Storing CO2 in deep underground rock formations isn’t a new idea. Large underground reservoirs of CO2 occur naturally, and have existed for millions of years.
Permanently storing CO2 that has been captured from aboveground industrial projects returns the CO2 to deep, secure, underground rock formations. The CO2 is stored at geological depths of 1 to 5 kilometres whereas drinking water is found only a couple of hundred metres below the surface, thus ensuring the safety of groundwater. Proper storage site selection, a barrier of impermeable cap rock above the CO2, and natural trapping mechanisms ensure that CO2 will remain permanently stored.
More than enough suitable storage capacity has been identified by reputable and knowledgeable sources worldwide. The Intergovernmental Panel on Climate Change has pointed out that globally there is enough storage capacity to store emissions for the next 200 years.
In Canada, a report by the National Advisory Panel on Sustainable Energy Science and Technology identified the “unique opportunity” that Canada has to store large amounts of CO2 in the Western Canada Sedimentary Basin: preliminary estimates of storage potential are equivalent to at least 100 years and potentially 1,000 years of Canada’s current total annual CO2 emissions. The combination of a porous carbonate base rock with an impermeable cap rock makes the Western Canada Sedimentary Basin a reliable storage site.
EXPERIENCE AND RESEARCH
CO2 injection has been operational in the United States since 1972 and extensive international research has already been, and continues to be, conducted by respected scientists and
institutions in countries all around the world. Their findings have confirmed, and continue to confirm, that Carbon Capture and Storage (CCS) is technically feasible and based upon proven technologies. The overall safety and security of underground storage is a well researched and studied subject that is supported by years of operating experience and pilot projects around the
world. They all confirm that underground storage is feasible, practical and can be done safely.
Underground storage of CO2: extensive research and operating experience show it can be done safely
Den Norske Veritas (DNV), a global independent foundation specializing in risk management services,
recently concluded that CO2 geologic storage technology is by no means fail-proof or risk-free, but carefully selected and qualified storage sites that are operated according to effective regulatory supervision should be safe… it is a mature technology that has been used at industrial scale at several large sites both onshore and offshore. Geologic storage technology can be applied immediately, at a much larger scale, at tens to hundreds of sites globally. DNV pointed to “almost 100 years of natural gas storage at hundreds of sites in North America and Europe, 35-plus years of experience with CO2 enhanced recovery in North America, 15-plus years experience with acid gas injection in Western Canada, 14-plus years experience at dedicated projects in the North Sea and Algeria, plus a number of research-focused pilot projects on five continents.”
How storage works: It gets even safer over time
Structural Trapping – When the CO2 is pumped deep underground, it is initially more buoyant than water and will rise up through the porous rocks until it reaches the top of the formation where it becomes trapped by an impermeable layer of cap rock, such as shale.
Residual Trapping– Reservoir rocks act like a tight, rigid sponge. Liquid CO2 pumped into a rock formation becomes stuck within the pore spaces of the rock and does not move even under high pressure.
Dissolution – Some of the CO2 dissolves in brine (extremely salty water). Because the brine with CO2 is heavier than the water, around sinks to the bottom and is trapped by the water pressure above.
Mineral Trapping – CO2 dissolved in the saltwater brine is weakly acidic and can react with the minerals in the surrounding rocks, forming new minerals, as a coating on the rock (much like shellfish use calcium and carbon from seawater to form their shells). This process can be rapid or very slow (depending on the chemistry of the rocks and water) and it effectively binds the CO2 to the rocks.
There is a Canadian research initiative that is particularly noteworthy because of its size and scope, the success of its operations, and the fact that it involves enhanced oil recovery at WeyburnMidale in Saskatchewan. A major project to measure and monitor CO2 injection there involves the nternational Energy Agency, with the Petroleum Technology Research Centre (PTRC) as manager of an 11-year $85 million study. This extensive measurement and monitoring program, under way since 2000, has been undertaken in co-operation with researchers from Canadian and international universities, independent research institutions, consultancies and government agencies. And according to the PTRC, they have “never identified a leak.”
These research efforts, and others like them in countries around the world, continue to confirm that underground storage of CO2 is feasible, reasonable, and can be done safely