What is CCS?
CCS stands for carbon dioxide capture and storage.
To live more comfortably and more conveniently, humankind has developed and utilized fossil fuels that have lain deep in the earth's crust millions of years. By consuming fossil fuels carbon dioxide (CO2) is generated as a by-product, resulting in increase of CO2 concentration in the atmosphere. It is recognized that this should be one of the main causes of global warming. CCS is the technology to capture CO2 from power stations or industry processes without emitting it to the atmosphere, transport it to sites suitable for geological sequestration, and store it stably underground for a long term. With its larger potential to lower CO2 emissions at an early stage, CCS is expected as a key option to mitigate global warming.
CO2 is injected into porous geological layers such as aquifers (Sandstone formations etc.), or oil and gas reservoirs at depths below 1000 m onshore or offshore underground. Injected CO2 is blocked upward migration by thick and impermeable layers (known as the Caprock) so that CO2 stored safely and stably.
CONCEPT OF CCS
RESERVOIR & CAPROCK
In order to trap CO2 in the subsurface, a geological structure with a suitable reservoir overlain by a caprock is required. The caprock blocks the leakage of injected CO2 from the reservoir.
Features of a caprock
Mudstone etc., made of fine mud grains
Impervious
Sufficient blocking ability
Covering reservoir layer widely and thickly
Features of a reservoir
Sandstone, volcanic rock, etc., made of coarse grains
Sufficient pore spaces to store CO2
Pervious