Infrared Spectroscopy for Drillhole Lithology and Mineralogy

Abstract

Infrared spectroscopy has been used to identify rocks and minerals for over 30 years. The technique is sensitive to primary silicates as well as alteration products. Minerals can be uniquely identified based on multiple absorption features in reflected and emitted radiation. We are currently establishing methods and protocols in order to use the technique for rapid assessment of downhole lithology during drilling operations.

Initial work performed includes spectral analysis of both chip cuttings and core sections from drill sites around Desert Peak, NV. Kratt et al. (GRC 2004) have reported on the analysis of the DP23-1 chip board cuttings housed at the University of Utah using a portable field spectrometer set-up. We have recently performed laboratory measurements of 15 core sections from a variety of additional holes to examine spectral variability of ashflow tuffs. We will describe the utility of the technique for lithologic and mineralogic discrimination as well as field methods that can be employed during drilling operations.