Feasibility study of enzyme-induced calcium carbonate precipitation (EICP) for CO2 leakage prevention

This study tried to examine the feasibility of enzyme-induced calcium carbonate precipitation (EICP) for CO2 leakage prevention in a subsurface condition. For this, the effects of 1) concentrations of urease enzyme and reactants (urea and CaCl2), 2) initial pH (3–9), and 3) temperature (30–50 °C) on the precipitation of calcium carbonate were tested in the batch experiments. In addition, the core-plugging experiment was conducted to test the potential application of EICP to a porous medium with high permeability. The batch experiments showed that the 0.25 M urea was completely hydrolyzed by urease (above 1000 U/l). However, 0.4 M and 0.5 M urea were not completely decomposed because of the insufficient quantity of urease. Our result also showed that urea hydrolysis was not observed at pH 3, while the efficiency of calcite precipitation was not affected in the pH range of 5 to 9. Temperature also affected the hydrolysis of urea. The efficiency of calcite precipitation increased with increasing temperature from 30 °C to 50 °C. In addition, the result of the core-plugging experiment showed that the permeability of the sandstone core decrease by approximately 42% due to the precipitation of calcite in the pores. From our results, this study suggested that EICP can be a potential for CO2 leakage prevention from a storage reservoir within the pH and temperature ranges of this study.