The Cenomanian-Early Turonian Mishrif Formation, which has been studied in selected Oilfields of Tuba Well (TU-5, TU-24, TU-40) and Zubair Well (ZB-41, ZB-42, and ZB-46), which are located in the Mesopotamian basin, southern Iraq, and considered major carbonate reservoir in Iraq and the Arabian Gulf. Seven microfacies types are identified showing that Mishrif formation deposited in five sedimentary facies: 1. Basin Facies Associations; 2. Deep Marine Facies Associations: Bioclast pelagic foram mudstone-wackestone; 3. Shallow Open Marine Facies Associations: Foraminiferal bioclastic wackestone-packstones; 4. Rudisted Reef Facies Associations; 5. Shoal Facies Associations: Peloidal packstone-grainstone; 6.aBack-shoal Facies Association: a. Foraminiferal-bioclastic wackestone-packstone, b. Rudisted-foraminiferal wackestone-packstone; 7. Lagoon Facies Associations: a. Fossiliferous mudstone-wackestone, b. Bioclast foraminiferal wackestone, c. Benthic foraminiferal wackestone.