Low-enthalpy geothermal systems in the Western Canadian Sedimentary Basin

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Canada has enormous geothermal resources which could supply the country with a renewable and clean source of power. Traditionally, fluid temperatures >150°C are used to produce electricity, which require deep boreholes in sedimentary basins such as the Western Canadian Sedimentary Basin (WCSB). However, low-enthalpy, low-temperature (<150°C) resources can also be used in binary cycle power plants, which circulate a secondary fluid with a low boiling point. These geothermal power plants have great potential in sedimentary basins to provide base load electricity. However, its current use is limited worldwide because the geothermal use of sedimentary basins is new and barely tested. As such, substantial knowledge gaps remain related to thermal, hydraulic, geomechanical, and (geo)chemical (THMC) behavior of fluids and reservoirs. Geochemical and temperature data from boreholes are often scarce or contain high uncertainties. This has led to complications and failures when deep geothermal reservoirs have been targeted in the past (e.g. Hesshaus et al. 2013). Additionally, the systems require significant financial investment so that field testing is limited, and knowledge development is based on numerical modeling. Unfortunately, several of the numerical models cannot be verified against measurements because such benchmarks are unavailable. A novel attempt is to use evaporite formations such as Prairie Evaporite in the WCSB for geothermal systems since these formations have positive thermal anomalies. However, these formations are highly soluble and salt minerals can self-heal so that the permeability of the geothermal reservoir will change throughout its operation. My envisioned research program aims for a better, natural science-based approach to model the development of geothermal energy, including from highly saline environments. My current proposed research will focus on three areas: i) develop physically based benchmarks for groundwater flow near evaporite formations, ii) assess impact of mineral dissolution and precipitation on reservoir permeability, and iii) assess impact of geomechanical processes on reservoir permeability. I will use coupled THMC modeling to better understand flow and transport occurring in deep geothermal wells. The highly saline systems require careful consideration of fluid density, dispersivity, geochemical reactions, and changes in permeability. The permeability of these formations must be increased by hydraulic stimulation. Past work from my group characterized host rocks, the physics involved in the breakthrough technology, and the fluid flow and heat transport in single fractures and at reservoir scale. The proposed research will expand our findings to evaporite formations and develop the physics to integrate self-healing to allow for fully coupled THMC modeling. The results will contribute to wider acceptance and deployment of this technology due to be higher predictability of processes in deep geothermal reservoirs.