Application of a novel amphiphilic polymer for enhanced offshore heavy oil recovery: Mechanistic study and core displacement test

A molecular modified polyacrylamide with Gemini surfactant monomers, named as HA1, was evaluated in this paper as an alternative to enhance the offshore heavy oil recovery. The physical properties of HA1 solution including apparent viscosity, rheological properties, static adsorption, interfacial activities (IFT, interfacial visco-elasticity and contact angle), emulsification ability, as well as oil recovery capacity were comprehensively investigated. Our results indicate that due to the hydrophobic and Gemini surfactant monomers on the acrylamide backbone, this novel amphiphilic polymer possesses more advanced functions than conventional polymers. HA1 demonstrates pronounced aqueous-phase viscosifying ability by forming 3D network in solution when the concentration is above CAC. In addition, the IFT, interfacial visco-elasticity and contact angle response illustrate that HA1 interacts strongly with the oil-phase which gives rise to its significant interfacial activity. Thereby, HA1 is able to reduce the heavy oil viscosity by emulsifying oil into water phase even at relatively low water content (20%) and also avoids dehydration difficulty by reducing the oil-brine interfacial rigidity. Furthermore, the asphaltene morphology change due to HA1 observed by SEM and AFM proves that HA1 can disperse the asphaltene aggregates in the crude oil, leading to a direct reduction of the heavy oil viscosity. At last, the coreflooding in an artificially synthesized triple-layered porous media shows that HA1 gives rise to an additional oil recovery of 27.04%, at the optimum concentration of 1600 ppm, by improving sweep efficiency, microscopic efficiency and dispersion of the asphaltene aggregates. Therefore, the potential of HA1 to enhance heavy oil recovery is comparable to traditional multi-component polymer-surfactant flooding. Since HA1 is single-component, it can also mitigate incompatibility issues like chromatography separation and surfactant-polymer interactions. Overall, this new self-assembly system shows potential for applications in heavy oil recovery.