A field expedition into the British Columbia wilderness involving helicopter drops, mountain and landslide traverses, and treacherous ice caves aimed to facilitate geothermal exploration in Canada.
As Canada attempts to transition from a hydrocarbon-based economy to a renewable clean energy economy, the country seeks new options. Canada has abundant hydropower potential as well as wind and solar potential, but each of those energy sources comes with challenges, from controversies over new large dam construction to issues with intermittent generation. So Canada is also examining geothermal energy, a resource with many benefits compared with other renewables, to meet its goal of achieving net zero emissions by 2050.
Geothermal power plants have small footprints (unlike hydropower plants), low emissions, and direct-heat-use opportunities, but most important, they provide stable baseload power, unlike intermittent wind and solar sources. Offsetting the many positive aspects of geothermal energy is the higher exploration risk; it is much easier for planners to establish where it is sunny and windy than where there are exploitable heat sources deep underground.
Geothermal energy also requires pumping hot fluids from depth to the surface. The high fluid production rates needed to run a power plant (at least 100 kilograms per second) necessitate discovery of deep high-permeability aquifers that continuously deliver sufficient fluid to a well. Finding these permeable rocks in the subsurface is a key geothermal exploration risk that is tied to the expense of drilling. High exploration risk is one of many barriers that has limited investments by industry in geothermal projects. But this is a risk that geoscience research can reduce, which is where our wide-ranging team of geoscience experts—and our recent adventure into the Canadian Cordillera—comes in.
Geothermal Potential Near Mount Meager
To encourage geothermal energy exploration, the Geological Survey of Canada, with support from Geoscience BC, a nonprofit geoscience research organization, and the Natural Resources Canada Emerging Renewable Power Program, initiated a new project in 2019 focused on reducing exploration risk. A highlight of this project is a recent multidisciplinary field program aimed at developing novel tools to predict the occurrence of highly permeable zones within the Mount Meager volcanic complex, Canada’s only currently active volcano.
Lying 160 kilometers north of Vancouver, B. C., Mount Meager is in the northern part of the Garibaldi Volcanic Belt, representing the northern segment of the Cascadia Subduction Zone. Volcanism over the past 2.6 million years along this volcanic arc is a result of the continuing subduction of several microplates (the Juan de Fuca, Explorer, and Gorda plates) beneath North America. The most recent volcanic activity at Mount Meager was an explosive eruption about 2,400 years ago; however, fumaroles and numerous thermal springs at the volcano suggest a currently active geothermal system.
During the energy crises of the 1970s, research and exploration at Mount Meager revealed world-class geothermal resources with fluid temperatures exceeding 250°C at about 2-kilometer depth. However, the fluid production rates were insufficient to justify the expense of building power lines to the site, so plans to develop geothermal power there were abandoned.
Now the world faces a new energy (and climate) crisis, and geothermal once again looks like an appealing option. But the challenges haven’t gone away. Renewing exploration at Mount Meager, as well as within other volcanic belts in western Canada, requires new ideas and methods for the prediction of high-permeability zones at depth.
The geoscience team assembled by the Geological Survey of Canada to tackle this challenge comprised 34 researchers from a total of seven universities and government agencies. We brought together people with expertise in geological and structural mapping, volcanology, geophysics (especially gravity, magnetotelluric, and passive seismic surveying), geochemistry, regional stress field analyses, and hydrogeology into one coherent research project and sent everyone into the field from July to October 2019. The goal of the fieldwork was to use an integrated geophysical, geochemical, and geological approach to see into the heart of the mountain and enable clearer identification of high-permeability zones within the known thermal anomaly.
Into the Mountains
The Mount Meager area provides a number of challenges, so our fieldwork started with a lot of planning. First, we met with representatives of the Squamish and Lil’wat First Nations, as the field locations we intended to visit lay within their traditional lands. Our conversations resulted in a very positive collaborative approach to coplanning the field surveys. Through this coplanning, we eliminated unintended intrusions onto Spirited Grounds or ancestral burial areas by relocating some proposed survey sites to alternative locations that still supported the project’s scientific mission. We also moved some planned survey sites from pristine areas to previously disturbed grounds to limit our overall impact on the landscape. In the field, we were accompanied by a wildlife monitor from Lil’wat First Nation, who provided valuable support to minimize the risk of team members encountering bears (and all of whom she seemed to know by name).
