Thermal-hydro-mechanical modeling of short-term ground responses due to the borehole thermal energy storage operations in a Canadian subarctic region

Seasonal borehole thermal energy storage (BTES) has been recommended as a strategic technology to make an energy transition in the off-grid communities. However, the running of BTES can create thermal disturbance to the surrounding soil formation and bring a thermal-hydro-mechanical coupled process. This coupled process is particularly significant in less permeable formations, where the clay bound water is abundant. The role of clay bound water on the ground response during thermal storage has not been investigated previously. This study aims to numerically assess the short-term ground response due to the thermal disturbance during BTES operations in a Canadian subarctic region. The numerical analysis is conducted using our in-house developed finite element code. Our numerical results demonstrate the significance of considering bound water dehydration in characterizing the ground heave process during the short-term BTES operation in an over-consolidated soil formation. The ground expansion behavior is due to the high excess pore pressure generated from thermal disturbance. The surface heave is mainly from a poroelastic impact leveraging the release of some in-situ effective stress. The neglect of bound water dehydration will underestimate the magnitude of ground heave.