0016-2361(95)00016-X zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA Foe/ Vol 74 No. 6. pp. X74-879. 1995 Copyright I’ 1995 Elsevier Science Ltd Printed in Great Britain. All rights reserved 0016-?361,95.S10.00+0.00~ Oil sands are a complex mixture of clays, bitumen (an Characterization of minerals in oil sands by reflectance spectroscopy Edward A. Cloutis, Michael J. Gaffey” and Thomas F. Moslow? ER Georesearch Ltd, 4 Huntstrom Road NE, Calgary, Alberta, Canada T2K 5W3 * Department of Geology, Rensselaer Polytechnic Institute, Troy, NY 02 187, USA t Department of Geology, University of Alberta, Edmonton, Alberta, Canada T6G 2E3 (Received 16 August 1994) Diffuse-reflectance spectra (0.3-2.6 pm) of oil sands and mineral separates display a number of absorption bands which can be assigned to the spectrally significant minerals present in the samples. Minerals with strongly featured spectra such as kaolinite, illite and siderite can be identified even when they are minor constituents. Absorption bands in the 1.4 and 1.9 nm regions are most useful for identifying the presence and types ofclay minerals, whereas the LO-l.2 pm region is most useful for identifying the presence of siderite. (Keywords oil sands; minerals; reflectance spectroscopy) array of various hydrocarbons), quartz grains, water and minor accessory minerals”2. A detailed knowledge of the physical and chemical properties of these materials is essential for improving bitumen extraction processes and understanding the genesis and evolution of oil sand deposits3. A large number of analytical techniques have been applied to the study of oil sands because of their complex nature4*‘. In the present work, the ultraviolet, visible and near-infrared diffuse spectral reflectance properties of oil sands have been examined in the laboratory in order to ascertain which physical and chemical properties of these materials are amenable to spectral detection and analysis. A total of 18 oil sand samples from the Athabasca deposit in northeastern Alberta, which span a range of bitumen contents as well as selected phase separates, were characterized by reflectance spectroscopy and X-ray diffractometry (XRD). Diffuse reflectance spectroscopy (DRS) possesses a number of advantages over many other analytical tech- niques. Conventional infrared transmission spectroscopy requires extensive sample preparation which can alter the chemical and physical structure of oil sand@. Little or no sample preparation is required to yield usable diffuse reflectance spectra; consequently, the physical arrangement of the constituent phases can often be preserved and data can be acquired in near-real time. This is of particular importance in industrial process streams, where continuous monitoring of feedstocks may be required’. Some spectrometers are fully portable, allowing spectral data to be acquired in the field, such as on-site examination of drill cores, drill cuttings or outcrops. In addition, visible and near infrared spectroscopy can be used to study many liquid and amorphous phases and phases which occur in solid solution rather than as discrete mineral phases (unlike X-ray diffraction) and lighter elements such as C, 0, H and N which are not amenable to study by techniques such as electron microprobe analysis and X-ray fluorescence. The ultraviolet, visible and near-infrared spectral regions are useful for detecting combinations and overtones of the various fundamental absorption bands found in the middle and far infrared spectral regions as well as crystal field transitions and charge transfer absorption bands - . * lo These various types of absorption involve atomic processes acting over various distances, allowing the internal structure of a material to be examined at a number of scales. Perhaps the biggest drawback to DRS is the fact that information is obtained from, at best, the uppermost few millimetres of the material, the depth of examination being constrained by the optical density of the sample’ ‘,12. EXPERIMENTAL The oil sand samples used in this study were obtained from the Syncrude Canada Ltd and Suncor Inc. leases near Fort McMurray, Alberta. Each sample was chopped by hand to minimize any inhomogeneities. Although this disturbed the physical structure of the material, it was necessary in order to obtain homogeneous duplicate samples for XRD and DRS analysis. A portion of each sample, -2-3 g, was extracted in a micro-Soxhlet assembly using 10 x 50 mm cellulose thimbles and 10 ml of toluene. Extraction was completed in -45 min. The solvent extract was transferred to a tared evaporating dish and allowed to dry overnight. Each dish was then weighed to obtain the bitumen content. The tared thimbles were dried at 100°C for 1 h before and after extraction and reweighed after extraction to obtain the solids content. This procedure was adopted to minimize analytical errors which could result from the liberation of water and volatile organics’39’4. The extracted solids were ultrasonically disaggregated 874 Fuel 1995 Volume 74 Number 6