Sedimentological Study of Bajawan Formation (Late Oligocene) in Selected Wells from Kirkuk Oil Field, Northeastern Iraq

Abstract

The sequences of the Bajawan Formation (late Oligocene), have been studied in three sub surfaces sections from the Kirkuk oil field. These wells (K-183), (K-218), and (K-246) are located on the Baba dome of the Kirkuk anticline. The study included an analysis of 60 cutting-thin sections at different depths of the Formation in the three wells. The successions of the formation, which have a thickness of about 35,20 and 60 meters respectively, consist of limestone and dolomitic limestone. Petrographically the formation consists from skeletal grainswhich includs shells and bioclastes of benthic foraminifera represented by the genera Miliolid (Quinquiloculina sp., Triloculina sp.) and the rotalids represented by the genus (Rotalia sp.), as well as red and green algae, echinoderms, bryoza, sponges and It also contains non-skeletal grains such as peloids and rock fragment. The formation sequences have shown the effects of digenesis processes represented by dissolution, dolomitization, cementation, micritization, and neomorphism.Microfacies analysis studies have shown that the sequences of the Bajawan Formation consist of two mains successive microfacies: lime wackstone facies, and lime packstone facies. In turn, these three microfacies are subdivided into thirteen sub-microfacies, indicating that the formation was deposited in the environment of the inner ramp and the middle ramp, which reflects a relative shallwing in the depositional environment of the formation