Experimental Analyses of Pore-Size Dependent Biomineralization in Porous Media Under Various Flow Rate and Bacterial Density Scenarios

Abstract

We document results of a set of laboratory experiments aimed at exploring impacts of injection rate and bacterial density on biomineralization across water-saturated porous media. The study relies on a Low-Field Nuclear Magnetic Resonance technology and the ensuing transverse spin-spin relaxation time distributions. The latter is documented to provide a robust quantification of temporal histories of pore size distributions during biomineralization. As such, our work explores and quantifies pore-size dependent biomineralization across the three-dimensional pore space. The study also provides a quantitative analysis of alterations in porosity and permeability induced by biomineralization, together with a quantification of (time-averaged) rates of pore volume change. A plugging ratio efficiency index is introduced to quantify the strength of pore-size-related biomineralization. Our results reveal that biomineralization induces significant alterations in the pore size distribution within a porous medium, these changes being modulated by bacterial density and injection rate. We find that CaCO₃ mainly precipitates in macropores, consistent with the presence of favorable local hydrodynamic conditions and large surface areas therein. Precipitated CaCO₃ volume is found to increase with bacterial density. High bacterial densities amplify rate of pore volume change within macropores and adequate plugging ratio of biomineralization and contribute to a significant permeability reduction. Otherwise, a diminished strength of biomineralization in mesopores and micropores is documented for the highest injection rates considered.