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The impact of CO 2 on the electrical properties of water bearing porous media – laboratory experiments with respect to carbon capture and storage
Author(s) -
Börner Jana H.,
Herdegen Volker,
Repke JensUwe,
Spitzer Klaus
Publication year - 2013
Publication title -
geophysical prospecting
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.735
H-Index - 79
eISSN - 1365-2478
pISSN - 0016-8025
DOI - 10.1111/j.1365-2478.2012.01129.x
Subject(s) - supercritical fluid , electrical resistivity and conductivity , porous medium , pore water pressure , conductivity , saturation (graph theory) , porosity , mineralogy , materials science , petrophysics , soil science , geology , geotechnical engineering , thermodynamics , chemistry , composite material , mathematics , combinatorics , electrical engineering , engineering , physics
We conducted a detailed experimental investigation of the effect of CO 2 injection on the electrical conductivity of water bearing porous media, needed for an improved geophysical monitoring of CO 2 storage reservoirs. Therefore, we developed an experimental set‐up that allows to investigate electrical characteristics of the injection process as well as the impact of dissolved CO 2 on pore water conductivity. We found that a gaseous, fluid and supercritical pure CO 2 phase bears no relevant conductivity at pressures up to 13 MPa and temperatures up to 50° C. When CO 2 dissolves in pore water, pressure‐dependent dissociation processes can double the pore water conductivity, that can be used in leakage detection. This is quantified by an adaptation of Archie’s law. The empirical adaptation and the experimental data are confirmed by combined geochemical‐geoelectrical modelling. Furthermore, water‐saturated sand samples were investigated while CO 2 displaced the pore water at pressures up to 13 MPa and temperatures up to 40° C. A decrease in electrical conductivity by a factor of up to 33 was measured, corresponding to a residual water saturation of 14–19%. Qualitatively, a decrease was also demonstrated under supercritical conditions. As an integrative interpretation, a conceptual model of electrical rock properties during CO 2 sequestration is presented.