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A review on remediation of spilled oil-contaminated soil from a pore-scale perspective
Get PDFMany innovative decontamination techniques, such as pulsed pumping and surfactant flushing, have been proposed to enhance the remediation performance of oil-contaminated soils. Their practical application is dependent on injection and extraction well. Therefore, these techniques can be viewed as an enhanced version of pump-and-treat technology. Since macroscopic flow phenomena are determined by microscopic fluid flow behaviors, conducting pore-scale studies on soil remediation will contribute to a deeper understanding of the remediation mechanisms associated with different pumping methods. This study examines the application of microfluidic experiments and pore-scale numerical simulations to the fluid dynamics of immiscible fluid displacement processes. The main application scenarios are reservoir development and CO₂ geological sequestration. Additionally, the primary distinction between soil remediation studies and the aforementioned scenarios is pointed out, i.e., the unsaturated initial fluid distribution. Finally, future research directions in soil remediation are discussed, emphasizing the fluid dynamic effects of initial contaminant distribution.Document Type: Invited reviewCited as: He, Z., Meng, J., Zhang, S., Zhou, Y., Zhao, Z. A review on remediation of spilled oil-contaminated soil from a pore-scale perspective. Capillarity, 2025, 16(1): 18-26. https://doi.org/10.46690/capi.2025.07.0
Wetting behaviors of water on kerogen surfaces from molecular level: Implication for gas extraction and hydrogen storage in shale
Get PDFShale formations serve as primary reservoirs for natural gas and emerging candidates for hydrogen storage, where the wetting behaviors of organic matter (i.e., kerogen) play a critical role in fluid retention and transport. This study employed molecular dynamics simulations to investigate the pressure-dependent wettability of kerogen surfaces in H2 and CH4 environments under geological conditions (333 K, 10-100 MPa). Results reveal distinct gas-specific mechanisms governing wettability evolution. For CH4-H2O systems, increasing pressure induces a wettability transition from weakly water-wet to gas-wet due to the strong interaction between CH4 and the kerogen surfaces, which results in a smaller gas-solid interfacial tension compared with liquid-solid interfacial tension . Meanwhile, both the reduced gas-liquid and gas-solid interfacial tension contributes to a linear rise in contact angles (88° to 119°). In contrast, H2 exhibits weaker interactions with the kerogen surfaces and experiences a minimal decrease in gas-liquid interfacial tension, thus presenting persistently water-wet characteristics (53° to 69.5°) even at 100 MPa. Crucially, the Young-Laplace equation remains valid at the nanoscale, as evidenced by direct capillary pressure measurements aligning with theoretical predictions, confirming classical interfacial thermodynamics govern nanoconfined fluid behavior. These mechanistic insights elucidate how gas-specific molecular interactions dictate shale wettability, providing a physicochemical basis for optimizing CH4 recovery through pressure-managed wettability alteration and ensuring H2 storage security in hydrophobic kerogen network.Document Type: Original articleCited as: Zhang, M., Huang, J., Wang, H., Niu, W. Wetting behaviors of water on kerogen surfaces from molecular level: Implication for gas extraction and hydrogen storage in shale. Capillarity, 2025, 14(3): 72-81. https://doi.org/10.46690/capi.2025.03.02
Methane hydrate formation characteristics under different initial conditions and their impact on coal seam propertie
Get PDFDue to the unique structural characteristics of hydrate, it has a potential application value in coal and gas outburst prevention in coal mines. Given the complexity of subsurface environments, it is essential to investigate the hydrate formation kinetics under varied initial conditions, as well as the subsequent impacts of hydrate formation on coal seam properties. This research mainly focuses on the hydrate formation process in coal samples with different coalification degrees under different initial pressure and water saturation conditions by using the designed hydrate formation system. The results show that gas consumption and hydrate saturation can be greatly enhanced by increasing the initial water saturation and pressure, which is favorable to reduce the coal seam gas pressure and improve the coal seam peak strength. The calculation results suggest that hydrate formation at varying