Maximizing energy efficiency in hydrocarbon extraction remains hampered by water channeling in heterogeneous reservoirs, where conventional pre-synthesized nanoparticles often fail due to the unresolved migration–aggregation dilemma. We report a novel strategy that addresses the long-standing migration–aggregation dilemma of pre-synthesized nanoparticles by enabling the in situ formation of functional silica nanonetworks directly within reservoir pore throats. Our approach employs a tetraethyl orthosilicate (TEOS) emulsion that, upon controlled demulsification, undergoes hydrolysis and condensation to generate silica nanoparticles in situ. Glycerol mediates dielectric tuning and modulates nanoparticle zeta potential, allowing precise control over particle size and distribution to match medium-to high-permeability zones (100–1000 mD). Displacement experiments demonstrate exceptional performance, achieving a water shutoff efficiency of over 90% while retaining more than 70% of oil-phase permeability. Mechanistic studies reveal that surfactants released during demulsification play a dual role. They enhance silica nucleation rate by reducing the interfacial energy barriers and adsorb onto nanoparticle surfaces, conferring strong hydrophobicity for selective water shutoff. Furthermore, the in situ-generated SiO2 nanoparticles form a stable three-dimensional plugging network through physical bridging, aggregation, and surfactant-mediated anchoring on rock surfaces. Compared to conventional high-viscosity systems, the ultra-low viscosity and in situ formation strategy of this system results in lower operational energy consumption. This strategy improves nanoparticle delivery efficiency and provides an energy-efficient approach for enhanced oil recovery.