BENEFIT OF COMPLEMENTARY METHODS FOR CHARACTERIZING SANDSTONE CORES

ABSTRACT: This Paper is based on detailed mineralogical, structural, petrophysical and geochemical studies of sandstone core samples, using routine methods. These include Magnetic Resonance Imaging (MRI), Nuclear Magnetic Resonance (NMR), X-ray Computer Tomography (CT) Scanning, particle size analysis, point counting based on petrographic thin sections, Environmental Scanning Microscopy (ESEM), X-Ray Diffraction (XRD), and X-Ray Fluorescence (XRF). In this study we demonstrate the feasibility of combing these complementary methods of measurements in the characterization of sandstone cores. Four types of sandstones (Slick Rock Aeolian, Fife, Locharbriggs and Berea sandstones) that differ in grain size, porosity and mineralogy have been characterized. The results of the different methods used were found to be consistent with each other, but the combination of a variety of methods has allowed a more complete characterization of the rock samples than each method used on its own. This study has shown that rock heterogeneity at the sub-cm scale may have a significant effect on reservoir petrophysical characterization

Prediction of reservoir permeability from petrography characterization

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A Simple Method Based on the Application of a CCD Camera as a Sensor to Detect Low Concentrations of Barium Sulfate in Suspension

The development of a simple, rapid and low cost method based on video image analysis and aimed at the detection of low concentrations of precipitated barium sulfate is described. The proposed system is basically composed of a webcam with a CCD sensor and a conventional dichroic lamp. For this purpose, software for processing and analyzing the digital images based on the RGB (Red, Green and Blue) color system was developed. The proposed method had shown very good repeatability and linearity and also presented higher sensitivity than the standard turbidimetric method. The developed method is presented as a simple alternative for future applications in the study of precipitations of inorganic salts and also for detecting the crystallization of organic compounds

Hydraulic versus pneumatic measurements of fractured sandstone permeability

This paper investigates the issue of ascertaining whether gas can replace water for determining the flow parameters in fractured porous media. This is accomplished by the determination of the hydraulic parameters using brine, the pneumatic parameters using air, and the study of the correlation between these two parameters. The measurements are obtained for fractured sandstone cores from the middle Stubensandstein unit in the Southwest German Trias. In most cases, the intrinsic liquid permeability is lower than the intrinsic gas permeability. Intrinsic gas permeability (kg) ranged from 32 to 159 md, while intrinsic liquid permeability (kl) ranged from 12 to 47 md. The ratio of intrinsic gas permeability to intrinsic liquid permeability (kg/kl) shows two subgroups: (1) ratios ranging from 1 to 2 (62.5 % of samples) and (2) ratios ranging from 4 to 5 (37.5 % of samples). The reduction in the intrinsic liquid permeability is governed by three phenomena: physicochemically, by the migration of the clay particles which clog the pores, mechanically, by the breakdown of original fabrics caused by the passage of wetting fronts across relatively delicate clay mineral complexes, and experimentally, by the undersaturation of samples during liquid permeability measurements. This study concludes that gas permeability is more accurate than liquid permeability because it measures more closely intrinsic permeability especially for clay-rich rocks. In addition, because gas experiments can be conducted much faster than liquid flow experiments, gas is a desirable replacement fluid