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Integrated Core Studies of the Mishrif Formation, Rumaila Field, Southern Iraq


The carbonates of the Cenomanian/Turonian Mishrif Formation form world-class reservoirs in fields across the Arabian Plate. Across the oil fields of Southern Iraq the Mishrif carbonates are some of the most prolific producing horizons. Extensive core studies were performed on the Rumailia Field in order to understand the stratigraphy, depositional environment, diagenesis, and reservoir architecture. More than 4000m of core have been taken over Rumaila since the field was discovered. Over 1500m of core were described and studied in detail by the Joint Venture operating the field. Most of the core was acquired historically and required reconstruction and sampling before it was slabed for the first time. In addition, four new cores were taken in the last 5 years to cover the entire stratigraphy of the Mishrif interval in areas which are critical to understand its dynamic behavior. An extensive conventional core analysis program, together with detailed sedimentological and biostratigraphic, chemostratigraphic, and diagenesis studies were performed. A detailed sequence stratigraphic framework and depositional model was established and tied into the newly established bio- and chemostratigraphic framework. Major sequence stratigraphic surfaces and intervals were identified in the core and linked to static data (logs, image logs, and poro/perm data). Furthermore these conventional core analysis and sedimentological studies were linked to the dynamic data obtained by an extensive reservoir surveillance program. The new understanding gained from linking core data to dynamic data were used to build new reservoir models, subsurface concepts and to help change development strategies. The core studies had a tremendous impact to understand and explain the reservoir performance of the Mishrif.