Fabrication and characterization of microcapsule encapsulating EOR surfactants by microfluidic technique

During the process of enhanced oil recovery (EOR), surfactants are injected underground in order to draw more oil from the reservoir. Surface active agent molecules, however, can be easily absorbed by the pore surface of the reservoir rock, causing a massive waste. This paper introduces a novel method for designing a type of microcapsule loading EOR surface activator to solve the absorption problem for surfactants injection. The approach employs microfluidic technique to generate O/W/O double emulsion templates that can be used to fabricate hollowed microcapsules coupled with free radical polymerization. Factors including emulsifier concentrations, flow rates, viscosities and densities of the inner, middle and outer fluids which can affect the formation and morphology of emulsions and microcapsules have been systematically investigated and optimized as well. Additionally, morphological analysis confirms that the as-prepared monodisperse microcapsule has the capacity of encapsulating surfactant molecules owing to its hollowed structure. Finally, the diffusion permeability of the prepared microcapsules is examined, indicating that permeability of the microcapsule membrane can be controlled by adjusting the thickness and cross-linking degree of the microcapsule membrane. Overall, this study provides controllable and versatile preparation for this kind of microcapsule with potential in the field of enhanced oil recovery. The results can also provide valuable guidance for further investigation regarding the "smart" controllable release of EOR surface active agent.