Cretaceous formations have been studied in number of wells at Al_Daww depression by taking /57/ crashed samples for preps of studying their content of fossils of Foraminifers and Ostracoda, study of Ostracoda reveals their important beside the foraminifera in stratigraphic determine and bled up layer correlations. Also, it reveals their important in locating their sediment environment, wither shallow to medium depth in general but it became relatively deep at upper Shiranish formation, and it may be concordant with natural sediment formations studied. Layers correlation reveals’ increase formations thickness and depth from north east toward North West that make more hope for oil in this directions.