A multi-sequestration concept of CO2 geological storage: Shale-Sandstone-Basalt system in Northwestern Taiwan

Miocene lenticular basaltic volcanics that have mineral-trapping capability enclosed in the potential sandstone reservoirs in Northwestern Taiwan inspired a CO2 multi-sequestration shale-sandstone-basalt system. To analyze the behavior of injected CO2 and the mineral trapping capability in the proposed multi-sequestration shale-sandstone-basalt system, numerical simulations were conducted with the reactive geochemical transport code TOUGHREACT. Results indicate that the main storage mechanism in shale-sandstone system is solubility trapping, and the mineral sequestration is only 3.5 kg/m3-rock in 1000 years in 1D simulation and 2-3 kg/m3-rock in 500 years in 2D simulation. However, the mineral sequestration in shale-sandstone-basalt system quickly reaches to 130 kg/m3-rock in 200 years in 1D simulation, and 12 kg/m3-rock in 20 years and 45 kg/m3-rock in 100 years in 2D simulation. The majority of CO2 is trapped to form dolomite, calcite, and ankerite. Optimum injection point and injection pressure can achieve the maximum CO2-basalt interaction volume and best storage efficiency of this system. The basalt intrusion bodies, which have mineral trapping capability, act as a “sponge” to rapidly fix CO2 as carbonate minerals and the long-term safety of storage is improved in the multi-sequestration shale-sandstone-basalt system.