Speaker
Description
Active-distributed temperature sensing (DTS) thermal test uses resistive heat as a thermal tracer source to measure Darcy fluxes in the subsurface, with high spatiotemporal resolution. However, most applications neglect the influence of thermal dispersion and small-scale hydraulic heterogeneity, which can influence heat transport in a porous medium surrounding the fiber optic cable, potentially biasing parameter estimates for high flow velocities. Particularly, thermal dispersivity is one of the key parameters governing heat transport in the shallow subsurface, yet remains highly challenging to quantify in situ. To assess their impact and investigate how dispersivity may be estimated from active-DTS tests, we performed two-dimensional numerical simulations under various Darcy fluxes (q, 1 – 10 m/d) and hydraulic heterogeneity conditions (σ2lnK, 0.1 – 2). We further adapted the moving infinite line source model to incorporate thermal dispersion. According to our simulation, the temperature initially increased log-linearly under conduction dominance, and then stabilized as advection and dispersion became more influential. Both thermal dispersion and hydraulic heterogeneity were found to lower the stabilized temperatures and delay the time to temperature stabilization. Based on these results, we discuss how these experiments may be used to estimate thermal dispersion and improve the accuracy of Darcy flux estimates. We expect that these findings will contribute to deepen our understanding of active-DTS thermal tests for improved applications and open new possibilities for estimating in-situ thermal dispersivity in the field.
Keywords: Thermal dispersion; Small-scale heterogeneity; Active-DTS; Aquifer characterization
| Country | France |
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