Variations in brine density are crucial for both CO₂ plume migration and long-term geological CO₂ storage. These variations are primarily controlled by three factors: pressure buildup, CO₂ dissolution, and thermal effects. However, previous models have generally neglected these processes or focused mainly on density variations induced by CO₂ dissolution. This study establishes a comprehensive thermo-hydro-mechanical framework to capture CO₂ migration dynamics in heterogeneous saline aquifers, accounting for brine density variations driven by multiple factors. Eight heterogeneous scenarios, including both high- and low-permeability reservoirs, are constructed to represent realistic subsurface conditions. Results indicate that thermal effects generate a localized cold front in the near-wellbore region, where CO₂ thermodynamic properties are highly temperature-sensitive and differ by several-fold from those of the undisturbed reservoir. Additionally, thermal effects lead to a noticeable decrease in brine density and induce thermal deformation. Brine-density variation is governed primarily by pressure buildup and CO₂ dissolution. The incorporation of CO₂ dissolution in the thermo-hydro-mechanical model shortens the CO₂ plume length by more than 230 m. Pressure buildup is the primary driver for brine density increases in low-permeability reservoirs, whereas CO₂ dissolution plays a more significant role in high-permeability reservoirs. Furthermore, high-permeability reservoirs are more conducive to density-driven convection, where vigorous convective fingering enhances mixing and promotes solubility trapping. Cited as: Jin, A., Park, E., Li, C., Shi, W., Wang Geological CO₂ storage in heterogeneous saline aquifers: Insights into the mechanisms of thermal and density effects. Advances in Geo-Energy Research, 2026, 19(3): 216-230. https://doi.org/10.46690/ager.2026.03.02

Energized pre-fracturing has emerged as an effective approach for enhancing reservoir energy, fracture complexity and oil recovery in tight reservoirs. However, the mechanisms by which fracture propagation induced by different energized pre-pad fluids governs subsequent imbibition-driven oil recovery remain insufficiently understood. To address this issue, an integrated experimental framework was established to investigate the coupled evolution of fracture networks and pore-scale oil displacement during energized prefracturing. By combining X-ray computed tomography for quantitative fracture characterization and dynamic nuclear magnetic resonance for monitoring imbibition-driven oil recovery, the interactions between fracture-scale architecture and pore-scale fluid redistribution were systematically elucidated. The results demonstrate that, compared to conventional fracturing, energized pre-fracturing not only lowers breakdown pressure but also promotes the formation of more complex, highly connected fracture networks, which in turn substantially enhance ultimate oil recovery. Notably, gaseous pre-pad fluids exhibit clear advantages over aqueous systems, with supercritical CO2 generating the lowest breakdown pressure and the most intricate multi-branch fracture networks, as indicated by higher fracture fractal dimension and area ratio. These fracture characteristics significantly facilitate imbibition efficiency, resulting in higher oil recovery. Pore-scale analysis further reveals that oil mobilization is dominated by contributions from micropores and mesopores, underscoring the critical role of energized pre-fracturing in activating oil stored in small-scale pore systems. The proposed multi-scale methodology, integrating fluid properties, fracture network evolution, and imbibition dynamics, provides a mechanistic basis and practical guidance for optimizing energized fracturing and improving the efficient development of tight conglomerate reservoirs. Document Type: Original article Cited as: Qu, H., Wu, M., Gan, J., Peng, Y., Zhou, F., Chen, Z. Impact of energized pre-fracturing on fracture network evolution and imbibition in tight oil reservoirs. Advances in Geo-Energy Research, 2026, 19(2): 131-145. https://doi.org/10.46690/ager.2026.02.03

Deep mining safety relies on the dynamic stability of cemented tailings backfill; however, its failure mechanisms in intricate loading scenarios are not yet well understood. This study utilized a split Hopkinson pressure bar apparatus to investigate the dynamic mechanical characteristics of this material, specifically contrasting its response under single and repeated impact loads. The results indicated that both compressive and tensile strengths exhibit a pronounced dependency on the strain rate. A significant contribution of this work is the identification of a unique spalling circumferential fracture pattern under cyclic impact loading for the first time, which stands in contrast to the axial splitting failure observed during single impacts. Numerical simulations further demonstrated that this unique failure mode arises from compression-induced plastic damage. Besides, while the energy absorption capacity exhibits strain-rate hardening, cyclic loading triggers a progressive degradation of energy dissipation efficiency. Compared to natural rocks, the backfill exhibits an enhanced peak stress under repeated impacts, particularly at lower loading rates. This research offers novel perspectives on the fracturing characteristics and rate-dependent behavior of cemented tailings backfill, contributing to the enhancement of safety protocols in deep mining engineering operations. Document Type: Original article Cited as: Liu, L., Xiang, Y., Wang, T., Liu, K., Liu, W., Yan, B. Dynamic response and spalling of cemented tailings backfill under cyclic impact. Advances in Geo-Energy Research, 2026, 19(2): 101-117. https://doi.org/10.46690/ager.2026.02.01

