Magnetic quantum dots-stabilized foam fluid for enhanced oil recovery

Nanoparticle-stabilized foam fluid provided excellent efficiency in tertiary oil recovery, and a more appealing technique is to exploit reusable low-dimensional nanomaterials, which can achieve better oil-displacement efficiency during the period of global decarbonization. Herein, the magnetic quantum dots (MQDs) were synthesized and then modified by a silane-coupling ionic liquid (SIL) to produce unique quantum dots MQDs@SIL. A series of characterizations and foaming measurements reveal that MQDs@SIL with an average surface grafting density of 1.01 functional chains nm(-2) at an ultra-low concentration (0.005 wt%) demonstrated distinct foam stability and salt resistance capability, as well as a unique defoaming performance in a constant magnetic field for regulated foam performance at high temperature. The stretched-straight functional chains and adequate hydrophilic-hydrophobic surface of MQDs@SIL substantially favor the nonreversible adsorption of MQDs@SIL on the gas-liquid interface, leading to an increased surface elasticity, and thus an enhanced foam stability. MQDs@SIL-stabilized foam liquid demonstrated exceptional plugging performance and achieved an enhanced oil recovery of 18.2 % in the stage of foam fluid flooding, exceeding most nanoparticle-stabilized foam fluids ever reported. Furthermore, MQDs@SIL with the unique magnetic property provided unique recycling and reusing benefits, emphasizing their potential applications for enhanced oil recovery.