Geological carbon storage and compressed gas energy storage: current status, challenges, and prospects

Abstract

Carbon capture and storage (CCS) and geological energy storage are essential technologies for mitigating global warming and achieving China’s “dual carbon” goals. Carbon storage involves injecting carbon dioxide into suitable geological formations at depth of 800 meters or more for permanent isolation. Geological energy storage, on the other hand, involves compressing air or other gases using surplus electricity during off-peak hours and temporarily storing them in underground reservoirs. These gases are then released during peak hours for power generation. Both technologies share commonalities in reservoir selection, with aquifers, depleted oil and gas reservoirs, and salt caverns all serving as potential storage sites. Carbon storage demands long-term containment, while geological energy storage necessitates multiple cycles of storage and release, requiring careful consideration during site evaluation. CCS projects are rapidly increasing globally, evolving towards networked and clustered configurations. In China, CCS projects are primarily focused on CO2-enhanced oil recovery, with fewer dedicated storage projects. However, direct storage projects are projected to dominate in the future and are also transitioning towards clustered development. China possesses favorable geological conditions for carbon storage, with relatively accurate estimates for oil and gas reservoir storage potential. Nevertheless, significant uncertainties persist regarding the storage capacity of saline aquifers. Compressed air energy storage in salt caverns is currently the predominant type of geological energy storage projects. Germany, the USA, and China have a total of five operating compressed air salt cavern energy storage power plants. China has abundant salt cavern resources, albeit with complex geological conditions. Suitable construction sites are concentrated in the eastern regions, and numerous projects are already underway. Compared to salt caverns, porous formations such as aquifers and depleted oil and gas reservoirs are more widespread and offer higher storage potential. However, technical challenges related to multiphase flow and chemical reactions need to be addressed. However, current site selection, potential assessment, efficiency optimization, and monitoring technologies face considerable challenges in meeting the demands of large-scale practical applications. Traditional hydrogeological exploration methods prove inadequate for selecting suitable sites, highlighting the need for efficient monitoring and risk control techniques. Additionally, there is a lack of cost-effective and accurate continuous monitoring technologies specifically designed for pressure and stress changes in storage and caprock formations. The development of key equipment components, such as monitoring and power generation systems, with independent intellectual property rights remains limited. Moreover, our reservoir simulation software requires further advancements to effectively simulate complex reservoirs at large scales. It is crucial to prioritize research and development in resource exploration, site selection technologies, and engineering equipment for both carbon sequestration and geological energy storage. The establishment of diverse demonstration projects and facilities for various storage options such as saline aquifers, depleted oil/gas fields are needed in the future as well.

Keywords

• geological carbon storage
• geological compressed gas energy storage
• saline aquifers
• depleted gas/oil reservoirs
• salt caverns
• survey and evaluation