The main objective of the topic “Low Permeability Media” is to improve our understanding of the hydro-mechanical behavior of low permeability materials, which are directly involved in numerous geological settings in the context of production of energetic resources (gas, oil, nuclear, geothermal), energy and waste storage, CO2 storage, geothermal exchangers to mention a few. There is no clear definition of a low permeability porous material. Generally speaking, we can define a limit at 10-16 m2 below which a material is assumed to have a low permeability. Different areas of research are concerned by such low permeability: material sciences, biological sciences and geosciences, on which we will focus. In geosciences we will address questions related to:
- Study of cap rocks for geological reservoirs (both for hydrocarbons and water) like shales,
- Study of geological targets for waste storage,
- Fractured reservoirs in low permeability formations (typically aquifers in fractured crystalline rocks),
- Volcanic, crystalline or metamorphic rocks used for deep geothermal projects.
Challenges
Our ambition is to provide answers to the following questions:
- How can we accurately describe the physics of fluid flow in porous media where the pore size is smaller than the micrometer range?
- How can we accurately describe the thermo-hydro-mechanical coupling for low permeability materials in response to mechanical or thermal stresses?
- What is the impact of matrix – fluid interactions which might become important for small pore sizes and the nature of the matrix (clays)?
- Can we better account for the effects of anisotropy, connectivity and heterogeneities at all scales?
- Is it possible to define innovative experimental protocols for conducting laboratory experiments with a better control on low permeability materials (control of saturation, impact of transient stages)?
- Can we better account for interactions between matrix permeability and fracture permeability in low permeability environments?
- How can we estimate the long-term evolution of cap rocks and in situ storage sites in low permeability rocks (sealing capability over long time scales)?
- How can we estimate fluid fluxes at long-time scales?
- How can we account for the scale effect and propose efficient upscaling methods? How can we integrate data at different scales (e.g. tracers)?
- Can we improve imaging techniques for characterizing pore structures at the nano-scale, in particular for providing better data for numerical modelling?
- How relevant are geophysical “proxys” (e.g. electrical conductivity, diffusion) for the estimation of permeability at different scales?
Bringing together the skills of each partner involved will contribute to improve our efficiency in addressing these questions. Two priorities will be given:
1 the first one on experimental studies through the development of collaborative research on the improvement of direct measuring techniques and indirect methods based on “proxys” for estimating low permeabilities.
2 the second one on the development of models for transport properties in low permeable media.
A research project is already in progress under this topic : KG2B