Nanomodification: An efficient method to improve cement integrity in CO2 storage sites

Abstract

Carbon Capture and Sequestration (CCS) technology is an effective strategy to mitigate greenhouse gases released into the atmosphere. One of the challenges of the CCS sites, however, is the degradation of class G cement used to seal-off the injected intervals. It is known that in the presence of brine in depleted reservoirs or aquifers, cement may degrade due to the interaction of its alkaline component (Portlandite) with carbonic acid, causing seepage of CO2 and environmental contamination. Given the surface area, stability and inhibition characteristics of nanomaterials, they might be a good option to improve the performance of the cement in CO2 storage sites. In this study, attempts are made to show how two reliable nanomaterials (Nano Glass Flakes (NGFs) and Multiwall Carbon Nano Tube (MWCNTs)) can be used to improve the integrity of the cement in CO2 storage sites. A series of pre-carbonation and post-carbonation tests were conducted on the cement samples modified by NGFs and MWCNTs to compare their performances under a real storage site condition. It was found that the samples with 0.5 wt% NGFs and 0.05 wt% MWCNTs have the best performance against the attack of CO2. They could significantly resist against the carbonation and prevent the severe chemical reactions taking place in the presence of CO2. Given the fact that NGF is significantly cheaper than MWCNT, it could be a good choice to reinforce the cement used in the CCS storage site.