In situ osmotic experiment in the Callovo-Oxfordian argillaceous formation at the Meuse/Haute-Marne URL (France): Data and analysis

This paper presents results obtained through a chemical-osmotic in situ experiment (“PEP”), carried out at the Meuse/Haute-Marne URL, aiming at interpreting pore pressure and permeability measurements in the undisturbed rock throughout the Callovo-Oxfordian argilillites. One of the objectives of this experiment was to determine the possible impact of water salinity on pore pressure, in particular due to osmotic effects.A series of tests, consisting of water/rock exchanges with fluids of a range of salinities (1–100 g/L) was carried out in several intervals of a dedicated borehole.The pressure variations and salinity evolution, was analysed with numerical simulations using a radially symmetric advective-diffusive solute transport model, coupled with chemico-osmotic flow. Results obtained from the simulations provided an effective diffusion coefficient ranging between 1 × 10−11 and 5 × 10−11 m2/s, and an osmotic efficiency coefficient ranging from 5% to 18%, which are very consistent values with mean distances between clay platelets (20–50 Å).