saturation reduces the gas pressure by 53.05% ∼91.33% and increases the peak strength of coal across the tested confining pressure by 36.45% ∼ 59%. Furthermore, this study found that hydrate formation kinetics are significantly enhanced in lignite compared to that in anthracite, which may be attributed to structural variations associated with the coalification degree. The underlying mechanism requires further research in the future. The data obtained in this study regarding the effect of hydrate formation under different initial conditions on coal seam properties demonstrate the feasibility of preventing gas disasters in coal via controlling the initial conditions.Document Type: Original articleCited as: Sun, C., Liu, S., Li, S., Wang, K., Dong, Z., Kong, S. Methane hydrate formation characteristics under different initial conditions and their impact on coal seam properties. Advances in Geo-Energy Research, 2025, 16(3): 229-243. https://doi.org/10.46690/ager.2025.06.0
Recent progress of coal seam water injection technology for dust prevention: A comprehensive review
Get PDFCoal seam water injection constitutes a fundamental measure for ensuring safe and efficient coal mine production, preventing pneumoconiosis hazards, and protecting the environment. However, systematic reviews integrating its dust reduction theories and technologies remain scarce. This paper reviews the foundational theories and technological advancements in coal seam water injection for dust control, revealing the regulatory mechanisms of dust reduction through coal’s seepage-wetting behavior from dual perspectives of the internal structural features of coal and the evolving stress-water pressure environment. Additionally, it evaluates the technologies for modifying coal’s physical properties and technologies for injected fluids modification. Finally, it identifies the challenges faced by coal seam water injection technology and proposes future research directions. Our review found that pore-fracture network connectivity governs water transport pathways, while dynamic equilibrium between interfacial tension and chemical group interactions determines wetting efficiency at the microscopic level. Macroscopically, hydro-mechanical coupling effects induce multi-stage fracture network evolution through stress redistribution, forming multi-level interconnected topological structures that significantly enhance wetting homogeneity. From a technological perspective, this study establishes a geology-adaptive technical framework based on coal seam characteristics and physicochemical parameter compatibility. The review promotes the transition of water injection technologies from experience-driven “extensive pressurization” to data-driven “precision wetting,” providing a theoretical foundation for developing safe, green, intelligent, and source-controlled dust reduction technologies.Document Type: Invited reviewCited as: Wang, H., Wang, H., Tan, J., Du, J., Zhou, W., Zhang, Y. Recent progress of coal seam water injection technology for dust prevention: A comprehensive review. Advances in Geo-Energy Research, 2025, 16(3): 181-198. https://doi.org/10.46690/ager.2025.06.0
Unlocking the shiny surface features of shale shear fractures at micro-nanoscale
Get PDFShale shear fracture mirrors are key indicators of localized shear deformation, yet their high reflectivity origin remains unclear. This study employs electron microscopy and Raman spectroscopy to analyze fracture mirrors from the Lower Cambrian Qiongzhusi shale. Results reveal the shiny surface is not merely a product of mechanical polishing but is primarily attributed to the formation of highly ordered nanocoatings on fracture surface. The coatings comprise aligned clay minerals and, crucially, organic materials that have undergone shear-induced partial graphitization. Transmission electron microscopy reveals a about 0.46 nm lattice fringe spacing, and Raman spectroscopy confirms a moderate structural order and an elevated thermal maturity of organic matter. This transformation yields a dense material dominated by ultra-micropores, which minimizes light scattering of fracture surface. The formation of fracture mirrors results from shear displacement and frictional heating, which lead to mechanical comminution and microstructural reorganization. This finding establishes the shear fracture mirrors as the key indicators for revealing bedding-parallel slip history in shale-involved detachment and, more practically, for assessing fluid migration pathways, seal integrity, and natural fracture networks in shale gas systems.Document Type: Short communicationCited as: Zhu, H., Qi, B., Li, J., Li, C., Raza, A., Guo, C. Unlocking the shiny surface features of shale shear fractures at micro-nanoscale. Advances in Geo-Energy Research, 2025, 18(2): 202-206. https://doi.org/10.46690/ager.2025.11.1
