Mitigation strategies for sealing high permeability regions in cap rocks, such as fractures or improperly abandoned wells, are important considerations in the long term security of geologically stored carbon dioxide (CO(2)). Sealing technologies using low-viscosity fluids are advantageous in this context since they potentially reduce the necessary injection pressures and increase the radius of influence around injection wells. Using aqueous solutions and suspensions that can effectively promote microbially induced mineral precipitation is one such technology. Here we describe a strategy to homogenously distribute biofilm-induced calcium carbonate (CaCO(3)) precipitates in a 61 cm long sand-filled column and to seal a hydraulically fractured, 74 cm diameter Boyles Sandstone core. Sporosarcina pasteurii biofilms were established and an injection strategy developed to optimize CaCO(3) precipitation induced via microbial urea hydrolysis. Over the duration of the experiments, permeability decreased between 2 and 4 orders of magnitude in sand column and fractured core experiments, respectively. Additionally, after fracture sealing, the sandstone core withstood three times higher well bore pressure than during the initial fracturing event, which occurred prior to biofilm-induced CaCO(3) mineralization. These studies suggest biofilm-induced CaCO(3) precipitation technologies may potentially seal and strengthen fractures to mitigate CO(2) leakage potential.

than two orders of magnitude. This single high pressure experiment suggests MICP can be used to reduce permeability in fractures under relevant subsurface conditions. This study also suggests that the high pressure vessel is suitable for testing a range of biogeochemical processes in meso-scale fractured porous media samples under pressure. The high pressure test system could also be well suited for studying microbially-enhanced methane production from coal, wellbore and cement integrity challenges with corrosive fluids, proppant and hydraulic fracturing fluid investigations, enhanced oil recovery, microbially-induced corrosion, or biofouling among many other industry-related biogeochemical processes.

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