Surfactant adsorption onto solid surfaces is a major issue during surfactant flooding in enhanced oil recovery applications; it decreases the effectiveness of the chemical injection making the process uneconomical. Therefore, it was hypothesized that the adsorption of surfactant onto solid surfaces could be inhibited using a surfactant delivery system based on the complexation between the hydrophobic tail of anionic surfactants and b-cyclodextrin (b-CD). Proton nuclear magnetic resonance spectroscopy was used to confirm the complexation of sodium dodecyl sulfate (SDS)/b-CD. Surface tension analysis was used to establish the stoichiometry of the complexation and the binding constant (K a ). Static adsorption testing was applied to determine the adsorption of surfactant onto different solids (sandstone, shale, and kaolinite). The release of the surfactant from the b-CD cavity was qualitatively evaluated through bottle testing. The formation of the inclusion complex SDS/b-CD with a 1:1 stoichiometry was confirmed. The K a of the complexations increases as salinity and hardness concentration increases. The encapsulation of the surfactant into the b-CD cavity decreases the adsorption of surfactant onto solid surfaces up to 79 %. Qualitative observations indicate that in the presence of solid adsorbents partially saturated with crude oil, the b-CD cavity releases surfactant molecules, which migrate towards the oil-water interface.

Surfactant adsorption onto solid surfaces is problematic in some industrial processes, such as in surfactant flooding for enhanced oil recovery. In this work, it was hypothesized that the use of a surfactant delivery system could prevent surfactant adsorption onto solid surfaces. Therefore, the encapsulation of sodium dodecyl sulfate (SDS) into the hydrophobic core of β-cyclodextrin (β-CD) to generate a surfactant delivery system (SDS/ β-CD) was evaluated in this work. This complexation was characterized using optical and scanning electron microscopy (SEM), and Fourier transform infrared spectroscopy (FT-IR). Dynamic adsorption evaluation was applied to determine the effectiveness of the complexation in inhibiting surfactant adsorption onto a variety of solid adsorbents including sand, and mixtures of sand-kaolin and sand-shale. Surfactant adsorption was also evaluated applying the quartz crystal microbalance technology (QCM-D). The formation and morphology of the complexation was confirmed by optical microscopy, SEM, and FT-IR. Dynamic adsorption tests demonstrated the effectiveness of the surfactant delivery approach in preventing the adsorption of surfactant (up to 74 % adsorption reduction). The QCM-D technology confirmed these observations. Several mechanisms were proposed to explain the inhibition of surfactant adsorption including steric hindrance, self-association of inclusion complexes, hydrophilicity increase, and disruption of hemimicelles formation.

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