AN INVESTIGATION INTO THE EFFECT OF CLAY TYPE, VOLUME AND DISTRIBUTION ON NMR MEASUREMENTS IN SANDSTONES

Abstract

Nuclear Magnetic Resonance (NMR) measurements on reservoir core samples are beneficial for improved interpretation of NMR log data. Estimates of permeability, pore size distributions, free fluid and bound volumes from NMR logs are significantly improved if the logs are calibrated with NMR measurements on representative and well characterised core samples. We present results from a study into the effects of clay type and volume on NMR T2 spectra of synthetic sandstone packs. Samples containing varying amounts of randomly distributed montmorillonite or illite clay have been constructed. The porosity and permeability for each sample were measured at elevated stress. The relationship between these petrophysical properties and the T2 spectra is investigated. An analysis of the applicability of various NMR permeability models is discussed. Samples were desaturated using the continuous oil injection technique and irreducible water saturations calculated. The effect of clay type and volume on the T2 cut-off between free fluid and bound fluid is investigated.