By Brad Hayes, Ph.D., P. Geol, President, Petrel Robertson Consulting Ltd.
Carbon Capture and Storage (CCS) stands as a pillar in Canada’s strategy to mitigate its net greenhouse gas emissions. With a strong track record as a global leader in the operation of CCS facilities, Canada possesses the necessary tools and expertise to foster substantial industry growth.
The optimal conditions for effective carbon capture are found in locations where carbon dioxide can be extracted from high-concentration gas streams, notably within refineries, cement plants, waste-to-gas facilities, and various industrial sites. The keys to success revolve around identifying and characterizing subsurface reservoirs possessing the necessary geological characteristics for secure CO2 storage spanning millions of years.
As depicted in Figure 1, the ideal subsurface scenario for carbon storage contains porous and permeable rock formations characterized by abundant pore space to store CO2 and high permeability, facilitating the swift injection of CO2 (see Fig. 2). It is worth noting that these characteristics closely resemble those of promising oil and gas reservoirs, giving Western Canada a substantial advantage, as explorations of the subsurface have persisted for well over a century.
These reservoirs are naturally full of fluids, whether hydrocarbons or saline water. When introducing CO2 into these reservoirs, the existing fluids must either be compressed or displaced. Depleted oil and gas reservoirs, where oil and gas have already been extracted, are ideal targets due to their known pore space availability. The search is focused on substantial, contiguous volumes of reservoir rock, enabling large-scale CO2 injection into each wellbore without encountering obstructive subsurface impediments.
The most suitable sequestration reservoir is situated at depths exceeding 800 meters, where CO2 resides in a supercritical phase, combining the density of a liquid with the low viscosity of a gas. This
unique state allows for efficient packing of CO2 into pore spaces and facilitates its movement.
Geologists are essential in identifying effective sealing rock layers above the sequestration reservoir. These layers, with minimal porosity and permeability, serve as barriers, confining injected CO2 deep within the reservoir. Geomechanical analyses are indispensable in ensuring the integrity of these sealing rocks, especially as they are exposed to changing subsurface pressures during injection.
Under stringent standards, engineers drilling sequestration wells must safeguard shallow freshwater reserves from contamination from deeper reservoirs or drilling fluids (see Fig. 1). This precautionary measure underscores the responsibility associated with subsurface operations involving fluids from deep reservoirs.
CCS Projects in Canada
The landscape of CCS projects in Canada is vibrant and expanding. Currently, 25 carbon hub projects have gained approval from the Alberta government. A notable initiative in the Cold Lake region, led by the Pathways Alliance — a consortium of oilsands operators, involves the assessment of the Basal Cambrian sandstone as a storage medium for CO2 from oilsands projects. This initiative is set to commence by 2030, buoyed by the impressive performance of the Shell Quest project, injecting millions of tonnes of CO2 into the Basal Cambrian near Edmonton for over seven years.
Further south, the Alberta Carbon Trunk Line plays a crucial role, transporting emissions from the Industrial Heartland to the Clive area near Red Deer. The CO2 is injected into oil reservoirs within the Leduc Formation. Extensive geological and engineering analysis guides this endeavour to enhance oil recovery and increase oil extraction efficiency.
The Aquistore project in Saskatchewan is pivotal; CO2 from the Boundary Dam coal-fired power station is sequestered in another Basal Cambrian sandstone reservoir. British Columbia is also on the CCS map, with the Clarke Lake Gas Field being assessed for its capacity to store CO2.
Across Canada, diverse industrial operations require CCS to reduce their carbon emissions. However, regions that don’t have a history of oil and gas drilling lack the necessary knowledge about the
subsurface. Recognizing this, Natural Resource Canada (NRCan) and other institutions are allocating resources to research projects to bridge these knowledge gaps. Nonetheless, it will be several years
before we can conclusively determine the existence of substantial potential in these regions.
Scovan is working with clients in Western Canada on early-stage feasibility and FEED studies for CCUS applications. As these technologies continue to advance, Scovan is poised to provide expertise in the complex applications of Carbon Capture and sequestration.
Figure 1. Block diagram illustrating the relationship between deep saline formations for CO2 storage, shallow freshwater aquifers and surface
Figure 2. Photomicrograph of Basal Cambrian sandstone, cut and polished so thin that light can pass through it. Under a microscope, we see individual sand grains (in white) up to 0.5mm across and blue pore spaces where fluids like CO2 can be stored. This rock has a porosity of about 12%, and the pore spaces are well connected in three dimensions, making it highly permeable.
Originally published in Scovan’s IGNITE Vol. 7
