New evidence for the combined influence of vapor condensation and thermal convection on groundwater monitoring wells

Synthetic Convection Log — Characterization of vertical transport processes in fluid-filled boreholes

“…Free convective flows in boreholes or monitoring wells and their adulterating effects on in-situ measurements and groundwater samples were reported by Solodov et al (2002) and systematically investigated by Börner (2006, 2008). Strong convective flow within the fluid column may adversely affect fluid samples.…”

In‐Well Degassing of Monitoring Wells Completed in Gas‐Charged Aquifers

“…Rayleigh's theory is commonly used to conduct thermal stability analyses and evaluate the potential for the occurrence of thermally driven convection (or mixing) in boreholes and groundwater wells (Solodov et al 2002; Love et al 2007; Berthold and Börner 2008; Berthold 2010). Thermally driven convection occurs in vertical water columns when the thermal Rayleigh number ($$$ {Ra}_T $$$) exceeds the critical thermal Rayleigh number ($$$ {Ra}_{TC} $$$; Rayleigh 1916), where a dimensionless Rayleigh number for thermal driven convection $$$ {Ra}_T $$$ can be determined as: $$$$ {Ra}_T=\frac{ge\left(\Delta \mathrm{T}\right){r}^4}{hvd} $$$$ where $$$ g $$$ is the gravity acceleration (m s −2 ), $$$ e $$$ is the thermal expansion coefficient of water (°K −1 ), ∆T is the temperature gradient within the well water column (°K), $$$ r $$$ radius of the well water column (m), $$$ h $$$ is the height of the water column (m), v is the kinematic viscosity of water (m 2 s −1 ), and $$$ d $$$ is the thermal diffusivity of water (m 2 s −1 ).…”

“…Rayleigh's theory is commonly used to conduct thermal stability analyses and evaluate the potential for the occurrence of thermally driven convection (or mixing) in boreholes and groundwater wells (Solodov et al 2002;Love et al 2007;Berthold and Börner 2008;Berthold 2010). Thermally driven convection occurs in vertical water columns when the thermal Rayleigh number (Ra T ) exceeds the critical thermal Rayleigh number (Ra TC ;Rayleigh 1916), where a dimensionless Rayleigh number for thermal driven convection Ra T can be determined as:…”

“…Despite some minor fluctuations, the thermal gradient between the two monitoring points remained relatively constant over the entire monitoring period (Appendix S1 and Figure S2), indicating that the observed values were likely associated with the in situ temperature gradient in the SWC. Previous studies have demonstrated that the occurrence of thermally induced convection currents in vertical water columns at a normal in situ gradient (Solodov et al 2002;Berthold and Börner 2008).…”

“…In‐well mixing can occur for several reasons in groundwater monitoring wells, including hydraulic gradient‐driven advection (particularly in wells with long screens) and advective flows driven by density and/or temperature gradients in the SWC (Barczewski et al 1993 ; Solodov et al 2002 ; Berthold and Börner 2008 ). Furthermore, the buoyant migration of FPG (i.e., rise of bubbles) in vertical water columns can induce solute mixing by inducing turbulence without mechanical agitation in industrial applications (Climent and Magnaudet 1999 ; Almeras et al 2015 ).…”