Applicability of thermal response tests for assessing in-situ CO2 storage in a saline aquifer

The study aims to evaluate the method of Thermal Response Tests (TRTs) in assessing in-situ residual saturation of CO2 storage in saline aquifers. Similar to TRTs, mathematically the same type of an exact analytical solution presented by Theis is well-established for the transient drawdown in an infinite uniform confined aquifer. With the change of supercritical CO2 and saline water in pore space, the inverse models of temperature change over time either heating or cooling may lead to the detection of a change in thermal properties of fluids and sold matrix. In assessing the overall thermal conductivity using the three inverse models, the Wang model describes the saline aquifer of the interest structurally well among the chosen four conductivity models. The results of the Wang model and the arithmetic model showed almost insensitivity to the residual CO2 saturation up to 50 percents in the estimation of the overall thermal conductivity, while they did a sensitivity to porosity variation of the same range. Accuracy analysis of the three inversion models showed that a developed nonlinear least square inverse model produces the least error in the estimation consistently with the wide range of the residual saturation variation of CO2.