Dispersion of bacterial cells during microbially induced calcium carbonate precipitation in fracture sealing

Abstract

Fluid leakage through fracture networks is one of the primary environmental issues in water reservoir management, oil extraction, and geological carbon sequestration. Microbially induced calcium carbonate precipitation (MICP) offers a promising alternative to seal fractures and improve the performance of those relevant engineering over their service life. The dispersion of bacterial cells plays an important role in the growth and distribution of CaCO3 during the MICP process. The effect of calcium ion concentration, and flow rate on the diffusion behaviors of bacterial cells are studied by directly observing the mixing of two streams of solution, i.e., bacterial solution and cementation solution, in a microfluidic chip. Micromodel experiments show that the high concentration of calcium ion results in a significant retarding effect in the diffusion of bacterial cells given the chemotaxis. The transverse diffusion of motile bacteria might be suppressed by high-rate fluid flow or promoted by low-rate flow. Our work illustrates the significant impacts of solute concentrations and fluid flow rate on the dispersion of bacterial cells and deepens the understanding of the delivery of bacterial suspensions in fracture sealing with MICP.