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Mauddud Formation (Albian stage-the Early Cretaceous) is an important oil reservoir in Ratawi field of southern Iraq. Four wells, R T-2, R T-3, R T-6, and R T-7, located 70 km northwest of Basra, were selected to study microfacies properties and petrophysical associations with the probability of oil production. Seventy-seven core samples are collected, and thin sections for petrographic analysis. The self-potential, Gamma-ray, resistivity, and porosity logs are used to determine the top and bottom of the Mauddud Formation. Water saturation of the invaded and uninvaded zones, shale volume, and porosity were calculated. The study area results showed that the quantity of shale is less than 15% for most of the wells, and the dominant porosity is the secondary porosity. In contrast, the primary porosity is low in all study wells, and the formation contains varying proportions of producing hydrocarbons. The results suggest the formation comprises light-colored dolomitized lime and pseudo-oolitic white limestone with green to blue-gray shale. The petrographic analyses of 65 thin sections of the Mauddud Formation reveal that most skeletal grains are shallow marine-derived faunas, while non-skeletal grains include peloids and ooids. The facies analysis showed that the Mauddud Formation was deposited within different sedimentary environments ranging from deep to very shallow environments, which was represented by a large variation in Five microfacies and ten submicrofacies, the microfacies "Mudstone, wackestone, packstone, grainstone, and Rudstone "submicrofacies" Peloidal wackestone to packstone, Bioclastic wackestone to packstone, Miliolids wackestone to packstone,Orbitolina wackestone, Peloidal packstone to grainstone, Orbitolina packstone, Mudstone to wackestone,Bioclastic wackestone, Miliolids and Bioclastic wackestone to packstone, Bioclastic packstone, and Peloidai grainstone". This variance suggested that the formation might be deposited within the carbonate platform's variety of environment, such as "deep sea, restricted, shallow open marine, mid-ramp, rudist biostrome, and shoal." Seven different kinds of pores have been found in the carbonate sideman of the Formation: Interparticle, Intraparticle, moldic, Vuggy and fracture.

A petrographic and microfacies analysis was conducted to understand better the sequence development of Shiranish Formation in Mergasur area within Erbil governorate (Lailuk section), Northern Iraq. These analyses interpreted the depositional environment, an essential aspect of stratigraphic analysis. Shiranish Formation is overlying Bekhme Formation in Lailuk region, with an unconformable contact. Shiranish series consists of four main microfacies: lime mudstone, wackestone, packstone, and grainstone. These microfacies are further divided into seven sub-microfacies: planktonic foraminiferal lime mudstone, planktonic foraminiferal lime mudstone to wackestone, planktonic foraminiferal wackestone, bioclastic planktonic foraminiferal wackestone, bioclastic planktonic foraminiferal wackestone to packstone, planktonic foraminiferal packstone, and planktonic foraminiferal packstone to grainstone. The sub-facies are associated with four discrete depositional settings: profound shelf, abyssal or cratonic deep basin, incline, and the inclined base. The studied region, Shiranish Formation, contains three asymmetrical depositional sequences (A, B, and C). The sequence disparity suggests a correlation between sea level and carbonate production variation. Asymmetrical cycles represent a phase of increasing sea level after a calm period. Shiranish sequence was formed over a discontinuous surface, creating a clear distinction from the underlying Bekhme Formation. The surface is represented using a type two-sequence boundary (SB-2). the Shiranish succession in the research region is created in an area of high subsidence. A significant transgression caused by a series of sea level occurrences resulted in the formation of the Shiranish Formation on a carbonate platform with significant subsidence. A significant transgression that caused several periods of sea level rise and stillstand is responsible for the formation of the Shiranish Formation on a carbonate platform that has seen significant subsidence. The depositional sequence stratigraphy, Shiranish sequences A to C, is distinguished by three maximum flooding surfaces (MFS-165, MFS-170, and MFS-175). These sequences have a notable correlation with comparable stratigraphic patterns reported in Iraq and other regions of the Arabian plate.

One of the oil field's main reservoirs is the Mishrif Formation, which is found in the Nasiriyah oilfield in the southern part of Iraq (Late Cenomanian-Early Turonian). It was one of the three oil wells selected for this study. To extract various petrophysical parameters for open wells indicated by gamma ray, density, neutron, self-potential, acoustic, and resistance, a variety of well logs were analyzed. The qualitative interpretation of the logs allowed for the identification of different types of rocks, the boundaries and thicknesses of the strata, the depths of the formation, and the zones that contained water and hydrocarbons. The quantitative interpretation, which assesses the reservoir's attributes by computing its porosity, the quantity and distribution of the shales, the levels of water and oil saturation, and other elements, that are necessary to evaluate the reservoir’s units in the research wells. The features of the study wells and the used logs were reported, to make clear how these features were distributed among the sample wells. The collected petrophysical characteristics were handled and shown as charts. There are two types of units within the Mishrif Formation: reservoir-containing CR-I, MA, CR-II, and MB. In most wells, reservoir units are made up of hard, low-porous rocks that are positioned between highly porous reservoir units. For a few wells, the MA unit had low residual and mobile hydrocarbon percentages, whereas the MB unit had large percentages, while the hard rocks had significant percentages of water saturation.