There are several ongoing carbon sequestration projects active in Western Canada, and 26 new projects proposed in Alberta as of 2023. We know that Canada emits 708 megatons and sequestration targets for proposed projects vary between 1 megaton and 40 megatons of Carbon Dioxide, it is relatively hard to assess the size of emissions and the size of sequestration. To visualize the amount, we propose reducing quantities to a one dimensional unit of measurement, as thickness of carbon dioxide column. Let’s have a look at how much we have, how much we add and how much we want to put away.
The Size of the Problem
Planet earth has a diameter of 6,371 kilometers on average. The atmosphere envelops the earth, as a blanket ranging from 7 to 10 kilometers in thickness. When looking at the one dimension column, the 9,000 thick atmosphere represents 0.14% thick envelope to the planet.
The atmosphere is composed of 78.08% Nitrogen, 20.95% Oxygen, 0.93% Argon, and 0.04% other gases, mostly Carbon dioxide (0.0407%) and methane (0.00018%). Projecting that on the single dimension, we get a column of 7028 meters of Nitrogen, 1,885 meters of Oxygen, 84 meters of Argon, 3.66 meters of CO2 and 0.02m of CH4.
The carbon dioxide layer, if seen as a blanket around the world, would stand 3.66 meters thick, about as high as two humans, on top of each other, end to end. The CO2 layer represents 0.00006% of the length of a line from the center of the earth to the top of the atmosphere.
That is how much we have, but how much are we adding to the system?
There are 3.3 million megatons of CO2 in the atmosphere. Humankind is adding 46 thousand megatons each year, an addition of 1.35% to existing atmospheric carbon each year. Canada is contributing 708 megatons, or 1.5% of world emissions; 270 of those megatons are coming from Alberta emitters (the province has a significant 38% contribution to Canada’s emissions).
Canada’s emissions adds to atmospheric CO2 at a rate of 0.02% each year. Is that significant, or alarming? Let’s go back to the one dimension representation. If atmospheric carbon is a 3.66 meters thick blanket, the world is adding 5 centimeters to the blanket each year, slightly more than the size of a matchbox. A matchbox may seem small, but the entire planet covered in matchboxes is a disturbing image. Canada’s emissions, if distributed equally around the globe, would be slightly larger than the thickness of a matchstick. Not very large if compared to the size of the planet, but a layer of matchsticks added each year is not a pleasant view.
Alberta would contribute emissions in the order of a 0.03 cm thick blanket around the world, and the proposed sequestration targets, which will be detailed later, equate to 0.01cm.
If we imagine Canada as an island, and if all its emissions would accumulate on top of it’s land, the one dimension gets a lot bigger, to the equivalent of 3.9 centimeters, a bit larger than a walnut. Alberta’s emissions, on the other hand, if piled on top of Alberta’s landscape, would be 22.7 centimeters, as thick as a watermelon. If we keep our emissions to ourselves, and not spread emissions across this large planet, we would be knee deep in emissions, a significant addition to the two-person high layer of atmospheric carbon dioxide. Alberta covered in watermelons is a weird sight. Time to bring up proposed carbon sequestration projects. Along with currently active projects, the sequestration target is 137 megatons, reducing emission by 50%, or taking away a banana size layer of CO2 gas from the watermelon size layer poured over Alberta each year.
While these volumes are tremendous, the key to sequestration is injecting CO2 into reservoirs in supercritical fluid form. While a metric ton of CO2 occupies 534 cubic meters at atmospheric pressure and 20 degrees Celsius, the same ton would be 2.6 cubic meters in supercritical state, at 20°C and 10 Mega Pascal of pressure (the typical pressure of a geological reservoir that is more than 1 kilometer deep).
Injecting carbon dioxide in supercritical fluid form changes the size of the solution drastically.
The Size of the Solution
When looking at carbon dioxide in supercritical state, the volume is 200 times smaller than that of gas CO2. So how much are Alberta’s emission as supercritical CO2?
Alberta’s 137 megatons of emissions would occupy 715 million cubic meters, or a sphere with a radius of 0.55 kilometers, a quarter the size of downtown Calgary. Proposed capture, at 137 megatons, or 339 million cubic meters in supercritical fluid form, would be a sphere with a radius of 432 meters, a sphere about 4 times as tall as the Bow building in Calgary (the Bow building measures 236 meters in height).
A few capture projects are currently operational in Alberta and Saskatchewan. 26 projects were proposed, in two phases: a first phase with six projects around Edmonton and the Alberta Industrial Heartland, and a second phase with 19 projects scattered around the province. Lease areas range from 1.7 million hectares to 22 thousand hectares, and proposed sequestration range from 40 megatons to less than 100 thousand tons of CO2.
