Janus nanographene oxide with aerophilic/hydrophilic characteristics for enhancing foam stability in high-temperature reservoirs

Abstract

Foam technology is currently recognized as one of the most promising technical means to further enhance oil recovery. However, the poor stability of foam in harsh reservoirs with high temperatures limits the further application of foam fluids in oil fields. Based on the Pickering emulsion template method, this paper proposed a synthesis strategy for Janus nanographene oxide with aerophilic/hydrophilic characteristics as a novel foam stabilizer. A high-stability foam reinforced by Janus nanographene oxide was constructed. In addition, this paper clarified the relationship between foam stability and the interfacial characteristics of foam and revealed the probable mechanism by which Janus nanographene oxide enhances foam stability. The results showed that the synthesized Janus nanographene oxide has a typical two-dimensional lamellar structure with an obvious asymmetric characteristic. The negatively charged Janus nanographene oxide showed a small particle size, high ζ potential, high thermal stability, satisfactory amphiphilicity, and high interfacial adsorption, which was beneficial for enhancing foam stability at high temperatures. The foam stability was positively correlated with the interfacial viscoelastic modulus of the foam. Janus nanographene oxide was irreversibly adsorbed onto the gas–liquid interface, which increased the interfacial viscoelastic modulus, especially the interfacial elastic modulus increased from 2.94 mN·m−1 to 16.21 mN·m−1. As a result, the ability of the foam to resist deformation due to external forces was enhanced, which can be reflected in the enhancement of the foam stability. The half-life of foam at high temperature increased from 26 min to 49 min. An appropriate amount of Janus nanographene oxide can form a solid-like film with high mechanical strength on the gas–liquid interface and gradually fill the Plateau boundary of the foam. It can not only effectively reduce the drainage rate of the liquid film but also hinder gas diffusion between adjacent bubbles, which delays the further thinning of the film and coarsening behavior of the foam. Therefore, the constructed reinforced foam can be considered as a promising candidate for further enhancing oil recovery in high-temperature reservoirs, especially for steam channeling control. In addition, this work contributes to a better understanding of the mechanism by which Janus nanomaterials can enhance foam stability and provides theoretical guidance for the further application of foam technology.