oa Characterisation of the Mid-Cretaceous Mishrif Reservoir of the Southern Mesopotamian Basin, Iraq

The Cenomanian-early Turonian Mishrif Formation reservoir of the Mesopotamian Basin accommodates<br>more than one third of the proven Iraqi oil reserves within rudist-bearing stratigraphic units. Difficulty<br>in predicting the presence of reservoir units is due to the complex palaeogeography. Extensive<br>accumulation of rudist banks occurred along an exterior shelf margin of the basin along an axis that<br>runs from Hamrin to Badra and southeast of that, with interior margins around an intrashelf basin.<br>Buildups were stacked or sometimes shingled as thicker shallowing-up cycles of several smaller-scale<br>accommodation cycles. As a result, each field shows different combinations of pay zones, barriers and<br>seal geometries.<br>The sequence stratigraphic analysis led to three complete 3rd order sequences being distinguished.<br>Eustatic sea level changes controlled development of the sequence stratigraphy. Tectonism primarily<br>defined the sites of platform development that complicated the architectural heterogeneity of the<br>depositional sequences.