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  4. INJECTION & STORAGE

INJECTION & STORAGE

In the compression and injection process, the high-purity CO2 is sent to underground far away from our living environment, geological layers at depths below 1000m, where CO2 will be stored for a long time.

Storage Area

Oilfields and gas fields no longer in use or geological layers containing a lot of salt water (aquifer) far away from active faults, etc., are selected as CO2 reservoirs. The layer used as reservoir is mainly made up of sandstone (rock made of sand), where plenty of pore spaces between sand grains are filled with salt water. CO2 is stored in these pore spaces.

From past surveys on available reservoir resources, the total reservoir capacity in Japan is estimated at 140 billion tons, equivalent to 100 years of the country’s annual CO2 emission.

Mechanism of Storage

CO2 is injected to the area deeper than 1,000m as a mixture of gas and fluid. As the reservoir layer is covered by another layer capable of blocking CO2 migration (caprock), CO2 will be stored safely and stably for a long time. After a long period of time, stored CO2 is considered to dissolve in salt water or become mineralized between sand grains.

At the large-scale demonstration project, temperature and pressure fluctuations of the reservoir after CO2 injection, as well as the behavior of injected CO2, will be monitored. This monitoring will regularly take place following the completion of CO2 injection. Its effect on the surrounding environment will also be evaluated.

Injection & Storage