The amount of carbon dioxide that can be sequestered varies significantly depending on the method and site conditions. Different methods include geological storage, ocean storage, and terrestrial storage, each with different potentials and technical requirements for CO2 sequestration. Geological storage is one of the most promising methods for long-term storage of CO2. It involves injecting and storing CO2 deep underground, typically in saline formations, depleted oil and gas reservoirs, and unmineable coal seams. The potential for CO2 storage in these geological structures is influenced by various factors such as the size, depth, and permeability of the formations, as well as the existence of impermeable cap rock to contain the CO2. Deep saline formations are porous and permeable rocks filled with saltwater that can store CO2 in various forms such as free gas, dissolved in brine, or mineralized after reacting with the host rock. Depleted oil and gas reservoirs offer another option for CO2 storage. After hydrocarbon extraction, these fields have remaining pore space that can be used to inject and store CO2. Unlike saline formations, they often have pre-existing infrastructure for drilling and injection, which can reduce the cost of storage. Unmineable coal seams, also known as coal bed methane (CBM) reservoirs, can store CO2 through a process called enhanced coal bed methane recovery. In this process, injecting CO2 into coal seams displaces methane, which can be recovered as a energy source while sequestering the CO2. Ocean storage involves dissolving CO2 in seawater at great depths where it remains isolated from the atmosphere. This method relies on either natural processes like ocean upwellings or engineering techniques such as direct injection or pipeline delivery systems. While the exact storage capacity is difficult to estimate due to complex ocean dynamics, studies suggest that the global ocean could theoretically absorb thousands of gigatons of CO2. Terrestrial storage focuses on enhancing the natural processes by which ecosystems capture and store carbon. This includes reforestation, afforestation, and soil management practices that increase carbon stocks in vegetation and soils. The potential for terrestrial storage is significant but varies widely depending on factors like climate, soil type, and land use practices. Globally, it is estimated that forests alone could potentially sequester hundreds of gigatons of CO2 over several decades.
The amount of carbon dioxide that can be sequestered varies significantly depending on the method and site conditions. Different methods include geological storage, ocean storage, and terrestrial storage, each with different potentials and technical requirements for CO2 sequestration.
Geological storage is one of the most promising methods for long-term storage of CO2. It involves injecting and storing CO2 deep underground, typically in saline formations, depleted oil and gas reservoirs, and unmineable coal seams. The potential for CO2 storage in these geological structures is influenced by various factors such as the size, depth, and permeability of the formations, as well as the existence of impermeable cap rock to contain the CO2. In China, major basins such as the Bohai Bay Basin, Songliao Basin, and Ordos Basin have been identified as having substantial CO2 storage potential due to their favorable geological conditions.
Deep saline formations are porous and permeable rocks filled with saltwater that can store CO2 in various forms such as free gas, dissolved in brine, or mineralized after reacting with the host rock. The storage capacity can be estimated using different methods such as the pressure-volume-temperature (PVT) approach and geochemical modeling. For example, studies have shown that the Coal Creek Sequestration Project in Wyoming has a working storage capacity of approximately 50 million metric tons of CO2 equivalent (MtCO2e).
Depleted oil and gas reservoirs offer another option for CO2 storage. After hydrocarbon extraction, these fields have remaining pore space that can be used to inject and store CO2. Unlike saline formations, they often have pre-existing infrastructure for drilling and injection, which can reduce the cost of storage. In the United States, the Rangely Oil Field in Colorado has an estimated storage capacity of 30 MtCO2e.
Unmineable coal seams, also known as coal bed methane (CBM) reservoirs, can store CO2 through a process called enhanced coal bed methane recovery. In this process, injecting CO2 into coal seams displaces methane, which can be recovered as a energy source while sequestering the CO2. The Allison Unit in Texas has an estimated storage capacity of 75 MtCO2e using this method.
Ocean storage involves dissolving CO2 in seawater at great depths where it remains isolated from the atmosphere. This method relies on either natural processes like ocean upwellings or engineering techniques such as direct injection or pipeline delivery systems. While the exact storage capacity is difficult to estimate due to complex ocean dynamics, studies suggest that the global ocean could theoretically absorb thousands of gigatons of CO2.
Terrestrial storage focuses on enhancing the natural processes by which ecosystems capture and store carbon. This includes reforestation, afforestation, and soil management practices that increase carbon stocks in vegetation and soils. The potential for terrestrial storage is significant but varies widely depending on factors like climate, soil type, and land use practices. Globally, it is estimated that forests alone could potentially sequester hundreds of gigatons of CO2 over several decades.
In conclusion, the amount of CO2 that can be sequestered through different methods ranges from several million metric tons for specific geological sites to potentially thousands of gigatons for ocean and terrestrial storage. The choice of method depends on various factors including economic viability, technical feasibility, and environmental impact. Advances in technology and better understanding of storage processes will continue to enhance the capabilities and effectiveness of CO2 sequestration across different sectors.