ملخص
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.