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ABSTRACT: Results are reported of an NMR spin-lattice relaxation study on a suite of sandstone cores fully saturated with brine. Relaxation curves of 1H nuclei of water filling the pores, obtained by Inversion Recovery pulse sequence, were analyzed to extract relaxation lifetime values. These lifetimes have been recently proposed as suitable to characterize the relaxation behavior of fully saturated sandstones as well as able to predict permeability in conjuction with porosity. An improvement in the comprehension of interplay among geometry and transport properties of the pore space can be obtained from the comparison between these lifetimes and conventionally measured properties. The results obtained are in agreement with previous results on sandstones and reproduce very well results on model systems. They led to a functional dependence among permeability (k), porosity (φ) and average lifetimes (Tls) that allowed a good estimation of k from φ and Tls. The dependence of the error in the permeability estimation in terms of the variations of φ and Tls exponents in the relationship that predicts k was also discussed. The reason of the correlation between k and Tls lies in their common dependence on the surface-to-volume ratio S/Vp. In this way, 1H spin-lattice relaxation lifetimes behave as a bridge between structural and transport properties and may be viewed as a dynamically weighted version of S/Vp. The discussion of these results can help in clarifying the informative content of 1H spin-lattice relaxation curves on a broad spectrum of heterogeneous systems with high surface-to-volume ratio.
Journal of Petroleum Science and Engineering. 01/1991;