Abstract
Surfactant tolerance in the presence of mono and divalent reservoir ions, as well as the solubility of surfactant in high salinity and low salinity brine, are the two major requirements for any surfactant that is subjected to oilfield application. Herein, six poly(ethylene oxide) zwitterionic surfactants having different ionic headgroups and hydrophobic tail were synthesized for oilfield applications. They were characterized by various instrumental techniques (Fourier-transform infrared spectroscopy (FTIR), matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-ToF-MS), Nuclear Magnetic Resonance (NMR)) and the combination of these techniques allowed for us to deduce the structure. All of the surfactants revealed prominent solubility in high salinity and low salinity brine due to the presence of ethoxy units between the aromatic ring and amide group. The surfactant samples were oven aged for 90 days at reservoir temperature and a clear solution implies their excellent aqueous stability. Rendering to thermal gravimetric results, decomposition of surfactants was found to occur around 300 °C, which is higher than the reservoir temperature (≥90 °C). It was observed that the hydrophilic headgroup has no significant impact on the critical micelle concentration and other surface properties. However, the hydrophobic tail bearing benzene ring significantly alters the critical micelle concentration and other surface properties.
Highlights
Surfactants are extensively applied in various oilfield applications, such as drilling fluid, well stimulation, filter cake removal, swelling inhibitor, corrosion prevention, fracturing, and enhanced oil recovery [1,2,3,4,5,6,7,8]
Scheme 1 represents the synthesis of zwitterionic surfactants (TEAC, tert-butylphenyl ethoxylate amidopropyl sulfobetaine (TEAS), Tert-Butylphenyl Ethoxylate Amidopropyl Hydroxy Sulfobetaine (TEAH), Nuclear Magnetic Resonance (NMR) of zwitterionic surfactant (NEAC), nonylphenyl ethoxylate amidopropyl sulfobetaine (NEAS), nonylphenyl ethoxylate amidopropyl hydroxy sulfobetaine (NEAH))
NEAC, NEAS, and NEAH were prepared by following a similar procedure using intermediate
Summary
Surfactants (surface active agents) are extensively applied in various oilfield applications, such as drilling fluid, well stimulation, filter cake removal, swelling inhibitor, corrosion prevention, fracturing, and enhanced oil recovery [1,2,3,4,5,6,7,8]. Kumar et al reported the adsorption, imbibition, and wettability alteration studies of zwitterionic surfactant on carbonate and sandstone rocks. Zhang et al synthesized gemini zwitterionic surfactant containing the sulfonic head group They emphasized that the gemini zwitterionic surfactant is a better choice when compared to positively charged gemini because of surfactants due to ultra-low sensitivity towards salts and it can be applied as a seawater-based clean fracturing fluid [16]. Six betaine based zwitterionic surfactants with various hydrophobic tail containing benzene ring and hydrophilic headgroups, namely: 4-tert-butylphenyl ethoxylate amidopropyl carboxybetaine (TEAC), 4-tert-butylphenyl ethoxylate amidopropyl sulfobetaine (TEAS), 4-tert-butylphenyl ethoxylate hydroxy sulfobetaine (TEAH), 4-nonylphenyl ethoxylate amidopropyl carboxybetaine (NEAC), 4-nonylphenyl ethoxylate amidopropyl sulfobetaine (NEAS), and 4-nonylphenyl ethoxylate amidopropyl hydroxy sulfobetaine (NEAH) were prepared. The amide functionality (-NH-C(O)-) is known to provide biodegradability, low CMC, and environmentally friendly properties [21]
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