Scholarly Work - Chemical & Biological Engineering
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Item Kinetics of Calcite Precipitation by Ureolytic Bacteria under Aerobic and Anaerobic Conditions(2019-05) Mitchell, Andrew C.; Espinosa-Ortiz, Erika J.; Parks, Stacy L.; Phillips, Adrienne J.; Cunningham, Alfred B.; Gerlach, RobinThe kinetics of urea hydrolysis (ureolysis) and induced calcium carbonate (CaCO3) precipitation for engineering use in the subsurface was investigated under aerobic conditions using Sporosarcina pasteurii (ATCC strain 11859) as well as Bacillus sphaericus strains 21776 and 21787. All bacterial strains showed ureolytic activity inducing CaCO3 precipitation aerobically. Rate constants not normalized to biomass demonstrated slightly higher-rate coefficients for both ureolysis (kurea) and CaCO3 precipitation (kprecip) for B. sphaericus 21776 (kurea=0.10±0.03 h−1, kprecip=0.60±0.34 h−1) compared to S. pasteurii (kurea=0.07±0.02 h−1, kprecip=0.25±0.02 h−1), though these differences were not statistically significantly different. B. sphaericus 21787 showed little ureolytic activity but was still capable of inducing some CaCO3 precipitation. Cell growth appeared to be inhibited during the period of CaCO3 precipitation. Transmission electron microscopy (TEM) images suggest this is due to the encasement of cells and was reflected in lower kurea values observed in the presence of dissolved Ca. However, biomass regrowth could be observed after CaCO3 precipitation ceased, which suggests that ureolysis-induced CaCO3 precipitation is not necessarily lethal for the entire population. The kinetics of ureolysis and CaCO3 precipitation with S. pasteurii was further analyzed under anaerobic conditions. Rate coefficients obtained in anaerobic environments were comparable to those under aerobic conditions; however, no cell growth was observed under anaerobic conditions with NO−3, SO2−4 or Fe3+ as potential terminal electron acceptors. These data suggest that the initial rates of ureolysis and ureolysis-induced CaCO3 precipitation are not significantly affected by the absence of oxygen but that long-term ureolytic activity might require the addition of suitable electron acceptors. Variations in the ureolytic capabilities and associated rates of CaCO3 precipitation between strains must be fully considered in subsurface engineering strategies that utilize microbial amendments.Item Darcy-scale modeling of microbially induced carbonate mineral precipitation in sand columns(2012-07) Ebigbo, Anozie; Phillips, Adrienne J.; Gerlach, Robin; Helmig, Rainer; Cunningham, Alfred B.; Class, Holger; Spangler, Lee H.This investigation focuses on the use of microbially induced calcium carbonate precipitation (MICP) to set up subsurface hydraulic barriers to potentially increase storage security near wellbores of CO2 storage sites. A numerical model is developed, capable of accounting for carbonate precipitation due to ureolytic bacterial activity as well as the flow of two fluid phases in the subsurface. The model is compared to experiments involving saturated flow through sand-packed columns to understand and optimize the processes involved as well as to validate the numerical model. It is then used to predict the effect of dense-phase CO2 and CO2-saturated water on carbonate precipitates in a porous medium.Item Reducing the risk of well bore leakage using engineered biomineralization barriers(2011-04) Cunningham, Alfred B.; Gerlach, Robin; Spangler, Lee H.; Mitchell, Andrew C.; Parks, Stacy L.; Phillips, Adrienne J.If CO2 is injected in deep geological formations it is important that the receiving formation has sufficient porosity and permeability for storage and transmission and be overlain by a suitable low-permeability cap rock formation. When the resulting CO2 plume encounters a well bore, leakage may occur through various pathways in the “disturbed zone” surrounding the well casing. Gasda et al. , propose a method for determining effective well bore permeability from a field pressure test. If permeability results from such tests prove unacceptably large, strategies for in situ mitigation of potential leakage pathways become important. To be effective, leakage mitigation methods must block leakage pathways on timescales longer than the plume will be mobile, be able to be delivered without causing well screen plugging, and be resistant to supercritical CO2 (ScCO2) challenges. Traditional mitigation uses cement, a viscous fluid that requires a large enough aperture for delivery and that also must bond to the surrounding surfaces in order to be effective. Technologies that can be delivered via low viscosity fluids and that can effectively plug small aperture pathways, or even the porous rock surrounding the well could have significant advantages for some leakage scenarios. We propose a microbially mediated method for plugging preferential leakage pathways and/or porous media, thereby lowering the risk of unwanted upward migration of CO2, similar to that discussed by Mitchell et al. .We examine the concept of using engineered microbial biofilms which are capable of precipitating crystalline calcium carbonate using the process of ureolysis. The resulting combination of biofilm plus mineral deposits, if targeted near points of CO2 injection, may result in the long-term sealing of preferential leakage pathways. Successful development of these biologically-based concepts could result in a CO2 leakage mitigation technology which can be applied either before CO2 injection or as a remedial measure. Results from laboratory column studies are presented which illustrate how biomineralization deposits can be developed along packed sand columns at length scales of 2.54 cm and 61 cm. Strategies for controlling mineral deposition of uniform thickness along the axis of flow are also discussed.Item Wellbore Leakage Mitigation Using Engineered Biomineralization(2014-12) Cunningham, Alfred B.; Phillips, Adrienne J.; Troyer, E.; Lauchnor, R.; Hiebert, R.; Gerlach, Robin; Spangler, Lee H.Research on microbially induced calcite precipitation (MICP) is reported. MICP may serve to reduce near-wellbore permeability, reduce CO2– related corrosion, and lower the risk of unwanted migration of CO2 or other fluids. MICP research on the lab scale has demonstrated the ability to seal sandstone cores using injection strategies engineered to control precipitation. Experimentation was also aimed at transitioning MICP strategies for field implementation. MICP was evaluated in the field in a hydraulically fractured sandstone formation at a Walker County, Alabama well. The field experiment resulted in greatly reduced injectivity indicating that the fractured formation was plugged after MICP treatment.