CO2 Convective Dissolution in Oil-Saturated Unconsolidated Porous Media at Reservoir Conditions

During CO2 storage, CO2 plume mixes with the water and oil present at the reservoir, initiated by diffusion followed by a density gradient that leads to a convective flow. Studies are available where CO2 convective mixing have been studied in water phase but limited in oil phase. This study was conducted to reach this gap, and experiments were conducted in a vertically packed 3-dimensional column with oil-saturated unconsolidated porous media at 100 bar and 50 degrees C (representative of reservoir pressure and temperature conditions). N-Decane and crude oil were used as oils, and glass beads as porous media. A bromothymol blue water solution-filled sapphire cell connected at the bottom of the column was used to monitor the CO2 breakthrough. With the increase of the Rayleigh number, the CO2 transport rate in n-decane was found to increase as a function of a second order polynomial. Ra number vs. dimensionless time tau had a power relationship in the form of Ra = cx tau(-n). The overall pressure decay was faster in n-decane compared to crude oil for similar permeability (4 D), and the crude oil had a breakthrough time three times slower than in n-decane. The results were compared with similar experiments that have been carried out using water.

Automated summary

This study aimed to investigate the convective mixing of CO2 in oil phase under simulated reservoir pressure and temperature conditions. Experiment results showed that the CO2 transport rate in n-decane increased with the Rayleigh number, while the overall pressure decay was faster in n-decane compared to crude oil, leading to a breakthrough time three times slower in crude oil than in n-decane.