Study on the stabilization mechanism of crude oil emulsion with an amphiphilic polymer using the β-cyclodextrin inclusion method

Abstract

To investigate the contribution of hydrophobic groups of hydrophobically modified polyacrylamide (HMPAM) to stabilizing crude oil emulsion, the β-cyclodextrin (β-CD) inclusion method based on host–guest interaction is proposed. Dynamic light scattering is employed to study the stability of O/W emulsions prepared by HMPAM and inclusion complexes. The emulsions are evaluated in terms of droplet size distribution, rheological properties and interfacial tension. It is found that the stability of emulsions stabilized by HMPAM decreases with the increase of β-CD, indicating that β-CD can effectively shield the hydrophobic groups in the emulsification process of crude oil through the formation of an inclusion complex. Consequently, the network structure composed of associated amphiphilic polymers is destroyed, resulting in released polymer molecules with none of the hydrophobic groups. Moreover, the emulsion stabilizing mechanism of HMPAM with different β-CD amounts is discussed. Based on Turbiscan Stability Index (TSI) analysis, the contribution degree of the hydrophobic group of HMPAM in stabilizing emulsions (EC_h) is determined for the first time. The emulsifying ability of amphiphilic polymers is mainly attributed to the hydrophobic groups (EC_h > 80%) of the amphiphilic polymers while the concentration of HMPAM is above the critical aggregation concentration (CAC). This research provides theoretical guidance for studying the emulsification and de-emulsification mechanism of emulsions stabilized by amphiphilic polymers which are widely applied in tertiary oil recovery.