A Novel Portland Cement for CO2 Sequestration by Nanoparticles

Abstract Global warming is a critical issue that has garnered significant attention during the last few decades. This temperature increase results from the emission of greenhouse gases into the atmosphere, most notably CO2. Carbon Capture and Storage (CCS) technology has been established as one of the most successful ways to store CO2 in underground layers and prevent it from being released into the atmosphere. However, CO2 is difficult to contain in subterranean layers subjected to high-pressure, high temperature (HPHT) conditions due to the degradation of Portland cement caused by chemical interaction with wet/dry CO2. Numerous studies have been conducted to increase the cement's resistance to CO2 attack, but limited effectiveness has been found when these methods have been evaluated under various settings. Given the distinctive properties of nanomaterials, such as high surface areas, quick contact, and resilience to heat, Nano Glass Flake (NGF) and Multiwall Carbon Nano Tube (MWCNT) were deemed to be suitable additional materials for increasing cement efficiency. On cement samples treated with NGFs and MWCNTs, a number of pre-carbonation and post-carbonation tests were performed. The pre-carbonation tests revealed that the density of NGFs-based cement remained constant with that of neat cement while the plastic viscosity increased. Additionally, it was recommended not to add more than 1wt% NGFs to the cement, as this would result in a high viscosity paste, which would negatively affect the pumping operation. On the other hand, this threshold for the viscosity of MWCNTs was roughly 0.25wt%. It was found that by using nanoparticles and employing a proper dispersion process, the cement's overall physical performance can be improved, and a lower amount of Portlandite is formed, which is critical for increased resistance to CO2 attack. In a static reactor, samples with the best pre-carbonation performance were subjected to water saturated supercritical CO2 for 56 days. It was then discovered that CO2 diffuses into cement and increases cement decomposition in the post-carbonation stage of the experiment. Samples weighing more than 0.5wt %. NGFs and 0.05 wt% MWCNTs had the smallest carbonated regions, indicating carbonated cement. However, the number of nanoparticles added to each sample resulted in a variable level of carbonation. Cement made using MWCNTs has a higher compressive strength due to its ability to manipulate CaCO3 crystal shape. NGFs-based cement, on the other hand, could be a better solution in terms of CO2 resistance. Due to their substantially lower cost than MWCNTs, it is possible to increase cement performance in CCS operations without imposing a high cost on projects.