Study and three-dimensional modeling of the Dariyan Formation Electrofacies by using Geostatistics, in one of the Persian Gulf Oilfields

In the absence or limitation in of petrographical studies, Electrofacies determination and three-dimensional modeling of the carbonate reservoirs can have an important role in petrophysical assessment such as porosity and permeability. Study of gamma ray and density logs of the Dariyan Formation in 27 wells of one Persian Gulf oilfields that have limit amount of thinsections, lead to recognition of 12 Electofacies bases on geostatistic clustering. Correlation of identified Electrofacies with core data in the Dariyan Formation at studied oilfields, indicate that Electrofacies 1 is the best and Electrofacies 11 and 12 have low reservoir quality in compare to others. With using of porosity and permeability relation in each zone of the Dariyan reservoir and placement of effective porosityinsted of core porosity, the loge of estimated permeability was drawn. Also, structural modeling show that the studied oilfield is an anticline with NE-SW trend that have a gentle dome structure with 1 – 3 dip degree in flanks and the crest of the dome is very flat in reservoir layers. Three-dimensional modeling of identified Electrofacies of the Dariyan reservoir with Sequential Indicator Simulation (SIS) Method indicate that, Zone 1 due to high frequency of Electrofacies 11 and 12, high water saturation, pyritization and low porosity and permeability can be considered as a non-reservoirs zone. While zone 2 due to high frequency Electrofacies with high reservoir quality, high porosity and permeability and low water saturation is the best reservoir quality. Zone 3 of the Dariyan Formation has Electrofacies with high gamma ray that show low reservoir quality, but has a higher quality in compare to zone 1. The upper section of zone 3 has low water saturation. Frequency of Electrofacies with high reservoir quality in zone 4 in compare to zone 2 is lower, but this zone has higher reservoir quality than zone 1 and 3. However, for the most part of zone 4 water saturation is high.