Pore-scale spatiotemporal dynamics of microbial-induced calcium carbonate growth and distribution in porous media

Abstract

The naturally occurring bio-geochemical microbial-induced calcium carbonate precipitation (MICP) process is an eco-friendly technology for rehabilitating construction materials, reinforcement of soils and sand, heavy metals immobilization and sealing subsurface leakage pathways. We report pore-scale spatiotemporal dynamics of the MICP process in porous media, relevant for reduced environmental risk by leakage during CO2 geological storage. Effects of hydrodynamics and supersaturation on the MICP with Sporosarcina pasteurii stains were studied using a high-pressure, rock-on-a-chip microfluidic device. Bacterial cell numbers and variation in cementation concentration controlled the crystal size and pore-scale distribution by influencing the local supersaturation. Local pore structure determined crystal nucleation, where low velocity regions tended to nucleate more crystals. CaCO3 crystallization was observed at subsurface pressure (100 barg) with a reduced sealing performance due to the low microbial activity from elevated pressure. We identify that hydrodynamics and supersaturation determine crystal nucleation and growth in porous systems, providing important experimental evidence for subsurface environmental applications and validation of upscaled MICP models.