In-situ experimental study of the coupled thermal-hydro-mechanical behavior at WIPP using resistivity and distributed fiber optic sensing
Abstract
The salt body is an ideal repository for permanent isolation of heat-generating radioactive waste due to the ultra-low permeability and ability to creep that could close fractures. However, brine movement stimulated by the waste generated heat also brings challenges, such as waste package corrosion and radionuclide transport. Understanding the brine migration in the coupled thermal-hydro-mechanical (THM) process is vital for safe radioactive waste disposal. At the underground Waste Isolation Pilot Plant (WIPP), we conducted joint in-situ observation with controlled heater, electrical resistivity tomography (ERT), and high-resolution distributed fiber optic sensing (DFOS) to study THM induced brine migration. Both ERT and fiber optic sensors were placed in the boreholes that are away from the heater borehole. ERT is sensitive to permeability, brine content, and the rock temperature. The high-resolution DFOS was calibrated for temperature sensing.
During the heating and cooling processes, the resistivity changes from ERT correlate well with temperature changes. The fiber optic sensing also revealed correlating temperature measurements at the similar depth. Significant resistivity changes are also correlated with brine losses and restoration from the formation during the experiment. The results from the fiber optic sensing and the ERT measurement are consistent with the brine migration mechanism that is enhanced due to thermal expansion during the initial heating phase, and the salt contraction induced permeability and flow stimulation during cooling. These results are validated by separate numerical modeling, which also suggests a correlation between pore pressure in the static rock matrix and the temperature.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2020
- Bibcode:
- 2020AGUFMMR005..05W
- Keywords:
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- 1009 Geochemical modeling;
- GEOCHEMISTRY;
- 1011 Thermodynamics;
- GEOCHEMISTRY;
- 1822 Geomechanics;
- HYDROLOGY;
- 1829 Groundwater hydrology;
- HYDROLOGY