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[1313-18-06] Investigation of CO2 Dissolution Mass Transfer in Porous Media by utilizing CT X-ray Microtomography
司会: 末包哲也（東京工業大学）
Keywords:CO2, dissolution, mass transfer, multiphase system , geological storage
Geological Carbon Sequestration (GCS) is one of the promising solutions to
overcome climate change by sequestering CO2 into subsurface formations. However, the possibility of CO2 leakage from the formation can decrease the efficiency of sequestration.
Dissolution trapping is one of the important trapping mechanisms to retain CO2 under the subsurface. It dissolves the CO2 phases from gas to liquid by keeping the liquid CO2 as a solute in the groundwater solutions. Therefore, its behavior is important for the safety analysis of GCS.
Experimental investigation of CO2 dissolution in porous media has been performed with X-ray CT microtomography. Plastic resin particle with the size of 250-425 um was used to simulate the porous media model. To observe the effect of the groundwater flow rate, experiments were performed under various water flow rate (Re = 0.04 – 0.0016).
Observation shows that the CO2 dissolved under two stages. At the first stage, dissolution front is observed propagating from the inlet, and CO2 dissolved rapidly to certain amount of gas saturation (about 0.03). At the second stage, another dissolution front propagates from the inlet dissolving the remaining CO2 gas.
From the analysis of trapped CO2 gas bubble size, interfacial area, concentration, and mass transfer coefficient, the reason of the existence of dissolution stages is probably because the remaining CO2 gas at the second dissolution stage is located at low local hydraulic conductivity area where the water flow has a difficulty to reach. Nevertheless, higher water flow rate seems to alleviate this effect.
This result implicates that the dissolution trapping can be enhanced by performing intermittent CO2 injection to the subsurface; thus, the dissolution process can be maintained at the first stage, where the dissolution rate is high. In addition, reservoir with higher water flow rate is preferable to enhance dissolution trapping.
overcome climate change by sequestering CO2 into subsurface formations. However, the possibility of CO2 leakage from the formation can decrease the efficiency of sequestration.
Dissolution trapping is one of the important trapping mechanisms to retain CO2 under the subsurface. It dissolves the CO2 phases from gas to liquid by keeping the liquid CO2 as a solute in the groundwater solutions. Therefore, its behavior is important for the safety analysis of GCS.
Experimental investigation of CO2 dissolution in porous media has been performed with X-ray CT microtomography. Plastic resin particle with the size of 250-425 um was used to simulate the porous media model. To observe the effect of the groundwater flow rate, experiments were performed under various water flow rate (Re = 0.04 – 0.0016).
Observation shows that the CO2 dissolved under two stages. At the first stage, dissolution front is observed propagating from the inlet, and CO2 dissolved rapidly to certain amount of gas saturation (about 0.03). At the second stage, another dissolution front propagates from the inlet dissolving the remaining CO2 gas.
From the analysis of trapped CO2 gas bubble size, interfacial area, concentration, and mass transfer coefficient, the reason of the existence of dissolution stages is probably because the remaining CO2 gas at the second dissolution stage is located at low local hydraulic conductivity area where the water flow has a difficulty to reach. Nevertheless, higher water flow rate seems to alleviate this effect.
This result implicates that the dissolution trapping can be enhanced by performing intermittent CO2 injection to the subsurface; thus, the dissolution process can be maintained at the first stage, where the dissolution rate is high. In addition, reservoir with higher water flow rate is preferable to enhance dissolution trapping.
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