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. Document Type: Perspective Cited as: Nie, X., Song, J., Wei, W., Cai, J. Digital rock physics and resistivity well logging interpretation in unconventional reservoirs: Advances and prospects. Advances in Geo-Energy Research, 2025, 18(3): 287-290. https://doi.org/10.46690/ager.2025.12.07

Underground hydrogen storage has emerged as a pivotal component of the low-carbon energy transition, providing a viable solution to the intermittency of renewable energy sources. The distinctive physical and chemical properties of hydrogen, together with its interactions with surrounding rocks and fluids, introduce unique challenges for subsurface storage. This perspective presents recent advances in experimental and modeling efforts of underground hydrogen storage from a multi-scale perspective, highlighting that established methods from hydrocarbon recovery and carbon dioxide storage remain valuable for studying hydrogen systems, yet effectively translating and scaling the relevant physical processes requires renewed attention. Improving the purity and recovery efficiency of stored hydrogen will be central to guiding future reseach on hydrogen storage in geological porous media. Document Type: Original article Cited as: Zhao, Q., Bo, Z., Pan, B., Wang, Y. Characterization and simulation of underground hydrogen storage across scales. Advances in Geo-Energy Research, 2025, 18(2): 195-198. https://doi.org/10.46690/ager.2025.11.08

Accurate prediction of the mechanical and thermal properties of CO₂ hydrates is essential for their applications in carbon sequestration and refrigeration, yet remains challenging with empirical forcefields. In this work, a deep potential machine learning potential for CO₂ hydrate, trained on density functional theory datasets, is for the first time developed to serve as a unified and accurate computational framework. The as-developed deep potential machine learning potential achieves near-density functional theory accuracy in energy, force, and virial stress predictions while enabling large-scale molecular dynamics simulations at significantly reduced computational cost. Uniaxial stress-strain analyses demonstrate that the model captures the tensile strength and progressive ductile-like failure behavior. Thermal conductivity prediction agrees closely with experimental measurements within 2% deviation, outperforming empirical forcefields. Vibrational dynamics and phonon analyses reveal that the deep potential machine learning potential more accurately describes the anharmonicity and phonon scattering, especially in high-frequency modes, yielding physically realistic thermal transport behavior. This work establishes deep potential machine learning potential as a robust tool for advancing CO₂ hydrate-based technologies by providing a path for accurate and efficient multi-property prediction. Document Type: Original article Cited as: Xiong, K., Li, Y., Lin, Z., Luo, G., Wu, J. Machine learning potential insights into mechanical response and heat transfer in CO₂ hydrate. Advances in Geo-Energy Research, 2025, 18(1): 38-50. https://doi.org/10.46690/ager.2025.10.04

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. Document Type: Original article Cited as: Liu, J., Xiao, D., Li, J., Cheng, L., Wang, H., Cai, J. Enhanced oil recovery via CO₂ flooding in tight reservoirs: A pore-scale analysis. Advances in Geo-Energy Research, 2025, 17(2): 162-175. https://doi.org/10.46690/ager.2025.08.07

In this work, the potential influences of grain-coating clays on water-CO₂-rock interactions in sandstones and subsequent ramifications for CO₂ storage were investigated using reactive transport simulations. The results indicated that, compared to pore-filling smectite, grain-coating smectite leads to significant pH decrease, increases in the CO₂-species concentrations, and decreases in smectite dissolution and the precipitation of secondary minerals. Moreover, it was revealed that smectite and chlorite coats dissolve preferentially over detrital K-feldspar being covered, while K-feldspar is dissolved preferentially over illite and kaolinite coats. While the mineral trapping mechanism is only important for smectite and chlorite coats, sandstone porosity is significantly reduced for chlorite coat but increased for the other three clay coats. The main causes of the differences between pore-filling and grain-coating scenarios for smectite and chlorite coats are ascribed to the inhibitory effect of clay coats on the growth of secondary quartz and the dissolution of clay. In addition to the above two factors, the decelerating effect of clay coats on the dissolution of K-feldspar is also important for illite coat; meanwhile, for the kaolinite coat, the dissolution of clay is less important and the other two factors are more critical. Furthermore, the coverage and thickness of clay coats, fluid flow rate, detrital grain size, detrital lithology, partial pressure of CO₂, and temperature may all impact the role of clay coats. Document Type: Original article Cited as: Li, H., Hu, Q., Zhu, R., Liu, B., Mishara, A., Ansah, E. O. Reactive transport modeling of water-CO₂-rock interactions in clay-coated sandstones and implications for CO₂ storage. Advances in Geo-Energy Research, 2025, 17(2): 121-134. https://doi.org/10.46690/ager.2025.08.04