Abstract This study covers the Fields producting from the Gialo Formation a reservoir which is composed of Limestone and Dolomitic-Limestone and consists mainly of highly altered Nummulitic Packstone. This study was achieved through three parts of study including a petrographic study, petrophysical study of reservoir properties from core analysis and borehole logs. The general geological framework was obtained from petrographical study of thirty six thin sections, 129 representative core plug data and logs from 5 different wells are utilized to better understanding the petrophysical framework of the formation. The plots correlating petrophsical parameters and the frequency histograms suggested the presence of distinctive reservoir trends. These discriminations were also represented in Winland porosity- permeability cross plots resulted in clusters for different port-size that are responsible for different flow characteristics. Linear and multiple regression were used for the study of each unit. The permeability models were constructed and their reliabilies were compared by the regression coefficients for predictions in un-cored well. The combination of all data revealed the worst ranked reservoir quality corresponded to moldic and intergranular pore types, which occurred mainly in the Bioclastic Wackstone facies. The highest ranked reservoir quality corresponded to intragranular and intergranular which occurred mainly in the Nummulitic Packstone Facies.
وردة الشوشان (2010)

Abstract The Nubian Sandstone of Lawer Cretaceous Formation is located in Sarir Oil Field, in the Southeastern Sirte Basin in Libya. After conductiog 300 point counts on 24 thin sections from C4 -65&C3 -65. The deposition environment and diagenesis that affected the variability of porosity and permeability within a given lithologic unit. I found the Nubian Sandstone bodies of Sarir-C-North can also be divided on the basis of grian size and sedimentary structure into type: - 1) medium to coarse- grained sandstone 2) very fine grains sandstone. Association in the former lithologic, the siltstone and silty sandstone are grey and usually laminated; while in the latter they form white-grey or reddish siltstone and shaly siltstone beds, commonly intensively burrowed, and locally contain fragments of coal. A different depositional environment deposited each lithology. The Nubian Sandstone is interpreted to include several lithofacies deposited in fluvial environment. It informal these facies controlled both the primary porosity and diagenetic events. Peterophysical properties of formation under study were determined using different well logs. Porosities are calculated using sonic, neutron, and density logs. It is clear that the primary porosity in (well C3 -65) of formation represents dominant one and the secondary is (well C4- 65) of rare.
ليلي المبروك (2008)

Abstract The Nubian Sandstone Formation is a significant hydrocarbon reservoir in the Concession 59D, Eastern Sirt Basin, Libya. This formation is underlain uncomfortably by granitic basement and/or by the Hercynian unconformity and overlain uncomfortably by Pre-Upper Cretaceous followed by an Early Upper Cretaceous Transition beds. The Nubian formation is a thick sequence comprises mainly of sandstone, siltstone and shale.The Nubian Formation in this area has been subdivided into three stratigraphic members; namely Lower Sandstone, Middle Shale and Upper Sandstone (main reservoir well be focus of this study).The Upper Sandstone is the upper most subdivision of the Nubian Sandstone sequence consists mainly of white, grey to brown sandstones, ranging from fine to medium, locally coarse grained, moderately cemented with straight to concavo convex or slightly sutured grain contacts. This reservoir is a complex of fluvial sands deposited in Braided and Meandering streams.The reservoir fluids are very rich retrograde condensate gas and waxy oil with pressure at slightly above the saturation pressure. Most of this hydrocarbon in this reservoir has been sourced from the Nubian Middle Shale Member, but the Upper Cretaceous shale and Evaporates belonging to the Transition beds sequence have a significant potential source. The trapping mechanism in the field is a combined structural and stratigraphic trap for the Nubian Sandstone with the southern closure against the tight Nubian facies and basement of the Gialo High. Reservoir properties across the North Gialo Study Area vary in terms of porosity, permeability fluid saturation. These variations are indicated through the porosity, permeability and saturation maps and charts based on well log analysis and lab core sample measurements. These properties are discussed in the reservoir characterization part of this thesis.
عواطف عبد الله بودربالة (2012)