Task 1-4 : Petrophysical characterization [GM, ISTerre, IC2MP]
Objectives :
Measure petrophysical properties of the samples in Nojima and Soultz characterized in tasks T1.1-T1.3, to derive a petrophysical proxy of alteration. The main target property will be electrical resistivity, also measured by borehole geophysics [T1.5]
Description of planned work :
(1) A first part of this work will extend the preliminary work undertaken by Ph. Pezard on electrical resistivity, to target more specifically the main fault zone. Complex resistivity measurements [GM] provides also induced polarization of the samples on a broad frequency range. Resistivity is depending (i) on surface conductivity, which could be related to Cation Exchange Capacity [IC2MP] and mineralogy [T1.1] and (ii) on the porous network and its tortuosity (X-Ray CT scan [T1.2], 14C-PMMA [IC2MP]). Hence, resistivity is both dependent on alteration and on damage.
(2) On the other end, sonic velocities [ISTerre] are expected to be primarily dependent on damage.
(3) By comparing both datasets, we plan to derive a calibration of resistivity and sonic velocities as petrophysical proxies of alteration
| Analysis | Purpose | Institute in charge | Nojima | Soultz |
|---|---|---|---|---|
| Complex resistivity | Measurement of complex resistivity at several frequencies, for samples imbibed with fluids of increasing electrical conductivity → Geophysical proxy of alteration & damage |
GM (Gibert + Pezard++ PhD) | Selected samples | Selected samples |
| Sonic velocities | P- and S- wave velocities under ambient pressure. → Geophysical proxy of damage |
ISTerre Grenoble (Doan) | Systematic | Selected samples |
| CEC | Cation Exchange Capacity (method NF X31-130) → rough proportion of swellable clays, zeolites → Surface conductivity |
IC2MP Poitiers (Patrier, Baron) | Systematic | Selected samples |
| 14C-PMMA | Radiography of samples impregnated by 14C-PMMA → fine imaging of fracture network (down to 50 Å) |
IC2MP Poitiers (Sardini + Billon + M2 Poitiers #2) | Selected samples |
Updated on 1er avril 2024