Multi-field coupled mathematical modeling and numerical simulation technique of gas transport in deep coal seams
Get PDFCoalbed gas production contributes to energy diversification and effectively mitigates the risk of mine gas outbursts. However, the complexity and nonlinear characteristics of multifield coupled gas migration in deep coal seams pose significant challenges that traditional prediction and control methods struggle to address. This paper explores the effects of coupled multi-physics fields on gas migration and reviews a numerical simulation method that integrates fractal theory with discrete fracture network modeling, aiming to overcome the limitations of conventional models in capturing the interactions among seepage, heat transfer, stress distribution, and gas adsorption/desorption. The study highlights the interactions between fractures and pores, as well as the coupling effects between fluids f low, heat transfer, and solid mechanics. It further presents a more accurate prediction method to enhance the simulation accuracy of gas migration in deep coal seams.Document Type: PerspectiveCited as: Wang, Q., Ji, M., Liu, G., Fan, S. Multi-field coupled mathematical modeling and numerical simulation technique of gas transport in deep coal seams. Advances in Geo-Energy Research, 2025, 15(1): 87-90. https://doi.org/10.46690/ager.2025.01.0
Integration of image recognition and expert system for real-time wellbore stability analysis
Get PDFWellbore stability is a key factor affecting safe and efficient drilling. At present, it is difficult to conduct real-time and accurate analysis of wellbore stability in related research. To address the current research shortcomings, this study proposes a real-time analysis model of wellbore stability integrating image recognition and an expert system, which mainly includes caving image segmentation and recognition, and a wellbore stability expert system. The caving image recognition proposes a new dynamic threshold segmentation method based on simple linear iterative clustering superpixel segmentation and visual geometry group 19-layer image classification. After completing the segmentation of the caving image, the geometric features of the caving are calculated, and the multi-source feature fusion GoogleNet model is established by integrating the geometric features with the convolution features extracted by GoogleNet to identify the caving types efficiently. After segmentation and recognition of caving images. The wellbore stability expert system uses the caving features to establish an expert system model to determine the mechanism of wellbore instability and provide reasonable solutions. Finally, the wellbore stability integrating image recognition and an expert system model was applied to a well in field production, accurately determining the mechanism of wellbore instability in real time and effectively solving the corresponding wellbore instability problem based on the measures provided by the model.Document Type: Original articleCited as: Fan, Y., Pang, H., Jin, Y., Meng, H., Lu, Y., Wei, S., Wang, H. Integration of image recognition and expert system for real-time wellbore stability analysis. Advances in Geo-Energy Research, 2025, 15(2): 158-171. https://doi.org/10.46690/ager.2025.02.0
Integrated detection of micro-pore structures and macro-mechanical responses for hydrate-bearing sediments
Get PDFMicro-pore structures determine the macro-mechanical behaviors of porous media, whereas their quantitative linkages remain ambiguous owing to the limitations of test techniques, especially for hydrate-bearing sediments. This study proposes an integrated approach that combines low-field nuclear magnetic resonance high-frequency detection with triaxial shearing, enabling the in-situ simultaneous monitoring of both the macro-mechanical parameters and micro-pore structures. The device, which consists of a high-pressure specimen vessel, a low-field nuclear magnetic resonance measurement module, a temperature and pressure control module, and a data acquisition module, allows the real-time acquisition of transverse relaxation time distribution and magnetic resonance images during triaxial loading, facilitating the detection of pore water distribution and crack development. Preliminary verification illustrates the high reliability of the device. Under relatively low strain, the signal intensity ratio of micropores rises with a transverse relaxation time of less than 10 ms, while