Petrophysical Properties and Reservoir Modeling of the Mishrif Formation in North Rumaila Oilfield, Southern Iraq

The Mishrif Formation in the North Rumaila oilfield was studied using data from eight wells (R-27, R-36, R-250, R-470, R-491, R-493, R-520, and R-521). In addition, the petrophysical analysis was based on well log data (Caliper, GR, RHOB, NPHI, DT, and Resistivity). The qualitative petrophysical analysis showed that the main rock type of the Mishrif Formation is clean limestone and porous, whereas wells R-250 and R-520 contain argillaceous limestone and porous. According to the resistivity log data, the reservoir is highly saturated with hydrocarbons compared to water. The quantitative petrophysical analysis showed a decrease in the shale volume content within the reservoir. Therefore, the effective porosity was identical to the total porosity values for the studied wells with the exception of wells R-250 and R-520. The lower secondary porosity compared to primary porosity indicates that diagenetic processes had no significant impact. Furthermore, the low bulk volume of water relative to that of hydrocarbons indicates high hydrocarbon saturation. The Mishrif Formation was split into three reservoir units (mA, mB1, and mB2), and the number of subunits was developed based on the petrophysical characteristics (porosity, permeability, hydrocarbon and water saturation, and shale volume) using well log data. The mA unit has the highest oil content at wells R-27 and R-491 in the crest of the field, whereas the lowest at R-470 in the southwest. Meanwhile, the mB1 unit has the highest oil content at R-493 in the north and R-521 in the south, whereas the lowest oil content is observed at R-470. Finally, the mB2 unit has the highest oil content at R-493 in the North and R-250 in the northwest, whereas the lowest is at R-521. The mA unit was divided into two subunits mA1 and mA2, whereas the mB1 unit was divided into three subunits mB1.1, mB1.2 and mB1.3. Moreover, the mB2 unit was not divided into a subunits. Based on the petrophysical analysis and reservoir model, the mB1 unit is identified as the best and most highest reservoir quality. Furthermore, among the subunits mB1.3 and mB1.2 exhibit the best reservoir characteristics.