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Advances and challenges in foam stability: Applications, mechanisms, and future directions
Get PDFFoam 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.Document Type: Invited reviewCited as: Wang, Z., Li, S., Xu, Z., Aryana, S. A., Cai, J. Advances and challenges in foam stability: Applications, mechanisms, and future directions. Capillarity, 2025, 15(3): 58-73. https://doi.org/10.46690/capi.2025.06.0
Impacts of multi-scale water-rock interaction on mineral alteration, mechanical weakening and pore-fracture evolution in marine shales
Get PDFWater-rock interaction triggered by drilling and fracturing fluid retention in shale gas reservoirs induces secondary processes and the subsequent alteration of rock physical properties, critically modulating reservoir productivity. In this study, X-ray diffraction, nanoindentation, focused ion beam-scanning electron microscopy, and micro-computed tomography were utilized to characterize and analyze the mineral alteration, mechanical weakening and pore-fracture evolution of marine shale in the Longmaxi Formation, Sichuan Basin. The results reveal that the water-rock interaction preferentially dissolves clay minerals (mainly illite), feldspars and pyrite via hydration and redox reactions while promoting quartz and carbonate mineral recrystallization. The hydration-dissolution precipitation process significantly weakens the rock mass by reducing cohesion and the friction angle. This mechanical degradation is evidenced by a substantial decrease in elastic modulus, exhibiting pronounced anisotropy relative to stratifications. The resultant hetero-geneous stress fields initiate and propagate secondary pores and fractures, dramatically increasing the number, volume and surface area of pores. These newly formed structures integrate with pre-existing pore-fracture networks, markedly elevating overall porosity and enhancing interconnectivity, which consequently amplifies permeability by orders of magnitude. Additionally, water preferentially enters the reservoir through stratification, and the associated difference in water-rock interaction strength further enhances the heterogeneity of structural and mechanical heterogeneity. These findings link micro-scale physical-chemical reactions with the meso-scale mechanical properties and macro-scale pore-fracture structures, emphasize the key role of water-rock interaction in reshaping reservoir characteristics, and provide important insights for optimizing hydraulic fracturing strategies and improving shale gas recovery.Document Type: Original articleCited as: Mu, Y., Zou, C., Hu, Z., Duan, X., Guo, Q., Jing, Z. Impacts of multi-scale water-rock interaction on mineral alteration, mechanical weakening and pore-fracture evolution in marine shales. Advances in Geo-Energy Research, 2025, 17(1): 68-81. https://doi.org/10.46690/ager.2025.07.0
Experimental investigation into gas migration mechanism in submarine sandy sediments at pore-scale
Get PDFThe dissociation of natural gas hydrate usually induces gas migration within shallow marine sediments, which has been widely reported to trigger geological hazards and submarine facility failure. To date, the mechanisms by which gas migration governs internal structural evolution and seafloor morphological changes remain poorly understood. This study investigates the gas migration behavior and associated morphological changes in sandy sediments using a novel experimental setup that integrates X-ray computed tomography scanning technology with a custom-built seepage apparatus. The apparatus enables gas injection with constant flow rate and real-time observation of the occurrence and migration process of gas within sediments. Experiments were conducted on Fujian sand with different particle sizes and gas flow rates, demonstrating that gas migration follows a particle-displacement pattern in fine-grained sediments and a pore-invasion pattern otherwise. The study further explores the dynamics of gas pocket formation, as well as the channel healing and re-opening behavior. The results demonstrate the porescale mechanism governing morphological evolution of seabed, with pockmarks and knolls at the surface and elongated chimney-like channels underneath. This work also highlights the advantage of X-ray computed tomography techniques for understanding gas migration processes in marine sediments.Document Type: Original articleCited as: Sun, W., Kong, D., Li, Z., Peng, Y., Chen, Y., Cheng, Y. P., Zhu, B. Experimental investigation into gas migration mechanism in submarine sandy sediments at pore-scale. Advances in Geo-Energy Research, 2025, 17(1): 30-42. https://doi.org/10.46690/ager.2025.07.0
Experimental investigation and multi-scale simulations of CO₂ foam flooding for enhanced oil recovery
