Microbially induced calcite precipitation for sealing anhydrite fractures with gouges

Sang, Guijie and Lunn, Rebecca and Minto, James M. and El Mountassir, Grainne (2022) Microbially induced calcite precipitation for sealing anhydrite fractures with gouges. In: 56th US Rock mechanics/Geomechanics Symposium, 2022-06-26 - 2022-06-29, New Mexico/Online. (https://doi.org/10.56952/ARMA-2022-0277)

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Caprock formation forms a natural barrier for geological storage of CO2, nuclear wastes, and hydrocarbon resources. Fault and natural/artificial fractures that crosscut the storage systems represent potential leakage pathways. Sealing of caprock fractures/faults is of great importance to ensure its long-term sealing integrity. In this study, we conduct microbial-induced-calcite-precipitation (MICP) experiments for sealing anhydrite fractures (artificially cut) with gouges. MICP involves a bio-chemical reaction for calcite precipitation using ureolytic microorganism - Sporosarcina pasteurii. The precipitated calcite, which occurs initially from finer pores to larger pores, induces a 10.7% decrease of porosity inside the fracture after the 1st 12 cycles of MICP treatment. After 18-21 cycles of MICP treatment, the fracture permeability of the two fractured core samples effectively decreases by 2-3 orders of magnitude. Our study also indicates that the MICP sealing efficiency could be improved by lowering the injection rate, optimizing fluid chemistry for a better bacteria retention inside the fracture. The study provides a baseline for using MICP technique to seal anhydrite fractures.