Evaluating thermal response tests using parameter estimation for thermal conductivity and thermal capacity

Colloquium 2016: Assessment of subsurface thermal conductivity for geothermal applications

“…Two options are then possible to analyze a TRT: 1) observed temperature increments can be fitted to computed temperature increments with equation 11 adjusting unknown parameters manually or using a non-linear solver (Wagner and Clauser 2005;Raymond et al 2011b;Bozzoli et al 2011;Pasquier 2015); 2) observed temperature increments can be plotted as a function of logarithmic time to calculate the subsurface thermal conductivity with the slope from equation 14 (Sanner et al 2005) and the borehole thermal resistance from the intercept with equation 15 (Beier and Smith 2002). For the first option or the calculation of the thermal resistance with the second option, the analysis requires an estimation of the subsurface volumetric heat capacity that can be found with rock or unconsolidated sediment type in order to calculate the thermal diffusivity when necessary.…”

New Methods to Spatially Extend Thermal Response Test Assessments

“…Field improvements included the development of TRT units with power regulations to decrease fluctuations in heat injection rate (Witte et al 2002), downhole temperature measurements with optical fibers (Acuña and Palm 2013;Acuña et al 2011;Fujii et al 2009Fujii et al , 2006 and wireless sensors (Martos et al 2011;Rohner et al 2005), as well as the use of a heating cable to avoid water circulation and reduce the power requirement (Raymond et al , 2010Raymond and Lamarche 2014b). The test analysis has been improved to take into account groundwater flow (Raymond et al 2011c;Signorelli et al 2007;Wagner et al 2013), thermal recovery (Raymond et al 2011a(Raymond et al , 2011b, variable heat injection rates (Beier and Smith 2003), parameter estimation (Choi and Ooka 2015;Wagner and Clauser 2005) and uncertainty (Witte 2013). The research presented in this manuscript is to address an additional problematic related to the spatial limitation of TRT.…”

Thermal response test for shallow geothermal applications: a probabilistic analysis approach

“…Anyway, the random choice of ground volumetric heat capacity based on literature values can lead to non-negligible errors (10% to 15%) (Witte 2012). In order to increase confidence of TRT, some coupled parameter estimations have been made, mainly based on finite element models and coupling thermal conductivity with volumetric heat capacity (Wagner and Clauser 2005).…”

“…Recently, it is a common scientific thought that the uncertainty component of the test, mainly related to natural variability of several of the involved parameters, cannot be neglected, so that some statistical and probabilistic techniques have been set up, especially related to multi-step parameter estimation (Wagner and Clauser 2005;Bandos et al 2011;Bozzoli et al 2011), sensitivity analysis (Li and Lai 2012), and error analysis (Witte 2012).…”