[H-SC05] 地球温暖化防⽌と地学（CO2地中貯留・有効利⽤、地球⼯学）

[HSC05-P09] Mathematical Modelling of Permeability Reduction in Porous Media Using a Microscopic CO₂ Hydrate Formation Simulation

*山口 アラン¹、佐藤 徹¹、鳥羽瀬 孝臣² (1.東京大学大学院 新領域創成科学研究科　海洋技術環境学専攻、2.電源開発㈱ 茅ヶ崎研究所)

キーワード：二酸化炭素分離・回収と貯留、CO2ハイドレート、有効浸透率係数、フェイズフィールド法、孔隙スケール砂層

Carbon capture and storage is a promising technique for reducing the significant quantities of carbon dioxide (CO₂) gas emitted into the atmosphere. CO₂ can be stored in aquifers under the seabed, although the risk of leakage poses a threat to the marine environment. Gas hydrates are ice-like structures formed by the enclosure of a gas molecule by a cage of water molecules. The formation of CO₂ hydrate occurs under conditions of high pressure and low temperature, such as in sub-seabed shallow formations. If a CO₂ leak occurs at an offshore storage site with a water depth conducive to the formation of hydrates, their formation within the leakage flow can be used to suppress or even block the outflow. This study provides a mathematical model of the permeability reduction caused by hydrate formation using microscopic numerical simulations at the pore scale and assuming sub-seabed sandy sediment layers. Sand images were created numerically from the CT scan data of Toyoura sand using the particle growth method. A phase field model was used to simulate hydrate growth, and lattice Boltzmann method was used to calculate the permeability reduction. The initial water saturation was investigated to determine its impact on hydrate growth and the subsequent reduction in permeability, which was modelled using the Kozeny–Carman equation.