High-efficiency CO2 capture and oil displacement by amine-engineered silica nanofluids enabling advanced CCUS

Abstract

The escalating global demand for energy and the urgent need to mitigate climate change have spurred the development of next generation carbon capture utilization and storage (CCUS) techniques. This study introduces novel amine-functionalized silica nanoparticles (PEI@SiO₂-KH550 NPs) as a high-performance CO₂ carrier for CCUS applications. The nanoparticles were synthesized via a facile two-step modification process: grafting 3-aminopropyltriethoxysilane (KH550) onto silica nanoparticles, followed by coating with polyethyleneimine (PEI). This design significantly enhances CO₂ absorption capacity by enriching the surface amine groups, so more CO₂ will be carried into the target formation, interact with the oil and be stored underground. The resultant nanofluid (0.8 wt% concentration) demonstrated exceptional CO₂ uptake (∼100 cm³ under ambient conditions in 40 minutes) and dispersion stability (zeta potential: +38.21 mV). Rheological analyses revealed its shear-thinning behavior, ensuring injectivity in porous media. Remarkably, CO₂-saturated nanofluid reduced the dynamic interfacial tension (IFT) between crude oil and water from 19.24 mN m⁻¹ to 7.82 mN m⁻¹, primarily attributed to nanoparticle adsorption at the oil–water interface and in situ generation of surface-active carbamates. In addition, the pressure drop experiment revealed that the presence of PEI@SiO₂-KH550 in the aqueous phase could significantly promote the CO₂ diffusion rate and facilitate the mass transfer. Besides, molecular dynamics simulations demonstrated that PEI@SiO₂-KH550 enhanced the CO₂ saturated-nanofluid/crude oil interaction through impacting the interfacial energy (IFE), the radial distribution function (RDF) of light and heavy oil components, the interface thickness and the CO₂ diffusion coefficient. Core flooding experiments validated the dual effectiveness of the developed nanofluid, achieving 79.8% oil recovery (10% higher than the carbonated water) and 48.6% CO₂ sequestration rate (16.7% higher than carbonated water). The innovation lies in the nanoparticles' scalable synthesis, dual functionality (CO₂ capture and interfacial modification), and compatibility with harsh reservoir conditions. This work may provide enlightening insights for integrating CO₂-enhanced oil recovery (EOR) with CO₂ geological storage, advancing next-generation CCUS technology.