Geothermal Energy — A Future In Western Canada?
When we talk about “energy transitions,” many people think about wind and solar as the energy sources of the future. But more thoughtful conversations recognize that future energy supplies will be like today’s — complex and multifaceted, addressing a huge range of demands and situations.
Even in the simplest power systems, the intermittency of wind and solar and the enormous challenges in building networks and storage to manage those intermittencies dictate that we look to other low-emission energy sources to provide stable and reliable baseload.
Geothermal energy — energy from within the earth — can be a stable and long-term energy supply, and is generally regarded as a “renewable” energy option. But how big a contribution can it make to future energy systems? And can we harness our oil and gas skills and knowledge to make it work in Western Canada?
In the simplest scenario, geothermal energy provides heating and cooling for buildings, based on the fact that shallow (a few to tens of metres) subsurface temperatures are moderate and consistent year-round. A geothermal heat pump can circulate fluids to provide heat in the winter and cooling in the summer — although the pump does require a power source. This technology is very local — buildings are connected to a local well and pipe network, and fluids are circulated very short distances to minimize heat loss.
Shallow geothermal heating and cooling has been around a long time. There are more than 100,000 installations across Canada, but more widespread application is limited by high upfront costs (on the order of $20,000 for a typical house). Lots of available space, a long-term planning point of view and good architectural / engineering design are critical to successful installations.
All well and good, but we don’t need oil and gas technology for shallow geothermal. However, the big geothermal prize lies in hotter rocks and fluids (ideally >120 C) at much greater depths. These can be tapped for larger-scale geothermal heating, and where resources are sufficient, electrical power generation.
Geothermal heating — for homes, commercial and even industrial applications and greenhouses — works best in densely populated areas where a heat distribution network can service many clients in a small area. Some schemes are operating in Europe; for example, much of Paris is heated with hot water from the Dogger aquifer at about 2000m depth, augmented by gas-fired cogeneration and advanced heat exchangers.
Geothermal electrical power is generated by using high-pressured water and steam from deep reservoirs to drive turbines, either directly if the source is hot enough, or through a heat exchanger employing a lower boiling-point fluid if the geothermal source is cooler. Performance depends on the energy available — a product of geothermal water temperature and volumes delivered.
Delivering large volumes of hot fluids from great depths, safely and efficiently — now we’re talking Western Canada oil and gas technology! That said, although deep geothermal heat is used in many places, and geothermal electricity is generated in more than 70 countries (with a total installed capacity of >12,000 MW), Canada produces neither. So where do we start?
Geoscience BC completed “An Assessment of the Economic Viability of Selected Geothermal Resources in British Columbia” in 2015 which included review of two sites in the Western Canada Sedimentary Basin — at Clarke Lake and at Jedney. A 34 MW facility in the deep hot (130 to 190 C) Devonian carbonate reservoir at Clarke Lake was judged to have potential to deliver relatively high cost power (17.6 cents/kWh). Follow-up reservoir modeling and engineering pre-feasibility studies for a pilot geothermal plant are now underway. More detailed geothermal research is underway at both Clarke Lake and in the deep Devonian carbonate reservoirs at Swan Hills in west-central Alberta.
These results are both encouraging and discouraging — progress is being made, but some of our best geothermal reservoir candidates struggle to achieve economic viability. However, they were evaluated assuming development using current technology, where fluid production rates are limited by reservoir permeability and pressure, and cold fluids must be returned to the reservoir to maintain pressures.
A new geothermal technology to bypass these limitations is being promoted by Calgary-based Eavor. (Eavor is a client of my firm, Petrel Robertson Consulting). Eavor proposes to drill a series of multilateral horizontal wellbores through a deep hot reservoir and to link them toe to toe using magnetic ranging technology to form a continuous loop circulating fluids — essentially a “40 km heat exchanger” (Fig. 1). Wellbores will be sealed so that fluids circulate continuously, picking up heat from the reservoir but not exchanging fluids. Reservoir porosity and permeability are thus not important, and there is no need to undertake hydraulic fracturing or to handle hot saline brines.
The key technology borrowed from oil and gas is in drilling multilateral horizontals with such precision that the network is linked in the subsurface to complete the loop, and that optimal horizontal spacing is maintained. Closed-loop geothermal can take advantage of existing oil and gas infrastructure, including availability of drilling and completion rigs. Geological and geophysical mapping can identify “hot spots” for best application of the technology, and can scope out the subsurface for faults or other heterogeneities that could reduce project efficiency. Eavor is currently planning a two-leg multilateral demonstration pilot in west-central Alberta at a depth of about 2400m.
Two other companies are piloting deep geothermal in Canada. In 2018, DEEP drilled a 3530m well into basal sandstones in southern Saskatchewan, and plans a second well this summer to complete a production / injection doublet. DEEP’s long-term goal is to develop substantial baseload power from small, scalable 5-20 MW power plants, and to sell geothermal heat as a byproduct. Borealis Geopower has identified a number of project areas in B.C. and N.W.T., from which they hope to produce commercial power, micropower, and geo-heat, primarily from highly fractured igneous rock.
Further in the future for geothermal power generation, researchers in the Department of Mechanical Engineering at University of Alberta are working on advancing Stirling engine technology — where temperature differences drive an engine to turn over and generate power. The dream is to place engines on low-grade geothermal heat sources — perhaps repurposed oil and gas wells — to drive power production.
Many challenges remain to bring significant geothermal power online in Alberta, including regulation and policy, and competition from very cheap natural gas. The scope of the potential is large, but not yet defined. Creative innovators are showing that we can build on our oil and gas legacy — technology, infrastructure, and entrepreneurial attitude — to make it happen.