compared with the observed changes in the streaming potential coefficient. The observed dependence is therefore interpreted in terms of a difference in the evolution of the electrical and hydraulic connectivity patterns during deformation. This effect causes the streaming potential coefficient, and consequently the inferred ξ potential, to be reduced by a geometrical factor R_G representing the electrical efficiency of the hydraulic network. Estimates of the R_G factor varying between 0.2 and 0.8 for electrolyte resistivity larger than 100 Ωm are obtained by comparing the values of the ξ potential inferred from intact rock samples with the values obtained from crushed rock samples, where the geometrical effects are assumed to be negligible. The reduction of the streaming potential coefficient observed during compaction or uniaxial compression suggests that the tortuosity of the hydraulic network increases faster than the tortuosity of the electrical network. Before rupture, an increase in the streaming potential coefficient associated with the onset of dilatancy was observed for three samples of Fontainebleau sandstone and one sample of Villejust quartzite. The changes in streaming potential coefficient prior to failure range from 30% to 50%. During one experiment, an increase in the concentration of sulfate ions was also observed before failure. These experiments suggest that observable streaming potential and geochemical variations could occur before earthquakes.
|Additional Information:||© 1999 by the American Geophysical Union. Received 3 April 1998; accepted 20 April 1999; published 10 August 1999. The authors are grateful to the Laboratoire de Détection et de Géophysique for financial and technical support. Funds were also received from the French Ministry of Environment. Most of the experiments were performed with the help of Thierry Froidefond and Pierre Lalance. In addition, Jean Aupiais and Denise Fresquet helped with advises, equipment, measurements, and analysis of the electrolytes. Patrick Dupont is thanked for the fabrication of many pieces of the apparatus. The authors thank Laurence Jouniaux and Jean-Pierre Pozzi for initial guidance. Fruitful discussions with Steve Pride, Michel Darot, André Revil, and Yves Bernabé are acknowledged during the early stages of the experiments. Laurence Jouniaux, Steve Pride, and Paul Glover are thanked for their inspiring suggestions on an early draft. Last but not least, M. Johnston and B. J. Wanamaker are thanked for their extremely detailed and constructive review.|
|Official Citation:||Lorne, B., F. Perrier, and J.-P. Avouac (1999), Streaming potential measurements 2. Relationship between electrical and hydraulic flow patterns from rock samples during deformation, J. Geophys. Res., 104(B8), 17,879–17,896, doi:10.1029/1999JB900155|
|Usage Policy:||No commercial reproduction, distribution, display or performance rights in this work are provided.|
|Deposited By:||Tony Diaz|
|Deposited On:||14 Sep 2012 17:45|
|Last Modified:||26 Dec 2012 16:10|
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