Feasibility Study of a Nanoparticle as a Conformance Control Agent in CO2 Flooding Reservoirs

Excessive CO2 emissions cause global warming, while CO2 interaction with crude oil can enhance oil recovery (EOR). To capture and reuse CO2, nano-SiO2 was cationically modified to synthesize nanoparticles (SCR2). The structure and performance of SCR2 were characterized by FT-IR, DLS, and TEM, confirming its excellent CO2 adsorption capacity and surface activity. Compared with unmodified nano-silica, SCR2 increased CO2 adsorption capacity by 254.3% and reduced the core surface contact angle from 112.1° to 24.5°. Core flooding experiments showed that in low-permeability reservoirs, SCR2 achieved a plugging rate of 87.5%, an enhanced oil recovery of 24.8%, and an ultimate oil recovery of 74.8% (23.8% higher than unmodified nano-silica). Mechanistically, SCR2 plugs gas channeling pathways via its inherent nanoparticle properties and adsorption of dissolved CO2 in the aqueous phase while improving rock surface wettability, thereby enhancing sweep efficiency and total oil recovery during CO2 flooding. This study provides a promising approach for EOR and CO2 resource utilization in low-permeability reservoirs.