Frequently Asked Questions about CO2 Capture and Sequestration
What is carbon capture and sequestration?
To address climate change, CO2 emissions must be controlled. Experts have identified carbon capture and sequestration as one of the most promising and viable options to help reduce these emissions. With carbon capture and sequestration (CCS), facilities currently emitting CO2 to the atmosphere will instead capture the CO2 and inject it into deep geologic formations, where it then remains trapped. The idea of storing CO2 in geologic formations is not far-fetched, since gases such as carbon dioxide, natural gas, helium and hydrogen exist naturally in geologic formations, trapped for millions of years. The process of sequestration essentially recycles or returns the carbon or gases to the subsurface, where it originated.
Are there environmental or safety concerns related to carbon sequestration?
Environmental and safety concerns are minimal. CO2 is not toxic, flammable or explosive. Monitoring during the injection process, combined with careful selection of an optimal geologic formation, will provide the assurance that the CO2 will be permanently contained.
Is sequestration permanent?
In geologic sequestration, carbon dioxide would be stored in deep underground formations, such as depleted oil and gas reservoirs, unmineable coal seams, and deep saline formations. Many of these formations have naturally stored carbon dioxide and other gases and fluids (i.e., petroleum) for millions of years, and have the potential to store hundreds of years’ worth of human-generated carbon dioxide emissions.
Can CO2 be stored anywhere else?
There is already a strong base of industry experience in enhanced oil recovery, where water and then carbon dioxide are pumped into depleted oil wells to increase oil production. Recent sequestration research is building on this experience.
How are sequestration sites selected?
Several factors and criteria are considered when selecting a host site. They include distance from drinking water supplies, appropriate topography and geologic formations, and the willingness of industry and municipal hosts to become partners. Also, the area must be seismically inactive to prevent potential CO2 leakage and protect underground sources of drinking water.
Does the carbon stay deep underground?
Researchers are investigating improved monitoring methods and techniques to ensure that carbon dioxide remains trapped deep underground. The Dept of Energy’s geologic sequestration program includes a portfolio of research projects to investigate the feasibility of safely performing carbon sequestration from pilot scale to large industrial commercial scale. The network of seven Regional Carbon Sequestration Partnerships formed by the department is an important component of this broader program.
Is CO2 a waste product?
In 2007, the U.S. Supreme Court indicated that CO2 and other greenhouse gases can be regulated by the EPA as pollutants. However, CO2 is not a waste product in the ordinary sense; while it is a human-caused greenhouse gas, it also has commercial uses that set it apart from other gases. Industrial uses of CO2 include chemical and biological processes where CO2 is a reactant, such as those used in urea and methanol production, as well as technological applications that use CO2 directly – for example in the horticulture industry, refrigeration, food packaging, welding, beverages, and fire extinguishers. Additionally, CO2 occurs under natural conditions and is not toxic, flammable or explosive.
How are drinking water supplies protected?
Researchers, regulators, geologists and engineers understand that storage sites must be selected, designed and installed very carefully to ensure drinking water is protected. The injection wells consist of multiple layers of steel and cement to protect the shallow water aquifer and residential water wells. Additional protection is provided by multiple geologic layers of dense, tight, low permeability seal – or cap – rock, which prevent vertical leakage For detailed explanations of how sequestration works and why the CO2 stays underground, see the International Energy Agency’s publications titled, “Storing CO2 Underground and Geologic Storage of Carbon Dioxide: Staying Safely Underground.”
How can we be sure that geologic seals will remain intact?
As with all things in nature, nothing is absolutely sure. However, in the petroleum producing areas of the United States, oil and gas deposits, as well as naturally occurring CO2 gas, have been trapped within subsurface geologic formations for millions of years. With proper engineering design and monitoring, these same seals will also prevent the significant upward migration of CO2.
What is a seismic survey?
A seismic survey is a technique similar to an ultrasound that uses reflected sound waves to develop images of the rock layers below ground. The information gathered helps researchers better understand the geologic properties and reveals faults or fractures in those rock layers. Can seismic surveys cause earthquakes? No. Truck-mounted equipment sends vibrations into the earth for a few minutes at a time. These vibrations are far too weak to result in earthquakes.
How noisy will the drilling process be?
As is the case at sites where heavy equipment is in use, noise is produced in the drilling process. While operations are normally conducted around the clock, actual drilling will be periodic. Distance from the drill site helps to minimize noise, as does the site’s terrain and other characteristics such as forests, dense vegetation and hills. Operators can also construct special noise curtains to further dampen noise.
How large is a drill pad?
A typical drill pad will cover less than two acres – an area measuring roughly 250 by 250 feet. This area is enough to accommodate all related equipment.
What visual impacts can neighbors expect?
Any visual impacts will be temporary. The combined activities of constructing the drill rig, drilling the borehole and dismantling the rig last 40 to 50 days on average. Sites are typically selected that are as far away from homes and businesses as possible. When the drill rig is removed from the site the property is returned to its original condition and the borehole is plugged from bottom to top.
How wide is the borehole?
The borehole itself is 12 ¼ inches in diameter at the surface, and will house a 9 5/8 -inch steel casing, which extends to a depth of 1,500 feet. The casing is cemented in place to protect shallow groundwater aquifers. A borehole 8 ½ inches in diameter is drilled from 1,500 feet down to 8,000 feet. It houses a 4 ½ inch steel casing, also cemented in place.
How deep will you drill?
The total depth of the borehole will be approximately 8,000 feet — or about 1 ½ miles.
How tall is the drill rig?
The derrick – the tower extending upward – is about110 feet in height.