This research deals with the study of the types and distribution of petrographic microfacies and Paleoenvironments of Mishrif Formation in Halfaya oil field, to define specific sedimentary environments. These environments were identified by microscopic examination of 35 thin sections of cutting samples for well HF-9H as well as 150 thin sections of core and cutting samples for well HF-I. Depending on log interpretation of wells HF-1, HF-316, HF-109, IIF-115, and IIF-272, the sedimentary facies were traced vertically through the use of various logs by Petrel 2013 software in addition to previous studies. Microfacies analysis showed the occurrence of six main Paleoenvironments within Mishrif succession, represented by basin, slope, shoal, Rudist biostrome, back shoal, and lagoon. Mishrif Formation was divided into six reservoir units depending on well logs and CPI. These units are separated by low porosity and high-water saturation of barrier beds. The reservoir beds from top to bottom are MA, MB1, MB2, MCI, and MC2. The reservoir units MB1, MB2, and MCI are the most important in the field of interest due to good reservoir properties and being the principle oil-bearing units in Mishrif Formation.
