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In collaboration with the Yukon Geological Survey, the Geological Survey of Canada, and other project partners, Innovate Geothermal Ltd. performed an analysis of geoscience data in southwestern Yukon as part of an effort to better understand the potential for geothermal energy resources that, if present, could be utilized to help reduce fossil fuel use. The study area for this project is located in the vicinity of the Village of Haines Junction (Dakwäkäda) and lies between the Denali and Shakwak fault zones. The main aim of this project is to analyze and interpret a variety of pre-existing and newly acquired geological and geophysical datasets to evaluate where geothermal reservoirs may be present within the study area. A secondary aim is to propose favourable drilling locations, if warranted, for exploratory wells to collect information on subsurface temperature and permeability. The geoscience work accomplished here includes both 2D map interpretation as well as construction of a 3D geologic model that was guided by geophysical inversion modelling of gravity, magnetic and audio-magnetotelluric survey data. At a regional scale, multiple lines of evidence suggest that subsurface temperatures are above the crustal average. More importantly, a municipal water well drilled in 2002 in the Village of Haines Junction produce warm (~20 °C) water from a depth of ~350 m. This water well proves that at least one permeable sediment-hosted geothermal aquifer is present under Haines Junction. Additional geothermal aquifers within the pile of young sediment that sits atop the bedrock are likely present. However, due to a lack of deep drilling in the area, the exact location, temperature, thickness and permeability of such aquifers remains unknown. In this study, a depth-to-bedrock model has been generated to aid with the identification of favourable target areas for exploratory drilling of geothermal wells. The four areas where the top-of-bedrock is deepest have estimated depths in the range 650 to 1225 m below ground surface. Temperature data from two wells in the Haines Junction area suggests the temperature gradient is ~60 °C/km. Thus, geothermal aquifers located near the top-of-bedrock in the four areas identified could have temperatures in the range of 39–74 °C. Production of geothermal fluids from these areas requires permeability in the sediments that sit above the bedrock. Deeper drilling is needed to measure actual subsurface temperatures beneath the village and to identify permeable intervals. Geologic structures and faults that may control permeability in the bedrock remain poorly constrained.

This talk was presented November 22, 2022, at the Yukon Geoscience Forum.

As part of the Canadian government’s commitment to establishing clean energy in the North, the Yukon Geological Survey is collecting subsurface temperature data near communities in the southern part of the territory. The research is a collaborative effort among federal and territorial geoscientists, universities, First Nation governments, and geothermal consultants. A major goal of the project is to determine whether ground temperatures warrant further geothermal exploration in the territory. The study also presents an opportunity for Yukon Geological Survey to educate the public about geothermal energy. This paper summarizes the methods and results of the drilling of two ~500 m geothermal temperature gradient wells. The first was drilled in the fall of 2017 in the Whitehorse area, near Takhini Hot Springs, where a surface water seep measures 46°C. The second well was drilled in winter 2018 in the Tintina fault system, near Ross River. Results to date suggest warm fluids and possible permeable rocks in the Takhini well between 450 and 500 m from surface, and a higher than average geothermal gradient of ~31°C/km in the Tintina Trench near Ross River. The results do not indicate temperatures for power generation at economic depths, however, they are encouraging enough to warrant further geothermal studies in southern Yukon.