Finding appropriate survey sites and wildlife encounters were just a couple of the challenges of this fieldwork. The group also contended with rough terrain, high elevations, and snow and ice. The Mount Meager massif includes some of the most rugged terrain of the Canadian Cordillera, and access has been limited since a 53-million-cubic-meter landslide in 2010 (Canada’s largest historic event) destroyed bridges on old logging roads. So the research teams had to be deployed via helicopters.
Every day, helicopters dropped teams of two to four people, carrying heavy backpacks and equipment, onto ridges, peaks, and otherwise inaccessible valley bottoms. Field survey teams hiked along high mountain ridges, on old overgrown logging roads, or through thick bush. For some geophysical surveys, groups of four or more people were required to carry the heavy, bulky survey equipment in addition to personal survival gear. And at times, clever solutions—such as helicopter slinging and using precarious mountain goat trails—were needed to move delicate equipment across narrow ridges and down steep slopes. Accessing fumaroles was a particular challenge, as they are located in subglacial ice caves filled with deadly hydrogen sulfide gas, so we had to take oxygen-supplying rebreather masks with us.
Over the course of the summer (375 person-days in the field), the research teams installed a temporary (2-month) network of 59 three-component seismic sensors along with a distributed acoustic sensor cable; they also conducted magnetotelluric (MT) measurements at 107 sites and gravity measurements at 79 sites, and made geological and structural observations at 903 sites. We analyzed the geochemistry of four thermal springs, which, although they required long hikes to reach, did provide the side benefit of easing sore muscles. We tried to sample the fumaroles in the ice caves but ran into trouble because of late-season ice melt that slowed our progress and because we could cover only short distances with the limited air supply provided by the rebreathers.
Imaging Mount Meager Anew
Over the coming year, we will use the data collected during the field campaign and from the installed sensors to examine surface and subsurface features of the volcanic complex. We will use data from the seismic and MT arrays to image magma chambers as well as the distribution of fractures and high-permeability zones that carry geothermal fluids through the subsurface, linking deep magma chambers with thermal springs and fumaroles at the surface. Spatial gravity measurements in conjunction with other geophysical methods will allow comprehensive mapping of subsurface magmatic and hydrothermal features.
Geological mapping and field observations, meanwhile, will help define the nature and spatial distribution of volcanic and basement rock types and structures making up the Mount Meager volcanic complex. One focus will be on locating geological domains that potentially display high-permeability reservoir properties—those rocks that hold hot water and through which water easily flows. As solid volcanic rock often has low porosity—and thus low capacity to hold water—we have so far examined areas where the rock is naturally highly fractured, measuring the density and orientation of the fractures to predict likely directions of water movement.
The data are currently being processed (into projects by three postdoctoral fellows, six doctoral candidates, one master’s candidate, and one undergraduate at universities in Canada) and will be integrated into a new 3-D model of the geothermal and volcanic plumbing system of the Mount Meager complex. This model should greatly reduce the risk associated with drilling for geothermal reservoirs in volcanic systems of British Columbia and help support Canada’s transition to a clean energy economy.
This research project could not have occurred without the contributions of all the researchers and students involved, including the following: from the Geological Survey of Canada, R. Bryant, Z. Chen, J. A. Craven, J. Liu, S. M. Ansari, and V. Tschirhart; from Simon Fraser University, A. Calahorrano-Di Patre, M. Muhammad, and G. Williams-Jones; from the University of Calgary, J. Dettmer, H. Gilbert, R. O. Salvage, and G. Savard; from the University of Alberta, C. Hanneson and M. J. Unsworth; from the University of British Columbia, M. Harris and K. Russell; and from Douglas College, N. Vigouroux-Caillibot. The research team greatly appreciates support from pilots Marco Accurso, Denis Vincent, and Ralph Sliger of No Limits Helicopters; planning and field support by Maxine Bruce and Tammie Jenkins of Lil’wat First Nation; and ongoing field support by Wayne Russell of Innergex Renewable Energy Inc. In addition, the field program was substantially supported by Innergex Renewable Energy, which provided lodging and logistical resources at its nearby run-of-river facility. Christian Stenner provided the unique skills required to enter volcanic glacial ice caves.
Stephen E. Grasby (email@example.com), Geological Survey of Canada, Calgary, Alta.; and Carlos Salas, Geoscience BC, Vancouver, B. C.
Originally published by eos.org – Science News by AGU- under CC BY-NC-ND 3.0 licence