Class VI Wells

In 2010, the EPA established a new class of wells under the authority of the federal Safe Drinking Water Act’s Underground Injection Control (UIC) Program to adequately regulate the geologic sequestration of CO2. The regulatory code defines Class VI Wells as “wells that are not experimental in nature that are used for geologic sequestration of carbon dioxide beneath the lowermost formation containing a USDW”. In the case of Class VI wells, the EPA is primarily focused on protecting underground sources of drinking water (USDW). To do this, the agency has set forth a number of minimum federal technical criteria to ensure the safety of USDWs before, during, and after a Class VI well operation. Below are some new criteria that apply to Class VI wells.1USEPA. (n.d.). Requirements for Class VI wells. Retrieved 10/27/2020 from https://www.epa.gov/uic/class-vi-wells-used-geologic-sequestration-co2,2USEPA. (n.d.). Federal requirements under the Underground Injection Control (UIC) Program for carbon dioxide (CO2) geologic sequestration (GS) wells final rule. Retrieved 10/27/2020 from https://www.epa.gov/uic/federal-requirements-under-underground-injection-control-uic-program-carbon-dioxide-co2-geologic

Class VI Well

Class VI wells inject CO2 for long-term storage to reduce emissions to the atmosphere.

Site Characterization

Class VI permit applicants must provide extensive information about the local and regional geology and hydrogeology of the proposed site. The purpose of the UIC Program’s evaluation of this information is to inform a determination that the Class VI well will be sited in an area with a suitable geologic system, consisting of an injection zone with sufficient capacity to receive the CO2 to be injected and a confining zone that is free of transmissive faults or fractures. The EPA recommends a two-phase approach to reviewing site characterization information (i.e., a review of the geologic information and a comprehensive evaluation of that geologic information to confirm site-suitability).3USEPA. (2018, January). Geologic sequestration of carbon dioxide: Underground Injection Control (UIC) Program Class VI implementation manual for UIC Program Directors. https://www.epa.gov/sites/production/files/2018-01/documents/implementation_manual_508_010318.pdf

Well Construction

Class VI permit applicants must submit proposed schematics and construction procedures for the injection well. The purpose of the UIC Program’s evaluation of well construction information is to ensure that the injection well will be constructed in a manner that is appropriate to planned operations, is compatible with the CO2 and subsurface chemistry, and will maintain integrity throughout its duration. Reviewing proposed injection well construction plans is necessary to ensure that the proposed well materials and cement have adequate strength and design appropriate to the site-specific conditions, and to confirm injectate and formation fluid compatibility. In addition, the EPA recommends reviewing the procedures for constructing monitoring wells with similar considerations for subsurface conditions to ensure that the monitoring wells will not become conduits for fluid movement.4USEPA. (2018, January). Geologic sequestration of carbon dioxide: Underground Injection Control (UIC) Program Class VI implementation manual for UIC Program Directors. https://www.epa.gov/sites/production/files/2018-01/documents/implementation_manual_508_010318.pdf

Well Operations

After injection is authorized, the owner or operator will begin to inject CO2 and perform required testing and monitoring. The information the owner or operator will generate and submit should demonstrate that the project is operating within permitted limits and that the well maintains mechanical integrity. Monitoring data should demonstrate that the plume and pressure front are behaving as predicted, confirm that USDWs are not endangered and validate modeled predictions or identify the need for appropriate responses.5USEPA. (2018, January). Geologic sequestration of carbon dioxide: Underground Injection Control (UIC) Program Class VI implementation manual for UIC Program Directors. https://www.epa.gov/sites/production/files/2018-01/documents/implementation_manual_508_010318.pdf

Monitoring

Prior to Construction

Prior to construction, the Class VI Rule requires Class VI permit applicants to develop and implement a comprehensive testing and monitoring plan for their projects that includes injectate monitoring, corrosion monitoring of the well’s tubular, mechanical and cement components, mechanical integrity testing, pressure fall-off testing, groundwater quality monitoring, CO2 plume and pressure-front tracking, and, at the UIC Program Director’s discretion, surface air and/or soil gas monitoring.6USEPA. (2018, January). Geologic sequestration of carbon dioxide: Underground Injection Control (UIC) Program Class VI implementation manual for UIC Program Directors. https://www.epa.gov/sites/production/files/2018-01/documents/implementation_manual_508_010318.pdf

Prior to Operation

Prior to operation, owners or operators must submit an amendment to the Testing and Monitoring Plan if needed to address newly identified information gathered via pre-operational testing or other pre-operation phase activities.7USEPA. (2018, January). Geologic sequestration of carbon dioxide: Underground Injection Control (UIC) Program Class VI implementation manual for UIC Program Directors. https://www.epa.gov/sites/production/files/2018-01/documents/implementation_manual_508_010318.pdf

During Injection

During the injection phase, Class VI well owners or operators will conduct injection activities and perform testing and monitoring as described in the permit and project plans. The information generated and submitted by the owner or operator should demonstrate that the well is maintaining integrity and the CO2 plume and pressure front are behaving as predicted.8USEPA. (2018, January). Geologic sequestration of carbon dioxide: Underground Injection Control (UIC) Program Class VI implementation manual for UIC Program Directors. https://www.epa.gov/sites/production/files/2018-01/documents/implementation_manual_508_010318.pdf

