Oil-based foams hold significant potential for enhancing oil recovery and regulating subsurface fluid flow, yet their stability under high-temperature reservoir conditions and their transport mechanisms within pore-throat structures remain insufficiently understood. To address this gap, this study systematically investigates the behaviour of an oil-based foam system through temperature-dependent stability experiments, complemented by pore-scale numerical simulations that characterize bubble deformation and breakthrough within porous media. Experimental results show that increasing temperature accelerates liquid drainage and gas diffusion within the foam films, leading to a reduction in the number of bubbles, enlargement of average bubble size, and a pronounced decline in overall foam stability. Simulation results further demonstrate that pore-throat diameter and injection pressure jointly govern bubble morphology evolution and breakthrough behaviour, with the competition between capillary forces and external driving pressure emerging as the key mechanism influencing oil-based foam mobility. By integrating these findings, this work establishes a unified mechanical framework linking temperature effects and pore-throat confinement, thereby providing theoretical support for the application and optimization of oil-based foams in high-temperature reservoirs.

Building on the “one-journal-one-forum” (OJOF) mode first proposed by the inaugural event in 2024, the editorial department of Advances in Geo-Energy Research (AGER), under the guidance of several professional associations, successfully hosted the second “International Geo-Energy Frontier Forum” from April 10 to 13, 2026. Under the theme “New Opportunities and Challenges in Geo-Energy Exploration and Development,” the forum retained and further refined several innovative organizational approaches introduced at the inaugural edition. The event reached unprecedented scale and influence, further demonstrating that the OJOF mode is not only feasible but also an excellent framework for the synergistic development of a journal and a conference. Another notable feature of this forum was its effective promotion of the platform’s internationalization. In addition to participants from China, experts and scholars from nine other countries joined the conference both in person and virtually. The event significantly expanded AGER’s service capabilities and fostered international interdisciplinary collaboration across various disciplines and industries.

Shale reservoirs contain abundant micro/nanoscale pores, which facilitate capillarity-dominated imbibition as an effective mechanism for enhancing hydrocarbon recovery. During hydraulic fracturing, the penetration of low salinity fracturing fluids can induce clay hydration and swelling, leading to pore structure alterations. However, the effects on imbibition behavior remain insufficiently understood. In this study, high temperature and high pressure imbibition experiments coupled with nuclear magnetic resonance are performed on continental shale. Furthermore, the structural and mineralogical evolution of shale following interaction with deionized water is evaluated by scanning electron microscope. Finally, the pore fracture structure model incorporating clay swelling is constructed and the flow of fracturing fluids is simulated by the lattice Boltzmann method. The results indicate that cores exhibit greater imbibition recovery at higher salinity. The recovery shows a strong positive correlation with pore structure, with denser and less connected pores leading to reduced recovery. Exposed to deionized water, clay is observed to swell and compress both pore space and fracture. After swelling, the flow channels in the two-dimensional model are narrowed or even closed, resulting in fewer effective flow pathways and a reduced swept zone of the oil phase. Meanwhile, the oil phase is prone to snap-off, producing discontinuous droplets that disperse within the pore space. This ultimately leads to a reduction in imbibition recovery after swelling. High salinity effectively suppresses clay mineral swelling and preserves the original pore structure, thereby resulting in higher imbibition recovery. Understanding the imbibition mechanisms under different salinity provides valuable insights for the design of hydraulic fracturing in oilfield applications.

