Abstract

The current study includes building a 3D geological facies model of the Mishrif Formation (Cenomanian-Early Turonian) in Tuba oilfield, southern Iraq. Microfacies study and core samples examination reveals the occurrence of six facies associations within Mishrif succession represented by; Basin, deep marine, rudist biostrome, shoal, back- shoal, and lagoon. Each reservoir unit is characterized by distinct facies distribution that controls their quality. High reservoir quality is predominantly developed in rudistid facies that are productive from units MB1 and MB2. The 3D facies model shows that these units have greater continuity and thickness along Tuba anticline and control the structural and stratigraphic trapping. Units MA and Mishrif have lower reservoir quality due to the dominance of mud-dominated facies. The unit CR2 consists of non-reservoir facies, and can be captured along the oilfield structure.

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