# Progress on the Application of Nanomaterial Expansion in Oil Displacement
## 1 Introduction
[18] reported that carboxyl/alkyl composite silica hydrophilic Janus nanosheets achieved an 18.31% improvement in sweep efficiency. [PERSON] et al. [19] engineered water-in-oil (W/O) and oil-in-water (O/W) emulsion systems by tuning the hydrophilic-hydrophobic domain ratio of Janus particles. However, limited studies exist on Janus nanoparticle-stabilized O/W/O triphase Pickering emulsions and their EOR applications. Concurrently, mechanistic insights into silica nanoparticle-driven conformance control and capillary-driven oil mobilization remain underexplored. Expansion oil recovery technology involves injecting nanomaterials into reservoirs to improve oil recovery efficiency. Due to the influence of nanomaterials, the expanded crude oil is more easily stripped and migrated in the pores. The application of nanomaterials provides possibilities for the further exploitation of remaining oil in low-permeability reservoirs. Current challenges in low-permeability reservoir development include escalating injector wellhead pressures and declining fluid intake capacities; producer wells exhibit suboptimal performance, significant reservoir pressure depletion, and acute productivity decline, leading to diminished waterflood rates, hydrocarbon yields, production velocities, and recovery factors [20; 21; 22]. Concurrently, severe fracture-dominated water channeling and coning occur, while injectors distal to fracture networks demonstrate negligible sweep efficiency--summarized as \"inaccessibility to injection, unviable production, and ineffective conformance control\" [23; 24; 25]. Throughout reservoir management evolution, a diversified innovation framework has emerged, integrating techniques such as microbial enhanced oil recovery (MEOR), polymer conformance flooding, composite chemical EOR, gas miscible injection, thermal stimulation [26; 27], and swelling-based displacement technologies. Afterdecades of field trials and refinements, these methods have gained broad acceptance across upstream operators, significantly elevating ultimate recovery rates. The expansion oil displacement technology injects special materials into the reservoir. Due to the influence of special materials, the expansion of crude oil is more likely to fall off from the rock wall or dead pores, and the material itself causes little harm to the environment [28; 29]. As shown in Figure 1, this paper summarizes the research results of nano-oil displacement technology in recent years from three aspects: the principle of using nanomaterials to enhance oil recovery, the mechanism of nanomaterial expansion and oil displacement, and the future research prospects of nanotechnology. The mechanism of nano-oil displacement technology to improve oil recovery is mainly introduced, and the related experimental research is deeply analyzed. At the same time, the mechanism of enhanced expansion of nano-silica oil droplets is deeply studied. The application status of nanomaterials in complex reservoirs is summarized, and its development trend is prospected. This study provides an important reference for the practical application and future development of nano-expansion profile control technology. Figure 1: Nanomaterials in enhanced oil recovery: principles, mechanisms, and prospects [30].