Experimental study on gas permeability of mudstones

The paper presents the results of gas permeability measurements of mudstones from MHM (Meuse/Haute-Marne) site by the help of measurement facilities in GIG laboratory. The transient pulse technique was used, which can measure very low permeabilities (up to 10−22 m2). Cylindrical 40 mm diameter and about 40 mm length samples come from different distances with respect to the wall of the main access shaft of the MHM URL. The relationship between the permeability and the state of stress is studied and the problem of gas transfer in the saturated sample is analyzed. The relationship between the rupture of sample and the permeability will be also discussed. Experimental (and numerical) results show that the Callovo-Oxfordian stratum of MHM has very low gas permeabilities (∼2 × 10−21 m2). The disturbance linked to the excavation of shafts is not significant. Results show that the interstice gradient of gas pressure can induce pore water displacement. Furthermore, it was found that the permeability does not change very much even if a rupture occurs in tests with a confining pressure (11 MPa) equivalent to the lithological pressure at the depth of about 467 m.