Application of Microbial Technology for Enhancing Carbon Dioxide Geosequestration in Shallow Seabed Caprock

The utilization of fossil fuels releases a large amount of carbon dioxide (CO2) gas, leading to global temperature changes and climate warming. Carbon dioxide geological sequestration (CCS) is an effective solution, including the use of shallow seabed hydrate reservoirs as a geological sink. However, the sealing and strength of the caprock affect the sequestration effectiveness. Therefore, this study assessed the strength and sealing properties of a shallow seabed layer reinforced with Microbial-induced Carbonate Precipitation (MICP) technology through a combination of triaxial tests and X-ray CT. In addition, carbon dioxide sequestration experiments were conducted to investigate the factors influencing the ability of MICP technology to accelerate the mineralization and sequestration of carbon dioxide. The results demonstrate that MICP technology can enhance the sealing capacity of caprock by increasing its strength, reducing its porosity, and accelerating CO2 mineralization. After 120 h of treatment, the CO2 concentration in the air decreased from 887 ppm to 310 ppm, showing a significant mineralization effect. The bacteria used, Bacillus megaterium, can simultaneously secrete urease and carbonic anhydrase (CA). During the urease hydrolysis of urea, this not only increases the rate of calcium carbonate formation and improves the sealing performance but also accelerates the catalytic mineralization of CO2 by carbonic anhydrase by creating an alkaline environment.