Upper Cretaceous Oceanic Red Beds (CORBs) are pelagic sediment deposits that deposited in the Upper Cretaceous basin, with widespread in part of the world as well as in Iraq. This research investigates the deposition of cyclic marl and marly limestone CORBs of six selected sections at the active southern margin of the Tethys during the Late Campanian - Maastrichtian with petrography, microfacies, and depositional environment.
The measurement of carbonate content (CaCO3 %) in the rocks, 180 samples of all the geological sections were studied twice for each sample and the average readings were taken.
This examination proved the following major oxides wt. % concentrations domination SiO2, CaO, Al2 O3 and Fe2O3 with average values of 3

Shuaiba Formation is an important formation in Iraq, because of their deposition in the important period during the geological history of Arabian plate. The study is focused on a number of selected wells from several fields in southern Iraq, despite the many of oil studies to Shuaiba Formation but it lacks to paleontological studies. Four selected wells are chosen for the current study, Zb-290, Ru-358, R-624, WQ1-353, the selected wells are located within different fields, these are Zubair, Rumaila and West Qurna Oil Fields. In this study fourteen species followed to genus Hedbergella were discovered for first time as well as three genera followed to genus Heterohelix in the Shuaiba Formation at the different oil fields, Hedbergella tuni

This study is achieved in the local area in Eridu oil field, where the Mishrif Formation is considered the main productive reservoir. The Mishrif Formation was deposited during the Cretaceous period in the secondary sedimentary cycle (Cenomanian-Early Turonian as a part of the Wasia Group a carbonate succession and widespread throughout the Arabian Plate. There are four association facies are identified in Mishrif Formation according the microfacies analysis: FA1-Deep shelf facies association (Outer Ramp); FA2-Slope (Middle Ramp); FA3-Reef facies (Shoal) association (Inner ramp); FA4-Back Reef facies association. Sequence stratigraphic analysis show there are three stratigraphic surfaces based on the abrupt changing in depositional

Yamama Formation (Valanginian-Early Hauterivian) is one of the most important oil production reservoirs in southern Mesopotamian Zone. The Yamama Formation in south Iraq comprises outer shelf argillaceous limestones and oolitic, pelloidal, pelletal and pseudo-oolitic shoal limestones. The best oil prospects are within the oolite shoals. Yamama Formation is divided into seven zones: Upper Yamama, Reservoir Units YR-A & YR-B separated by YB-1, and YR-B Lower & two Tight zones: low (porosity, permeability and oil saturation) with variable amounts of bitumen. These reservoir units are thought to be at least partially isolated from each other.

The L. Cretaceous succession is the main reservoir rock in the south of Iraq. Although the upper Jurassic Sargelu Formation is the main source rock in this area; however, the organic-rich interval within the studied succession, is contribute in these huge accumulations of petroleum. The pyrolysis parameters of the succession; Sulaiy, yamama, Zubair, and Nahr Umr formations showed that the main kerogen type is type III and II with moderate to good HI, which they refer to gas and/or oil prone especially in Zubair, Nahr Umr, and Sulaiy formations. The quantity parameters indicate potential source intervals in respect to (TOC). The maturity parameters suggest the threshold and peak of petroleum generation, which Tmax values ranged around 430

Mishrif Formation regards one of the most important reservoirs in Iraq. Well logging represents one of the most important tool in the formation evaluation. According to the Petrophysical properties that have been gotten from well logging, Mishrif Formation in terms of reservoirs units, consist of several reservoirs units. Major reservoirs units divided into three reservoir units,MA,MB&MC. Each of these major units divided into minor reservoirs units (MB11,MB12,MC2&MC3).MB major reservoir units represent the best reservoir unit. These reservoirs units separated by cap rocks(mainly tight limestone)(CR1,CR2,CR3,CR4,CR5,CR6,and CR7).CPI were demonstrated for all wells.Hydrocarbon saturation vs.

The Yamama Formation belongs to the late Berriasian-Aptian succession, which was deposited during the Lower Cretaceous period within the main shallow marine depositional environment.

Petrographic study and microfacies analysis enabled the recognition of six main microfacies for three association facies. These are the Semi-restricted, Shallow open marine and Shoal environments. The study succession represents deposition of three third order cycles, these cycles where deposited during successive episodes of relative sea level rises and still stand.

The presence of shoal association facies (oolitic packstone microfaces) between the Sulaiy and Yamama formations refer to continue the deposition during the same stage, and may s

The aim of this study is to determine and evaluate the units and subunits of Mishrif Formation in Garraf oil field 85 km north of Nasiriyah city depending mainly on the geophysical well logging data and other amiable geological information. The sets of the geophysical well logs data acquired from GA-4, GA- AIP, GA- B8P, GA-3 and GA-5 wells of Garraf oil field are used to determine the petrophysical and lithological properties for each zone in Mishrif Formation to locate, define and evaluate hydrocarbon production from each zone in the reservoir which is also known as formation evaluation. The digitization was done by using Didger software and the interpretations were made using Interactive Petrophysics Program v 3.5 and Petrel software.

The Nahr Umr Formation, one of the most important Cretaceous formations and one of the main generating reservoirs in southern Iraq and neighboring regions, was chosen to study and estimate its petrophysical properties using core plugs, lithofacies, and well logs from five wells in the Noor oilfield. Reservoir properties and facies analyses are used to divide the Nahr Umr formation into two-member (limestone in the upper part and main sandstone in the lower). Limestone members are characterized by low reservoir properties related to low effective porosity and permeability while the main sandstone member is considered as a reservoir. Four lithofacies were recognized in the main sandstone member of the Nahr Umr Formation according to petrog

The Carbonate-clastic succession in this study is represented by the Shuaiba and Nahr Umr Formations deposited during the Albian - Aptian Sequence. The present study includes petrography, microfacies analyses, and studying reservoir characterizations for 5 boreholes within West Qurna oil field in the study area. According to the type of study succession (clastic – Carbonate) there are two types of facies analyses:-Carbonate facies analysis, which showed five major microfacies were recognized in the succession of the Shuaiba Formation, bioclastic mudstones to wackstone, Orbitolina wackestone to packstone, Miliolids wackestone, Peloidal wackestone to packstone and mudstone to wackestone identified as an open shelf toward the deep basin.