The importance of whole system considerations for sustainable, long-term CO₂ injection and storage: Interplay between infrastructure-related corrosion and reservoir rock chemistry effects on the evolution of the CO₂ storage capacity

As global emissions fail to reduce rapidly, Carbon Capture and Storage (CCS) is attracting ever-growing attention. CCS involves capturing, treating, transporting and storing CO₂ to ensure its long-term removal from the atmosphere. To design a viable CCS system, the different interactions and impacts of injected CO₂ (either as sub-critical or supercritical fluid) across the whole CCS system need to be considered. However, it is unclear how changes in fluid chemistry and the pre-existing reservoir rock chemistry influence the evolution of the two key storage properties, porosity and permeability.

This study investigates how upstream corrosion-induced fluid chemistry changes and realistic rock composition could affect the injectivity and storage capacity of reservoirs. The condition and material chosen for this project fall into the possible envelope of conditions of interest during CO₂ injection and storage. Corrosion occurring during CO₂ injection through saline aquifers was simulated at 40 bar, 60°C for two weeks, using X65 carbon and ¹³Cr steel. The fluid resulting from the experimental fluid-metal interaction was then reacted at ∼40 bar, 60°C for another two weeks with two fine-grained arkoses, with and without lithic clast, representative of siliciclastic reservoir rocks.

Results show that upstream corrosion caused a change in fluid chemistry and decreased fluid acidity. The corrosion-induced chemical changes had a marked effect on the evolution of porosity and permeability within the reservoir rocks. The storage capacity of reservoir rocks with diverse mineralogy is highly dynamic, and directly affected by rock chemical composition and, importantly, the chemical evolution of the incoming fluid.