More Carbon Capture and Storage FAQs
Carbon capture and storage involves capturing carbon dioxide (CO2) that would otherwise be emitted into the atmosphere from sources such as power stations and industrial processes, and transporting it to a suitable storage site for safe, long-term storage deep underground. Carbon capture and storage is also known as CCS or carbon geosequestration.
Carbon capture and storage technologies are being investigated because they have the potential to significantly reduce greenhouse gas emissions. Victoria offers world-class potential for CCS - the Gippsland Basin's geology provides potential to safely store large quantities of CO2 while also being located close to the Latrobe Valley.
How does the carbon dioxide remain within its storage site?CO2 is contained within suitable, porous rock overlaid by thick layers of non-porous ‘mudstone cap rock’.
These naturally occurring, underground ‘storage reservoirs’ are at depths of greater than 800 metres. Depleted oil and gas fields generally offer excellent potential CO2 storage sites, with a geological trap, a porous reservoir and a sealing cap rock. These sites have always held oil and gas, as well as other gases including CO2, securely for millions of years.
Prospective storage sites are subject to extensive studies to confirm their suitability. Studies can involve 3D model simulations over long time frames (thousands of years), seismic testing with sound waves and appraisal drilling to retrieve rock samples and verify data.
Key geological characteristics sought when selecting potential storage sites include a storage reservoir, which is porous and permeable to hold the CO2, a trapping mechanism for the stored CO2, and a cap rock to contain the CO2.
Image source: CO2CRC
Trapping mechanisms include:
- Structural/stratigraphic trapping – the most common trapping mechanism where the CO2 (which is lighter than water) rises within the reservoir and is trapped by the overlying cap rock. In many instances, this is similar to how oil and natural gas has been trapped for millions of years.
- Residual trapping – CO2 becomes trapped as residual droplets within the pore spaces in the reservoir rock.
- Solubility trapping – where CO2 dissolves into water present in the porous rock.
- Mineral trapping – where the dissolved CO2 reacts with and is bound to the surrounding rock to form solid carbonate minerals.
How far below ground is the carbon dioxide stored?Generally the sites in which CO2 will be stored are between one and three kilometres beneath the surface. CO2 needs to be injected at depths greater than 800 metres so that the pressure ensures that the CO2 remains in a dense liquid-like phase.
Could the stored CO2 leak to the surface?While any risk of leakage is taken very seriously and is investigated thoroughly during the storage site assessment and selection, it is considered extremely unlikely that CO2 will leak to the surface. Geological structures, such as those in the Gippsland Basin, have sealing layers or cap rock that have contained large volumes of oil and gas for millions of years.
Vigorous assessments and mapping out of storage sites, as well as extensive modelling to predict the behaviour of injected CO2, are undertaken in an effort to ensure sites meet strict selection criteria for the long-term, safe storage of CO2.
In the unlikely event of leakage beyond the sealing cap rock, secondary layers of rock create additional boundaries between the storage reservoir and the surface.
If CO2 was to permeate to the surface, a very gradual escape of CO2 would be expected, with migration potentially taking thousands of years. At spa baths, such as Hepburn Springs, Victoria, CO2 is naturally released into our atmosphere every day and these small levels do not pose a danger.
What about underground migration from the storage site?Detailed modelling will help geologists predict any potential movements of CO2 and the direction and distance it could travel if it was to migrate.
Storage sites will be monitored with the aim of informing regulators of any CO2 movement. If migration beyond the storage reservoir is detected, injection of further CO2 could be stopped. Detailed modelling conducted prior to injection will provide information such as how long after injection ceases the CO2 would continue to move.
The CO2 may also react with other minerals underground and form new rocks, such as calcium carbonate (commonly known as limestone). When this occurs the CO2 will be permanently trapped.
What safeguards are in place to manage the risk of CO2 leaks?When applying for an injection licence, an applicant must undergo a rigorous assessment to ensure the nominated storage site has an appropriate seal and is suitable for CO2 containment. The regulators will only grant licences that have met these strict criteria.
An applicant is required to prepare a monitoring and verification plan prior to conducting any injection operations. This plan includes an operator’s response to non-routine situations, including losses and migration of CO2, pressure reduction and other markers about the storage formation that may indicate a leak. If the CO2 is not behaving as predicted, the operator is able to act quickly to mitigate the leak as per response procedures. For example, if movement beyond the storage reservoir is detected, injection of further CO2 would be stopped, removing the pressure and reducing further leaks.
Where in Victoria potentially could CO2 be stored?Studies have identified Victoria’s offshore Gippsland Basin, located in the eastern part of the State, as having the highest potential for storing CO2. The Gippsland Basin is attractive to industry as it is located close to the Latrobe Valley coal fields. In the future, depleted natural gas and oil fields in the offshore Gippsland Basin appear to provide an opportunity for CO2 storage over the longer term.
