Microfacies Evaluation of Mauddud Formation in Ratawi Field, South Iraq

Abstract

This paper includes studying the microfacies evalution of Mauddud Formaion in
four wells(Rt-2, Rt-5, Rt17 and Rt-19). Seventy-seven(77) sampels were collected
of above mentioned wells. Based on fossil content of the samples under study, four
main microfacies were identified: packstone , wakestone , grainstone and lime
mudstone microfacies ,which deposited in shallow open marine and restricted
marine environments. Petrographic examination of thin section indicated that
diagenesis vary in intensity from one site to another, such as dissolution,
cementation, compaction, dolomitization and micritization, which led to the
improvement and deterioration of porosity. The dominant pore types are vuggy,
interparticle and intercrystal.The lithology, mineralogy and the matrix were
determined by using crossplot method, which showed that the predominant
lithology of the formation is limestone with the presence of dolomite in very few
percentages and the mineralogy is calcite. Based on the relationship between
porosity and permeability the resevoir performance of the microfacies classified
into four types: bad, fair, good and very good. Based on petrophysical properties
and core description of well study Mauddud Formation was divided into four rock
units A,B,C and D , in terms of reservoir, units A and C are considered good ,while
B and D are bad.