Project abstract:

Clay materials play a crucial role in advancing a carbon-neutral and sustainable energy system. Clay formations serve as caprock for the underground storage of greenhouse gasses and energy vectors like hydrogen and play a key role in geothermal resources. To address future needs for efficient geophysical characterization tools for clay strata, we propose to further develop broadband dielectric methods. Given their sensitivity to crucial properties like clay mineralogy, porosity, permeability, water content, and (surface) diffusivity, their non-intrusiveness and real-time imaging capabilities, geoelectrical and electromagnetic exploration methods are promising tools for the characterization of clay formations. Although dielectric spectra in the mHz to MHz frequency range are known to contain valuable information on clay material microstructure, more research is needed to improve their use for quantitative interpretations and predictions. The BARRIERS project, leveraging a strong collaboration between French and German research teams with complementary expertise in the fields of geophysics and geochemistry, aims to address this gap. The project involves the development of novel experimental techniques and numerical modeling approaches to investigate the broadband dielectric response of clay materials and understand the underlying processes. In particular, BARRIERS comprises a detailed experimental investigation into the surface properties and surface diffusion in pure clay systems, which is crucial for accurately modeling diffusion-controlled electrical conduction and polarization processes taking place at the nano and micro scale. The project aims to incorporate these microscopic electrical properties into suitable upscaling approaches and predict the measurable, macroscopic electrical properties of clay materials. These predictions will be compared to a new, extensive experimental data set of broadband dielectric and microstructure characterization measurements collected under varying physico-chemical conditions in the mHz to MHz frequency range. The results of this research will contribute to improving our basic understanding, deriving reliable empirical relationships and advancing efficient geophysical characterization of clay barriers in the context of carbon-neutral and sustainable energy systems.