The unique Dielectric Scanner multifrequency dielectric dispersion measurement solves a perennial problem encountered in mature fields, especially those with fresh water sands, or those that have been produced using steam flooding or fresh water injection techniques. The new tool overcomes limitations of earlier technology in three critical areas with its articulated sonde that can achieve high quality measurements in rugose boreholes; its multifrequency-multispacing operation can provide radial resistivity profiling of reservoir rocks to quantify hydrocarbon mobility; and its ability to discriminate hydrocarbons from water irrespective of water salinity. Two case studies are presented taken from California’s San Joaquin Basin, both providing greatly improved answers.