Investigation of the Mineral Composition of Shales by Far Infrared Spectroscopy

Abstract

The interest in shales has increased over the past decade and extensive research has been undertaken to understand the technical and fundamental challenges facing gas shale exploration and production. Many of the physical and mechanical properties (i.e., porosity, rock strength) of shales that influence gas production are linked to the mineralogical and organic composition of the rock. Fourier transform infrared spectroscopy (FTIR) has been widely used to provide chemical and structural information regarding the mineral and organic phases that are present in shale rocks. Most of the spectral data has been acquired in the mid-infrared (MIR) region between 4000 to 400 cm-1 and a number of papers have been published by our research group [1] and others [2–4] on the characterisation of shales in this frequency range. However, the far-infrared (FIR) region between 400 to 10 cm-1 has been neglected despite a great deal of information regarding the vibration of molecules containing heavy atoms and crystal lattice vibrations. We show that the FIR range possesses characteristic absorption bands that can be used to identify and distinguish between many different minerals in shales. Furthermore, we demonstrate that mineral quantification is also possible and reliable when using partial least squares fitting methods. This paper will review some of the differences between MIR and FIR for characterising shales. The objective of this research is to evaluate the suitability of FIR spectroscopy for the identification and quantification of minerals and organic matter in shale rocks. References 1. Muller, C.M., Pejcic, B., Esteban, L., Dell Piane, C., Raven, M., Mizaikoff, B., Infrared attenuated total reflectance spectroscopy: An innovative strategy for analyzing mineral components in energy relevant systems, Scientific Reports, 2014, 4, 6764. 2. Snyder, R.W., Painter, P.C., Cronauer, D.C., Development of FT-I.R. procedures for the characterization of oil shale, Fuel, 1983, 62(10), 1205–1214. 3. Brown, J.M., Elliott, J.J., Quantitative analysis of minerals in oil shales by Fourier transform infrared spectroscopy Abstracts of Papers of the American Chemical Society, 1987, 193, 67-PETR. 4. Chen, Y., Furmann, A., Mastalerz, M., Schimmelmann, A., Quantitative analysis of shales by KBr-FTIR and micro-FTIR, Fuel, 2014, 116, 538–549.

AAPG Datapages/Search and Discovery Article #90217 © 2015 International Conference & Exhibition, Melbourne, Australia, September 13-16, 2015