Electrical thermal response test

Thermal response tests (TRT) are commonly used to estimate the ground thermal conductivity k and, to a lesser extent, the volumetric heat capacity C s . While k can be estimated with relatively good accuracy, the estimation of C s is typically less accurate, mainly because this volumetric property is inferred from point temperature measurements collected only within the borehole. The present work addresses this limitation by introducing an electrical TRT (E-TRT) that performs electrical resistivity (ER) monitoring during a conventional TRT. To analyse the experimental measurements, a coupled thermal–electrical model was developed to simulate the ER response to temperature variations during heat injection in a standing column well. Bayesian inversion was applied to both direct temperature and ER datasets. A synthetic experiment confirms that ER data are sensitive to C s as well as the ER temperature coupling parameter m , and reduces uncertainty of C s by about 50% to 70%. A field validation during a 256-hour E-TRT resulted in stable estimates of all parameters, with uncertainties of 3.8% for k , 12.4% for C s and 4.7% for m . E-TRT offers an approach that can help estimate C s and provide a field-scale alternative to laboratory-based measurements in estimating m . This strategy can be extended to monitor the entire standing column well and adapted to closed-loop systems. • Electrical resistivity measurements are integrated in thermal response test. • Electrical resistivity significantly reduces uncertainty in volumetric heat capacity. • Field-scale estimation of the temperature–resistivity coupling parameter.