CO2 Injection Wells

What types of wells are used to inject CO2 underground?

The United States Environmental Protection Agency (EPA) regulates the construction, operation, permitting, and closure of injection wells used for underground for storage or disposal into porous geologic formations. Injection wells are sorted according to the type and depth of the fluid injected. Because wells that inject carbon dioxide (CO2) into deep isolated formations need to be safe, they have sophisticated construction and are designed to provide multiple layers of protective casing and cement. 

The Underground Injection Control (UIC) program consists of six classes of injection wells. UIC regulations mandate the consideration of a variety of measures to assure that injection activities will not endanger underground sources of drinking water (USDWs). 

EPA UIC Fact sheet

However, CO2 can only be injected into two types of wells:

  • UIC Class II wells: They are exclusively Oil and Gas related injection wells used for enhanced oil recovery, hydrocarbon storage or oilfield waste disposal (brines and/or gases – mainly H2S & CO2)
  • UIC Class VI wells: They are the requisite for any Carbon Capture and Sequestration (CCS) project and are only designed for the specificities of geologic sequestration of CO2. 

To learn more about UIC Class II and VI wells visit:

EPA UIC Class II wells
EPA UIC Class VI wells

For technical and program guidance visit: https://www.epa.gov/uic/uic-program-guidance

You will find details for Class VI:

  • Project Plan Development
  • Area of Review Evaluation
  • Site Characterization Guidance
  • Construction
  • Testing and Monitoring
  • Plugging, Post-injection Site Care, and Site Closure

More information on EPA Class VI wells:

UIC primary enforcement responsibility (primacy)

EPA’s Class VI Well Program Key to Deploying CO2 Geologic Storage – Patrice Lahlum – Great Plains Institute

EPA released its Class VI Permitting report to Congress. The report provides recommendations to improve Class VI permitting procedures for commercial and research carbon
sequestration projects.