Microfacies Analysis and Depositional Environments of Lower Sa’adi Formation, Southern Iraq

The Sa’adi Formation is a part of the late Cretaceous period in Santonian-Campanian stage that represents potential hydrocarbon-bearing reservoir across many oilfields Mesopotamian Basin, South Iraq. was divided into two main parts as stratigraphy sequence. It consists chalky limestone with argillaceous upper and marly lower part. considered an important stratigraphic unit marked by petroleum shows. Thus, current research constructs depositional environment, evaluates reservoir, predicts best zones good quality. microfacies analysis carried out on thirty-five thin sections to reveal primary well logs data were used evaluate petrophysical properties Formation. Four appeared related carbonate ramp, which identified system track from mid inner ramp. These are; mudstone, wackestone, packstone, grainstone. Twelve sub-microfacies interpreted are pelagic lime mudstone benthic foraminiferal-argillaceous wackestone middle ramp experienced burial diagenesis syngenetic intra-fossil pores. results characterize bioclast echinoderms, bivalves, algae packstone grainstone (open marine shoal environments) pore-water diagenesis, meteoric freshwater dissolution, diagenesis. Shoal facies open favorable Diagenesis processes represented dissolution improved porosity permeability higher quality ramp; besides that, it recognized cementation micritization reduced