ABSTRACT The accuracy of formation fluid saturations determined by log analysis has improved steadily over the years. However, the problem of what values to use for the exponents "m" and "n" in the saturation equation remains. Laboratory measurements on core samples show that these exponents can vary significantly over short intervals, but assumed average values must be used in actual calculations. These average values may or may not be representative, depending on the formation homogeneity. The EPT (Electromagnetic Propagation Tool) measurement allows the calculation of saturations near the borehole without a knowledge of "m" or "n". Using the EPT saturation, a method is developed to calculate "m" and "n" from the logs as a continuous record. These calculated values provide an improved water saturation calculation from the regular resistivity and porosity logs. Several examples are shown to demonstrate the application of the new method. Core analyses, core descriptions, and drill stem test results are included which support these improvements.