Petrophysical Evaluation of the Jurassic Carbonate Intervals in Northeast Iraq: Insights From Integrated Log Analysis

Abstract

The East Baghdad (EB) Field, part of the Foredeep Basin of central Iraq and Mesopotamia, is one of the largest but least exploited hydrocarbon deposits of the Middle East. The present study combines both the interpretation of well logs and petrophysical analysis of two sample wells (EB-84 and EB-93) to assess the reservoir potential of the Upper Cretaceous Tanuma, Khasib, and Kifl formations. Neutron density and M-N crossplot lithological identifications show that the successions are dominated by carbonate facies, the major one being limestone with some areas of dolomitization and traces of secondary porosity enhancement in EB-84 through diagenetic dissolution. The petrophysical analysis shows that the Khasib Formation is the most promising unit of the reservoir, with an effective porosity (PHIE) of between 16 and 19 percent and net pay thicknesses of over 85 m, which is comparable to prolific Cretaceous carbonate deposits of the Arabian Plate. Conversely, the Tanuma formation is mostly shale-prone with high water saturations (>0.80 in EB-93), whereas the Kifl Formation, although there are local regions of extensive porosity (>30% in EB-84), is primarily water-bearing. The bulk volume water (BVW) analysis confirms that the EB-84 has hydrocarbon potential (BVW less than 0.06), but lowers the quality of the reservoir of EB-93. These results demonstrate the heterogeneity of the Cretaceous carbonate deposits in the Mesopotamian Foredeep Basin and underline the significance of diagenetic processes to improve the quality of oil reservoirs. The Khasib Formation dominance as a major unit of reservoir is verified by the regional comparison with similar formations (e.g., Mishrif Formation in southern Iraq and Abu Dhabi carbonates) in which Tanuma and Kifl serve as a secondary or marginal interval. This combined research offers an enhanced framework of reservoir quality that underpins the enhancement of exploration and development approaches towards the EB Field.