The CarbonNet Project is currently investigating the potential for large scale CCS in the Gippsland region. The project is at feasibility stage, evaluating potential storage sites while investigating possible capture plants and transport pipeline routes
Will the injected CO2 affect the water table or groundwater quality?
The CarbonNet Project acknowledges the concern over the water table and research and modelling work is being done in this area. While groundwater aquifers are typically less than 200 metres below ground, CarbonNet is investigating injecting CO2 at least 800 metres under the bed of the sea, at sites that are situated offshore in the Gippsland Basin.
Would CO2 leak if there was an earthquake?
Earthquakes within Victoria to date have had very little impact. The CarbonNet Project acknowledges there are some concerns about the potential impacts of earthquakes. Research on this issue is being undertaken and earthquake data from countries, such as Japan, is also being reviewed.
Is there a possibility of the injected CO2 exploding?CO2 cannot burn or explode. In fact CO2 is used in fire extinguishers to put out fires.
Will the temperature of the ground change as a result of CO2 injection?While the CO2 injected may be at a range of temperatures, it is unlikely these would be noticable or even measurable at ground level. Research will be undertaken to investigate this further.
Is carbon capture and storage a proven technology?Many of the technologies involved in CCS are already well developed and have been used by industries (in particular the oil and gas industry) for decades.
What is now being investigated is the use of CCS for capturing emissions from power plants and other industries at a large scale that is also commercially viable.
The Global CCS Institute lists 43 CCS projects at various stages worldwide, including in Norway, the USA, Saudi Arabia, Canada and Australia. Demonstrations of these technologies are currently underway around the world including in Victoria’s Latrobe Valley and Otway regions. Read more about global CCS projects in the Institute's Annual Global Status of CCS report.
Leading Australian and international scientists and international authorities such as the Intergovernmental Panel on Climate Change (IPCC) and the International Energy Agency (IEA) have identified CCS as having the potential to help the energy sector reduce its greenhouse gas emissions effectively.
Has the successful underground storage of carbon dioxide been demonstrated?
Successful injection and storage projects are operating in Norway, Canada and the United States. In Victoria, the Cooperative Research Centre for Greenhouse Gas Technologies (CO2CRC) Otway Project, located near Port Campbell, is Australia's first demonstration of CO2 geological storage. This project has demonstrated that over 65,000 tonnes of CO2 can be safely transported, injected, stored and monitored while following industry best-practice standards.
For over 50 years the oil and gas industry has routinely injected CO2 underground as part of enhanced oil recovery process - where the injected CO2 displaces oil and gas and allows for greater quantities to be extracted. The Global CCS Institute states there is more than 6,000km of dedicated pipelines transporting approximately 50Mt CO2 per year from natural and anthropogenic sources in America (Global CCS Institute, Carbon dioxide (CO2) distribution infrastructure, 2012).
In addition, oil and gas are also routinely stored underground in depleted hydrocarbon reservoirs, where the geological structures are used. The stored oil and gas is kept underground as either a strategic reserve or until it is needed by the consumer. Such operations currently take place at the Iona facility in south west Victoria, near Port Campbell. These gas storage projects demonstrate the ability to safely process gases similar to CO2, in underground storage sites.
Can the CO2 be used for other purposes?
There are several existing commercially available technologies for CO2 capture that have been developed to produce high purity CO2 for commercial markets such as enhanced oil recovery, chemical manufacturing and food processing.
Some known CO2 uses are:
- growth medium for algae production which can then be used for oil production or as a source of stock feed
- raw material for the production of formic acid, an organic substitute for inorganic acids such as hydrochloric and sulphuric acids
- base for producing large volumes of calcium carbonates (limestone) and sodium bicarbonates (baking soda)
- supplement to greenhouses as a plant growth accelerant
- carbonation of soft drinks.
It is not anticipated that these alternate uses for CO2 will ever be able to cater for the large volumes that need to be captured to make a significant impact on climate change. Therefore other methods of reducing CO2 emissions are required.
How will CCS be regulated?
Several key pieces of legislation underpin the sequestration of CO2 depending on whether it is onshore or offshore in the Victorian or Commonwealth jurisdiction, including:
- Victoria's Greenhouse Gas Geological Sequestration Act 2008 (GGGS)
- Victoria's Offshore Petroleum and Greenhouse Gas Storage Act 2010
- The Commonwealth's Offshore Petroleum and Greenhouse Gas Storage Act 2006.
Who will take ultimate responsibility for the stored CO2?
Ownership and responsibility for the stored CO2 depends on a number of factors relating to the individual project and the relevant legislation.