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Novel experimental evidence on the impact of surface carboxylic acid site density on the role of individual ions in the electrical behavior of crude oil/water

Farhadi, H ; Sharif University of Technology | 2022

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  1. Type of Document: Article
  2. DOI: 10.1016/j.molliq.2022.119730
  3. Publisher: Elsevier B.V , 2022
  4. Abstract:
  5. Perceiving the electrical behavior of the rock/brine and the crude oil/brine interfaces gives insight into the performance of engineered waterflooding. Compared to the rock surface, few studies have attempted to comprehend the complex behavior of the crude-oil surface electrical behavior. To reveal the impact of each ion on the surface charge of crude oil, the zeta potential of crude oil/single-salt brines (including NaCl, CaCl2, MgCl2, Na2SO4, and NaHCO3) was measured in a wide range of salinity. Then, the counterpart interfacial tension (IFT) was measured to determine the capability of each brine in bringing carboxylic acid groups from crude-oil bulk (COOH) to crude oil/brine interface (>COOH). Based on the values obtained for the zeta potential and IFT, chloride and sulfate ions show neutral affinity toward the charge of the crude-oil surface. The results showed that an increase in Ca2+ and Mg2+ results in higher values for zeta potential, which approves the adsorption of these divalent ions on the crude-oil surface. Also, the tendency of Mg2+ to be adsorbed on the >COO– sites is less than that of Ca2+ ions. The role of calcium and magnesium in crude oil/brine electrical behavior is not significantly affected by the variation of >COOH. On the contrary, the impact of Na+ on the zeta potential varies for different trends of >COOH density vs. salinity. In the case of constant IFT values for different salinities, an increase in Na+ concentration leads to higher zeta potential. The observed behavior is attributed to the shrinkage of the electrical double layer due to the higher ionic strength. Based on the results, an increase in Na+ does not lead to an increase in Na+ adsorption on the >COO–. Therefore, similar to Cl− and SO42−, Na+ is also neutral specious toward the charge of the crude-oil surface. However, as IFT decreases with salinity, an increase in Na+ concentration leads to a significant reduction of the zeta potential. The observed behavior is attributed to the transport of more carboxylic acid groups to the interface for the low IFT condition. © 2022 Elsevier B.V
  6. Keywords:
  7. Interfacial tension ; Ionic strength ; Magnesium compounds ; Oil well flooding ; Sodium bicarbonate ; Sodium chloride ; Sodium sulfate ; Sulfur compounds ; Surface charge ; Surface tension ; Zeta potential ; Acid site density ; Ca 2+ ; Carboxylic acid groups ; Crude oil/brine interface ; Electrical behaviors ; Engineered water flooding ; Experimental evidence ; Floodings ; Na concentration ; Surface electric charge ; Crude oil
  8. Source: Journal of Molecular Liquids ; Volume 362 , 2022 ; 01677322 (ISSN)
  9. URL: https://www.sciencedirect.com/science/article/abs/pii/S0167732222012685