Nonmobile water quantified in fully saturated porous materials by magnetic resonance relaxation and electrical resistivity measurements

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Abstract
Irreducible fluid saturation in porous media is the fraction of the wetting phase which remains trapped in the solid matrix after displacement with a nonwetting phase. Methods have been proposed to estimate irreducible saturation in fully water-saturated porous samples by means of proton nuclear magnetic resonance relaxation times, but the results are quite varied. Some features are discussed of the trapped fluid and it is shown that the fraction of nonmobile water can be well estimated for a varied suite of clean sandstones, using only measurements on the fully saturated samples. This is done by combining relaxation measurements with those of electrical resistivity factor F. One of several simple correlations is Swi ∝√F/T1s, where T1s is the stretched-exponential relaxation time.