Laboratory monitoring of CO2 injection in saturated silica and carbonate sands using spectral induced polarization
Abstract
Series of experiments were performed to study the spectral induced polarization (SIP) response of sands fully saturated with water, into which gaseous CO 2 or N 2 was injected, in the frequency range 0.5 Hz–20 kHz. Three main observations were made. (1) SIP parameters were always most affected by gas injection when the frequency of the injected signal was in the intermediate range (1 < f < 20 kHz). This point emphasizes the interest of broadening the frequency range of SIP surveys toward intermediate frequencies. It also implies that more work is needed in order to understand and quantify the parasitic effects that occur at this frequency range (EM coupling and electrode polarization). (2) Through all the experiments performed, we were able to distinguish the parameters variations caused by a reduction of the water saturation level (invasion of a resistive gas phase in the porous space) from those resulting from dissolution processes (increase of the electrical conductivity of the saturating water). (3) The quadrature conductivity σ , which is mainly linked to the capacitive properties and inductive response of the media, always shows relative variations stronger than the resistivity of the media, hence demonstrating the interest of the additional information provided by the SIP method as against the classical resistivity method.
Origin : Publisher files allowed on an open archive
Loading...