Preliminary assessment of Nevado del Ruiz geothermal potential from laboratory measurements of thermal properties

English Abstract:

This study aims to evaluate the geothermal potential of Nevado del Ruiz volcano, in Colombia, through determination of thermal properties of rock samples collected in the field. The Nevado del Ruiz is a stratovolcano located in Los Nevados Colombian Natural National Park between the limits of Caldas and Tolima departments. Exploitation of geothermal resources could help to supply the local energy needs, particularly for agriculture based mainly on coffee crops.

Geothermal research in this region began in 1968 with a geothermal regional reconnaissance study. In 1983, a prefeasibility study located a promising area on the South Western side of Nevado del Ruiz, due to the presence of various active volcanoes (Santa Isabel, El Cisne and Ruiz) and the existence of fumaroles having a temperature up to 83 °C. At the end of 1990s, the geothermal potential of the Ruiz complex was estimated to 50 MWe.

Recent researches concerned hydrothermal alteration, kinematic characteristics of westward faults, geochemical and thermal evolution, and rock resistivity profiles. Other studies shown that faults may act as preferential flow paths for geothermal fluids. Nevertheless, there are no published studies about rock thermal properties, which can improve resource assessment.

Therefore, this work focuses on the evaluation of thermal properties of 62 rocks samples collected in surface outcrops. Thermal conductivity and specific heat will be measured using a needle probe and a calorimeter, allowing the calculation of thermal diffusivity. These thermal properties coupled to geothermal gradient values will lead to estimation of heat flow, extrapolation of temperature at depth and improvement of the geothermal resources assessment.

This work represents a first step towards the construction of a simple conceptual model for the geothermal reservoir of Nevado del Ruiz volcano.