Reduced Carbon Dioxide Mobility in Experimental Core Flood Using Surface Coated Silica Nanoparticles as a Foaming Agent

Carbon dioxide (CO₂) is the most used solvent in enhanced oil recovery (EOR), as it can have a high displacement efficiency in favorable conditions. Its disadvantages are relatively low sweep efficiencies caused by a viscosity and density that is lower than the fluid it displaces. Surface-coated silica nanoparticles create in-situ CO₂ foam, which has a more favorable mobility ratio and therefore better sweep. These nanoparticles can also be used in carbon capture and storage (CCS) applications in injecting CO₂ foam into brine aquifers.

This paper presents the results of core flood experiments that aimed to study surface coated silica nanoparticles as an in-situ CO₂ foaming agent. In these experiments, pressure drop was measured across the core as a whole and in five individual sections. The core was placed vertically, and liquid CO₂ was pumped at the top of the core. Surface coated silica nanoparticles suspended in the brine is used in some of the floods and compared to a control flood that had no nanoparticles.

In these experiments, pressure drops in nanoparticle cases were a multiple of 5-10 those in the control cases. In addition, total core pressure drops in nanoparticle cases increased as the core got more saturated with CO₂, and the increase was observed sequentially in each section as it got invaded by CO_2.The mobility of CO₂ was reduced by an order of magnitude on average compared to the control. The CO₂ moved slower through the core and breakthrough was delayed in the nanoparticle case.

The study provides quantitative nanoparticle CO₂foam mobility measurements and calculations, compared to those in control cases. Properties calculated from this study can be used to improve both EOR and CCS applications of CO₂ flooding by scaling the results to the reservoir scale.