The Assessment of microfacies and reservoir potential relationship (porosity and pore size) of the Sarvak Formation in SW Iran

Abstract

Bangestan Reservoir in Ahvaz Oil Field is one of the important carbonate reservoirs in Dezful Embayment in the southwest of Iran. This reservoir consists of Sarvak and Ilam formations. Core samples were used to study microfacies and to determine the relationship between microfacies and reservoir potential of Ahwaz oil field. To highlight pores and throats, Blue Dye Epoxy was injected. According to petrographic study, 10 microfacies and 8 types of porosity were recognized. Our observation suggests a significant relationship between pore types and pore sizes to porethroats. The relationship between petrographic porosity and laboratory measurement of porosity was also investigated, that pores had undergone more porosity. Correlation coefficient of petrographic porosity with that of laboratory measurement porosity was calculated and poor correlation was found. The reason for this was the elimination of pores smaller than 1 μm by the petrographic analysis software and the elimination of extremely small pores (0.005 μm) in the helium injection method. Correlation in grainstone and packstone microfacies was stronger. In analyzing the relationship between throats and pores to microfacies, no significant relationship was observed, because of the intensity of diagenetic processes and destruction of the primary sedimentary texture. Generally, it was found the pore classification can be used in studies on pore sizes, flow units, and even rock types. Because of the significant relationship between pore types and pore-throat sizes, and finally because of the direct relationship of these sizes to petrophysical properties (porosity, permeability, and capillary pressure)