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

碳捕集与封存（CCS）是指从大型点源（如发电厂、制氢设施、水泥厂和钢铁厂）捕获二氧化碳，然后将二氧化碳压缩并输送到适当的地下储层进行封存或提高石油采收率的一系列技术。然而，这些技术的实施需要长期保持井筒完整性，以防止二氧化碳泄漏回大气中。研究强调，潜在的失效临界点与套管水泥相关的碳化反应以及套管本身的外部完整性有关。据报道，通过环空发生的二氧化碳泄漏比通过地层岩石发生的地质泄漏要快得多，这会导致经济损失，降低储存效率并危及储存位置。此类泄漏的可能性引起了人们对长期井筒隔离和水化水泥耐久性的极大关注。SLB的研究通过一系列长期暴露实验，研究了地聚合物水泥与普通波特兰水泥相比具有更好的抗二氧化碳能力的潜力。该项目旨在了解和量化地聚合物水泥与波特兰水泥相比的抗二氧化碳能力，并特别关注(1)在超临界二氧化碳条件下评估碱活性水泥的整体物理化学演化和相关孔隙结构，以及(2)套管材料与此类水泥接触的反应机制。该项目的成功完成将使我们能够在实验模拟钢-水泥界面的系统中同时了解这两个过程的演变，从而使我们能够理解钢-水泥界面的局部生长/溶解，并将其与脱粘和二氧化碳泄漏的倾向联系起来。

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.