The construction of underground gas storage (UGS) in a large-scale low-permeability lithologic gas reservoir presents an immense engineering challenge. Under the context of UGS, research on structural characteristics and storage capacity at the microscopic scale is insufficient, making it difficult to provide effective support for the engineering scheme. In this study, the microscopic storage spaces of a typical lithologic gas reservoir (i.e., YL block in the Ordos Basin) are comprehensively analyzed through experimental techniques (represented by computed tomography scanning), digital core analysis, and fractal analysis. Furthermore, the feasibility of UGS construction is examined. The results demonstrate that the large-scale low-permeability lithologic gas reservoir exhibits significant zonal heterogeneity in its microscopic structural characteristics at both morphological and statistical levels. Specifically, the microscopic storage spaces of the core zone within the YL block are notably higher than those in the transition and periphery zones, characterized by larger aperture, less tortuous, higher aggregation and connectivity. Consequently, the core zone provides adequate storage capacity and injection-extraction capability for large-scale underground storage of natural gas. In contrast, the transition and periphery zones exhibit inferior microstructural, storage, and flow properties, which are not suitable for rapid injection and production. However, these zones show a fairly strong lateral sealing capability, which can be utilized as a monitoring area to evaluate UGS integrity. These findings indicate that the reservoir's microstructural features meet the essential requirements of storage capacity, injection-extraction capability, and lateral sealing property for UGS construction. Based on this understanding, a series of zone-differentiated UGS engineering suggestions are proposed, including zonal function specification, well type selection, well deployment scheme, and management of old wells. These findings can provide valuable insights for the assessment and implementation of UGS projects from such gas reservoirs.

On November 16, 2025, the editorial office of Advances in Geo-Energy Research (AGER) successfully held the 100^th AGER Forum, jointly supported by several academic partners, and attended by more than 10,000 people online. With the theme focusing “Digital rock physics and fluid flow in the context of energy transition”, the event gathered renowned experts from UK, Belgium and China to discuss frontier progress in fluid flow, pore-scale simulation, and geo-energy storage research. The forum emphasized that digital rock physics and multiscale imaging technologies are becoming essential research tools in next-generation low-carbon energy systems. The AGER forum included expert lectures and interactive discussions, enhancing the influence of AGER within the global geo-energy field. The 100^th Forum marks an important milestone in the development of the journal. In the future, the AGER Forum will continue serving as a platform for advancing science and technology in the field of geo-energy.

Unconventional hydrocarbon reservoirs, characterized by multiscale and complex pore architectures, diverse mineralogical compositions, and pronounced heterogeneity, present significant limitations to conventional saturation estimation and reservoir evaluation methods, with resistivity well logging data based on classic models such as Archie's equations. Digital rock physics technology, integrating multi-scale imaging, three-dimensional reconstruction, and numerical simulation, enables the precise characterization of pore structures and conductive mechanisms, markedly enhancing the accuracy of electrical response simulations and well logging evaluations in complex reservoirs. Through this perspective, this study systematically compares the application limitations and associated impacts of conventional resistivity logging in unconventional reservoirs of various lithologies and evaluates the applicability and merits of distinct rock physics numerical simulation approaches, highlighting existing constraints and challenges. Furthermore, this work outlines future directions for integrating digital rock physics with well logging evaluation.

Microscopic flow and reactive transport in the subsurface are fundamental to understanding the coupled physical, chemical, and biological processes governing subsurface environments. These processes play a critical role in sustainable water resource management, groundwater contamination control and remediation, geological carbon storage, and subsurface energy exploitation. With the escalating impacts of global climate change and anthropogenic activities, interactions among physical and chemical processes in geological media have grown increasingly complex. Consequently, research on flow and reactive transport has emerged as a vibrant and rapidly evolving frontier. A dedicated session entitled “Microscopic Flow and Reactive Transport in Geological Media” was featured at the “2025 International Symposium on Subsurface Reactive Transport” successfully held in Changchun, China, September 19-21, 2025. The symposium served as a platform for interdisciplinary collaboration and knowledge exchange, providing new perspectives and establishing a solid foundation for future scientific cooperation in the field of subsurface reactive transport.

