Unification of fluid flow and electrical conduction in rocks and soils

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Porous and fractured rocks and soils not only store fluids but also allow their movement through the earth. Consequently the study of fluid flow in rocks and soils is highly important to (i) provision of safe and plentiful water resources, (ii) production of oil and gas, and (iii) safe disposal of domestic, industrial and nuclear waste. Fluid flow and electrical flow are linked at a fundamental level by electro-kinetic phenomena, where fluid flow through a rock causes an electrical current to flow or vice versa. These phenomena are important because electrical signals measured before major earthquakes and around volcanoes are linked to fluid flow by electro-kinetic mechanisms. Accurate description of the mechanisms would enable us to improve the prediction of both earthquakes and volcanoes. The link may also allow fluid flow in the deep earth to be mapped from electrical measurements, aid the development of new oil, gas and water borehole tools, and provide methods for cleaning contaminated soils. There are two major problems. The first is the lack of an AC theory linking fluid flow and electrical conduction through electro-kinetic processes. The second is the current lack of understanding of the major controlling influences on fluid and electrical flow through rocks and soils. This project aims at overcoming these two problems by two pathways of research. The first is to measure the electro-kinetic properties of rocks in the laboratory and to develop a full AC theory for it. The second is to measure the electro-kinetic fluxes of fractured and porous rocks and to understand the microstructural parameters that control these flows. Each pathway will include experimental measurements, computer modelling and the development of fundamental theory providing tools that should allow us a previously unparalleled insight into the processes involving electrical and fluid flow in any porous medium. The results of these two pathways will be combined and applied to data existing from earthquakes (e.g., Parkfield), volcanoes (e.g., Piton la Fournaise) and underground reservoirs. While in the UK, the applicant led a group developing these new approaches, and has developed an experimental facility for such research at Université Laval.