Comparison of Core Water Saturation with Electric Models in Kangan and Dalan Formations in the Central Part of the Persian Gulf

Reliable and accurate determination of water saturation above the oil-water contact of the hydrocarbon-bearing formations is essential for calculating hydrocarbon in place. In this study, water saturations were measured directly from 160 core samples by Dean-stark test in one well and thin sections have been used to identify geological properties. Archie coefficients were also determined on plug samples. The water saturation values obtained from the electrical models including Archie, Waxman-Smith, and dual water were measured in Geolog7 software and applied in Kangan and Dalan formations in one of the fields in the Central Persian Gulf. In this study, four methods have been used to determine the rock types, including Winland, reservoir quality index, pore type, and depositional texture to identify the parameters affecting the distribution of water saturation. Results showed that pore throat radius is a parameter that affects water saturation and this parameter is directly related to the increased permeability and reduction of the difference between the water saturation values of Archie with the Dean-stark test. Determination of rock types based on depositional texture and pore type revealed that the cement type and texture and the pore types, control the permeability and distribution of water saturation in the reservoir. It was also found that depositional texture, unlike pore throat radius, well separates sedimentary environments. The results of water saturation calculations showed that if the Archie coefficients are calculated in each flow unit, the water saturation resulting from it would be very close to the water saturation values in the core (Dean-Stark). The electrical model of water saturation, with different coefficients in samples with different reservoir quality index or pore types, yields the most accurate water saturation values compared to Dean-Stark.