Thermo-poro-elastic stress alteration around an EGS well due to cold fluid circulation

Wellbore cooldown via injecting and circulating cold fluid is a practical method to lower temperatures in the borehole and prevent damage to equipment associated with high temperature geothermal reservoirs in Enhanced Geothermal Systems. Extensive cooling often induces significant thermo-poro-elastic stresses, altering the near-wellbore stress distribution. A finite element model is developed in ABAQUS to investigate the magnitude of the thermally induced stresses during both the cooling and warmup phases. Our simulation results reveal a notable tensile near-wellbore stress in both directions for potential hydraulic fracturing initiation (longitudinal and transverse) due to cooldown. Such stress alteration is largely dependent on the duration of cooldown. Furthermore, the thermally induced stresses diminish with the increased waiting (warmup) time before hydraulic fracturing stimulation. Our findings highlight the pivotal role of borehole cooldown conditions in shaping the near-wellbore stress distribution.