Inject baby inject!

Class VI Wells Part 1

Vocabulary Housekeeping

Any topic can get myopic and esoteric enough that language becomes confusing. I’m sure I’ll get technical experts quibbling over the details but for most, the slight differences between these terms are unimportant, sorry geologists:

Storage / Sequestration: Can be used interchangeably to describe the act or space for keeping the carbon dioxide.

Reservoir: A subsurface body of rock having sufficient porosity and permeability to store and transmit fluids.

Basin, as in Sedimentary: region-scale depressions of the Earth's crust where subsidence has occurred and a thick sequence of sediments have accumulated to form a large three-dimensional body of sedimentary rock.

Aquifer: A water-bearing stratum of permeable rock, sand, or gravel. Important here due to sedimentary basins having brines (water and dissolved solids) between grains. See 2nd picture for visual.

A History of Injection

The world of climate solutions is large, ever-changing, and infinitely complex. One of the more seasoned veterans is the geologic sequestration of carbon dioxide (CO₂₎ in sedimentary basins, or, another way, pumping CO₂ deep underground into relatively porous rocks. We’ve been injecting CO₂ into the subsurface for at least half a century, with an incredible safety record, hundreds of millions of tons stored, without any significant leaks. For climate, most of the CO₂ we capture will need to stay sequestered (often called dedicated or permanent storage); however, the technology got its start from a process known as enhanced oil recovery (EOR).

EOR is accomplished by CO₂ flooding, a process whereby carbon dioxide is injected into oil reservoirs to increase output when extracting oil, especially in reservoirs where production rates have declined over time. The process was first attempted in 1977 in Scurry County, Texas. Since then, the process has become extensively used in the Permian basin region of the U.S. and is now more recently begun to be pursued in many different states, but it remains fairly uncommon outside of the United States.^[1]

In the 1980s, research began on using CO₂ as a means of reducing greenhouse gas emissions, and the concept of carbon capture and storage emerged. The first field-scale test of carbon capture and storage (CCS) was carried out in the Sleipner gas field in the North Sea in 1996, where Statoil (now Equinor) began injecting CO₂ into a deep saline aquifer. The Sleipner project demonstrated that it was possible to store CO₂ safely underground, and it has since become one of the most well-known CCS projects in the world, with over 150 scientific papers and several Ph.D. theses to its name.

As CCS became more prominent in climate discussions and projects, the need for regulations on the injection of CO₂ became important. The eventual regulation of CO₂ injection landed under the Environmental Protection Agency (EPA) in the Underground Injection Control (UIC) program but the regulatory regime for subsurface injection of any material had already been established before Class VI wells came into existence.

The UIC was established in 1974 under the Safe Drinking Water Act (SDWA) to protect underground sources of drinking water form contamination due to underground injection activities. Before this, there were no federal regulations in place, and in the early 1960s and 1970s, injection wells were used to dispose of a variety of wastes, including industrial wastewater, brine, and chemicals.

The UIC program underwent a major revision in 1980 with the promulgation of new regulations that clarified the types of wells subject to regulation and set more detailed technical requirements for permit issuance and compliance monitoring.

As it stands now there are six different well classes:

The aforementioned EOR wells are Class II wells, and for the permanent storage of CO₂, Class VI wells are available.

The history of Class VI injection wells dates back to the early 2000s when the concept of CCS began to gain traction as a potential tool for mitigating greenhouse gas emissions. In 2005, the U.S. Congress passed the Energy Policy Act, which included provisions for the UIC program to regulate Class VI wells.

In 2010, the EPA issued a proposed rule for Class VI injection wells and finalized the rule in 2015, which established requirements for the construction, operation, and closure of these wells. The rule also established a permitting process for Class VI wells and required that permit applicants demonstrate that the injection will not endanger underground sources of drinking water. These rules were the result of an effort by a team of experts and professionals within the agency, including scientists, engineers, policy analysts, and attorneys. Most importantly, these regulations were formed through the data from several test sites, with over ten million tons safely stored.

It’s important to note that these test wells, and the current permits, have been issued for saline storage in sedimentary basins. These types of geologies, like sandstones, are porous and permeable, which allow the CO₂ to flow through the entire storage reservoir, depicted in the graphic below. Upon hearing about storage, and associated words like aquifer or reservoir, people envision CO₂ being pumped into an underground lake of sorts. This is understandable, although inaccurate. The CO₂ is compressed until supercritical and then injected into the subsurface, and takes up pore space between sedimentary grains occupied by brine, the progression of (I) to (III) below.

This is important for the next post. Although sedimentary basins are the backbone of CO₂ storage, they are not the only geology that can be used. The current Class VI regulations were written for sedimentary basins, and other geologies, like igneous rocks, are de facto excluded from participating in Class VI permitting through specific pieces of regulation.

State of Permit Play

To date, the EPA has issued exactly two Class VI permits, both to the Archer Daniels Midland Ethanol facility in Decatur, Illinois. These permits have been successful in the injection of CO_2, with several million tons stored safely. There are 34 other Class VI applications listed on the EPA website but it is well known in the industry that many more applications exist and are coming down the pike due to policy changes in the Infrastructure Investment and Jobs Act (IIJA) and the Inflation Reduction Act (IRA), which I will discuss in the next post.

There is an alternate path to a federal Class VI permit when a state applies for primacy, giving it the right to run its own injection program.

To obtain primacy, a state must demonstrate that it has the legal and regulatory framework in place to manage injection wells and protect underground sources of drinking water. The state must also demonstrate that its regulatory program is at least as stringent as the federal regulations. Once a state has obtained primacy, the EPA defers to the state for the regulation of Class VI wells.

To maintain primacy, a state must continue to enforce its regulatory program effectively and make any necessary changes to keep pace with new scientific and technical developments. The EPA provides ongoing oversight to ensure that states with primacy continue to meet federal standards. North Dakota and Wyoming are the only states with primacy. However, Louisiana, Texas, Arizona, and West Virginia have active primacy applications. The Louisiana application has drawn some EPA consternation from the state and industry.

North Dakota has issued Class VI permits and Wyoming is currently reviewing permits.

Although Class VI is the focus of this piece, most states already have primacy over other injection wells.

To add another layer of complexity onto the total regulatory regime, The Bureau of Land Management (BLM) is charge of injection permits on federal lands, and Bureau of Ocean Energy Management (BOEM) is in charge of injection permits for federal waters. BLM granted injection permits in Wyoming in 2022.

As a recap, in order to inject CO₂ underground in the United States, you must obtain a federal permit from the EPA (Class II for EOR, Class VI for dedicated storage), or you must be a state with primacy over Class VI and/or Class II wells or you receive a permit from BLM to inject on federal lands or you receive a permit from BOEM to inject in federal waters (currently not possible because they have not finished rulemaking).

The UIC program remains committed to streamlining the permitting process with several tools on its website, including guidance documents, a compendium of computational tools to support geological storage, checklists, and application outlines. They’ve publicly stated some version of a model application will be available in the future.

Despite those tools and tips, the EPA has come under fire for the lack of permits issued and primacy applications granted. Recently EPA Administrator released a letter to state governors, reiterating his support for the Class VI program and steps the agency is taking to rectify the process. This is alongside permitting report sent to congress that centered on recommendations to improve Class VI permitting procedures for commercial and research carbon sequestration projects.

The history and regulation of CO₂ injection and Class VI wells are crucial to understanding how the IIJA and IRA changed the land scape for CO₂ storage. The opportunities for capture, removal, and storage have never been brighter. But a few hurdles remain—all that next time.