CLASS VI CARBON SEQUESTRATION PROGRAM
FREQUENTLY ASKED QUESTIONS
- What is carbon sequestration?
- What is carbon dioxide? What are the hazards?
- How does carbon sequestration work?
- What are injection wells?
- What are Class V injection wells?
- What are Class VI injection wells?
- How does the CO2 stay underground?
- How do we know where the CO2 is once it’s underground?
- If CO2 is going to be injected into aquifers, does that mean my water is going to be impacted?
- Who permits Class VI wells in Louisiana?
- How can I check the status of a Class VI application in Louisiana?
- Are there currently any Class VI wells in Louisiana?
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How long does the application process take? Will the public have the chance to have a say?
Can operators simply seize property?Has permanent carbon sequestration been done before? Is there proven science/operational history?
Carbon sequestration, sometimes referred to as geologic or CO2 sequestration, is the long-term containment of CO2 in underground geologic formations as the final step of Carbon Capture and Storage (CCS) operations. CO2 produced by emitters is captured, compressed for transportation and injected into deep underground rock formations for disposal to reduce the amount of CO2 emissions that enter the atmosphere.
What is carbon dioxide? What are the hazards?
Carbon dioxide (CO2) is a colorless, odorless gas that is naturally present in the Earth's atmosphere. CO2 is produced by various processes, such as respiration, combustion of fossil fuels and decomposition of organic matter.
CO2, in and of itself, is not classified as toxic or carcinogenic – its primary risks above ground are its role as a greenhouse gas in the atmosphere and as an asphyxiant when concentrated in a small area – basically, if there’s enough coming up or out to displace breathable air. The asphyxiant aspect is a particular concern because CO2 is heavier than air, so it is less likely to move up and away from people and dissipate than something like methane.
One of the below-ground concerns would be the formation of carbonic acid that occurs when CO2 mixes with water. Carbonic acid can cause traditional steel casing to corrode and become more brittle. Carbonic acid can also impact some of the cement typically used to construct and plug oil and gas wells. Additionally, the CO2 will be under significant pressure in pipelines and wellbores at depth, requiring similar precautions to those taken with any other gas or liquid at higher pressures.
How does carbon sequestration work?
Carbon sequestration requires extensive geologic and engineering assessments to determine if a site is appropriate to safely store CO2. There are two main types of formations used for this kind of sequestration:
- Deep saline aquifers where the water in the formation is too salty for human use
- Depleted oil and gas fields that are no longer in production
An injection well is used to dispose of fluids deep underground. These wells are typically drilled into porous rock formations that can safely contain the injected substances. Regulations are in place to ensure that injection wells are designed and monitored to prevent groundwater contamination and protect public health. EPA’s Underground Injection Control Program consists of six classes of injection wells that vary based on function, construction and operating features.
What are Class V injection wells?
Class V wells inject non-hazardous fluids into or above an aquifer. They are typically shallow, on-site disposal systems, such as floor and sink drains that discharge into dry wells, septic systems, leach fields and similar types of drainage wells.
Class V also includes stratigraphic test wells. These wells are not used for waste disposal but are a useful tool for site characterization. It can be utilized for logging, core collection, injectivity tests, etc. (CO2 cannot be injected as test fluid). There is possible future utilization as a monitor well or Class VI injection well. However, any proposal to convert a Class V to a Class VI well is still required to go through the full Class VI permitting process. Receiving a Class V permit does not lessen regulatory requirements or guarantee that a Class VI permit will be issued.
What are Class VI injection wells?
Class VI wells are used to inject CO2 into deep rock formations for long-term storage to reduce atmospheric CO2 emissions. Class VI wells have the most complex, robust permitting requirements of any class of injection well.
These requirements include detailed rules for siting, construction, operations, testing, monitoring and closure of the sequestration project. These rules account for the unique challenges of permanently storing CO2 underground, including:
- Buoyancy of CO2
- Mobility of CO2
- Corrosivity of CO2 dissolving into water
- Large injection volumes
A Class VI well application is a lengthy, highly technical document. Applicants must evaluate every aspect of the science and engineering that could impact the safety and effectiveness of a geologic sequestration project and must prove that underground sources of drinking water (USDWs) are always protected.
How does the CO2 stay underground?
Captured CO2 is compressed to a stage known as a supercritical phase where the CO2 no longer behaves like a gas but shares the physical properties of liquid and gas. Supercritical CO2 can then be injected into the approved geologic formation where it becomes trapped.
There are several ways that CO2 can be trapped underground:
- Structural trapping – Low permeability rocks, like shales, act as barriers and prevent the relatively buoyant CO2 from moving upwards.
- Residual trapping – CO2 becomes trapped in the tiny pore spaces within the rock.
- Solution trapping – Some of the CO2 dissolves into the salty formation water.
- Mineral trapping – Depending on the type of geology, the CO2 can react with the rocks to form a new mineral and become part of the rock formation itself.
How do we know where the CO2 is once it’s underground?
Tracking the CO2 plume is one of the most important parts of a sequestration project. Applicants are required to use their proposed plans for injection and the geologic details from site characterization to build detailed computational models of the CO2 plume. Creating reliable models based on accurate data is important because it helps predict how the CO2 will behave underground and how far a CO2 plume will extend over the life of the project.
Class VI wells also have extensive requirements for regular pressure and groundwater monitoring to help regulators ensure that the CO2 stays where it’s supposed to and doesn’t pose a threat to the drinking water.
If CO2 is going to be injected into aquifers, is my water going to be impacted?
No. Saline aquifers are deep rock formations where the pores, or small gaps between the rock grains, are filled with ultra-salty water that is too salty to be used by humans. These aquifers are usually thousands of feet deeper than the freshwater aquifers that we get our drinking water from.
