Dawsonite as a Temporary but Effective Sink for Geological Carbon Storage

Abstract

The possibility of using dawsonite mineral trapping as a carbon capture and storage (CCS) strategy intrigues many. In this study, we used a dawsonite-rich (∼10%) CO 2 gas reservoir in the Hailar basin in northern China as a natural analogue of a CO 2 storage site, along with numerical modeling, to demonstrate that a large amount of dawsonite can be generated in sandstone formations, provided sufficient Na-rich feldspar and CO 2 gas are available. While precipitated dawsonite can be preserved only in a hydrodynamically-closed system in the long term under high CO 2 fugacity and log((Na + )/(H + )) activities in solution, short-term trapping of CO 2 in dawsonite (on the order of 10 kyr) is possible and lowers CO 2 pressure, which mitigates the risk of CO 2 leakage to the ground surface or overlying drinking water aquifers. The re-dissolution of dawsonite after a few thousand years facilitates progressive dissipation of the gas phase CO 2 over time. Consideration of reservoirs or saline aquifers with minerals or formation water that can provide a high abundance of dissolved sodium, significantly increases the number of potential CCS sites globally. Furthermore, alternating water-and-gas injection regimens could enhance the precipitation of dawsonite in Na-rich aquifers. Future editions of the Carbon Storage Atlas should consider aquifer geochemistry in the site selection for secure long-term carbon storage in addition to the volumetric considerations for short-term operation.