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Theses

Geo-electrical methods for the detection and monitoring of CO2 transfers in the subsurface.

Abstract : The main objective of this thesis is to study the capacity of electrical resistivity tomography (ERT) and induced polarization (IP) methods to detect and follow carbon dioxide (CO2) transfers in the subsurface. This work contributes to the development of surface monitoring strategies of CO2 storage sites. First, we assessed this issue by performing experimental studies in controlled conditions. We designed and conducted metric scale laboratory experiments consisting of the injection of gaseous CO2 into homogeneous granular media fully saturated with water. Studying the evolution of ERT and IP parameters during these experiments allowed us to distinguish and quantify the effects induced by the introduction of a gaseous phase in the media from those related to dissolution processes. In the case of ERT method, we developed modeling tools that allowed us to study the sensitivity of several electrode configurations and designing new acquisition protocols that show a greater efficiency for the detection of gaseous CO2 plumes. This study highlights the importance of using measurement protocols adapted to the geometrical and spatial extension of the gas plume, in order to maximize the detection capacity of the method. In the case of IP method, laboratory-scale experiments showed that at high frequencies (f > 1 kHz), the capacitive properties of the studied media always showed greater sensitivity to the physicochemical changes induced by the CO2 injection than ohmic conduction properties. This observation underlines the significant interest of IP methods for the detection of CO 2 transfers in the subsurface. Using a theoretical mechanistic model, we managed to reproduce the shape and magnitude of the quadrature conductivity spectra associated with the studied media, and to develop simple empirical relationships linking the IP responses observed at high frequencies with some physicochemical parameters (water saturation level, the electrical conductivity of the saturating water). Then, we extended our studies to more complex environments by performing experiments on a small eld scale. Three separate experiments were performed. We monitored a shallow CO2 injection ( 5,5 m) using the ERT method, temporal induced polarization method (TIP) and spectral induced polarization method (SIP). Again, the geophysical parameters related to the capacitive properties of the medium showed greater variations during the experiments than those related to ohmic conduction properties. However, in some cases, instrumental effects are responsible for significant variations on the measured signals, and must be taken into account when interpreting the results.
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  • HAL Id : tel-02499188, version 1

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Thomas Kremer. Geo-electrical methods for the detection and monitoring of CO2 transfers in the subsurface.. Géophysique [physics.geo-ph]. Université Paris Sorbonne; Institut de Physique du Globe de Paris (IPGP), 2015. Français. ⟨tel-02499188⟩

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