Model prediction on the rise of pCO 2 in uniform flows by leakage of CO 2 purposefully stored under the seabed

Abstract

A numerical study was conducted to predict pCO 2 change in the ocean on a continental shelf by the leakage of CO 2, which is originally stored in the aquifer under the seabed, in the case that a large fault connects the CO 2 reservoir and the seabed by an earthquake or other diastrophism. The leakage rate was set to be 6.025 × 10 −4 kg/m 2/sec from 2 m × 100 m fault band, which corresponds to 3800 t-CO 2/year, referring to the monitored seepage rate from an existing EOR field. The target space in this study was limited to the ocean above the seabed, the depth of which was 200 or 500 m. The computational domain was idealistically rectangular with the seabed fault-band perpendicular to the uniform flow. The CO 2 takes a form of bubbles or droplets, depending on the depth of water, and their behaviour and dissolution were numerically simulated during their rise in seawater flow. The advection–diffusion of dissolved CO 2 was also simulated. As a result, it was suggested that the leaked CO 2 droplets/bubbles all dissolve in the seawater before spouting up to the atmosphere, and that the increase in pCO 2 in the seawater was smaller than 500 μ atm.