Get PDFCO₂ flooding in low-permeability and tight oil reservoirs is frequently compromised by severe gas channeling, which significantly reduces oil recovery and sweep efficiency. While foam flooding can effectively mitigate CO₂ channeling by trapping CO₂ within lamellae, its stability deteriorates under harsh high-temperature, high-salinity reservoir conditions, compromising its effectiveness. Furthermore, foam flow in porous media involves constant foam generation, collapse and propagation, making its flow behaviors difficult to predict. To address these challenges, a new foaming agent with satisfactory regenerative capability is developed to maintain gas mobility control under harsh reservoir conditions. The multiphase flow behaviors during CO₂ foam flooding are predicted using pore network modeling to obtain the corresponding relative permeability curves, which are further incorporated into a reservoir simulator to evaluate field-scale foam flooding performances, as well as optimize injection strategies. This multi-scale modeling approach establishes a quantitative link between pore-scale foam behaviors and field-scale oil recovery performances, offering new insights into carbon capture and utilization with enhanced oil recovery in low-permeability and tight reservoirs.Document Type: Original articleCited as: Peng, M., Zhou, Y., Yang, J., Wang, J., Lin, Z., Zhao, J. Experimental investigation and multi-scale simulations of CO₂ foam flooding for enhanced oil recovery. Capillarity, 2025, 16(2): 39-50. https://doi.org/10.46690/capi.2025.08.0
Interfacial dynamics and mass transfer in underground hydrogen storage applications: A review of H₂ flow, stability and storage performance
Get PDFHydrogen is emerging as a clean energy carrier in the global transition toward decarbonized energy systems. Leveraging established subsurface engineering expertise, underground hydrogen storage can be realized in salt caverns, depleted hydrocarbon reservoirs, and deep saline aquifers. However, the physicochemical characteristics of hydrogen including low viscosity, high diffusivity and strong chemical reactivity create unique challenges for its containment, transport and recovery from porous media. This review systematically analyzes the known interfacial and pore-scale mechanisms governing hydrogen migration, trapping and loss in heterogeneous reservoirs. The key processes comprise capillary trapping, molecular diffusion, interfacial reactions, and microbial activity. Interactions among hydrogen, brine and mineral surfaces are evaluated in terms of wettability, interfacial tension and pore connectivity, all of which directly influence storage efficiency and recovery performance. Advanced experimental methods such as nuclear magnetic resonance, microfluidics models, and X-ray computed tomography, combined with pore-scale simulations, are assessed for their ability to characterize multiphase flow and reactive transport behavior. Furthermore, the impact of operational factors like cushion gas composition, pressure cycling and injection-production strategies on storage integrity is discussed. Addressing these multi-physics and multi-scale challenges is essential for the safe and efficient implementation of underground hydrogen storage. Finally, this review identifies priority research directions aimed at improving mechanistic predictions and optimizing the operational management of hydrogen behavior in subsurface environments.Document Type: Invited reviewCited as: Ren, J., Sun, L., Li, X., Wang, P., Jiang, L., Song, Y. Interfacial dynamics and mass transfer in underground hydrogen storage applications: A review of H₂ flow, stability and storage performance. Advances in Geo-Energy Research, 2025, 18(2): 121-136. https://doi.org/10.46690/ager.2025.11.0
Investigation of conglomerate softening effect induced by supercritical CO₂-water-rock interaction via micro-scratch test
Get PDFSupercritical CO₂-water-rock interactions significantly impact the mechanical integrity of heterogeneous conglomerate reservoirs, challenging their suitability for CO₂ sequestration and enhanced oil recovery. To evaluate these microscale mechanical and structural changes, this study uses a combination of micro-scratch testing, scanning electron microscopy, and nuclear magnetic resonance. The results reveal that the micro-scratch method enables the acquisition of a continuous mechanical property profile, addressing the limitation of traditional rock mechanics that only allows discrete point measurements. Importantly, the scratch failure modes significantly depend on the lithology of conglomerate reservoirs: Felsic and quartz conglomerates exhibit sharp grooves with interfacial shear failure, whereas debris-rich variants develop wavy, fragmented paths. CO₂-water exposure reduces the deformation resistance and causes fracture toughness to initially increase and then decline, with the most severe reduction observed in quartz conglomerates. The degradation of mechanical properties is mainly through mineral dissolution and increased porosity. The findings of this study offer key insights for optimizing storage and recovery strategies in complex reservoirs.Document Type: Original articleCited as: Yang, L., Liu, Z., Lu, Y., Chen, H., Dong, Y., He, M. Investigation of conglomerate softening effect induced by supercritical CO₂-water-rock interaction via micro-scratch test. Advances in Geo-Energy Research, 2025, 18(1): 21-37. https://doi.org/10.46690/ager.2025.10.0
Microscopic flow and reactive transport in geological media: Recent advances and challenges
Get PDFMicroscopic 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.Document Type: EditorialCited as: Cai, J., Yang, X., Yang, Z., Yang, Y., Deng, H., Zhu, H. Microscopic flow and reactive transport in geological media: Recent advances and challenges. Capillarity, 2025, 17(3): 77-80. https://doi.org/10.46690/capi.2025.12.0
Multi-sphere interactions driven differential formation of the whole petroleum system
