The growing severity of global climate change has highlighted the importance of CO₂ sequestration as a key strategy for reducing CO₂ emissions and mitigating global warming. To this end, sedimentary basins worldwide contain extensive yet underexplored saline aquifers with substantial sequestration potential for long-term CO₂ sequestration. In this study, the suitability and mechanical responses of CO₂ sequestration in a representative half-graben saline aquifer were systematically unraveled through integrated theoretical analysis and multi-physics-coupled numerical simulations. Key factors, such as temperature, pressure, reservoir properties, and caprock distribution, were evaluated based on well logging and mud logging data. Taking the evaluation results as a basis, optimal reservoir-caprock combinations were identified and classified into three types according to their spatial distribution: Single caprock-reservoir, lower interlayer-caprock-reservoir, and upper interlayer-caprock-reservoir. To simulate the mechanical responses during CO₂ injection and sequestration, corresponding conceptual models were developed. The results indicate that Type Ⅲ reservoir-caprock combinations, featuring upper mudstone interlayers, exhibit the lowest caprock stress, reduced leakage risk and enhanced sequestration security, which should be prioritized in sequestration site selection. Our findings provide valuable insights for selecting safe and effective CO₂ sequestration sites in saline aquifers across regional sedimentary basins.

The accumulation of immobile residual water during CO₂ injection for brine displacement significantly impairs storage efficiency, injectivity, and fluid migration—key factors for scaling up CO₂-based energy technologies. This study investigates the factors governing residual water saturation under different CO₂ phases and effective stress conditions in simulated subsurface environments. The results indicate that under constant effective stress, gaseous CO₂ yields the highest residual water saturation, followed by its supercritical and liquid states. As such, an inverse relationship is observed between residual water saturation and storage efficiency/capacity, underscoring the potential for jointly optimizing energy recovery and CO₂ sequestration. The analysis of the CO₂-brine-rock system confirms that capillary forces control residual water saturation. Increased interfacial tension or contact angle cosine value raises capillary entry pressure, hindering displacement and elevating irreducible water saturation. Moreover, higher effective confining pressure reduces capillary radius and creates "dead pores", thereby increasing capillary pressure and enhancing water trapping in the core. The findings give critical insights into how CO₂ phase behavior and confining pressure govern residual water saturation, displacement efficiency and migration in the reservoir, directly informing strategies for optimal CO₂ storage reservoir selection and enhanced oil recovery operations.

The development of geo-energy resources plays a crucial role in transitioning towards a sustainable energy future and achieving carbon neutrality. Conventional experimental approaches, constrained by macroscopic-scale observations and high costs, often fail to capture critical microscale mechanisms. In contrast, microfluidic technology offers distinct advantages through high-resolution visualization, high-throughput screening, and precise simulation of practical conditions such as temperature, pressure, pore structures, and chemical reactions, effectively addressing key challenges in geo-energy extraction. This review systematically examines innovative applications of microfluidics in shale gas reservoir, carbon capture, utilization and storage, chemical enhanced oil recovery, enhanced geothermal system, and natural gas hydrate. It further investigates prevailing challenges regarding material compatibility, scale translation, and data extrapolation methodologies. The study demonstrates that microfluidic systems provide innovative experimental methodologies, enabling unprecedented precision in elucidating complex geological processes through enhanced mass transfer efficiency and high-throughput screening capabilities, thereby bridging microscale mechanisms with macroscale phenomena. In the future advancements, the microfluidic technology demands synergistic convergence with materials science, chemical reactions, artificial intelligence, and physical explanation to promote the geo-energy research. This interdisciplinary convergence will provide scientific foundation for developing efficient and sustainable energy solutions.

Methane metabolism, driven by methanogenic and methanotrophic microorganisms, plays a pivotal role in the carbon cycle. As seawater intrusion and soil salinization rise due to global environmental shifts, understanding how salinity affects methane emissions, especially in deep strata, becomes imperative. Yet, insights into stratigraphic methane release under varying salinity conditions remain sparse. Here we investigate the effects of salinity on methane metabolism across terrestrial and coastal strata (15–40 m depth) through in situ and microcosm simulation studies. Coastal strata, exhibiting a salinity level five times greater than terrestrial strata, manifested a 12.05% decrease in total methane production, but a staggering 687.34% surge in methane oxidation, culminating in 146.31% diminished methane emissions. Salinity emerged as a significant factor shaping the methane-metabolizing microbial community's dynamics, impacting the methanogenic archaeal, methanotrophic archaeal, and methanotrophic bacterial communities by 16.53%, 27.25%, and 22.94%, respectively. Furthermore, microbial interactions influenced strata system methane metabolism. Metabolic pathway analyses suggested Atribacteria JS1's potential role in organic matter decomposition, facilitating methane production via Methanofastidiosales. This study thus offers a comprehensive lens to comprehend stratigraphic methane emission dynamics and the overarching factors modulating them.