Fault characterization and heat-transfer modeling to the Northwest of Nevado del Ruiz Volcano

Abstract

The Nevado del Ruiz Volcano is an area of great interest for future geothermal exploitation in Colombia facing exploration challenges as hydrothermal fluids originate deep into the fractured basement. Fieldwork conducted on the Northwest of this volcano confirmed the existence of fault zones and enabled collection of thirty rock samples from outcrops. Permeability of these samples was then measured in the laboratory with a steady-state gas permeameter, taking into account the Klinkenberg correction. The Porchet method allowed to obtain an estimation of in situ hydraulic conductivity in fault zones directly in the field. Thermal conductivity and heat capacity of the rock units were estimated from previous studies. 2D heat transfer and groundwater flow in porous fractured medium were simulated in the study area, using the free modeling package OpenGeoSys with data collected during fieldwork.Three modeling scenarios were considered, investigating the influence of fault dip in groundwater flow and heat transfer processes. It was possible to reproduce the temperature measured at the Hotel Termales hot spring, where the Samaná Sur fault appears to behave as a pathway for geothermal fluids. It was additionally found that fault dip has an influence on the simulated temperatures. When the dip is in favor of the fluid flow (<90° facing fluid flow), the simulated surface temperature increases; on the other hand, if the dip of fault is opposite to the fluid flow (>90° facing fluid flow), the simulated surface temperature decreases.