many reservoirs of interest include heavy oil . in such reservoirs , partly at normal temperatures , many instruments commonly used for formation evaluation may not be able to distinguish between heavy oil and bound water in the formation . passive or active heating is used to elevate the temperature of the fluids in the formation . at elevated temperatures , distinguishing between heavy oil and bound water is easier . of particular interest is the increase in the resolvability of the transverse relaxation time t 2 of nmr spin echo measurements . additionally , the dielectric constant and the loss tangents of water and heavy oil show different temperature and frequency dependence .