Abstract
Yamama Formation is an important sequence in southern Iraq. Petrographic analysis was used to determine and analyze the microfacies and pore types. The diagenetic processes and the impacts on the petrophysical properties of the rocks were also identified. The petrographic identification was based on data of 250 thin sections of cutting and core samples from four wells that were supplied by the Iraqi Oil Exploration Company (O.E.C). The present study focuses on the depositional environment and the microfacies analysis of Yamama Formation. The results revealed several types of microfacies, including peloidal wackestone-packstone, algal wackestone-packstone, bioclastic wackestone-packstone, foraminiferal wackestone, bioclastic wackestone, and mudstone. The latter was divided into two submicrofacies, namely argillaceous lime mudstone and sparse fossiliferous lime mudstone. The study showed that Yamama Formation was deposited through various settings within the carbonate platform; these comprise inner ramp, middle ramp, and outer ramp settings. The inner and middle ramp settings, characterized at the top and middle Formation, have high effective porosity and low clay volume, due to dominant packstone.
Highlights
The Cretaceous rocks represent good oil potential rocks within the stratigraphic column in southern Iraq
This study targets Yamama Formation due to its good oil potential which attracted the interest of many researchers [4]
Sedimentation began with the deposition of the transgressive Sulaiy and Yamama formations and ended with deposition of the Ratawi Formation during the high stand stage [5]
Summary
The Cretaceous rocks represent good oil potential rocks within the stratigraphic column in southern Iraq. The main oil reservoirs are of the Cretaceous age, in addition to some important reservoirs from the Tertiary and upper Jurassic ages at most of the hydrocarbon within this point of view were confined to Suitable deposits for reserve especially in the lower and middle Cretaceous Formations in the south of Iraq [1, 2, 3]. This study targets Yamama Formation due to its good oil potential which attracted the interest of many researchers [4]. The Yamama paleogeography is represented by the Late Tithonian-Valanginian time at the Southern Neo-Tethys opened with the separation of the Bisitoun (Avroman) microplate from Arabia. The Upper Berriasian to Lower Valanginian palaeogeography (Yamama Formation) is summarized in (Figure 1) [5]. In southern Iraq, The Yamama Formation comprises outer shelf argillaceous limestones, as well as oolitic, pelloidal, pelletal, and pseudo-oolitic shoal limestones
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