Evaluation of microfacies of Mishrif Formation in Nassyria Oil Filed, south of Iraq


Four wells namely Ns-1, Ns-2, Ns-3, and Ns-5 were selected to study facies characteristics of the formation and try to correlate them with oil filed production. Thirty seven thin sections were taken from archive of south oil company, in addition to fifty seven thin sections which prepared by author to enhance results. Seven main microfacies and eight submicrofacies were identified depending on funa content, lithology, and texture. Results indicate that the formation was deposited under wide spectrum of depositional environments starting with open marine at lower part and ended with open lagoon at upper part. Diagenesis processes were observed through microscopic examination of thin sections including compaction, stylolite, newmorphism, cementation, dolomatization, solution, pressure solution, and mechanical distinegration. These processes play a role in deterioration and enhancement porosity of the formation. Bioclastic wackstone submicrofacies, benthonic form. wackstone submicrofacies, benthonic form. submicrofacies, and bioclastic grainstone microfacies are the most important reservoir microfacies founded.