No full textUsing the theories of multi-field coupling within a multi-sphere interaction framework and the Whole Petroleum System, this study investigates the formation, distribution and enrichment of hydrocarbon resources, promoting a shift in exploration philosophy from a singular to an integrated approach. By integrating disciplines such as geochemistry, geodynamics and structural geology, it systematically analyzes the coupling effects of tectonic stress, thermal, pressure and fluid potential fields in sedimentary basins and their controlling mechanisms on hydrocarbon generation, migration and accumulation. Combined with typical case studies from various basins, the distribution patterns of conventional, tight and shale oil and gas are revealed. The results demonstrate that multi-sphere interactions govern the ordered distribution of different hydrocarbon types by influencing the accumulation process, thereby establishing a hydrocarbon accumulation model described as “Spheres control Fields, then Fields control Thresholds, and Thresholds define Distribution”. This theoretical framework aids in enhancing exploration efficiency and optimizing resource development strategies, providing novel insights and perspectives for future petroleum exploration.Document Type: PerspectiveCited as: Hu, T., Liu, K., Wen, Z., Borghi, L., Carranza, E. J. M., Zhao, J. Multi-sphere interactions driven differential formation of the whole petroleum system. Advances in Geo-Energy Research, 2025, 18(3): 295-298. https://doi.org/10.46690/ager.2025.12.0
Experimental study on compound dynamic disaster in deep coal rock under gas and stress loading and unloading
Get PDFTo explore the occurrence mechanism of compound dynamic disasters in coal rocks, this study conducted a true triaxial test simulating gas extraction and stress loading and unloading conditions. To differentiate behaviors among disaster types, the effects of acoustic emission energy, temperature and impact force were analyzed during disaster incubation. The results revealed that different simulation depths lead to varying types of compound dynamic disasters. Compared to rockburst-outburst compound dynamic disasters, outburst-rockburst compound dynamic disasters exhibited higher relative outburst intensity and critical gas pressure. Deep coal rock disasters were characterized by long incubation and short excitation. As a threshold for disaster type transformation, a critical gas pressure range of 2.2 - 2.8 MPa was identified. During incubation, the temperature generally increased, with greater variation in the coal seam than at the coal-rock interface. During excitation, the temperature dropped sharply, with smaller variation in the coal seam. Outburst-rockburst disasters consistently showed higher temperature variation than rockburst-outburst disasters. Impact force evolution in roadways followed a similar pattern across disaster types: initial impact ￫intensification ￫peak ￫attenuation, with a peak effect. The peak impact force increased linearly with critical gas pressure, with outburst-rockburst peak growth rates being 47.76 times higher than rockburst-outburst peak growth rates. This study provides important insights into the multi-parameter evolution characteristics of deep coal rock compound dynamic disasters, offering a scientific basis for disaster prediction and control.Document Type: Original articleCited as: Zhang, X., Tang, J., Pan, Y., Ren, L., Huang, L., Zhang, Z. Experimental study on compound dynamic disaster in deep coal rock under gas and stress loading and unloading. Advances in Geo-Energy Research, 2025, 16(1): 60-76. https://doi.org/10.46690/ager.2025.04.0
Field-scale investigation of CO2 plume dynamics under spatial wettability variations: Implications for geological CO2 storage
Get PDFSubsurface formations typically exhibit heterogeneous wetting characteristics due to the complex pore system, mixed lithology, and prolonged contact with native fluids. This non-uniformity in spatial wettability distribution thus makes the subsurface formations exhibit more complex localized CO2/brine/rock interactions, introducing uncertainties in estimating trapping capacity and predicting CO2 plume migration. Field-scale investigation on the role of wettability in CO2 geo-storage has received limited attention, and previous studies typically assume an internal uniform wettability condition across the whole formation. However, the more realistic scenario of internal wettability spatial variations within a single formation is yet to be thoroughly examined. In this study, a range of experiment-derived wettability-dependent trapping coefficients were utilized to implement the internal wettability heterogeneity in a single formation model, and its impact on CO2 plume pattern and trapping efficiency was examined. Furthermore, mixed-wet systems with different CO2-wet fractions were also considered in this study. The results indicate that internal wettability variations result in changes in the local CO2 saturation pattern and thus impact the overall plume shape and migration. In addition, the internal heterogeneous wettability system exhibits an approximately 35% reduction and an approximately 20% increase in residual trapping capacity in comparison to internal uniform strongly water wet and uniform weakly water-wet systems, respectively. An increase in the fraction of CO2-wet regions in the mixed-wet system results in concentrated high-saturation clusters and reduced local CO2 residual saturation. This further results in reduced residual and dissolution trapping, followed by a linear correlation.Document Type: Original articleCited as: Zhang, H., Mahmoud, M., Iglauer, S., Arif, M. Field-scale investigation of CO2 plume dynamics under spatial wettability variations: Implications for geological CO2 storage. Advances in Geo-Energy Research, 2025, 15(3): 230-244. https://doi.org/10.46690/ager.2025.03.0