Minireview on CO<sub>2</sub> Storage in Deep Saline Aquifers: Methods, Opportunities, Challenges, and Perspectives
Rubaya Tasnin Mim, Berihun Mamo Negash, Shiferaw Regassa Jufar, Faizan Ali
Abstract
Deep saline aquifers have received much attention as storage sites of CO 2 due to their large storage capacity. However, many issues like CO 2 leakage, low solubility of CO 2 in brine, contamination of groundwater with CO 2, injectivity impairment, corrosion in the pipeline, salt precipitation, and pore plugging are still unresolved. When supercritical CO 2 is injected into the saline aquifer, its lower density causes it to migrate to the aquifer’s top, leaving the lower portion of the aquifer unswept. At the interface between free CO 2 and brine, part of the CO 2 slowly dissolves in the brine, developing a CO 2 saturated interface with brine on top of the free brine. The density difference between saturated and free brine triggers a slow density-driven convection process within the aquifer. Researchers have extensively investigated these challenges associated with CO 2 storage in saline aquifers and have explored various techniques to improve storage security. These techniques include injection of water-based fluid, brine, surfactants, polymer, and nanoparticles on or with CO 2 . Despite the reported success stories of these techniques, some limitations stand in the way of full-scale deployment. These include the cost of injectants, toxicity, adsorption, and pore plugging. Currently, there is a scarcity of comprehensive reviews that thoroughly analyze the methods utilized for CO 2 storage in saline aquifers. Hence, the primary objective of this Review is to highlight the issues that have been encountered during the storage of CO 2 in saline aquifers and to provide an overview of the benefits and challenges associated with the methods employed thus far. In addition, carbon capture and storage (CCS) projects face further hurdles due to corrosion within the pore space, leakage through injection wells, high cost of storage projects, uncertainty in the evaluation of storage capacity, and inaccurate interpretation of data. The study suggests the necessity for thorough research to address and overcome these issues.