Thermal-mechanical-hydrological-chemical responses in the single heater test at the ESF

Abstract

On-going Single Heater Tests (SHTs) are conducted in the Exploratory Studies Facility (ESF) to study the thermal-mechanical responses of the rock mass. In addition to the heater hole and those used for Sandia National Laboratory's (SNL's) thermal-mechanical studies, a set of 14 boreholes were drilled in the test region to conduct a scoping test of the coupled thermal-mechanical-hydrological-chemical (TMHC) processes. For the TMHC tests, the boreholes are equipped with electrical resistivity tomography (ERT), neutron logging/temperature, hydrological, and optical multiple point borehole extensometer measurement devices. The heater hole contains a 4-kW heater, which was energized on August 26, 1996. Our results show that some movements of the water around the heater have occurred, which might be associated with a possible dry-out region near the heater, and the water appears to be more dilute than the in situ ground water, except for the concentration of Ca. This indicates that fractures are the major water pathways, and the displaced water may have reached an equilibrium with carbonate minerals on the fracture surfaces. No mechanical-hydrological coupling has been observed yet.