By Valerie Wilson
With the growing focus on carbon management and Carbon Capture and Storage (CCS), companies are evaluating mature oil fields, around the world, for their potential for CCS projects. During these evaluations it will be important to keep in mind that mature oil and gas fields may have wells that have compromised well integrity concerns due to application/age of wells and operating history, etc. In addition, these mature fields may have legacy wells that may have been improperly plugged and abandoned providing a potential conduit for escape of reservoir fluids to groundwater aquifers or to the surface. Even if a well has the needed integrity, it still may not have the appropriate design to be suitable for CO2 injection use for other considerations (i.e. materials, corrosion, etc.).
In September of 2011 the U.S. Environmental Protection Agency (EPA) adopted the Class VI rule to define wells specifically utilized for carbon dioxide (CO2) injection for permanent storage, also referenced as sequestration. The EPA regulates the function, construction, operation and closure of various types of injection wells. Other countries may have similar authorities that stipulate rules for environmental protection. Under the EPA Underground Injection Control (UIC) Program, states can apply to EPA for delegation of primacy, allowing for states, not EPA, to hold primary enforcement responsibility of federal standards. To date, North Dakota and Wyoming have been granted primacy to regulate Class VI wells with several others in queue.
The EPA require many of the same integrity testing and considerations as it does for Class II (wells used for produced water reinjection) and other classes of wells, such as
- Extensive site characterisation requirements.
- Injection well construction requirements for materials that are compatible with and can withstand contact with CO2 over the life of the well.
- Injection well operation requirements.
- Comprehensive monitoring requirements that address all aspects of well integrity, CO2 injection and storage, and ground water quality during the injection operation and the post-injection site care period.
- Reporting and recordkeeping requirements that provide project-specific information to continually evaluate Class VI operations and confirm U.S. Drinking Water (USDW) protection.
Please reference requirements for CO2 injection wells in the country appropriate to your project. Some key references for CO2 well are: “The International standard covering CO2 geological storage”, ISO 27914:2017, as well as a brand-new Offshore Energies UK document on new well abandonment "OEUK Well Decommissioning for CO2 Storage Guidelines”.
It is an exciting time in the oil and gas industry as we transition and have the opportunity to utilize our knowledge and experience in new ways, but it is also important to not lose sight of the basic concepts of well integrity and the importance it brings!