Post Injection

After injection has ceased, the owner or operator must implement the Post-Injection Site Care and Site Closure Plan, which includes performing monitoring to track the position of the CO2 plume and pressure front and ensure that USDWs are not endangered. Post-injection testing and monitoring will likely be an extension of the injection phase testing and monitoring.9USEPA. (2018, January). Geologic sequestration of carbon dioxide: Underground Injection Control (UIC) Program Class VI implementation manual for UIC Program Directors. https://www.epa.gov/sites/production/files/2018-01/documents/implementation_manual_508_010318.pdf

Financial Responsibility

Class VI permit applicants must submit information to demonstrate financial responsibility for corrective action, injection-well plugging, post-injection site care and site closure, and emergency and remedial response. The purpose of the UIC Program’s review of financial responsibility information is to verify that the proposed instruments are sufficiently funded to cover all applicable activities, in consideration of specific information about the project. The UIC Program should also review the financial instruments to ensure they have appropriate wording and provisions. The goal of this review is to ensure that, in the event that owners or operators experience financial difficulties, financial resources are available for a third party (i.e., one that is retained by the EPA) to carry out activities related to closing and, if needed, remediating GS sites to ensure that USDWs are not endangered, without the use of taxpayer monies.10USEPA. (2018, January). Geologic sequestration of carbon dioxide: Underground Injection Control (UIC) Program Class VI implementation manual for UIC Program Directors. https://www.epa.gov/sites/production/files/2018-01/documents/implementation_manual_508_010318.pdf

Class VI well owners or operators must update their financial responsibility cost estimates annually or when any of the specified project plans have been updated. Given the likelihood that one or more project plans will change during the pre-operation phase, it is possible that an updated cost estimate may be needed during this phase. Cost estimate updates may also trigger revisions to third-party financial instruments.11USEPA. (2018, January). Geologic sequestration of carbon dioxide: Underground Injection Control (UIC) Program Class VI implementation manual for UIC Program Directors. https://www.epa.gov/sites/production/files/2018-01/documents/implementation_manual_508_010318.pdf

Well Plugging

Class VI well owners or operators must implement the approved Injection Well Plugging Plan during the post-injection phase. The timing of well plugging will be site- and project-specific. However, the activities to be performed to plug the well will be the same. Proper plugging of injection wells is necessary to ensure that the wells do not serve as conduits for fluid movement into USDWs following cessation of injection and site closure.12USEPA. (2018, January). Geologic sequestration of carbon dioxide: Underground Injection Control (UIC) Program Class VI implementation manual for UIC Program Directors. https://www.epa.gov/sites/production/files/2018-01/documents/implementation_manual_508_010318.pdf

Site Closure

After non-endangerment has been demonstrated and approved by the UIC Program Director, a final site closure process is initiated. During this process, the owner or operator submits a notice of intent to close the site for review and approval by the UIC Program Director. Following approval, the owner or operator closes the site as described in the approved Post-Injection Site Care and Site Closure Plan and submits a site closure report to the UIC Program Director.13USEPA. (2018, January). Geologic sequestration of carbon dioxide: Underground Injection Control (UIC) Program Class VI implementation manual for UIC Program Directors. https://www.epa.gov/sites/production/files/2018-01/documents/implementation_manual_508_010318.pdf

Proper site closure is necessary to ensure that all monitoring wells are plugged appropriately to prevent them from serving as conduits for fluid migration and to restore the Class VI project site for other uses. The documentation associated with site closure is needed to ensure that future land owners and planners will be made aware that CO2 is stored in the subsurface and help authorities impose appropriate conditions on subsequent drilling activities that may penetrate the injection or confining zone(s).14USEPA. (2018, January). Geologic sequestration of carbon dioxide: Underground Injection Control (UIC) Program Class VI implementation manual for UIC Program Directors. https://www.epa.gov/sites/production/files/2018-01/documents/implementation_manual_508_010318.pdf

Reporting, Recordkeeping and Data Management

Reporting, recordkeeping and data management are important components of the UIC Program, helping to ensure that the activities and operations regulated under the program are conducted as planned, are compliant with the regulations and permit conditions, and ultimately, are sufficiently protective of USDWs. The Class VI Rule requires owners or operators to submit information throughout the lifetime of a Class VI project to demonstrate protection of USDWs and maintain regulatory compliance. All required reports, submittals, and notifications must be submitted in an approved electronic format through the EPA’s centralized, integrated electronic reporting and data management system, the Geologic Sequestration Data Tool.15USEPA. (2016, September). Geologic sequestration of carbon dioxide: Underground Injection Control (UIC) Program Class VI well recordkeeping, reporting, and data management guidance for owners and operators. https://www.epa.gov/sites/production/files/2016-09/documents/rrdm_guidance_for_operators_final_2016.pdf

 

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