Alterations in petrophysical and mechanical properties due to basaltic rock-CO2 interactions: comprehensive review

Basaltic rocks, owing to their vast geological presence, have been identified as potential reservoirs for carbon dioxide (CO2) sequestration. Their inherent attributes, namely, a pronounced mineral trapping capability, distinct structural intricacies, and a potential storage capacity surpassing 100Gt, earmark them as prime candidates for CO2 storage. However, knowledge gaps exist in understanding the modifications in the petrophysical and mechanical characteristics of these rocks post-CO2 sequestration. Comprehending these CO2-induced petrophysico-mechanical alterations is crucial for assessing their potential for long-term carbon mineralization-based storage. Thus, this study provides a critical review of key parameters that can induce post-CO2 injection changes in the mechanical and petrophysical properties of basaltic rocks. Also, the implications of these changes for long-term CO2 storage efficiency in Basaltic rocks are succinctly presented. Findings from this review work show that the mineralogical composition of basaltic rocks can alter the petrophysical and mechanical behaviors during CO2 injection. The reaction processes tend to enhance CO2 storage and mineralization via an increase in the porosity of the basaltic tuff, which was caused mainly by their dissolution. Laboratory simulations of CO2 storage in basaltic rocks had revealed that when the experiment was run for a longer length of time, the distribution/concentration of reaction minerals, reaction rates of the minerals, and/or permeability development of the rock matrix either decreased, increased, or remained the same. Furthermore, the strength indices for all types of basalts demonstrate that as exposure duration increases, the material strength steadily decreases. Core experiments and laboratory simulations have revealed that permeability increased at a higher flow rate and decreased at a lower flow rate. This is because a higher flow rate (increased injection pressure) will yield more pore spaces. Also, precipitation of carbonate minerals is favored under alkaline conditions since this condition necessitates increased production of divalent cations. Understanding these changes is essential since they can be detrimental to the immediate environment of the storage site, especially when there is CO2 leakage and consequent contact with freshwater resources. Similarly, we highlighted how several reports have correlated the occurrence of low-scale seismic events bounding the storage sites, to CO2 storage. Lastly, based on the reviews synthesized, we recommend promising directions to provide more profound insights into CO2 storage in basaltic rocks.