Browsing by Author "Scheffer, Gabrielle"

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    Enzymatic degradation of carboxymethyl cellulose – A biotechnological approach for hydraulic fracturing operations
    (2019-12-19) Scheffer, Gabrielle; Gieg, Lisa Marie; Ng, Kenneth Kai Sing; Sen, Arindom
    Carboxymethyl cellulose (CMC) is a polymer used in different industrial sectors. In the oil and gas industry, CMC is often used during hydraulic fracturing (fracking) operations as a thickening agent helping for proppant delivery. Accumulations of CMC at fracture faces (filter cakes) can impede oil and gas recovery. Although chemical oxidizers are added to disrupt these accumulations, there is industrial interest in developing alternative, enzyme-based treatments. Little is known about whether CMC can be biodegraded under fracking conditions. Here, we enriched a methanogenic CMC-degrading culture, and demonstrated its ability to express extracellular enzymes able to utilize CMC under various conditions that typify oil fields. Finally, isolation and purification of the enzymes allowed for complete degradation of the polymer within 3 h, and allowed for the identification of putative purified cellulases. This study demonstrates that enzyme technology holds great promise as a viable approach to treating CMC filter cakes under field conditions.
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    Prevalence, persistence and consequences of microorganisms within oil field environments and mitigation strategies
    (2024-05-14) Scheffer, Gabrielle; Hubert, Casey; Gieg, Lisa; Wrighton, Kelly
    The deep biosphere is home to an abundance of microorganisms. However, limitations to accessing deep subsurface samples means that very little is known about microorganisms from the marine and terrestrial subsurface. Oil and gas industry technologies, including advancements in hydraulic fracturing and horizontal drilling, have increased access to samples for environmental microbiology, enabling microorganisms inhabiting those ecosystems to be studied. It is now better understood that microorganisms must withstand extreme conditions (high temperatures, high salinities, high pressures and the presence of toxic metals). Furthermore, these “extremophiles” can significantly impact oil production operations both negatively (i.e., reservoir souring) and positively (i.e., reservoir souring control). To date, most microbiology studies of hydraulically fractured hydrocarbon reservoirs have been performed on a limited number of unconventional shale formations in the United States (e.g., the Marcellus Formation) and do not represent the geological conditions in other unconventional formations. This work focuses on less studied unconventional tight formations in the Permian Basin Formation (United States) and the Montney Formation (Canada), as well as a conventional high salinity reservoir in the Gulf of Mexico. While it is known that microorganisms influence the oil and gas operations (souring, corrosion, bioplugging), their provenance remains a debated topic. It is unresolved whether microorganisms are pre-existing deep biosphere residents of unconventional formations or if they are introduced by the oil and gas operations. Results presented in this thesis demonstrate that some microorganisms are found in the Montney Formation prior to industrial intervention, featuring genome-encoded adaptations to the extreme conditions in this reservoir. Introduced microorganisms still play a major role in souring and corrosion, which can be mitigated by other microorganisms through nitrate addition to oil field systems.