Determining the Best Log Combination and Electrofacies in Water Saturation Calculation, Kangan and Dalan Formations in the Central Persian Gulf

Calculating water saturation is one of the most important reservoir parameters for determining the volume of hydrocarbons in place, which it must be calculated with high accuracy. In this study, after the necessary corrections were made on the Water-base-core in Kangan and Dalan formations, the core water saturation was calculated by the Dean-Stark test method. After electrical measurements and determination of Archie coefficients on the core, water saturation values were calculated from Archie electrical models, Waxman Smith, Dual Water, and Archie-Dual Water in Geolog7 software. To generalize water saturation to other wells in this field, three facies models were produced by Multi-Resolution Graph-based Clustering (MRGC) and applied in one of the fields in the Central Persian Gulf. Afterwards, in the whole well, the difference between the average water saturation of the Dean-Stark test method and the electrical models was measured in 3 facies models. The results showed that in all three facies models created, the average values of water saturation calculated from the equations were higher than the water saturation calculated from the Dean-Stark test method. By making a comparison between facies models, it is obvious that the facies models based on input logs, including electrical resistance, sonic, neutron, and density, showed the least difference between the average water saturation of the Dean-Stark test and the electrical models. Comparing the average water saturation in the Dean-Stark method and the electrical models between the electrical facies of a model based on its input logs, it was concluded that the petrophysical parameters including porosity, sonic wave transit time, shale volume and density, as opposed to electrical resistance, are directly related to the reduction of the average water saturation difference. But lithology has less effect on the difference in average water saturation between the Dean-Stark method and electrical models. Therefore, to select the sample for determining the coefficients of Archie, it is appropriate to use this method of determining the electrical facies.