Microbially induced carbonate precipitation under high temperature and high pressure: Implications for geological CO2 storage

The objective of this study is to investigate the potential of the microbially induced carbonate precipitation (MICP) method for leakage control in geological CO 2 storage. It is crucial to understand the influence of supercritical environmental factors on the MICP, as this is directly related to the safety of geological storage systems. This paper analyzes the impact of four key factors on the MICP process and the resulting CaCO 3 precipitation. These factors are temperature, CO 2 pressure, bacterial suspension (BS), and cementation solution (CS) concentration. The influence of the above four factors on the MICP process and the resulting CaCO 3 precipitation is investigated by solution tests, scanning electron microscopy (SEM) tests, X-ray diffraction (XRD) tests, and ultrasonic oscillation tests. The results indicate that the MICP process is inhibited in high temperature and CO 2 pressure environments. Under supercritical CO 2 (SC-CO 2 ) conditions, the quantity of CaCO 3 precipitation formed is reduced by approximately 35% compared to that produced under normal temperature and pressure conditions. The morphology and mineral composition of CaCO 3 crystals are influenced by temperature and CO 2 pressure, which in turn control their cementitious properties. The optimal concentration of CS is 0.5–0.75 mol/L, with a temperature of 45 °C and a CO 2 pressure of 7.5 MPa. Furthermore, increasing the BS concentration can mitigate the inhibition of SC-CO 2 in the MICP process. The findings of this study are significant for the application of the MICP method in geological CO 2 storage.