低炭素社会構築のためのCCS（CCS Technologies for low carbon society）

[1605-08-02] 多孔質内における、密度変化による三次元フィンガリング構造の解明

○蔡 詩彤¹、末包 哲也¹、王 蕾¹ (1. 東京工業大学)

司会：佐々木久郎（九州大学）
Chairman: Kyuro Sasaki (Kyushu University)

キーワード：fingering structure、displacing front、x-ray CT、three dimension、porous media

In the process of supercritical CO2 into oil field, fingering structure appears at a vertically displacing front even in a favorable ratio. Density increase by mixing at a vertically displacing front between the supercritical CO2 and oil is considered as the reason induced the fingering. In this study, we focused on the fingering structure during the mixing of the two fluids. Because of the difficulty to achieve the model of the injection of supercritical CO2 into oil in experimental condition, in our experiments, we use plastic particles packed bed as the porous medium. We use a solution of NaI (sodium iodide) and MEG (the mixture of Methanol and Ethylene glycol solutions) as supercritical CO2 and a solution of NaCl (sodium chloride) as oil. Before mixing, the MEG-NaI is less dense than the NaCl solution which is same condition as supercritical CO2 injection into oil. With the dissolution of MEG into NaCl solution, the density of mixture solution is increasing modeling the dissolution of CO2. In terms of the three-dimensional images obtained from our experiments, we present that with an increase in the injection rate of MEG, the fingering development speed increases and the fingering number decreases. An enhanced dispersion is also indicated by the comparison among the various increasing injection rates, as the scale of fingering structure becomes larger when rate becomes faster. When the injection is at a high rate, the vertically displacing front develops as compact. We consider that the reason of the phenomenon is the enhanced diffusion faster than the fingering development velocity at high injection rate. At low injection rate, fingering structure depends on the peclet number.