Depositional and Stratigraphic Evolution of the Mishrif Formation in Eridu Oil Field, Southwestern Iraq

Abstract

This study is achieved in the local area in Eridu oil field, where the Mishrif Formation is considered the main productive reservoir. The Mishrif Formation was deposited during the Cretaceous period in the secondary sedimentary cycle (Cenomanian-Early Turonian as a part of the Wasia Group a carbonate succession and widespread throughout the Arabian Plate. There are four association facies are identified in Mishrif Formation according the microfacies analysis: FA1-Deep shelf facies association (Outer Ramp); FA2-Slope (Middle Ramp); FA3-Reef facies (Shoal) association (Inner ramp); FA4-Back Reef facies association. Sequence stratigraphic analysis show there are three stratigraphic surfaces based on the abrupt changing in depositional environments, one of them ((Mishrif –Kifl unconformity) are regionally correlated with the other equivalent formations in surrounding countries within the Arabian Plate. And intra- Mishrif two surfaces are maximum flooding surfaces which represents the deepening up-ward association facies. Two major sequences are identified based on the behaviors of facies association within a sequence of stratigraphic boundaries and system tracts. These sequences include sequence I and sequence II.