The geologists and engineers at DENR who regulate Class VI wells are responsible for making sure that the CO2 injection doesn’t put Louisiana’s drinking water or residents at risk.
DENR staff is well aware of these risks, and their regulations and requirements are specifically engineered to address them. For instance, DENR requires special alloys of metal and types of cement designed to deal with both the CO2 and the specific underground conditions of the site being proposed. The rules also require that the site must have a natural confining zone (i.e. shale, clay or other impermeable rock) between the top of the injection zone and the lowest point of the USDW aquifer that’s thick enough to protect the USDW.
DENR also requires that all wells, active or plugged, that penetrate the confining zone be identified and cased/cemented appropriately. If they aren’t, the applicant will have to pay to get it done, even for plugged wells.
Additionally, DENR requires that the “area of review” – the area that is included in the application – include both the predicted CO2 plume and the area ahead of it where pressure would be expected to increase. DENR also requires an array of monitoring wells in the injection zone and the freshwater aquifer to ensure detection as early as possible if something down there is going where it shouldn’t.
Who permits Class VI wells in Louisiana?
The Louisiana Department of Energy and Natural Resources (DENR) – Injection and Mining Division (IMD).
How can I check the status of a Class VI application in Louisiana?
A Class VI Application Tracker is available on the Permits and Applications section of DENR’s Class VI Carbon Sequestration webpage. The tracker is regularly updated to reflect where each application is in the review process.
Are there any Class VI wells in Louisiana?
Not yet. The Environmental Protection Agency (EPA) began reviewing Class VI permit applications before transferring permitting authority, known as primacy, to DENR in February 2024. Reviews are currently underway at DENR, but no permits have been issued.
How long does the application process take? Will the public have the chance to have a say?
For a Class VI well, because of all the detailed engineering and geologic information DENR requires, the expectation is that if an operator turned in a perfect application where our staff saw no errors and had no questions that needed further information/clarification, the time from the start of a Class VI application review to opening the public comment period/holding a public hearing would be about 18 months. However, DENR expects that reviews for something as complex as a Class VI application will go through several rounds of review where the applicant is required to make revisions and submit additional technical information.
Once DENR staff has gotten an application review to the point where their technical and regulatory questions have been answered, a draft version of the permit will be made public (both on our website and locally) along with the application itself, and DENR will reach out to the public for a comment period of at least 30 days. That comment period will also include a locally-held public hearing. Both the hearing and the public comment period will be advertised through local journals and outreach to parish officials to help alert their constituents.
What the public should know about the public comment period is that all comments, whether written and sent in or spoken at public hearings, are given the same weight. Members of the public may also both write in comments and speak at public hearings. You should also know that the public hearings are not question-and-answer sessions. The hearing officer is there only to open the hearing, give a brief overview of what it is about, call members of the public up to speak, hear comments, and accept submitted documents/comments.
After the public comment period closes, DENR staff will review all comments for relevant information or questions that may lead to a need for further review of the application or revision by the applicant. When that review is complete, staff will provide a written response to those relevant comments, either to specific comments or to a general type of comment if many of the commenters are speaking/asking about the same thing. Review after the comment period can still take several months before a decision is made.
For projects that include a Class V test well, public hearings and comment periods are also held in the same manner as the Class VI process. Though the Class V applications are less complex and generally take less time to complete the initial review, it can still take several months before a decision is made. Even an approved Class V permit has no direct bearing on an associated Class VI application – it can only provide information the operator uses in filling out the Class VI application.
Can operators simply seize property?
While any CO2 pipelines have options for expropriation of right-of-way, the same as other kinds of pipelines, the process for acquiring pore space rights for CO2 sequestration projects is more akin to the way mineral rights are leased by oil and gas operators – through unitization. Louisiana’s Legislature in 2024 set an established law so that expropriation for carbon sequestration is not allowed and a unitization framework must be used. A key difference is that while oil and gas operators generally seek to get a minimum of half the acreage they seek in a drilling unit before the rest can be force-pooled without a lease. A carbon sequestration project, by law, must get at least 75 percent of the acreage under lease before force-pooling can be done on the remainder, with the manner for determining compensation paid to unleased owners set by DENR’s Commissioner of Conservation.
Has permanent carbon sequestration been done before? Is there a proven science/operational history?
While large-scale permanent carbon sequestration projects are new to the U.S. and Louisiana, Louisiana operators and regulators are already familiar with almost all of the components that make up the overall process. Underground injection projects have been taking place in Louisiana for generations, and the state has been enforcing modern underground injection regulations on behalf on the EPA since the 1980’s.
We have specifically been dealing with managing CO2 injection in enhanced oil recovery projects for many years – that involves injecting CO2 into depleted oil reservoirs to increase production. In that case, the CO2 isn’t trapped in the rock permanently – much of it comes back up with the oil – but it does provide us regulatory experience in dealing with CO2 in pipelines, wellbores and seeing how it behaves underground.
DENR has handled long-term storage of gases such as methane for decades, both in salt caverns and in natural underground formations, as well as overseeing pipeline transportation of them.
Successful and safe carbon sequestration requires expertise in a number of technical areas where DENR is already very experienced.
As to proven performance for long-term CO2 carbon sequestration, Norway’s Sleipner Project, which began injection beneath the North Sea in 1996, was the world’s first large-scale commercial carbon sequestration operation and continues to inject to this day. The study of this project has provided a great deal of background on how CO2 behaves in formation and reacts with natural and man-made aspects of the process.
DENR is also aware of the issues that the first U.S.-based permanent sequestration project, Archer Daniels Midland’s project in Illinois, has encountered with corrosion and potential CO2 migration and will be using lessons learned from it in reviewing permit applications and overseeing operations here.