Atomistic insight into oil displacement on rough surface by Janus nanoparticles

Janus nanoparticles (NPs) hold great potential in enhanced oil recovery (EOR), although the mechanism remains unclear. In the study, the displacement dynamics of trapped oil in the rough channel by Janus NPs are unraveled through atomistic modeling. The results indicate that Janus NPs with large polar faces significantly recover more oil from the nano-pocket (nano groove of the surface). The structure of adsorbed NPs on the wall of oil-trapping nano-pockets strongly causes the local wettability alteration, which ultimately determines the oil recovery. The crucial events in oil recovery by Janus NPs, termed 'adsorption invasion process', are identified, which comprise of anchoring onto the surface, pinning at the edge, and entering inside the pocket. The controlling factors are further detailed, including identification of the residual oil, displacement pressure, and the geometry of the oil-water interface inside nano-pockets. With the proposed analysis, the "huff-n-puff" mode is verified as the optimized application method for Janus NPs. For the first time, our results bring to light the dynamic wettability alteration on the rough surface by Janus NPs from atomistic insights. The findings reveal the intrinsic EOR mechanism of Janus NPs, which could guide the design and application of Janus NPs in EOR.(c) 2022 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).