that of macropores decreases gradually. Conversely, the signal intensity ratios for both micropores and macropores present the opposite tendency with the strain exceeding 5.1%. Besides, with the axial strain rising from 0 to 15%, there is an increase of about 16.9% in the peak area of macropores. Randomly distributed cracks observed under triaxial shearing correspond to the increasing peak area and signal intensity ratio of macropores, which is verified by comparing the magnetic resonance and computerized tomography images. This method provides a new possibility for characterizing the failure processes of hydrate-bearing sediments and establishing macro-to-micro equivalent relationships, enhancing the applications for porous media containing phase-reversible agents.Document Type: Original articleCited as: Zhang, Y., Ji, Y., Qi, M., Dong, L., Zhang, S., Li, Y. Integrated detection of micro-pore structures and macro-mechanical responses for hydrate-bearing sediments. Advances in Geo-Energy Research, 2025, 17(3): 184-195. https://doi.org/10.46690/ager.2025.09.0
Artificial intelligence applications and challenges in oil and gas exploration and development
Get PDFThe rapid integration of artificial intelligence into oil and gas exploration and development offers transformative opportunities within the context of the global energy transition. This article highlights the key advancements and challenges in artificial intelligence applications. Machine learning algorithms enable data-driven shale sweet spot prediction, overcoming the limitations of traditional methods by capturing complex controlling factors. Intelligent core image analysis, leveraging computer vision and foundation models, enables automatic mineral identification, pore analysis, and rock structure characterization, thereby providing a comprehensive framework for microscopic reservoir appraisal. Physics-informed neural networks address the limitations of purely data-driven reservoir simulation by embedding governing seepage equations into their loss functions, thereby ensuring physical consistency and improved generalization. Multimodal architectures significantly enhance unconventional shale gas production prediction by integrating geological heterogeneity with dynamic production behavior, leading to more accurate and stable forecasts. Collectively, these AI-driven approaches underscore the importance of combining domain expertise, multi-source data, and physics-aware modeling to achieve efficient and intelligent oil and gas development.Document Type: PerspectiveCited as: Hui G., Ren Y., Bi J., Wang M., Liu C. Artificial intelligence applications and challenges in oil and gas exploration and development. Advances in Geo-Energy Research, 2025, 17(3): 179-183. https://doi.org/10.46690/ager.2025.09.0
Evolution of microstructural damage in coal under supercritical CO₂-water exposure: A multi-scale study incorporating the indentation size effect
Get PDFCO₂ sequestration in coal seams represents an effective strategy for mitigating CO₂ emissions. However, the complicated interaction of CO₂-water-coal at the micro-scale may compromise the structural integrity and mechanical strength of coal, thereby adversely impacting the efficacy and safety of CO₂ sequestration in coal seams. This study introduces a novel indentation testing method that reveals the scale-dependent evolution mechanisms of coal microstructures, enabling the accurate and reliable quantification level of degradation in the micromechanical properties caused by supercritical CO₂ water-coal interactions. Using this method, the extent of mechanical degradation in three types of coal microstructures could be accurately evaluated under supercritical CO₂ water-coal interaction. The pure organic matrix exhibited remarkable stability under all fluid treatments, with minor changes in microstructure feature and a mechanical property reduction of less than 25%. In contrast, the mineral structures were significantly altered by treatment with fluid mixed with supercritical CO₂ and brine, with erosion depths and mechanical property reductions reaching 1.6 µm and 80% in granular structures, and 6.4 µm and 90% in banded structures. However, in the absence of brine or supercritical CO₂, the erosion depths and mechanical property reductions of fusinite were limited.Document Type: Original articleCited as: Deng, B., Jiao, B., Nie, B., Jiang, C., Li, M., Zhao, Y. Evolution of microstructural damage in coal under supercritical CO₂-water exposure: A multi-scale study incorporating the indentation size effect. Advances in Geo-Energy Research, 2025, 17(3): 212-225. https://doi.org/10.46690/ager.2025.09.0