PORE-SIZE DISTRIBUTIONS FROM NUCLEAR-MAGNETIC-RESONANCE SPIN-LATTICE RELAXATION MEASUREMENTS OF FLUID-SATURATED POROUS SOLIDS .1. THEORY AND SIMULATION

An improved model for the estimation of pore-size distributions by inversion of nuclear magnetic resonance (NMR) spin-lattice relaxation data is presented. The model is based upon the Brownstein-Tarr treatment of the spin-lattice relaxation behavior of a fluid confined within a pore. A computer program, porefit, has been written to invert the experimental relaxation data. Computer simulations show that, subject to the requirements of an adequate signal-to-noise ratio and a sufficient number of data points, the program produces realistic reconstructions of known input distributions. The technique should allow, inter alia, increased use of NMR relaxation measurements in the prediction of the petrophysical characteristics of rock samples from oil reservoirs.