UNDERGROUND-STORAGE OF CARBON-DIOXIDE IN DEPLETED NATURAL-GAS RESERVOIRS AND IN USELESS AQUIFERS

Depleted reservoirs of natural gas and petroleum can provide excellent traps for carbon dioxide. Deep aquifers, which are not used due to hi gh salinity, can host larger amount of carbon dioxide under their high formation pressure than natural gas and oil reservoirs. Small fractio ns of aquifers in sedimentary basins in the world are enough to host a bout 87 gigaton-C of carbon dioxide. A preliminary technical and econo mical survey on the carbon dioxide injection system suggests that the energy requirement for carbon dioxide injection into subterranean aqui fers is about 269 kWh/ton-C and that the investment and operation cost s for the system are 79 $/ton-C. By our preliminary cost estimation in Japan, the CO2-emission-free electricity generation may become possib le with a cost increase of 35% for natural-gas-fired power stations, a nd of 60% for coal-fired-power station.