Complexation of Surfactant/β‐Cyclodextrin to Inhibit Surfactant Adsorption onto Sand, Kaolin, and Shale for Applications in Enhanced Oil Recovery Processes. Part II: Dynamic Adsorption Analysis

Abstract

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.

Formulation of an Encapsulated Surfactant System, ESS, via β-CD Host–Guest Interactions to Inhibit Surfactant Adsorption onto Solid Surfaces

“…This clearly explains the higher incremental oil recovery obtained during ESS flooding. These experimental observations are in agreement with previous research. , …”

“…All sand-pack displacement tests achieved on average 62.3% oil recovery during the first waterflooding step (i.e., bottom water drive). This recovery % is in agreement with the characteristic oil recovery percentage during waterflooding, which ranges from 35% to 75% of the original oil in place (OOIP). , …”

“…According to Paria and Khilar (2004), the adsorption of surfactants at the solid–liquid interface takes place in an oriented manner that depends on the packing of the molecules, mutual repulsion, and steric constrains among the adsorbed surfactant molecules. Therefore, it is hypothesized that the encapsulation of anionic surfactants into the cavity of the bulky β-CD structure inhibits the adsorption of the surfactants onto the surface of solid surfaces (i.e., sand and kaolin) due to steric hindrance effects, which disrupt the organized formation of monolayers or bilayers of surfactant molecules adsorbed at the surface by impeding polar heads from reaching the adsorption sites on the solid surfaces (i.e., sand and kaolin surfaces) and by hindering chain interactions between the adsorbed surfactant molecules (i.e., alkyl chains), among other mechanisms previously discussed. ,,− Figure shows hypothetical schematics of the inhibiting effect of steric hindrance due to surfactant encapsulation onto the solid surfaces.…”

“…In the field of EOR, β-CD has been applied as an additive to modify the wettability of the porous media, , to formulate polymer/β-CD/surfactant systems for polymer flooding as mobility control agents, − and for the encapsulation of surfactants as surfactant carrier systems for surfactant flooding − to advance oil recovery. Readers are referred to refs , , and − and references therein for further details.…”

“…In the field of EOR, β-CD has been applied as an additive to modify the wettability of the porous media, , to formulate polymer/β-CD/surfactant systems for polymer flooding as mobility control agents, − and for the encapsulation of surfactants as surfactant carrier systems for surfactant flooding − to advance oil recovery. Readers are referred to refs , , and − and references therein for further details. Even though more research on the use of cyclodextrins for EOR applications is justified to gain more insights on this area of study, this body of research demonstrates the feasibility of cyclodextrins as advantageous additives for EOR.…”