Diagenetic Processes and their Effect on the Reservoir Quality of Ilam Formation, Maleh-Kuh Oilfield, NW Andimeshk

Ilam Formation is the reservoir rock of Maleh-Kuh oilfield located in folding-thrusting Zagros zone in Lurestan province. It is mainly composed of mud-supported lithofacies varying from mudstone to wackestone. The most important identified diagenetic processes are compaction (physical and chemical), aggrading neomorphism, different replacement (pyritization, dolomitization, glauconitization and silicification), cementation, several generations of fracture, and burial dissolution. The main recognized pore types are moldic, vuggy, stylolitic, intercrystalline, and intragranular. Paregenetic sequence interpretation of Ilam Formation indicates that a set of diagenetic processes such as syndepositional diagenesis in marine environment, as well as post-depositional shallow to deep burial diagenesis, and uplift have affected this reservoir rock. Porosity and permeability data plots show that these facies have very low reservoir quality and most diagenetic processes have not had a major effect on increasing reservoir quality, and, only in some cases, permeability has been increased by stylolitization and fracturing.