Depositional - diagenetic history and reservoir quality of the Ilam Formation in an oilfield in the Lurestan Province, West of Iran

The Ilam Formation is one of the important reservoir units in the Zagros area. Integrated sedimentological and petrophysical studies have been used to evaluate its depositional and diagenetic history, sequence stratigraphy and, finally, reservoir quality in an oilfield in the Lurestan area. Facies analysis has resulted in the recognition of 4 microfacies including pelagic mudstone/marl, planktonic foraminifera mudstone/wackestone, microbioclast wackestone to packstone, and oligosteginids planktonic foraminifera wackestone/packstone. Petrophysical logs of two wells A and B (Neutron, Sonic, Gamma-ray, and Resistivity( are used to define lithology, porosity and water saturation in the Ilam Fm. Clean to argillaceous limestone was the main lithology of the Ilam Fm. in studied wells. The formation has microscopic pores (up to 15%) as dominant pore types. Based on the MRGC method, 5 electrofacies have been defined and correlated with core-based microfacies. Finally, six integrated reservoir zones have been differentiated and correlated in a sequence stratigraphic framework.