Identification of pore types and their related reservoir characteristics in the Asmari Formation, one of the Southwestern Iranian oil field

Pore type distribution in reservoir rocks is the main factor controlling fluid flow in porous media. Therefore، determination of pore types in reservoir rocks leads to better prediction of the number of wells to be drilled in the field and to improved forecasts of recoverable hydrocarbon. Hydrocarbon reservoirs، especially carbonate rocks، have complex pore types and sizes. In this study، pore types of the Asmari formation are recognized with log data and are validated by core data. For determination of pore types from log data، a velocity deviation log method was used. Based on velocity deviation log and elastic properties، pore types were classified into three classes (positive، zero، and negative) and eight subclasses. They include intraparticle (intrafossil)، moldic or vuggy، microporosity، interparticle، intercrystalline، intergranular، shale microporosity، and fracture porosities. In this field both carbonate and clastic intervals had high potential for production. To determine reservoir quality، hydraulic flow units along with their pore type’s spectrum were investigated. For this purpose، flow units were determined with the flow zone index method. Results of this study led to the determination of three flow units in the carbonate section، with two flow units in the clastic interval. Accordingly، pore type distribution was investigated in each individual flow unit. Finally، results of this study showed that the production in this field is controlled with four pore types that were recognized by the velocity deviation log along the well bore.