Medium and Low-Grade Geothermal Energy: Geoscience and Geomechanics
Globally, countries are striving to gain control of the climate crisis by achieving carbon neutrality through significant and sustained reduction of fossil fuel based energy production. Access to energy remains vital however, so the importance of developing renewable energy technologies is paramount. Geothermal energy is a key opportunity to achieving the energy transition due to low carbon emissions, reliable energy production and relatively low operating costs. Determining the economic viability of geothermal energy is controlled by geographical and geological constraints, so thorough investigation of the subsurface geology is necessary in the evaluation of geothermal energy potential.
Steam-based geothermal systems have been well-studied and developed since the first small successes in Lardarello in 1911. However, geothermal steam for direct power generation is a rarity around the world, and extremely site-specific. The Iceland successes are well- known, as are fields such as Cerro Prieto and the Geysers, but >98% of the land mass of the world does not have High-T (steam) systems.
In this course, we will discuss global energy challenges and the energy transition, geological influences on geothermal energy sources, and focus on medium and low-grade systems in permeable reservoirs, and in hot dry rock at depth. We will also discuss geothermal energy storage, geothermal fluids, HOR stimulation, and related topics. Our intent is to leave you with a broad understanding of the thermal energy beneath our feet, how we might exploit it, and how we might even store heat in a “Thermal Battery” for power generation, or for habitat heating. Geothermal energy may fit comfortably with renewable energy sources (hydro, wind, sun) but integrating different combustion-free energy sources required careful planning and good geological and mechanical engineering.
- Understand basic geological concepts with influence geothermal energy systems
- Discuss the viability of developing a geothermal energy system in a given area (exercise)
- Discuss the different types of geothermal systems
- Consider basic risks of geothermal system development in a given area
- Understand basic geomechanical/engineering considerations of geothermal energy systems
- Geothermal systems (petroleum system elements format): i. High-T Steam systems - dry steam, wet steam; ii. SedHeat systems - hot aqueous fluids in porous permeable strata; iii. HOR systems - Hot (& warm) Dry Rock systems with minimal permeability;
- Low energy, high energy systems: i. Lowest energy systems are geothermal gradient systems; ii. Highest energy systems are supercritical water systems at moderate depth; iii. Intermediate energy systems in hot areas of sedimentary basins;
- Temperate and Northern climates: i. Extreme need for heat in sub-arctic and arctic climate zones; ii. Use of heat for power, habitats, agriculture;
- Tropical and Arid Environments: i. Extreme need for cooling in hot-dry and hot-humid climates; ii. Combining geothermal and other renewable energy sources for cooling.
- Clastic Reservoirs:
- Typical petrophysical properties (e.g. geopressured aquifers in the GOM);
- Adequate flow and energy flux.
- Carbonate Reservoirs:
- Carbonate systems, naturally fractured strata (dual porosity systems);
- Hot fluids from oil production.
- HOR - Hot Dry Rock:
- EGS - Enhanced Geothermal Systems;
- Naturally fractured systems and stimulation;
- Advective and conductive heat flux.
- Saline Aquifers and Salt
- Data collection and requirements
- Thermal information: T (z, t...), specific heats, porosities, thermal conductivities, etc.;
- Fluid flux information: reservoir characteristics, well stimulation effects;
- Geochemistry of fluids and scale potential in SedHeat and High-T systems;
- Microseismic surveillance, Deformation monitoring, Pressures...
- Geotechnical Constraints and Hazards
- Fluids management;
- Hydraulic fracture stimulation;
- Induced seismicity -11 T, b.p effects.
- Energy Storage
- Heat storage in shallow geo-repositories (<1000 m);
- Heat storage in deep geothermal heat reservoirs;
- Integrating geothermal energy with compressed air energy storage.
This course is designed for students and professionals in the geological and engineering fields who are interested in learning about the fundamentals of geothermal energy systems and modern energy challenges.
Participants should have prior knowledge of basic geology and/or geomechanics.
About the Instructors
Grant Wach began his career advising worldwide for multinational companies. He still works with the energy sector but now as Professor of Geoscience at Dalhousie University he serves as a mentor, helping students become successful geoscientists. Wach’s research goal is to understand the reservoir component of CCUS and Geothermal systems; understanding the internal complexity of the reservoir is not easy but part of the path to Energy Sustainability, and Carbon Neutrality. These steps are part of the Energy Transition the World is now undergoing.
Professor Wach is an expert advisor to the Energy Sustainability Committee of the UNECE. The committee just released their technology brief on CCUS (unece.org). He has advised the Nova Scotia government on Carbon Storage and Sequestration and completed the first evaluation of basins in the Maritimes for Carbon Storage. He was principal Investigator of the Gas Seepage Project (GaSP) evaluating methane (CH4) emissions from coal and oil and gas extraction sites in Atlantic Canada. Wach is a member of Geothermal Canada, and has recently presented invited lectures on Geothermal Technology in Canada (Future Pathways- Geothermal Technology 2020) and at KAUST in Saudi Arabia.
Professor Wach completed his doctorate in Geology at the University of Oxford (D.Phil. Geology). He was the first recipient of the AAPG Foundation Professor of the Year Award in 2012 and received the CSPG Stanley Slipper Gold Medal 2018 for outstanding contributions to exploration and development, teaching and mentorship.
Maurice Dusseault is a Professional Engineer and Professor of Geological Engineering at the University of Waterloo, where he has taught and carried out geomechanics research since 1982. His research is focused on deep subsurface engineering issues including oil production, hydraulic fracturing, energy storage, geothermal energy, carbon sequestration, and deep injection disposal of granular solids and liquid wastes. He holds over 90 international patents and has about 600 full-text papers published in journals and conferences. Maurice is a well-known educator and consultant, an advisor to companies and governments on matters relating to energy development, hydraulic fracturing, energy geostorage, wellbore integrity, technology and innovation. Maurice is deeply interested in energy technologies that can be scaled to community levels to provide robust and reliable heat and power. These include integrating natural gas, hydrogen, compressed air energy storage, and heat geo-storage. Another important component of his research is environmental geomechanics: safe and permanent sequestration of carbon (CO2, petcoke, biosolids...), particulate solid slurries, and waste fluids through injection deep into sedimentary strata.