Lithology Investigation of Shaly Sand Reservoir by using Wire Line Data, “Nubian Sandstone” SE Sirt Basin

Abstract

Scope of WorkMost sandstone reservoirs, worldwide, contain varying amounts of clay and/or shale. Therefore, shaly sands are heterogeneous producer reservoir. Petrophysical evaluation of these reservoirs type is needed to deal carefully with lithology investigation. However, the wire line logs using different formulas and cross-plots techniques. Most of these techniques have to be directed toward clay mineral identifications. However, this work on four wells was selected from different oil fields at eastern Sirt basin to present main inspect lithology, which is effect on reservoir qualification (porosity, permeability, etc.). The available data were wire line logs recording over than 750 feet reservoir thickness and each half feet analyzed. These logs are include; Neutron, Density, Sonic, Photoelectric factor (PEF), Natural gamma ray (NGS), and Induction resistivity. Previous workSeveral techniques have been proposed for determining lithology from wire line log data, such as principal component and cluster analyses and discriminate analysis. Subsurface lithology is traditionally determined from core or cutting analysis. Cores are generally not identification from well log based on not conventional cross plot proposed and studied, which is more easy continuous and consequently do not provide a complete description of formations crossed by a well. Well logs give a practically continuous survey of the formations crossed by a well. They allow measurement of apparent thickness and of real thickness if dipmeter data are taken into account. Burke et al. and Clavier and Rust [1,2] have shown that well log responses can give a good idea of the lithology. With the increase of physical parameters recorded by modern logging tools e.g., parameters recorded by modern logging tools e.g., photoelectric cross section, natural or induced gamma ray photoelectric cross section, natural or induced gamma ray spectrometry (GRS), and dielectric constant it becomes more obvious that their combination can give a good lithologic description of the formations. This evidence was the basis for the concept of "electrofacies" (Serra and Abbott) defined as "the set of log responses which characterizes a bed and permits it to be distinguished from other beds" (Serra). Applied to open hole logs, this electrofacies is AbstractIdentify the rock lithology has important meaning for estimating the reserve of petroleum as reservoir capacity and storage ability. The lithology identification from well log based on not conventional cross plot proposed and studied, which is more easier instead of rock core data observation results. However, this work carried out comparison between chart and analytical solution of matrix parameter (ρ ma and ΔT ma ) estimation values of producer shaly sand reservoir, and present the main depositional environment affects. In addition to influences of pyrite, ferruginous encrustations, organic material throughout this studied reservoir. Consequently, variety of matrix parameters values is contributed by clay minerals present i...