Understanding the physico-chemical evolution at the steel-cement interfaces in geological CO2 storage environments

Carbon capture and storage (CCS) refers to a number of technologies which involve capturing CO2 from large point sources (e.g. power generation plants, hydrogen production facilities, cement plants and steel production plants), followed by compressing and transporting the CO2 to appropriate subsurface reservoirs for sequestration or enhanced oil recovery. However, the implementation of such technologies necessitates long-term wellbore integrity to prevent CO2 leakage back into the atmosphere. Studies have highlighted that a potential critical point of failure is related to the carbonation reactions associated with casing cement as well as the external integrity of the casing itself. CO2 leakage through the annulus is reported to occur much more rapidly than geological leakage through the formation rock, leading to economic loss, reduction of storage efficiency and compromise of the storage location. The potential for such leaks raises considerable concern regarding long-term wellbore isolation, and the durability of hydrated cement. Research by SLB has reviewed the potential for geopolymer cements to afford better CO2 resistance in comparison to ordinary Portland cement through a series of long term exposure experiment. This project is directed towards understanding and quantifying the CO2 resistance of geopolymer cements in contrast to Portland cement with particular focus on (i) assessment of the bulk physico-chemical evolution of alkali-activated cement and the associated pore structure, under super-critical CO2 conditions, and (ii) the reactions mechanisms of casing material in contact with such cements. The successful completion of this project will enable to understand the evolution of both processes simultaneously in a system which experimentally simulates the steel-cement interface, thus enabling the local growth/dissolution at the steel-cement interface to be understood and related to the propensity for de-bonding and CO2 leakage.