Petrophysical Evaluation of Bangestan Group Formations in an Iranian Oil Field

Abstract

Ilam and Sarvak are two productive reservoirs in Iran. Despite wide petrophysical assessments, these two reservoirs have not been well investigated in Abadan plain located in the southwest of Iran. Reservoir investigation of Ilam and Sarvak formations as two important reserves is the main topic of this article. To that way, two wells of the studied field which are located in the Abadan plain were investigated. Well-logging data were used for the determination of petrophysical parameters of porosity, water saturation, and shale volume. Furthermore, core data were applied for the validation of final results. The best-fitted curve for the porosity and permeability of core data was selected for the permeability prediction throughout both reservoirs. Final consequences indicated that the lithology of Ilam and Sarvak formations are limestone and limestone-dolomite respectively. The two mentioned reservoirs have a shale volume of less than 10%, so they can be classified as clean formations. Average effective porosity ranges between 13.4 and 16% for Ilam Formation, while it varies from 10.6 to 11.4% for Sarvak Formation. Comparing porosities, Ilam Formation has a higher porosity than Sarvak Formation over depth in both studied wells. The results of water saturation show Sarvak Formation has relatively higher water than Ilam Formation. Moreover, the Net to Gross Ratio (NGR) index was calculated to 80 % in Ilam Formation. Although, Sarvak possessed proper reservoir properties in limited thicknesses, the overall value of NGR for this Formation was between 6-9%. Eventually, Ilam Formation had befitting reservoir quality whereas the quality of Sarvak Formation was low. The findings of this study can contribute to a better understanding of zonation and prospects of the penetration.