Petrophysical Characteristics of the Shiranish Formation from Two Selected Oilfields in the Kurdistan Region, North East Iraq

Petrophysical characteristics of the Shiranish Formation were analyzed at the Shewashan-2 (SH-2) and Bazian-1 (BZ-1) wells within the selected oilfields. The suggested lithology for the studied formation is limestone and marly limestone. Moreover, at the SH-2 well, the formation tends to have a lower shale content, which gradually increases downward in the well. Meanwhile, in the BZ-1 well, the middle of the studied formation consists mainly of shaly and shale intervals. In addition, it is observed that porosity values generally decrease deeper in the SH-2 wells, with most values being less than 7.0 %. However, there are a few intervals where porosity increases. On the other hand, the BZ-1 well indicates a pattern of higher porosity at the top of the formation, gradually decreasing towards the bottom of the Shiranish Formation. It appears that the studied formation shows a higher porosity in the BZ-1 compared to the SH-2 well. Additionally, the secondary porosity at the top of the Shiranish Formation in the SH-2 well measures around 2.0 to 5.0%. Nevertheless, in the BZ-1 well, it varies between less than 5.0% and 10%. Porosity along both SH-2 and BZ-1 wells is generally greater at the upper part of the Shiranish Formation. Regarding the permeability, it seems that the formation has a poor to fair permeability in the well of SH-2, meanwhile, it shows moderate to good permeability at the BZ-1 well. The Shiranish Formation can be divided into three reservoir units depending on the shale volume, porosity, and permeability. The RU-3 demonstrates the most significant reservoir characteristics in both of the studied wells. Nevertheless, the reservoir quality was found to be the lowest in RU-1 for the SH-2 and BZ-1 wells. Furthermore, a significant majority of the pore spaces in the formation are occupied by residual hydrocarbons.