Geologic Storage of Anthropogenic CO2

UIC Class VI

Effective January 10, 2011, the US Environmental Protection Agency (EPA) promulgated Underground Injection Control (UIC) regulations for a new Class VI program regulating the geologic sequestration of anthropogenic carbon dioxide (CO2). 

The federal requirements for the UIC Class VI program are much more complex than the requirements for the Class II program. With respect to the difference between UIC Class II and Class VI, the greatest influence on risk is the injection pressure and volume.

The Texas Legislature established a framework for geologic storage of anthropogenic CO2 in Texas in 2009.  The statutes split jurisdiction between the Railroad Commission (RRC) and the Texas Commission on Environmental Quality (TCEQ) and required both agencies to adopt regulations consistent with federal regulations and to seek primacy for the program.

RRC adopted regulations effective December 10, 2010, Texas Administrative Code (TAC), Part 1, Title 16, Chapter 5. Interest in CO2 sequestration until recently has been limited to storage associated with Class II enhanced oil recovery (EOR) injection wells. Carbon dioxide storage incidental to EOR may be a Class II activity and, therefore, may be permitted under the RRC's Statewide Rule 46. However, since the revisions to federal incentives under Section 45Q of the Internal Revenue Code, RRC has seen increasing interest in Class VI geologic storage unrelated to EOR.

The Governor recently signed House Bill 1284 (87th Legislature), which, among other things, consolidates state jurisdiction for the Class VI program under the RRC. Consolidation of the Class VI program into one agency will greatly ease EPA’s process for review of the state’s application for enforcement primacy.

Primacy and Permit Application

RRC staff are currently preparing the documents required for the Class VI primacy application. Staff have proposed amendments to Chapter 5 - Carbon Dioxide (CO2) rules to meet UIC Class VI federal standards which are required to receive primary enforcement authority from EPA. You may submit comments on our proposed rules until June 20, 2022. Staff has submitted the primacy pre-application to EPA and expect to submit the full primacy application to EPA by October 2022.

Staff have been coordinating with EPA and other states with primacy (North Dakota and Wyoming) as well as states that are in the process (Louisiana) through the Ground Water Protection Council’s (GWPC’s) working group to gain knowledge of these states’ experience during the primacy application process.

Until RRC receives Class VI primacy, any applicant for geologic storage of anthropogenic CO2 unrelated to Enhanced Oil Recover (EOR) will need to submit an application to both EPA and the RRC. However, RRC staff have been coordinating with EPA to ensure that both agencies perform the application review on a parallel track, using the EPA Geologic Storage Data Tool (GSDT) so that when the RRC receives primacy, the transfer will be as seamless as possible.

An applicant for geologic storage of anthropogenic CO2 incidental to EOR may submit an Application to Inject Fluid into a Productive Reservoir (Form H-1/H-1A). Additionally, an applicant may be entitled to a reduced state severance tax rate under Statewide Rule 50 - Enhanced Oil Recovery Projects and further reduced tax rate for storage anthropogenic CO2.

Geologic Information for a CO2 Storage Project

A drilling permit is required for an oil and gas operator in Texas to drill a test well. An operator under RRC jurisdiction does not need an injection permit to drill a test well and perform geologic or well testing if those tests are typical for oil and gas exploration.

How to Become a Class VI Well

Until RRC receives UIC Class VI primary enforcement authority, you must receive a permit from US EPA for a Class VI injection well to store anthropogenic CO2. These guidelines only apply to the process for receiving a permit from RRC. US EPA may have different or additional requirements. Please contact US EPA Region 6 for more information.

An operator must complete each of the following steps before beginning geologic storage of anthropogenic CO2, 16 TAC §5.202 (a)(2):

  1. Geologic Storage Facility Permit: You must submit an application for and receive a geologic storage facility permit under Title 16, Texas Admin. Code (TAC), Chapter 5 - Carbon Dioxide (CO2), Subchapter B – Geologic Storage and Associated Injection of Anthropogenic Carbon Dioxide (CO2) [Note: you may not apply for a permit unless you have an active Organization Report (Form P-5)];
  2. Permit to Drill: After you’ve received your geologic storage facility permit, you must submit an application (Form W-1)  for and receive a permit to drill, deepen, or convert the well for geologic storage;
  3. You must drill and complete the well;
  4. Notice of Completion and Completion Report: You must submit a notice of completion of construction to the Oil and Gas Director or their delegate and submit a completion report (Form W-2/G-1) to RRC Online;
  5. Inspection: An RRC inspector must inspect the injection well and find that it is in compliance with the conditions of the permit; and
  6. Permit to Operate: The Oil and Gas Director or their delegate must have issued a permit to operate the injection well.

New Class VI Well

Submit an application for a permit for a geologic storage facility for anthropogenic CO2 and complete the rest of the steps outlined above.

New Strat Test Well

You must have a Permit to Drill (Form W-1) prior to drilling the stratigraphic test well and file a completion report (Form W-2/G-1) once the well is completed. Subsequently, you must submit an application for a permit for a geologic storage facility for anthropogenic CO2 and, after approval, complete the rest of the steps outlined above, including re-completion of the existing strat test well for geologic storage. A permit will only be approved if the well construction meets all of the UIC Class VI requirements. You may follow the UIC Class VI Strat Test Well Construction Verification procedure to ensure that your conversion to a Class VI well is expedient and without issue.