A summary of proposed projects is outlined here:
Carbon Sequestration Proposals
Projects were evaluated based on sequestration intensity, by dividing proposed volumes to lease area. Sequestration intensity varies from 3 tons per hectare per year to over 45.
Pathways Alliance and Enhance Energy’s Origin projects have some of the largest sequestration targets, while Pathways and Heartland’s Battle River lead in area size, but the most intense injection is planned for InterPipeline’s Bow River project and Bison Low Carbon’s Meadowbrook project, with more than 40 tons per hectare per year. The least intense proposals intend to sequester 3 to 47 tons per hectare per year, an order of magnitude lower.
Reducing again these targets to a one dimension, this time a column of supercritical CO2, we calculate injection ranging from less than 1 millimeter to more than 1 centimeter (assuming all supercritical CO2 injected would be spread evenly across the entire lease area in each project).
It would be appropriate to issue a few disclaimers at this point:
- Column height is calulated based on average supercritical CO2 density
- Reservoir pressure regime was not considered in calculations
- All figures rely on oversimplified reservoir geometry and parameters
- Plume geometry and migration was not considered in calculations
- All parameters (porosity, isopachs, injectivity) are estimated regional averages
- Chemical reactions between carbon dioxide and rocks were not considered
So then, looking at columns of CO2 to be injected in these large lease areas, we see columns of supercritical CO2 in the range of 0.8 to 12.5 millimeters, less than the diameter of a loonie (one-dollar coin), to be injected evenly across lease areas each year.
The Alberta Energy Regulator granted evaluation leases covering over 10 million hectares, the equivalent of 1,130 townships, with almost 3 million hectares assigned in Phase 1, and almost 7 million hectares in Phase 2. It is worth mentioning that most projects are planned as open hubs, accepting carbon from an open market, but several are anchored by a large emitter.
Proposed storage capacity includes 50 megatons in Phase 1 and over 74 megatons in Phase 2. Compare that with ongoing sequestration of 16 megatons, and Alberta’s emissions of 256 megatons.
Of the 25 companies involved in carbon sequestration, a third are upstream oil and gas operators like Whitecap and Shell, another third midstream companies like Enbridge and Tidewater, and a last third are companies that operate exclusively in the carbon sequestration space, like Enhance and Entropy. A few emitters are also proposing sequestration, and many projects are envisioned as collaboration between different companies. Upstream companies tend to propose projects with higher sequestration targets.
Sequestration targets are deep saline aquifers, preponderantly Basal Cambrian Sandstone in the East of the province, and Woodbend Group carbonates in the center.
Not all reservoirs are created equal. Porosity, permeability and thickness vary across the leases, but generally the Basal Cambrian is 50 meters thick with 6 to 15% porosity, while the Leduc is thicker with more pore space. When considering the CO2 column injected in a reservoir, the supercritical liquid would be accommodated in the pore space in the form of a plume.
While injected fluid measures between 1 and 12 millimeters (when spread evenly across each lease area), the thickness of the plume is an order of magnitude higher, as it’s accommodated in a 6 to 15% pore space. The basal Cambrian Sandstone, with its large distribution across the province, has proposed sequestration of 79 megatons, but that equates to a carbon column of only 3 millimeters, and a plume of 3 centimeters thickness added per year. The Belloy and Nisku formations, with lower lease areas, expect more intense injection of 5 and 7 millimeters of supercritical CO2 per year, equivalent to plume thickness of 7 and 5 centimeters.
Injection intensity was calculated simply by dividing proposed storage capacity by lease area. Existing projects (Quest, Boundary Dam, Clive), have relatively low intensity, as do some of the larger proposed hubs. Not surprisingly, some of the hubs with smaller areas show higher sequestration intensity.
CO2 columns to be injected as supercritical fluid, assuming constant distribution and uniform geological conditions across the reservoir, are relatively small, between 1 and 10 millimeters per year.
There are copious amounts of pore volume available in saline aquifers in the subsurface of Alberta. When dividing existing pore volumes (computed from porosity and formation thickness), the available space can accommodate injection at proposed rates for centuries to millennia.
While individual sequestration projects may seem small compared to the vast amount of emissions, their collective impact can be significant. The sum of proposed projects in Alberta amounts to 51% of all emissions from the province, in line with Paris Agreement commitments (50% from peak emissions). Some frequently identified issues, such as limits in storage capacity and risks associated with injection seem to be largely exaggerated.
(c) 2024, based on the poster presented at GeoConvention 2024