Detecting Microbially Induced Calcium Carbonate Precipitation in Porous Systems Using Low-Field Nuclear Magnetic Resonance Relaxometry

Low-field nuclear magnetic resonance has been shown to be sensitive to the chemical and physical changes in a porous medium caused by microbially induced calcium carbonate precipitation (MICP), confirming its potential for detection of MICP for subsurface engineering applications. This investigation used a 2-MHz rock core analyzer, measuring T2 relaxation, in combination with scanning electron microscopy to characterize the daily chemical and physical changes occurring in various granular media including 1- and 0.5-mm soda lime glass beads and 1- and 0.45-mm quartz sand. An increase in T2 time was observed in all of the granular media in accordance with MICP progression. An estimate of the surface relaxivity, ρ, was obtained for the silica glass, quartz sand, and mineral precipitate, which allowed for correlation between mineral precipitation surface coverage and T2 relaxation time. The results indicated the potential for detailed in situ MICP progress monitoring during the early stages of the process by portable low-field nuclear magnetic resonance (NMR) devices.