RESTRICTED GEOMETRY FLUID-DYNAMICS IN NATURAL POROUS SYSTEMS BY QENS AND NMR PGSE

Quasielastic neutron scattering (QENS) and NMR pulsed field gradient s pin-echo (PGSE) techniques have been applied to three types of sedimen tary rocks, in order to monitor the diffusion process through the meas urement of the diffusion coefficient D (t) of the water trapped into t he rock pores. As it is expected for restricted diffusion, D(t) is fou nd to decrease by increasing the diffusion time, starting from the fre e water value D-0 at t --> 0 down to an asymptotic value D-infinity. F rom the behavior D(t) versus t, geometrical and physical properties of the rocks are deduced.