GNGTS 2014 - Atti del 33° Convegno Nazionale

In particular, in correspondence of flow rates reduction, a strong decay of both seismic density events and electric potential magnitude is observed. Successively, a rapid increase of electric potential corresponds with a similar raise of number of seismic events. This behavior confirms the linking between groundwater flow in geothermal media, persisting also after the wells shut-off, the electric potential anomalies and the induced seismicity. This confirms also the capability of SP method to represents an useful monitoring tools in evaluation of the seismic hazard. References Baria, R. et al., Microseismic monitoring of the world’s largest potential HDR reservoir, in Twenty-Ninth Workshop on Geothermal Reservoir Engineering, Stanford University, Stanford, CA (2004). Bernabé, Y. (1998). Streaming potential in heterogeneous networks. Journal of Geophysical Research: Solid Earth (1978–2012), 103(B9), 20827-20841. Bogoslovsky, V. A., & Ogilvy, A. A. (1970). Application of Geophysical Methods for Studying the Technical Status of Earth DAMS*. Geophysical Prospecting, 18(s1), 758-773. Bogoslovsky, V. V., & Ogilvy, A. A. (1973). Deformations of Natural Electric Fields Near Drainage Structures*. Geophysical Prospecting, 21(4), 716-723. Charléty J., Cuenot N., Dorbath C., Dorbath L. Tomographic study of the seismic velocity at the Soultz-sous-Forêts EGS/HDR site. Geothermics 2006;35:532-543. Corwin, R.F., and D.B. Hoover, 1979. The Self-Potential method in geothermal exploration, Geophysics, 44, 226- 245. Cuenot N., Charléty J., Dorbath L., Haessler H. Faulting mechanisms and stress regime at the European HDR site of Soultz-sous-Forêts, France. Geothermics 2006;35:561-575. Cuenot N., Dorbath C., Dorbath L. Analysis of the microseismicity induced by fluid injections at the EGS site of Soultz-sous-Forets (Alsace, France): Implication for the characterization of the geothermal reservoir properties. Pure appl. Geophys. 2008;165:797-828 Darnet, M., Marquis, G. and Sailhac, P., Estimating aquifer hydraulic properties from the inversion of surface streaming potential (SP) anomalies, Geophysical research letters, 30 (2003) De Groot, S. R. Mazur (1962) Non-Equilibrium Thermodynamics. North-Holland. Amsterdam, 1962. Dorbath L., Cuenot N., Genter A., Frogneux M. Seismic response of the fractured and faulted granite of Soultz-sous- Forets (France) to 5km deep massive water injections. Geophys. J. Int. 2009;177:653-675 Evans, K.F., Genter,A. &Sausse, J., 2005a. Permeability creation and damage due tomassive fluid injections into granite at 3.5 km at Soultz: 1. Borehole observations, J. geophys. Res., 110, B04204. doi:10.1029/2004JB003168. Evans, K.F. et al., 2005b. Microseismicity and permeability enhancement of hydrogeologic structures during massive fluid injections into granite at 3km depth at the Soultz HDR site, Geophys. J. Int., 160, 389–412. Geiermann, J., & Schill, E. (2010). 2-D Magnetotellurics at the geothermal site at Soultz-sous-Forêts: Resistivity distribution to about 3000m depth. Comptes Rendus Geoscience, 342(7), 587-599. Genter, A., Castaing, C., Dezayes, C., Tenzer, H., Traineau, H. & Villemin, T., 1997. Comparative analysis of direct (core) and indirect (borehole imaging tools) collection of fracture data in the Hot Dry Rock Soultz reservoir (France), J. geophys. Res., 102, 15 419– 15 431. Giardini, D., Geothermal quake risks must be faced, Nature, 462, 848–849 (2009) Haring, M.O., Schanz, U., Ladner, F. and Dyer, B.C., Characterisation of the Basel 1 enhanced geothermal system, Geothermics , 37, 469–495 (2008) Helmholtz, 1879, Wiss. Abhandl. physic. tech. ������������� �� ���� ���� ����� ����� ����� �������� �� �� ������� Reichsantalst I, 925, 186. Reuss F.F., 1809, Mémoires de la Société Impériale Naturaliste de Moscou, 2, 327. Ishido, T., and H. Mizutani, 1981. Experimental and theoretical basis of electrokinetic phenomena in rock-water systems and its applications to geophysics, J. Geophys. Res., 86, 1763-1775. Ishido, Tsuneo, Hitoshi Mizutani, and Kenzo Baba, Streaming potential observations, using geothermal wells and in situ electrokinetic coupling coefficients under high temperature, Tectonophysics , 91.1, 89-104 (1983) Ishido, T., & Pritchett, J. W. (1999). Numerical simulation of electrokinetic potentials associated with subsurface fluid flow. Journal of Geophysical Research: Solid Earth (1978–2012), 104(B7), 15247-15259. Jouniaux, L., & Pozzi, J. P. (1995). Streaming potential and permeability of saturated sandstones under triaxial stress: Consequences for electrotelluric anomalies prior to earthquakes. Journal of Geophysical Research: Solid Earth (1978–2012), 100(B6), 10197-10209. Kawakami, N., and S. Takasugi, SPmonitoring during the hydraulic fracturingusingtheTG-2well, paper I004 presented at 56th Meeting and Technical Exhibition, Eur. Assoc .of Explor. Geophys.,Vienna, Austria,June6-10, 1994. Lorne, B., F. Perrier, and J.-P. Avouac (1999a), Streaming potential mea- surements: 1. Properties of the electrical double layer from crushed rocks, J. Geophys. Res., 104(B8), 17,857–17,877. GNGTS 2014 S essione 1.3 229