This investigation focuses on the use of microbially induced calcium carbonate precipitation (MICP) to set up subsurface hydraulic barriers to potentially increase storage security near wellbores of CO₂ storage sites. A numerical model is developed, capable of accounting for carbonate precipitation due to ureolytic bacterial activity as well as the flow of two fluid phases in the subsurface. The model is compared to experiments involving saturated flow through sand‐packed columns to understand and optimize the processes involved as well as to validate the numerical model. It is then used to predict the effect of dense‐phase CO₂ and CO₂‐saturated water on carbonate precipitates in a porous medium.