Investigating the Role Pore Type and Pore Throat Size Radius in Determining the Flow Units using the Velocity Deviation Log and Core Data in Dorood Oilfield, Fahliyan Formation

Petrophysical rock type is a part of the reservoir that has the same properties such as geological and petrophysical characteristics. Therefore, the relationship between geological and petrophysical units can be useful for understanding the heterogeneity of the reservoir, especially in carbonates, which are highly variable from the pore type and pore throat size radius viewpoints due to the effect of diagenetic processes. The pore type and pore throat size radius as parameters which are relevant to the product of the geologic process (depositional and diagenesis) control the petrophysical properties of the reservoir. Accordingly, these two parameters are the best tools for communicating the geological and petrophysical characteristics of each petrophysical rock unit. In this paper, three methods including flow zone indicator, Winland R35, and discrete rock types (DRT) were used to determine the petrophysical rock type. The results show that the flow zone index outperforms the other methods, although the other two methods can have useful applications. To determine pore type and pore throat size radius in five flow units, which were identified by the flow zone indicator method, the velocity deviation log was used. Moreover, to determine the continuous distribution pore type the velocity deviation log was used. In addition, mercury injection data were employed to measure pore throat size radius. According to the results obtained from this study, the best flow units are in accordance with positive and zero velocity deviations, which have interconnected vuggy and intergranular which are the product of the dissolution (diagenesis) and depositional process. Finally, the results indicate that the reservoir quality of the Fahliyan Formation is affected by the two factors of diagenesis and sedimentation, but in general, diagenesis has the most contribution to determine the all reservoir quality of the formation.