Theses and Dissertations at Montana State University (MSU)
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Item Urease immobilization for advancing enzyme-induced calcium carbonate precipitation applications(Montana State University - Bozeman, College of Engineering, 2019) Frieling, Zachary James; Chairperson, Graduate Committee: Robin Gerlach and Adrienne Phillips (co-chair)Microbially induced calcium carbonate precipitation (MICP) is a widely studied field of research exploiting bacterial activity to form a calcium carbonate precipitate that has been used to modify porous media. MICP is an enzymatically driven process and uses the enzyme urease to change solution chemistry to favor calcium carbonate precipitation. An enzyme slurry can be used in lieu of microbial growth and can be applied in a similar fashion and is commonly referred to as enzymatically induced calcium carbonate precipitation (EICP). For some applications temperature can stunt microbial growth and EICP may be the preferred method. However, as the temperature increases further the urease enzyme is thermally inactivated inhibiting calcium carbonate precipitation. Thermal inactivation limits the potential use of EICP in higher temperature environments. To combat thermal inactivation, immobilization of the urease enzyme through entrapment in silica gel and adsorption on an internally porous ceramic proppant was evaluated, and the first order inactivation coefficient (kd) was determined for temperatures between 60°C and 90°C. It was found that immobilization of the urease enzyme drastically reduced the apparent k d when compared to the free, non-immobilized form. Column experiments were performed using the urease immobilized on the ceramic proppant at room temperature (~23°C) and at 60°C. It was found that the immobilized urease retained high activity for the duration of the experiments even when subjected to the elevated temperature condition. The immobilized form of the urease enzyme was indeed protected from thermal degradation. It also seemed that the immobilized form of the urease enzyme was shielded from inactivation from active calcium carbonate precipitation, as observed in previous EICP and MICP experiments, in which ureolytic activity decreased rapidly as calcium carbonate precipitated. As a result, the immobilized form of the urease enzyme showed promise for advancing EICP applications.Item A study of bio-mineralization for the application of reducing leakage potential of geologically stored CO 2(Montana State University - Bozeman, College of Engineering, 2019) Daily, Ryanne Leigh; Chairperson, Graduate Committee: Adrienne PhillipsA primary concern of carbon capture and storage (CCS) is leakage of the stored carbon dioxide (CO 2) from the subsurface back to the surface. To ensure long term storage of the CO 2, mitigation strategies are being developed to seal high permeability regions, such as fractures present in the caprock or the near wellbore environment. Ureolysis induced calcium carbonate precipitation (UICP) is a widely investigated technology utilizing the enzymatically driven process of ureolysis to alter the properties of porous media. The advantage of this technology over traditional fracture sealing methods, such as well cement, is the use of low-viscosity aqueous fluids enabling access to smaller fractures. However, CCS reservoirs provide a problematic environment for microbial activity due to the acidity of dissolved CO 2, high pressures, and elevated temperatures. A flow-through pressurized reactor experiment and batch high-pressure ureolysis rate experiments were conducted to investigate the application of UICP technology to mitigate CO 2 migration. First, UICP was induced in two composite rock cores in an environment simulating a CCS reservoir, using a high-pressure axial flow reactor, with an initial and final exposure of the rock cores to a carbonated brine. As a result of UICP, the apparent permeability of the rock cores were reduced by 5-orders of magnitude. The CO 2 challenge increased apparent permeability by 4-orders of magnitude, likely due to a preferential flow path created through the calcium carbonate (CaCO 3) seal, which was found with X-ray microcomputed tomography (micro-CT) imaging. The porosity of the composite rock cores was assessed throughout the experiment with two non-invasive technologies, micro-CT and nuclear magnetic resonance (NMR), both reported a significant decrease in porosity due to UICP and a slight increase after the CO 2 exposure. Second, ureolysis kinetics were assessed in the presence of a pressurized carbonated brine at pressures between 0 and 4 MPa. The kinetic studies were performed in a high-pressure batch reactor connected to high-pressure pH and conductivity probes. Samples could not be taken from the batch reactor without losing pressure; thus, conductivity was used as a surrogate measurement for urea concentration. It was found that, for the pressures tested, JBM urease was capable of hydrolyzing urea in the presence of a pressurized carbonated brine. It was also hypothesized that the rate observed at each experimental pressure may have been dependent on the buffered pH of the system. The combination of these studies suggests that, if the challenge of dissolution could be overcome, bio-mineralization may be used to enhance CCS by reducing the permeability of CO 2 leakage pathways.Item Kinetics of thermally inactivated ureases and management of sand production through ureolysis-induced mineral precipitation(Montana State University - Bozeman, College of Engineering, 2018) Morasko, Vincent John; Chairperson, Graduate Committee: Robin Gerlach; Adrienne Phillips (co-chair)Biocement has the potential to seal subsurface hydraulic fractures, manipulate subsurface flow paths to enhance oil recovery, treat fractured cement, stabilize soil structures and minimize dust dispersal. Biocement can be formed using the urease enzyme from various sources (bacteria, plant, or fungi) to break down urea into carbonate, combining with calcium for use in engineering applications such as biocement production. Higher temperatures, pressures, and extreme pH conditions may be encountered as these engineering applications expand deeper into the subsurface. Temperatures beyond 1000 meters can exceed 80°C, potentially rapidly inactivating the enzyme. The first part of this study focused on monitoring urea hydrolysis catalyzed by jack bean urease at temperatures ranging from 20-80°C. An increasing rate of urease inactivation was observed with increasing temperatures and first-order models described the kinetics of urea hydrolysis and enzyme inactivation properly. The second part of this study focused on developing a technology to mitigate sand transport in oil and gas wells. This study addressed a method to cement sand in the subsurface so that it is not returned when oil or gas is extracted. As the sand leaves the formation, it can cause damage in the subsurface, leading to economic concerns, as well as reducing the lifespan of pumps, piping and other components on the well pad. A reactor system was developed to mimic a subsurface oil well that produces sand. Biocement production was promoted within the reactor, utilizing common sources of urease (Sporosarcina pasteurii and Canavalia ensiformis or jack bean meal). The resultant calcium carbonate/sand mass was subjected to elevated flowrates, simulating field conditions where sand is potentially fluidized and potentially transported into the wellbore. It was shown that biocement can reduce sand transport while allowing for higher flow rates than conditions without biocement. The findings from this study broaden the potential application range of biocementation technologies into higher temperature environments. Applying biocement specifically to sand mitigation may have significant environmental, economic, and safety implications within the natural resource industry.