Potential application of novel amphiphilic Janus SiO2 nanoparticles for stable Pickering emulsion and enhance oil recovery

To improve the stability of Pickering emulsion under harsh reservoir conditions, polymer-grafted amphiphilic Janus SiO 2 particles were prepared via atom transfer radical polymerization (ATRP) on the phase interface . Two novel Janus SiO 2 particles (JSN-1 and JSN-2) have HLB values of ∼13 and ∼14, respectively, so both can form O/W emulsions. Pickering emulsions stabilized by JSN-1 and JSN-2 were characterized by Turbiscan stability index (TSI), emulsification index (EI), optical microscopy, and interfacial dilation elasticity (E′). Experimental results showed that the emulsion stabilized by JSN-2 showed better stability than JSN-1. The EI of 0.1 wt.% JSN-2 was ∼5 % and ∼50 % higher than that of JSN-1 and nano-SiO 2 after standing for 100 min, with a 3.2 % decrease at 90 °C. With the vibration frequency of 0.01 ∼0.1 Hz, E′ enhanced as the JSN concentration increased from 0.1 wt.% to 0.5 wt.%. The droplets were stabilized through the formation of a particle network. JSN-2 with a softer chain end had a larger E′ at the phase interface than JSN-1, resulting in more stable emulsion droplets. Atomic force microscopy (AFM) test showed that the adhesion forces between JSN and rock were 25 nN and 39 nN, respectively. The outcome indicated that the effective adsorption of JSNs altered rock wettability . Therefore, the Pickering emulsions of JSNs had great potential in EOR . The cumulative oil recovery of Pickering emulsions was about 1.8 times higher than that of nanofluid, and the recovery factor increased by 33−36 %.