Abstract The characterization of subsurface hydrologic properties remains a challenge in hydrogeology and geo‐resource applications, especially in fractured or heterogeneous reservoirs. Here, we investigate whether thermal recovery in an open borehole following fluid circulation can serve as an in situ method to estimate permeability and the spatial extent of permeable zones. Using numerical simulations of coupled fluid flow and heat transfer, we explore how hydraulic and thermal perturbations during circulation drive fluid infiltration and advective heat transfer when a horizontal permeable zone is intersected within otherwise low permeability rock. These processes modify the thermal recovery behavior in ways that depend on the permeability and thickness of the intersected zone. We find that thermal recovery becomes measurably longer in the presence of permeable zones, and that permeability values greater than approximately 10 −14 m 2 can be quantitatively estimated from recovery times and apparent thermal conductivity. The approach works particularly well when temperature time series data are collected at multiple depths following circulation associated with drilling or injection testing. These results support the plausibility of earlier interpretations suggesting that variations in recovery time with depth reflect zones of elevated permeability affected by fluid infiltration. Together, they demonstrate that depth‐resolved temperature monitoring in open wells offers a promising and efficient tool for estimating permeability and the thickness of permeable zones in the subsurface.
Purwamaska et al. (Sun,) studied this question.