Geothermal energy offers a number of advantages as a renewable energy source and is an important component of Canada's transition to a low-carbon energy future. In comparison to the intermittent output of traditional renewable energy sources, such as solar or wind power, it can provide constant, predictable baseload power year-round, with little fluctuation of power output. With proper reservoir management, geothermal resources are renewable in the sense that their thermal capacity can be assessed and designed to be maintained and replenished over the life of the power plants. In addition, geothermal power facilities typically have a small land footprint and a low carbon footprint, and consume less water than conventional power plants. Another perceived advantage in Western Canada is the potential to utilize the skillsets and experience of an existing oil and gas workforce and associated technologies, as well as the possibility of repurposing some oil and gas infrastructure.
Within Canada, prospective high temperature geothermal resources have been identified in British Columbia, the Northwest Territories, Yukon and Alberta.1 Several geothermal power projects at various stages of development currently exist in these jurisdictions with some attracting significant federal support in early financing rounds. These include projects located within the lower mainland of British Columbia, the foothills of the Rocky Mountains in Alberta and on the prairies in Saskatchewan. While several demonstration projects and feasibility assessments have been completed in recent years, two key projects currently in the design phase include a planned 5 MW geothermal power plant near Grande Prairie, Alberta and a plan for multiple small, scalable 20 MW geothermal power plants in southern Saskatchewan, near Estevan. Several other smaller scale projects, at earlier stages of development, are also underway in B.C. and Alberta.
Geothermal energy production is the harnessing of thermal energy from the naturally occurring thermal gradient within the earth. Around the world, this practice is common in areas with extensive volcanic and magmatic activity. In Western Canada, geothermal potential exists in deep portions of the Western Canada Sedimentary Basin (sometimes in excess of 3,000 m below ground surface) where basinal fluids and rock can reach temperatures above 80°C, as well as within mountainous metamorphic and igneous terrane complexes with magmatic root systems hosting geothermal fluid systems. Fluids in these deep aquifers can be produced at temperatures ranging from approximately 70°C to greater than 125°C. The hot fluid is brought to surface and the heat is captured for use in power generation or heating.
The main task when developing a geothermal energy project is to safely drill and complete the necessary wells to the required depths. This type of deep drilling is comparable to drilling in the oil and gas sector and the potential environmental concerns (e.g., management of drilling fluids, presence of entrained gas) are well understood. Accordingly, it is expected that these concerns will be managed consistently within the existing frameworks that regulate the environmental aspects of oil and gas drilling within each province.
One option under consideration by some geothermal energy developers is repurposing existing oil or gas wells. Under this scenario, the environmental liability of the existing infrastructure needs to be understood and managed. Typical due diligence activities associated with liability transfer (i.e., Environmental Site Assessments) can be used to quantify environmental liability. The liability management frameworks vary in each province and may require modifications to consider the geothermal potential of the infrastructure to offset the environmental liability (as discussed further below). However, there may be few existing oil or gas wells completed deep enough to safely access areas with material geothermal potential or with sufficient casing diameter to accommodate the pump sizes required for commercial scale development.
During operations, the main environmental consideration is the potential for brine release. Most concepts consider a facility designed to contain the brine fluid within a closed loop system where it is pumped to surface, cooled and then reinjected into the same formation. Geothermal facilities will need to be designed to consider appropriate response measures in the event of accidents or malfunctions related to brine handling. Operational maintenance plans would also need to consider the potential for scaling and fouling of pumps, piping and equipment. Depending on the chemistry of the fluids, robust integrity programs may be required to minimize the potential for releases. These environmental considerations are comparable to those encountered at existing oil and gas facilities and it is expected they will be managed in accordance with the existing approaches in the oil and gas sector.
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1. S. E. Grasby et al, Geothermal Energy Resource Potential of Canada (Geological Survey of Canada, 2012), http://geoscan.nrcan.gc.ca/starweb/geoscan/servlet.starweb?path=geoscan/fulle.web&search1=R=291488%0APembina.
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