Abstract:
The dual techniques of Computerised Tomography (CT) and Scanning Electron Microscopy (SEM) reveal significant subsurface processes are preserved in geothermal core that provide essential information for developing our conceptual models. CT scans image the spatial distribution of density changes at 0.02 mm increments enabling 3D mapping of density variations within rocks, both laterally and vertically. SEM images support the CT findings by documenting their associated subsurface processes. Dissolution, boiling of fluids, and thermal fluid flow are three important subsurface processes documented in this study. In some cases, multiple events are recorded. The cores examined show voids may be either connected with depth into the sample or shallow disconnected voids. Micro-fractures may be infilled with clays reducing the potential permeability of the channels, while others remain open with clay alteration confined to the host rock. The dual technique approach provides significant information on the spatial distribution and timing of various subsurface processes and provides important insights into permeability controls at the microscale.
