CO2 Capture

Carbon, originally extracted from the ground as gas, oil and coal is injected into deep geological formations, such as unmineable coal seams, depleted oil reservoirs, and other porous rock formations, in the form of condensed, supercritical CO2. Following its capture, large volumes of CO2 are compressed and injected deep underground in secure geological formations where it is permanently stored.

The process starts with the capture of CO2 generated by power plants and large-scale industrial facilities.

The CO2 Capture process is done using one of these three different methods of combustion:

• Pre-combustion: carbon and hydrogen in fuels are separated before they are burned, transforming into two gas streams—hydrogen and carbon dioxide.
• Post-combustion: the most commonly used process. A solvent, usually ammonia, is used to separate CO2 from other gases after the combustion of a fossil fuel.
• Oxy-fuel combustion: consists of the burning of a fossil fuel in the presence of pure oxygen. This removes contaminants from the exhaust, making the CO2 easier to capture.

The transportation process starts once the CO2 is separated from other gases. 

CO2 Transportation

The captured CO2 is dehydrated and compressed into a dense liquid substance, or supercritical fluid, making it easier and less costly to transport. Then, it is transported by pipelines to the storage location where it is injected into a suitable geological formation.

Smaller quantities of CO2 are transported by road tanker, rail tankers and ships, primarily for industrial use or enhanced oil and gas recovery.

All methods of transportation have been used in different CCS projects around the world and are well understood from decades of experience.

CO2 Storage

The storage of CO2 underground is a natural occurring phenomenon. Some natural CO2 reservoirs are thousands or millions of years old. There are hundreds of natural gas storage sites worldwide.

The industrial process begins with the pumping of CO2 under high pressure into an underground reservoir with specific geological features. A layer of stable porous rock at the correct depth, between 1 and 5 kilometers, is required for a suitable reservoir. An impermeable layer of “cap” rock seals the porous layer preventing leakage to the surface. The rock formations act as secure, natural traps to hold the gases and liquids deep underground, whether on land or at sea.

Every CO2 geological site is unique in terms of geology and structure. Three types of potential storage sites include:

• Depleted oil and gas reservoirs;
• Deep saline formations, and;
• Unmineable coal seams.

The Intergovernmental Panel on Climate Change (IPCC) estimates that the world has storage capacity for 200 years of global emissions.

Development of storage projects is typically conducted in 4 or 5 stages.

Site selection and development commences with geological characterization, reservoir simulation, and well engineering and monitoring.

During the operational phase, gas is injected while monitoring continues.

At closure and post-closure, all field facilities are closed and monitoring continues.