HR: 0800h
AN: H21B-1016 [Abstracts]
TI: Can rock electrical properties be used as quantitative tool for fluid reactivity interactions
responsible of rock permeability variations?
AU: Clavaud, J
EM: clavaud@ipgp.jussieu.fr
AF: Institut de Physique du Globe de Paris, 4, place Jussieu, Paris, F75252
France
AU: Zamora, M
EM: zamora@ipgp.jussieu.fr
AF: Institut de Physique du Globe de Paris, 4, place Jussieu, Paris, F75252
France
AU: * Zuddas, P
EM: zuddas@ipgp.jussieu.fr
AF: Institut de Physique du Globe de Paris, 4, place Jussieu, Paris, F75252
France
AU: * Zuddas, P
EM: zuddas@ipgp.jussieu.fr
AF: PEPS, Universite Claude Bernard, Lyon 1, Campus de la Doua, Villerbanne, F69245
France
AB:
In crystalline rocks, where the matrix permeability is small, fluid flow occurs essentially through a fracture network.
Fluid-rock interactions changing the fracture network geometry by mineral dissolution or precipitation may change the
effective permeability of the rock. The objective of this work is to experimentally quantify, the effective permeability
variation of the rock during the reaction of mineral dissolution-precipitation due to fluid flow through the fractures. An
original experimental device has been built to measure in situ and continuously the different physical parameters
(permeability, pH, electrical conductivity of both rock and fluid) during the solution flow through a single open fracture of
a cylindrical granite sample. In addition, the out put fluid was regularly sampled and the fluid chemical composition was
analyzed.
Experiments, where a granite rock reacts with CO2 saturated reactive fluids having an ionic strength of 0.1 mol/kg (similar
of natural fluids), shows a strong increases of the rock effective permeability (up to 15%) and a decrease of the electrical
formation factor. The increase of pH, calcium, silica and fluorine confirm the dissolution of the main fracture mineral
(calcite, fluorite and prehnite ) responsible for the `erosion' of the fracture walls as confirmed by both Scanning Electron
Microscopy and surface RAMAN determinations.
However in our experimental conditions, fluid chemical composition as well permeability and electrical formation factor
quickly reach steady state indicating the neoformation of secondary minerals.
DE: 1829 Groundwater hydrology
DE: 1832 Groundwater transport
DE: 1857 Reservoirs (surface)
SC: Hydrology [H]
MN: 2004 AGU Fall Meeting