Low-field NMR determinations of the properties of heavy oils and water-in-oil emulsions.

Low-field (< 50 mT) nuclear magnetic resonance (NMR) well-logging measurements are beginning to be used to obtain estimates of oil viscosity in situ. To build an interpretive capability, we made laboratory T1 and T2 relaxation measurements on a suite of high-density, high-viscosity crude oils. These measurements were also used to estimate oil viscosity and water fraction from T1 and T2 measurements on stable, water-in-oil emulsions. High-density, high-viscosity oils have components that relax faster than can be measured by nuclear magnetic resonance logging tools. This requires corrections to T2 logging measurements for accurate estimates of oil saturation and porosity.