CO₂ flooding has become a key technology for enhancing oil recovery in tight reservoirs, with great application potential. However, certain microscopic mechanisms of this technology still need to be further clarified. In this work, a multi-component and multi-phase lattice Boltzmann model based on the pseudopotential scheme is constructed considering different CO₂ flooding behaviors and verified for both immiscible and miscible phases, showing good agreement. On this basis, the effects of capillary numbers, extreme wetting at different velocities, Péclet numbers and injection patterns under fractured conditions on the CO₂ flooding process are systematically investigated. The results show that a larger capillary number enhances the displacement effect, whereas an excessively large value tends to cause viscous fingering, leading to accelerated CO₂ breakthrough. High-velocity extreme wetting conditions result in a higher displacement effect than low-velocity conditions. Moreover, an increase in displacement velocity weakens the wetting effect dominated by capillary force, thereby reducing the difference in oil recovery observed under high-velocity extreme wetting conditions. Different Péclet numbers dominate different fluid transport mechanisms. When the Péclet number is around the unity, the synergistic effects of molecular diffusion and viscous flow are balanced, jointly dominating fluid transport. The pore-fracture combined injection mode integrates the advantages of pore and fracture injections and effectively delays CO₂ breakthrough in the fracture system, resulting in an optimal displacement effect. This model can be extended to research on multiphase flow in tight and shale reservoirs as well as CO₂ geological sequestration.

Foam has wide applications in oil and gas resource development, environmental engineering, and chemical industries due to its favorable rheological properties and interfacial characteristics. However, foam stability is influenced by a complex interplay of external and intrinsic factors, including surfactant type, gas-to-liquid ratio, temperature, and pressure. The combined effects of these factors can significantly alter foam characteristics, with each influencing the other in ways that can either enhance or destabilize foam. This research investigates these factors in detail, exploring how they interact to impact foam stability and how their optimization can enhance foam performance for various applications. The study delves into the role of interfacial tension in foam stability, highlighting how surfactant properties, gas composition, and liquid characteristics contribute to foam formation and stability. The study also reviews advancements in foam technology, particularly in oil production, CO₂ storage, environmental pollution management, and the creation of novel materials, while examining strategies for boosting foam stability under extreme conditions. Findings indicate that the gas-to-liquid ratio, surfactant type, temperature, and pressure all play key roles in foam stability, and fine-tuning these parameters can lead to significant improvements in foam performance. In harsh environments, maintaining foam stability presents substantial challenges. This research further proposes methods to enhance foam stability. Foam technology demonstrates broad potential in fields like oil recovery and wastewater treatment, where optimized foam stability can improve both reservoir recovery and treatment efficiency. This review summarizes the latest advancements in foam stability research, providing valuable insights for the further development of foam technology.

Clayey-silt natural gas hydrate reservoirs in the South China Sea exhibit loose and unconsolidated structures, heterogeneous pore structures, high clay mineral contents, and strong hydrophilicity. These characteristics complicate the gas–water two-phase flow process in porous media following hydrate decomposition, posing challenges for efficient development. This study examines the transport response of clayey-silt reservoir samples from the Shenhu area using gas–water two-phase flow experiments and CT scanning to explore changes in pore structure, gas–water distribution, and relative permeability under varying flow conditions. The results indicate that pore heterogeneity significantly influences flow characteristics. Gas preferentially displaces water in larger pores, forming fracture-like pores, which serve as preferential flow channels for gas migration. The preferential flow channels enhance gas-phase permeability up to 19 times that of the water phase when fluid pressures exceed total stresses. However, small pores retain liquid, leading to a high residual water saturation of 0.561. CT imaging reveals that these hydro-fractures improve gas permeability but also confine gas flow to specific channels. Pore network analysis shows that gas injection expands the pore-throat network, enhancing connectivity and forming fracture-like pores. Residual water remains trapped in smaller pores and throats, while structural changes, including new fractures, improve gas flow pathways and overall connectivity. Relative permeability curves demonstrate a narrow gas–water cocurrent-flow zone, a right-shifted iso-permeability point and high reservoir capillary pressure, indicating a strong "water-blocking" effect. The findings suggest that optimizing reservoir stimulation techniques to enhance fracture formation, reduce residual water saturation, and improve gas flow capacity is critical for efficient hydrate reservoir development.