Characterization of fracture void space heterogeneity by electrical impedance measurement

BOSCHAN A., IPPOLITO I., CHERTCOFF R., HULIN J.P., AND AURADOU H.

Colonia, Uruguay

Congreso; XI Reunión sobre Recientes Avances en Física de Fluídos y sus Aplicaciones; 2010

Instituto de Física, Facultad de Ciencias, UDELAR

We investigate how to characterize fracture void space heterogeneity by measuring overall electrical impedance during displacement. Two model fractures with identical complementary rough walls but with a relative shear displacement either parallel or perpendicular to the mean flow velocity are used: the displacement creates respectively “barriers” or “channels” like permeability structures. In the first (channel) case, an initial linear resistance variation is followed by tailing reflecting the contrast between the transit times of slow and fast channels. In the second (barrier) case, the resistance variation displays changes in the slope suggesting the appearance of domains of different permeabilities along the length of the fracture. In both cases the experimental resistance variation is well reproduced by numerical modelling the front geometry and displacement by means of a parallel channel model (channels case), or by assuming an averaged aperture a(x) variable along the flow and constant across it (barriers case), and then computing the global electrical resistance by solving the equivalent array of resistors problem.