[HSC08-P02] 不均質堆積岩におけるマイクロバブルCO2流動の可視化と定量評価
キーワード：X線CT、マイクロバブルCO2、ノーマルバブルCO2、不均質岩
We carried out laboratory experiments of CO2 microbubble and normal bubble flooding in porous sandstone to confirm the difference in dissolution and sweeping effect. During the experiments, we obtained the specimen porosity and monitored fluid saturation process by using CT image analysis. Sarukawa sandstone (diameter: 34.80mm, length: 79.85mm, north central Japan) was used in this study. Porosity of specimen determined by X-ray CT imaging is 30.94%. The specimen has heterogeneous structure. The experiments were conducted under the pressure and temperature conditions that simulate underground environments; pore pressure: 10MPa, temperature: 40 degrees Celsius. The confining pressure selected in this study is 12MPa. The specimen was first saturated with KI aqueous solution (12.5%), and then oil was injected to make oil-water mixed state. Totally, ten steps of flooding were performed for each experiment. For each step, KI aqueous solution and oil were carefully recovered from the syringe pump (back pressure pump). We increased the differential pressure to examine the influence of differential pressure on oil recovery in heterogeneous media. The microbubble and normal bubble flooding tests were carried out until the total fluid injections reach about 3PV (pore volume). Figures a) and b) show the differential CT images when the CO2 microbubble and normal bubble injections reach 2.95PV and 2.98PV, respectively. It is clear that the CO2 microbubbles were able to sweep out more than the normal microbubbles. For example, the oil recoveries were identified as 56.04% and 45.12% after 1.0PV injection of CO2 in the specimen. The case of microbubbles is about 10.92 % point higher than the case of normal bubble.