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  • Writer's pictureTariq Siddiqui,

Class-VI Injection Wells: Tips For CO2 Project Developers

Updated: Nov 16, 2022

By: Tariq Siddiqui

If your CO2 injection project envisage geological storage in a saline aquifer in USA, a Class-VI injection permit is needed. Permitting for a geologic storage is one of the most important and time consuming step in a Carbon Capture & Sequestration (CCS) Project and policy & regulations must be understood before embarking on the project.

This articles provides a high-level overview and tips for the Class-IV injection wells for CO2 project developers, it is not a legal guidance and developers are encouraged to read Code of Federal Regulations (CFR) in 40 CFR 146.82.

Any underground injection in USA is regulated by EPA to protect potable underground water resources under Safe Drinking Water Act (SDWA). EPA administers this through Underground Injection Control (UIC) program that has six injection classes (see title slide). Two of these classes are relevant for CO2 injection, these are:

  • Class-II Wells - These wells relate to oil & gas production, mainly injecting brine and CO2 for EOR

  • Class-VI Wells - This is a new class of injection wells specific for CO2 injection in saline aquifer.

Key Tips for the Developers:

  • Class-VI is a new class of injection wells specific for CO2 geologic storage in saline aquifer

  • Lead time for Class VI well permitting can be significant (years)

  • A separate application is required for each injection well

  • Only N. Dakota and Wyoming have primacy to issue class VI permits

  • Stratigraphic wells and monitoring wells (including in-zone, above-zone & shallow wells) are not covered by Class-VI permit, these permits are obtained separately (through State, local or tribal etc)

  • Grant of class-VI permit does not guarantee credits like LCFS (see below).

  • Permits are issued in two-stages:

    1. Authorizes operator to drill/test the well & operator submit s the completion report with all the data.

    2. If regulatory authority findings are satisfactory, 2nd stage of permit allows injection to commence.

Key Components of Class-VI Permits Application

EPA’s offers a Geologic Sequestration Data Tool (GSDT) that is a centralized, web-based system that receives, stores, and manages Underground Injection Control (UIC) Class VI data for collaborating, communicating and facilitating the permit process. Below is high-level components of Class-VI application:


General project information (Facility name, location, address, Co2 source quantity, contacts and tribes an territories within Area of Review (AoR)

2-Site Characterization data

Fluid chemistry, geologic, depth and information on all USDW in the area is required for site screening and characterization

3-Site Maps

Showing the AoR and location of injection well. All other well penetrations, surface features, road buildings any known faults and fractures, etc.


Wells in the AoR that penetrate the confining zone and/or the injection zone; location of wells on the AoR map including well record ID numbers, location (latitude/longitude); well type (oil gas, test); depth; deepest formation penetrated; completion date; current status (active, inactive, plugged or unknown); and information about whether the well is in need of corrective action

5-Project Plans

Project plans that will become part of permit (AoR & Corrective action plan, Testing & Monitoring Plan, Injection Well plugging plan, Post-injection Site Care (PISC) plan Site Closure plan (CLP), Emergency & Remedial response Plan).

Class-VI Permit Does Not a Guarantee Certain Carbon Credit

Low Carbon Fuel Standards (LCFS) credits (~$130/Tonne) in California are significant driver for CCS projects, if project meets the California Air Resources Board (CARB) requirements that largely follow Green Hose Gas (GHG) Protocol. There are some notable differences between GHG Protocol and EPA/UIC requirement (less stringent), such that operator will not automatically meet the permeance requirement of CCS Protocol. These difference are:

  • Post injection site care in EPA requirement is 50 years vs 100 years in GHG protocol.

  • Operator, therefore needs to provide financial assurance for extended period (additional 50).

  • Class-VI regulation require only to maintain financial assurance for safety of USDA, whereas GHG protocol covers wider financial responsibility for the consequences.

  • Class-VI well permits allow maximum injection pressure of 90% of fracture pressure, rather than 80% in GHG protocol.

Despite these differences, the requirements of Class-IV wells are more closely aligned to the CCS Protocol then Class-II wells, that are more ambiguous (example no so- specific post-injection site care obligations).

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