Clay Content Mediates the Contribution of Suspended Sporosarcina Pasteurii to Microbial Mineralization in Sandstones

Abstract Bioaugmented microbially induced carbonate precipitation (MICP) is a potentially useful tool for permeability modification of the subsurface. There is, however, uncertainty surrounding how the transport and mineralization capability of augmenting organisms such as Sporosarcina pasteurii may vary with reservoir properties. Resolving these uncertainties requires further experimental work on natural rock samples; this necessitates, in turn, creative approaches to improving the reproducibility and generalizability of such experimental work. In this study, natural sandstones with different clay contents are processed to narrow grain size ranges and packed into columns, allowing the effect of clay content to be studied independently of pore size. Clay content is shown to have a significant effect on S. pasteurii attachment to rock surfaces, possibly due to the high specific surface area of clay minerals, while the effect of pore size is minor in the absence of straining. Furthermore, differences in S. pasteurii affinity for solid surfaces produce clear differences in the quantity and distribution of precipitate accumulation. When viable S. pasteurii cells are mostly surface‐attached, precipitate accumulation begins almost immediately and precipitates appear to form primarily on grain surfaces. When only a small fraction of S. pasteurii is surface‐attached, precipitate accumulation begins later but becomes significant with time. In this case, however, precipitates appear to form primarily in suspension, which may produce different precipitation efficiencies and precipitate morphologies based on mass transport conditions.