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 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 Abu-Shaybah Formation is located on the coastal of the Meditrranean sea South of Ghanimah North West of Libya, between Tripoli and Al Khumes, about 100 km East of Tripoli. It lies on the eastern end of Jabel Nafusa flank. Abu Shaybah Formation Ghanimah area of Late Triasic age, consists of sandstone. The sedimentary structure in the lower most part from studied outcrops reflect NW paleocurrent direction indicating that Jabel Nafusa uplift poorly effect the study area. The upper part of studied succession changing in pallaeocurrent dirction to NE due to Jabel Nafusa uplifting. The extreme changing of paleocurrent direction and paleoslope direction to East due to continuous increase in Jabel Nafusa uplift, direction of vertical joints in Wadi Qirrim presented from NW to SE dirction. The rocks of Abu Shaybah Formation analyzed using differnt kinds of technique, Polrized Microscpe, XRF, SEM techniques. The study of sedimentary texture (grain size, roundness, sorting, and sphiricity) and sedimentary structures showed that Abu Shaybah Formation outcrops deposited in response to two fining upword cycles, formed mainly in Braided Stream Rivers with some effects of meandering. The sequences of Abu Shaybah Formation outcrops that exposed in Wadi Qirrim have been identified on many types of sedimentary facies associated with given sedimentary stucture as, Planar cross bedding, Convolute bedding, Trouph cross bedding, Ripple bedding, Shrinkage cracks, Plant rootlets, Concretions, Unconformity, Channels, Massive bedding, Laminated bedding, and the results which located on the grain size of quartz also loacted on the grain size of heavy minerals like tormaline, zircon and reutile.
سليم معمر قجوم (2009)