Electro-facies analysis of the Sarvak Formation (Middle Cretaceous) and compliance with sedimentary microfacies in an oil field, SW Iran

Electro-facies analysis is a sure method in clustering petrophysical logs analysis that can well indicates the changes of geologic charactereristics of the different lithostratigraphic units as well. Petrographic studies of 120 prepared thin sections of the upper parts of the Sarvak Formation in studied oilfield¡ Southwestern Iran¡ has resulted in definition of 6 microfacies sedimentary types. These data suggested that the middle Creataceous sediments in the studied area were predominantly deposited in two subenviornments of patch organic barrier and lagoon corresponding to inner and shallow a homoclinal ramp. In addition¡ using petrophysical logs in the studied well¡ 10 electrical facies were determined. By analyzing the data petrophysical in Geolog software¡ 10 electerical facies were optimized and then their number was reduced to six. According to good adaptation of optimized electerical facies with sedimentary microfacies¡ we would generalized obtained dresults to all parts of the Sarvak Formation. Study of porosity changes in the electrical diagrams such as CGR corrected Gamma¡ and sonic curves in mentioned well¡ indicated a significant reduction in facies porosity of 1 to 6. In addition¡ the results showed that the reservoir quality reductionin studied microfacies is corresponded to Bioclastic Rudist debris floatstone/ Rudstone¡ Benthic foraminifera Rudist debris wackestone / packstone¡ Benthic Foraminifera peloid Grainstone/Packstone¡ with High diversity benthic foraminifera wackestone / packstone¡ Peloid bioclastic wackestone /packstone with Low diversity benthic Foraminifera and Mudestone/Wackestone¡ respectively. In this study¡ we concluded that comparison and correlation sedimentary facies with electric microfacies provide an efficient method to study the quality of the hydrocarbon reservoir system that especially can be used in other wells with no core.