In collaboration with the Yukon Geological Survey, Liard First Nation and other project partners, Innovate Geothermal Ltd. performed an analysis of geoscience data in southeastern Yukon as part of an effort to better understand the potential for geothermal energy resources that, if present, could be utilized to help reduce fossil fuel use in off-grid communities. The study area for this project is located near the Town of Watson Lake and straddles the crustal-scale Tintina fault zone. The main aim of this project is to analyze and interpret a variety of pre-existing and newly-acquired geological and geophysical datasets to evaluate whether geothermal reservoirs may be present within the study area. A secondary aim is to propose favourable drilling locations, if warranted, for exploratory wells to collect information on subsurface temperature and permeability. The geoscience work accomplished here includes both 2D map interpretation as well as construction of a 3D geologic model that was guided by geophysical inversion modelling of gravity, magnetic and magnetotelluric survey data. In the study area, the distribution of temperature in the subsurface remains a significant unknown; however, limited evidence suggests subsurface temperatures are modest. Regional-scale, Curie point depth estimates suggest an average geothermal gradient of only ~31°C/km. In contrast, two oil and gas exploration wells from the 1960s located 15–35 km outside the study area give a geothermal gradient range of ~38–50°C/km. Drilling is required to measure actual subsurface temperature gradients in the vicinity of Watson Lake. Evidence for substantial subsurface permeability is generally lacking in the study area. Analysis of the geoscience data did not reveal any specific locations along the Tintina fault that suggest a structural environment favourable for subsurface fracture permeability. Furthermore, the Tintina fault presents little evidence of active tectonism. Active tectonism helps maintain open fractures in the fault zone which could facilitate deep circulation of fluids to form a natural geothermal system. A lack of active tectonism could limit permeability in the fault zone. In addition, geophysical modelling suggests that large portions of the Watson Lake study area are likely underlain by shale-rich bedrock. This type of rock has very low permeability and is not favourable for maintaining open fractures. The only evidence for subsurface permeability found in this study is sand layers in the Cenozoic sedimentary rock of the Tintina trough. These sand layers could be permeable but are interbedded with low permeability layers such as silt and clay; the thickness and lateral extent of the sand layers is unknown. The 3D geologic model developed in this study suggests that the Cenozoic sedimentary rock of the Tintina trough is limited to less than ~1 km thick. This implies that fluids residing in sand layers in this rock unit would have a maximum temperature of between ~38 and 50°C. Geothermal fluids at these temperatures could potentially be utilized to help heat buildings in the community of Upper Liard. Many unknowns regarding the temperature and permeability of the subsurface still exist in the Watson Lake study area. The location of a 1 km deep scientific research well is proposed to help answer many of the remaining questions. However, considering the lack of evidence for bedrock permeability in the study area, other approaches to utilizing the Earth’s heat, such as Borehole Thermal Energy Storage (BTES) systems, could be considered to help the community of Watson Lake reduce dependence on fossil fuels for residential heating.

In collaboration with the Yukon Geological Survey, Teslin Tlingit Council, and other project partners, Innovate Geothermal Ltd. performed an analysis of geoscience data in south-central Yukon as part of an effort to better understand the potential for geothermal energy resources that, if present, could be utilized to help reduce fossil fuel use in Yukon communities. The study area for this project is located near the Village of Teslin and straddles the Teslin fault zone. The main aim of this project is to analyze and interpret a variety of pre-existing and newly acquired geologic and geophysical data sets to evaluate whether geothermal reservoirs may be present within the study area. A secondary aim is to propose favourable drilling locations, if warranted, for exploratory wells to collect information on subsurface temperature and permeability. The geoscience work accomplished here includes both 2D map interpretation as well as construction of a 3D geologic model that was guided by geophysical inversion modelling of gravity and magnetic survey data. In the Teslin study area, the distribution of temperature in the subsurface remains a significant unknown; however, limited evidence suggests subsurface temperatures are modestly above average. Specifically, regional-scale, Curie point depth estimates suggest the geothermal gradient in the area is ~45 °C/km. Drilling is required to measure actual subsurface temperature gradients in the vicinity of Teslin. Furthermore, subsurface permeability does appear possible in the study area. Analysis of the geoscience data shows evidence for a complex structural environment that appears favourable for subsurface fracture permeability in the Teslin fault zone area. In addition, geologic mapping and geophysical modelling suggests that large portions of the Teslin study area are underlain by quartzite and volcanic bedrock. Both rock types have a favourable potential for maintaining open fractures. Many unknowns regarding the temperature and permeability of the subsurface still exist in the Teslin study area. The location of a 500 m deep scientific research well is proposed to help answer many of the remaining questions.