Assessment of the Lower Cretaceous source rock using PetroMod approach in West Qurna Oilfield- Southern Iraq

Abstract

The L. Cretaceous succession is the main reservoir rock in the south of Iraq. Although the upper Jurassic Sargelu Formation is the main source rock in this area; however, the organic-rich interval within the studied succession, is contribute in these huge accumulations of petroleum. The pyrolysis parameters of the succession; Sulaiy, yamama, Zubair, and Nahr Umr formations showed that the main kerogen type is type III and II with moderate to good HI, which they refer to gas and/or oil prone especially in Zubair, Nahr Umr, and Sulaiy formations. The quantity parameters indicate potential source intervals in respect to (TOC). The maturity parameters suggest the threshold and peak of petroleum generation, which Tmax values ranged around 430-450 ºC, as well as the Ro values ranged 0.5 to 1.0. The Maturity factors is enhanced by PI (0.1 -0.4), which the main values are located in the oil window.The software modeling, namely PetroMod, assigned a transformation ratio up to 90% in respect to Sulaiy and Yamama formations, while it is around 5-30 % for Ratawi, Zubair, and Shuaiba formations. As though, Nahr Umr is less than 5% of transformation ratio. These facts indicates that Sulaiy and Yamama formations are within the peak oil generation, however, Ratawi, Zubair, and Shuaiba, and Nahr Umr formations are within the start.The generated oil migrates up dip toward the dome of West Qurna field, but the existence of longitudinal and transverse fault system in the area may lead to accumulate oil in the directions NE and SW for the field.