QEMSCAN ® (QUANTITATIVE EVALUATION OF MINERALS BY SCANNING ELECTRON MICROSCOPY): CAPABILITY AND APPLICATION TO FRACTURE CHARACTERIZATION IN GEOTHERMAL SYSTEMS

Abstract

Fractures are important conduits for fluids in geothermal systems, and achieving and maintaining fracture permeability is a fundamental aspect of EGS (Engineered Geothermal System) development. Hydraulic or chemical stimulation techniques are often employed to achieve this. In the case of chemical stimulation, an understanding of the minerals present in the fractures themselves is desirable to better design a stimulation effort (i.e. which chemical to use and how much). Borehole televiewer surveys provide important information about regional and local stress regimes and fracture characteristics (e.g. aperture), and XRD is useful for examining bulk rock mineralogy, but neither technique is able to quantify the distribution of these minerals in fractures. QEMSCAN ® is a fully-automated micro-analysis system that enables quantitative chemical analysis of materials and generation of high-resolution mineral maps and images as well as porosity structure. Initial applications of QEMSCAN ® technology were predominantly in the minerals industry and application to geothermal problems has remained limited to date. In this pilot study, the application of QEMSCAN ® technology to fracture characterization in geothermal systems was evaluated using samples from Newberry Volcano (Oregon) and Brady‟s geothermal field (Nevada). QEMSCAN ® results