MS Thesis Defense, by Vincent Morasko, ChBE
- Thursday, April 26, 2018 from 9:00am to 10:00am
- Cobleigh Hall, 429 - view map
"Thermally Inactivated Enzymes and Sand Control," by Vincent Morasko
ABSTRACT: Biocement has the potential to seal subsurface hydraulic fractures, manipulate subsurface flow paths to enhance oil recovery, treat fractures in well bore cements, stabilize soil structures and minimize dust dispersal. Biocement can be formed using an enzyme from various sources (bacteria, plants, or fungi) to break down urea into smaller units to be combined with calcium, ultimately for use in engineering applications. Higher temperatures, pressures, and extreme pH conditions may be encountered as these engineering applications expand deeper into the subsurface. Temperatures at these depths can reach beyond 100°C, which can immediately inactivate the enzyme. This research is focused on understanding how biomineralization occurs within the 20-80°C range using the plant-based source of the urease enzyme Canavalia ensiformis (jack bean) to model the thermal inactivation of the enzyme. Three different mathematical models were explored to determine the most computationally simple but accurate model. A first-order enzyme inactivation mechanism provided the best fit among the models tested; series, series-parallel, and first order inactivation. Additional research was conducted to potentially mitigate sand transport in oil and gas wells. This study addresses a method to cement proppant sand in the subsurface so that it does not return when oil or gas is extracted. The returned sand can cause damage in the subsurface, leading to economic concerns, as well as reducing the lifespan of pumps and pipes within the surface infrastructure. A reactor system was developed to simulate the subsurface oil well space filled with proppant sand. Biocement production was promoted within the reactor, utilizing common sources of urease (Sporosarcina pasteurii and jack bean meal). The resultant calcium carbonate/proppant sand mass was subjected to high flowrates, simulating field conditions where proppant sand potentially is fluidized, migrating out of the annular space. It was shown that microbially induced calcium carbonate precipitation can reduce the movement of proppant sand while allowing for fluid passage. The findings from this research will broaden the application range of urea-hydrolysis-induced calcium carbonate precipitation technologies into higher temperature environments. Applying calcium carbonate precipitation specifically to proppant sand mitigation may have significant environmental, economic, and safety implications within the natural resource industry.