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Hybrid Nanoparticle-Surfactant Stabilized Foams for CO2 Mobility Control at Elevated Salinities
- Publisher: European Association of Geoscientists & Engineers
- Source: Conference Proceedings, IOR 2021, Apr 2021, Volume 2021, p.1 - 14
Abstract
A major problem during CO2 enhanced oil recovery (EOR) and CO2 storage is reservoir heterogeneity and the high mobility of CO2 relative to reservoir fluids. Surfactant-stabilized CO2 foams are a viable method for mitigating the impacts of reservoir heterogeneity and reducing CO2 mobility. However, surfactant-stabilized foams can breakdown at harsh reservoir conditions with elevated temperatures, salinities and pH. The addition of silica nanoparticles to the surfactant-stabilized CO2 foam has gained attention for increasing the foam strength and stability at harsh conditions. Therefore, this work includes nanoparticles in the surfactant-based CO2 foam to evaluate their ability to increase foam stability at harsh conditions. The primary objective was to systematically determine the effect of salinity on hybrid nanoparticle-surfactant, surfactant-, and nanoparticle-based foam generation and stability. We implement a multi-scale approach that spans from pore- to core-scale to investigate foam generation and stability with low and high salinity brines at reservoir conditions.
At the pore- and core-scale, unsteady-state CO2 injections were performed in porous media pre-saturated with the hybrid-, surfactant-, or nanoparticle-based foaming solution at low and high salinity. High-pressure silicon wafer micromodels enabled direct pore-level visualization of fluid dynamics and foam morphology with different the foaming solutions. Bubble density and size (foam texture) were compared and the results were used to corroborate core-scale measurements. Pore-scale results showed an increase in the number of bubbles by 20 to 27% for the hybrid solution, compared to the surfactant solution, indicating stronger foam. At the core-scale the hybrid foaming solution generated a weak foam of 5 cP whereas the surfactant-based solution generated a foam of nearly 20 cP. Increasing the salinity from 3.5 to 15 wt.% NaCl increased the number of bubbles by more than a 100% at pore-scale for both the surfactant and hybrid solutions. At the core-scale, apparent viscosity increased from 5 to 18 cP using surfactant solution. The generation of CO2 foam with and without nanoparticles delayed gas breakthrough by approximately 65% and improved water displacement which is advantageous for combined CO2 EOR and CO2 storage operations.