Low temperature geothermal resources in abandoned mines of the Canadian Shield: A case study in the Chapais and Chibougamau area, Québec, Canada
Author: Andrea Louise Frances Morgan Year: 2018 Supervisors: Juliet Newson and Jasmin Raymond
Abstract:
With an average geothermal gradient of 7°C per kilometre, the Canadian Shield is not a conventional geothermal resource. However, due to the abundance of inundated mines within the province of Quebec, considerable volumes of water have been geothermally heated. This fluid can be used in conjunction with heat pump systems, where high flow rates are more important that fluid temperature, in order to heat nearby infrastructure. The area near the former mining centre of Chapais and Chibougamau, in the southern reaches of Nord du Quebec, is selected as a site in which to study this possibility.
A numerical model of the Copper Rand mine, considering both fluid flow and heat transfer, is created to simulate the extraction of water from the mine's main vertical shaft and its reinjection into another abandoned mine at a distance of 2.5 km. The results indicate that 1.32 x 10^8 MJ of thermal energy could be extracted annually from the mine for a period of 25 years, with a thermal power output of up to 4.35 MW. The main constraint on production is the hydraulic head build-up at the reinjection site. The abundance of abandoned mines in the region offer possibilities to utilize multiple reinjection sites, increasing the volume of water that can be extracted.
A regional assessment of the Chapais and Chibougamau area indicates that significant quantities of thermal energy is contained within the region's 24 flooded mines. Energy balance calculations were done in order to assess the energy contained within the mines. An easily adaptable numerical model was created in order to be able to quickly assess the extractable energy. This tool allows for a preliminary assessment of the potential geothermal heat extraction to determine if pursuing more detailed studies of specific mines is needed. Requiring only information regarding the total extracted ore and depth of the mine (parameters which are available for most mines), the model simulated the extraction of water from a vertical shaft and its reinjection elsewhere, in order to calculate the maximum sustainable production rate and the temperature of the produced water. If additional parameters are known, the model can easily be updated to incorporate mine geometry.
Keywords: Geothermal energy; Abandoned mines; Ground source heat pumps; Quebec; Numerical modelling; Preliminary assessment