Proposed Methods Accelerate Permanent CO2-Storage Process

This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 215352,“ Accelerating the Permanent CO2 Storage Process: A Safer and Faster Route to Net Zero,” by Shubham Mishra, SPE, Boston Consulting Group. The paper has not been peer reviewed. The complete paper proposes two methods of accelerating the solidification (or mineralization) of CO2 in subsurface conditions, thus reducing the time required in the CO2 storage process. It also reviews industry and academic works devoted to the subject. Two main concerns with CO2 storage in subsurface reservoirs and CO2 sequestration are the large time cycle involved in its permanent storage and the associated environmental risks. Because other CO2 trapping mechanisms can be reversible, these concerns hinge heavily on the time required for solidification or mineralization of CO2 into a component such as calcite (CaCO3). Using current technologies and practices, it is practically impossible to complete the soaking period—or, in simpler words, a CO2 storage project—in one lifetime. Thus, technological development of CO2 storage, which depends on field validations, becomes an extremely long, multigenerational process. On the other hand, environmental safety is always a concern with underground CO2 storage. Three of four CO2 trapping mechanisms (structural, solubility-based, and residual) pose greater risk to the environment than does the fourth, which is mineralization or solidification. Therefore, from the point of view of environmental safety, mineralization is the most permanent form of CO2 storage that minimizes the risk of CO2 existing in gaseous form in the reservoir and thus flowing upward to shallower zones or the surface. Several research projects devoted to finding a commercial solution for accelerating the mineralization process are ongoing, including the following: - The CarbFix project in Iceland is based upon injection of CO2 dissolved in water streams into basalt rocks for accelerating mineral trapping. Through tracer surveys and mass calculations, the project has proposed that mineralization can be achieved in as little as 2 years for the size of the reservoir under consideration and the amount of CO2 injected. - A Canadian startup (Carbon Engineering) is turning carbon emissions into pellets that could be used as a synthetic fuel source, while a Swiss company called Climeworks is pumping extracted carbon to farms for agricultural use. - Another start-up is using calcium oxide, a waste product from the steel industry called steel slag, to react with CO2 and form CaCO3. This is used in controlled surface conditions in a cement-industry setup. This process, however, highlights how the reactions converting CO2 into solid can be sped up. - University research projects are ongoing that focus on use of various catalysts for increasing the rate of the mineralization chemical reaction, resulting in the formation of CaCO3. While industry and academia are focusing on niche setups to solve this problem, not much focus is being placed on general large-scale applications such as increasing the mineralization chemical reaction rate in sandstone saline aquifers, where approximately 80% of potential carbon capture, utilization, and storage (CCUS) projects will be developed. Thus, technologies or workflows that can be applied in CO2 storage projects in saline aquifers to increase the mineralization reaction rate can be essential to bringing a shift to the larger vision of CCUS. In this effort, an integrated approach incorporating experience from oil and gas, cement, and other adjacent industries can help develop potential solutions.