Carbon capture and sequestration (CCS) is an emissions reduction technology helping combat the climate crisis. The CCS process captures carbon dioxide (CO2) produced from industrial and energy-related processes and stores it beneath the ground. The task involves separating CO2 from other gases and transporting it to a storage location, effectively preventing it from reaching our atmosphere.
Wells in the CCS process are defined as Class VI wells in accordance with Environmental Protection Agency (EPA) regulations. The sole job of these types of wells is to inject CO2 into rock formations under the ground or ocean. This process is also referred to as geologic sequestration (GS).
The longevity of these wells depends greatly on the materials used and their corrosion resistance. Other requirements for Class VI wells include:
The EPA has strict regulations and standards in place for the long-term protection of our drinking water sources. Corrosion within CCS wells can inhibit the process of storing CO2 and possibly contaminate nearby water sources.
Corrosion is a significant concern in downhole environments as it can lead to costly failures and production shutdowns. Dry CO2 alone isn’t corrosive. However, where water is present, it creates a very acidic environment. Water is likely to be encountered in the geological formation and may also precipitate from the injection gas where changes in temperature and pressure occur. The formation may also contain other corrosive constituents, such as chlorides and hydrogen sulfide (H2S).
Therefore, the construction of the well must consider both the composition of the injection gas and, more importantly, the environment of the injection zone and how that may change during the life of the well. Essential factors to be considered include temperature, pressure, brine composition, salinity, hydrogen sulfide (H2S), organic acids, pH, and microbial corrosion.
When planning for a CCS project, you must consider material selections for the chemical plant, power plant, wells, and pipeline transport. Temperature, pressure, velocity, and fuel composition affect the materials and alloys used in piping, equipment, and fittings for CCS projects. Steady operating conditions are vital, especially during shutdowns, startups, or upsets within the system.
Depending on the environment, materials considered for CCUS projects can include:
Selecting the most cost-effective material solutions for CCS projects isn’t always straightforward. The Association of Materials Protection and Performance (AMPP) has recently published AMPP Guide 21532-2023, Guideline for Materials Selection and Corrosion Control for CO2 Transport and Injection. However, AMPP cautions that this guidance is provided for initial design to help the engineer focus on the most critical issues related to CO2 transport and injection, but isn’t meant to act as definitive requirements. The association continues to say “it is a rapidly growing subject area and much exploratory technical work is still being executed, and as such this document should be seen as a starting point with future updates and new insights to be expected.” source
Admittedly, there is still much to learn, however, the process of material selection for CCUS can begin with considerations that apply to all types of injection wells. The composition of the gas to be injected, the environment of the reservoir, and transitory conditions which may occur during operation are all determining factors in proper material selection to meet life-of-well expectations. The composition of the gases being injected varies widely depending upon the source. They may be of a consistent quality, such as in blue hydrogen production, or be from industrial gases containing a mix of corrosive gases with fluctuating composition.
Carbon steel may be sufficient above the packer if the gas is dry and high purity CO2. However, below the packer, where the gas comes in contact with groundwater, a corrosion-resistant alloy should be considered. If unable to guarantee that dry gas can be maintained throughout the life of the well, then CRAs should be considered for the entire string.
Where the corrosive gas is predominantly CO2, a 13 Chrome alloy may be a cost-effective solution. However, if the reservoir or injection stream contains chlorides, H2S, or other corrosive gases, a more highly alloyed material such as Super 25 Chrome may be required.
CRA’s Alloy Solutions for CCS Wells include:
Corrosion Resistant Alloys offers high-quality corrosion-resistant alloy piping and tubing to support your upcoming carbon capture and storage project. Our experienced metallurgical team is available to evaluate the unique conditions of your CCS project and guide you during the material selection process.
Contact our team of experts at Corrosion Resistant Alloys to learn more about our solutions for your next CCS project.
*While every effort has been made to ensure the accuracy of the above review, assessment, conclusions, and report, the appropriateness of their application and their interpretation remain the sole responsibility of the user.
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