Recomplete Existing O&G Well or Injection Well

Request a permit for geologic storage and, after approval, complete the rest of the steps outlined above, including re-completion of an existing O&G well, injection well or beginning geologic storage of anthropogenic CO2 in a previously permitted injection well [for example, CO2 EOR or Acid Gas Disposal well(s)]. A permit will only be approved if the well construction meets all of the UIC Class VI requirements. Be advised that most O&G wells and O&G injection wells (UIC Class II) will not meet these requirements, and that P&A’d UIC Class I wells are prohibited by law from receiving a UIC Class VI permit. It is recommended that you contact the Injection-Storage Permits Unit at before beginning a project to convert an existing O&G well or injection well.

Commission-Required Class VI Permit

RRC may make a determination that operation of your Class II injection well [CO2 EOR or Acid Gas Disposal well(s)] is no longer being used for the primary purpose of enhanced recovery operations or has increased risk to USDWs and the well(s) must be converted to a Class VI permit, 16 TAC §5.201 (b)(2).

UIC Class VI Strat Test Well Construction Verification

A UIC Class VI Strat Test Well is a well drilled for the purpose of collecting in-situ geologic data and will be completed as a UIC Class VI injection well. Although not required, you may follow the steps below so that RRC staff can verify that the well construction and completion will meet UIC Class VI injection well rule requirements:

  1. Submit a letter of intent to to apply for a drilling permit for a stratigraphic test well to be converted to UIC Class VI well.
    1. The letter should include all information necessary for RRC staff to determine that the well will be constructed in accordance with 16 TAC §5.203 (e), but must include at a minimum:
      1. A draft Completion Report (Form W-2/G-1)
      2. Wellbore Diagram
      3. Well completion specifications to demonstrate CO2 resistance
  2. RRC staff will review the letter and respond within approximately 30 days. Staff will provide either:
    1. A letter stating that the proposed completion meets the requirements and you may apply for a drilling permit, or
    2. A letter stating that the proposed completion does not meet the requirements and the deficiencies in the proposal.
  3. After receiving a drilling permit and drilling and completing the well, you must submit a Completion Report as required by 16 TAC §3.15. To facilitate staff’s review, you should attach staff’s UIC Class VI Strat Test Well approval letter to the completion report and send an email to to notify RRC staff that the well completion report has been filed.

Acid Gas Disposal Wells with CO2

Acid gas disposal wells can continue to be permitted as Class II wells when the fluid is generated from oil and gas activities from a single lease, unit, field, or gas processing facility. It is understood that the CO2 thus injected is essentially sequestered if the injection meets the UIC requirement that the CO2 is confined in the permitted injection interval. Therefore, geologic storage of CO2 can continue to be permitted under the UIC Class II program under these limited circumstances.

Acid gas disposal well operations that are focused on oil or gas production will be managed under the Class II program. If acid gas disposal associated with an oil or gas lease, unit, field or gas processing facility is no longer a significant aspect of a Class II permitted operation, the key factor in determining the potential need to transition an acid gas disposal well from Class II to Class VI is the increased risk to Underground Sources of Drinking Water (USDWs) related to significant storage of CO2 in the reservoir, where the regulatory tools of the Class II program cannot successfully manage the risk. The most direct indicator of increased risk to USDWs is increased pressure in the injection zone related to the significant storage of CO2. Increases in pressure with the potential to impact USDWs should first be addressed using tools within the Class II program. However, transition to Class VI will be considered if the Class II tools are insufficient to manage the increased risk.

In determining if there is an increased risk to USDWs, the director will consider the following factors:

  • increase in reservoir pressure within the injection zone;
  • increase in CO2 injection rates;
  • distance between the injection zone and USDWs;
  • suitability of the enhanced oil or gas recovery AOR delineation;
  • quality of abandoned well plugs within the AOR;
  • the storage operator's plan for recovery of CO2 at the cessation of injection;
  • the source and properties of injected CO2; and
  • any additional site-specific factors as determined by the Commission.

Class II and Class VI directors will work together to address the potential need for transition of any individual operation from a Class II to a Class VI permit. The Class II program director will have the relevant data on pressure and volume of CO2 injected into Class II acid gas disposal wells, which will influence any transition decision.

Acid Gas Disposal Wells with COPermit Procedures

To ensure that Class II acid gas disposal wells with CO2 are properly permitted, the following UIC permitting procedures will be followed:

  • Any disposal permit application with CO2 as an injection fluid will be reviewed by the Chief Geologist or their delegate.
  • The applicant must submit CO2 source data in the permit application to ensure the well’s CO2 source is focused on oil and gas production.
  • The applicant should submit information regarding the well construction materials and any other precautions taken for injection of CO2.
  • Staff will evaluate the proposed injection volumes and pressures to ensure there is no increased risk to USDWs (e.g. to ensure an appropriate AOR distance). Staff may require pressure modeling for this review.
  • Acid gas disposal well permits will include a permit condition that states that the acid gas permit is not Class VI authority.
  • Permits may include the following conditions:
    • Annual tubing-casing annulus pressure test MIT and weekly tubing-casing annulus monitoring,
    • On-going pressure monitoring for increased risk to USDW, for example:
      • Initial and annual or 5-year bottom-hole pressure tests,
      • Reservoir pressure analysis,
      • Annual reporting of reservoir fluid migration and pressure monitoring, and
    • Notification if an event occurs that jeopardizes the mechanical and/or hydraulic integrity of any segment of the processing, injection or storage components of the permitted facility.