Effects of Hydrostatic Pressure on Proton and Deuteron Magnetic Resonance of Water in Natural Rock and Artificial Porous Media

The effect of pressure on the NMR longitudinal relaxation of D 2O and H 2O confined to the interstices of natural and artificial porous media is reported. Magnetization decays of fluid protons in natural porous media are known to be dominated by interactions between water molecules and the surface of the solid matrix. These decays are characterized by broad distributions of relaxation times. In some materials there is no pressure dependence of the proton relaxation time distribution, while in other materials minor effects are noted. The NMR relaxation of deuterium in D 2O is dominated by intramolecular effects. Assuming that the enhancement of relaxation at the surface is relatively independent of surface composition, one can estimate a surface-to-pore-volume ratio. The NMR S/V is more useful than that measured by conventional methods. The pressure dependence of D 2O relaxation in porous media follows that of the bulk liquid.