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Investigating the adsorption of select polar functionalities with the aqueous electrolyte/amorphous silica interface to understand the 'low salinity' effect
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Desmond, Jasmine L. (2015) Investigating the adsorption of select polar functionalities with the aqueous electrolyte/amorphous silica interface to understand the 'low salinity' effect. PhD thesis, University of Warwick.
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Official URL: http://webcat.warwick.ac.uk/record=b2866404~S1
Abstract
Low-salinity enhanced oil recovery (EOR) uses low-salinity seawater in the water flooding of sandstone reservoirs to maximise oil yields. Because oil is strongly adsorbed onto mineral surfaces, understanding the interactions involved at the oil/mineral interface, and how to weaken them, is crucial to design more efficient, low-cost EOR.
This thesis focuses on the influence of electrolyte concentration on the interaction of alkylammonium (R-NH+3) and alkylcarboxylic acid/carboxylate (R-COOH/COO- functionalities, present in crude-oil, with the amorphous silica (mimic for quartz grains in sandstone)/aqueous electrolyte interface. Both computational (molecular dynamics, MD) and experimental (chemical force mapping atomic force microscopy, CFM-AFM) techniques were used.
Firstly (Chapter 3), we tested the inter-operability of the new SPC/Fw water force-field with CHARMM. No significant differences were found between the data generated from SPC/Fw-CHARMM and TIPS3P-CHARMM, therefore the latter, computationally more efficient, was used in Chapters 4-6.
The behaviour of the four electrolyte solutions at two concentrations was tested in Chapters 4-5 (NaCl, KCl, CaCl2 and MgCl2 at 0.1 and 0.3 M); interfacial ion and water structuring has been investigated in Chapter 4, while the effect of the electrolytes on the adsorption of R-NH+3) and alkylcarboxylic acid/carboxylate (R-COOH/COO- was explored in Chapter 5. Interfacial ion concentration was greatest in the CaCl2 case, with various long-lived surface-site types involving different combinations of ions identified. CFM-AFM showed a substantial concentration-dependent difference in adhesion
for R-NH+3 in CaCl2 and R-COOH/COO- in the divalent ion solutions.
The free energy of adsorption for NH+3 CH3 was investigated using metadynamics. Force curves were calculated from the generated free energy profiles. The greatest force is, indeed, observed for one particular surface-site type in CaCl2 solution, prevalent in more concentrated solutions.
Finally, a more sophisticated computational model for the experimental AFM tip, a small array of S(CH211NH3+, is presented in Chapter 6, laying the basis for future work.
Item Type: | Thesis (PhD) | ||||
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Subjects: | Q Science > QD Chemistry | ||||
Library of Congress Subject Headings (LCSH): | Enhanced oil recovery | ||||
Official Date: | September 2015 | ||||
Dates: |
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Institution: | University of Warwick | ||||
Theses Department: | Department of Chemistry | ||||
Thesis Type: | PhD | ||||
Publication Status: | Unpublished | ||||
Supervisor(s)/Advisor: | Walsh, Tiffany R. ; Rodger, P. Mark | ||||
Extent: | xxix, 240 leaves : charts | ||||
Language: | eng |
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