Subsurface CO2 Sequestration: Advances, Challenges, and Pathways to Net Zero

CO2 is indispensable for life on Earth, driving photosynthesis and enabling the energy-dense fuels that power modern civilization and global connectivity. However, human activities have driven a sharp rise in atmospheric CO2 levels, contributing to global warming, with Earth's average surface temperature increasing by about 1.46 °C since preindustrial times as of 2024, and recent decades showing a warming rate of roughly 0.10 °C per decade. Emissions from both natural and human sources now exceed the planet's natural absorption capacity, leading to ongoing accumulation of CO2 in the atmosphere and intensifying climate impacts. To address this imbalance and meet net-zero emissions goals, geological CO2 sequestration offers a practical solution by capturing and storing CO2 in deep subsurface rock formations for long-term isolation. While the injection of captured CO2 into subsurface formations may seem straightforward in principle, its practical execution requires careful attention to a range of technical, operational, regulatory, and environmental factors for safe and effective implementation. Despite tremendous efforts over the years to understand these processes from both fundamental and operational viewpoints, and to resolve key issues that enable successful large-scale deployment, research remains active in addressing ongoing challenges such as long-term injectivity and storage integrity, site selection, and monitoring under different geological conditions.

The main aim of this special issue is to present the current state of the art in technical advances and challenges for subsurface CO2 sequestration in various geological formations, across scales, from pore to reservoir level. We seek contributions that address these topics through advanced analytical and numerical modelling, lab-scale experimental studies, and field-scale trials. A particular focus will be on how rapidly growing machine learning (ML) and artificial intelligence (AI) techniques have contributed, or can contribute, to advancing this field. By integrating these perspectives, the issue will identify practical pathways to scale up CO2 storage solutions for net-zero targets.

We welcome submissions on a wide range of topics related to subsurface CO2 sequestration, emphasizing technical advances, challenges, and innovative pathways toward net-zero target. Topics of interest include, but are not limited to the following:

• Advances in subsurface storage site characterization and selection.

• Injectivity issues and remediation strategies.

• Multiphase flow and CO2 trapping mechanisms in porous media.

• Geochemical reactions and mineralization mechanisms.

• Sealing and caprock integrity.

• CO2 leakage risks and mitigation strategies.

• Induced seismicity risks and geomechanical modelling.

• Monitoring, verification, and accounting techniques.

• Integration of ML/AI in numerical modelling and simulations across scales.

• CO2 storage in unconventional reservoirs.

• Subsurface CO2 utilization for energy recovery.

• Environmental impact evaluations.

• Case studies from field-scale projects and demonstrations.

This Research Topic invites original studies, reviews, perspectives, and methodological advancements, particularly those offering interdisciplinary angles that integrate experiments, simulations, and AI, as well as those that connect micro-scale physics with real-world reservoir engineering challenges.