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The mechanism of capillaries hydraulic conductivity evolution under confining pressure: Experimental modelling using 3D-printing approach
Get PDFThe effect of confining pressure on the hydraulic conductivity of capillaries in cylindrical samples is examined. The three-dimensional-printed samples were made from photopoly-mer resin. Capillaries in the samples were modeled by grooves of various geometric shapes. The mechanism of capillary deformation in the samples under increasing confining pressure has been identified. The change in capillary conductivity depending on their location (central and lateral) and configuration (sinuous) has been revealed. Based on correction functions for the geometric dimensions of the capillaries, it has been mathematically confirmed that under confining pressure, a capillary deforms primarily along the contact plane due to the sliding of the sample’s halves against each other. The width of a capillary is more sensitive to confining pressure than its depth. It has been established that the exponent in the conductivity (permeability) equation of the samples under cyclic loading is determined by the hydraulic area of the capillary. The obtained values of the width and depth correction factors allow for predicting changes in the filtration resistances of capillaries in various materials. Capillary deformation manifests as a change in its geometric dimensions (height and width), i.e., the crushing of the capillary banks is observed, leading to a reduction in the capillary’s hydraulic area, which causes a decrease in sample conductivity with an incomplete hysteresis.Document Type: Original articleCited as: Riabokon, E., Turbakov, M., Kozhevnikov, E., Kobiakov, D., Ivanov, Z., Guzev, M., Yu, L. The mechanism of capillaries hydraulic conductivity evolution under confining pressure: Experimental modelling using 3D-printing approach. Capillarity, 2025, 17(3): 97-108. https://doi.org/10.46690/capi.2025.12.0
Aminated nano-silica reinforced slickwater fracturing fluids with enhanced drag reduction, proppant transport and thermal stability
Get PDFConventional slickwater fracturing fluids undergo severe thermal degradation in hightemperature reservoirs, significantly impairing their drag reduction efficiency and proppant transport capability. To address this limitation, this study presents a novel temperatureresistant slickwater system by incorporating aminated nano-silica with an acrylamide-2acrylamido-2-methylpropane sulfonic acid copolymer and a flowback aid/clay stabilizer. Macroscopic experiments and molecular dynamics simulations reveal that the system achieves a drag reduction rate of 69.7% at 150 ◦C, a 10-percentage-point improvement over the non-reinforced system. It also reduces the proppant settling area by 21.2%, facilitating more uniform proppant distribution toward the fracture distal end, and retains 77.8% of its initial viscosity after thermal aging. Nanoparticles in the system exhibit a synergistic dualreinforcement mechanism: Their surface adsorption smooths wall roughness and thickens the elastic boundary layer, suppressing turbulence and mitigating energy dissipation; hydrogen bonding and electrostatic interactions between the amino groups of nanoparticles and the moieties of copolymer form an interfacial network, effectively restricting the segmental mobility of the copolymer. This method increases the glass transition temperature of the system by 57.5 ◦C, markedly enhancing its thermal stability. Molecular simulations confirm an 18.7% increase in hydrogen bond density and a 23.5% reduction in segmental mobility, collectively stabilizing the polymer against thermal degradation. This study provides valuable insights for developing high-performance fracturing fluids suitable for deep reservoirs.Document Type: Original articleCited as: Ding, F., Dai, C., You, Q., Yu, W., Sun, W., Song, X. Aminated nano-silica reinforced slickwater fracturing fluids with enhanced drag reduction, proppant transport and thermal stability. Advances in Geo-Energy Research, 2025, 18(2): 153-164. https://doi.org/10.46690/ager.2025.11.0
Impact of micro-scale characteristics of shale reservoirs on gas depletion behavior: A microscale discrete model
Get PDFShale gas has become increasingly significant in the global energy supply. Mineral heterogeneity in shales importantly impacts gas transport within the shale matrix and therefore the depletion history curve. A microscale discrete coupling model is introduced to clarify mass transfer and mechanical interactions, as well as their impact on gas transport properties, ranging from individual mineral through ensemble field scale. The model uses a mineral morphology thin-section obtained through tescan integrated mineral analyzer with the mechanical parameters, controlling both elastic and viscosity behavior of each mineral, achieved through nanoindentation. A coupled model for poromechanical evolution is proposed and solved using COMSOL. The applicability of the model results are validated against field data using a dimensionless approach. This confirms that in the early stages of gas depletion, gas is primarily liberated from inorganic minerals, whereas in later stages, it is predominantly sourced from adsorbed gas from the organic matter. Over time, the permeability of the inorganic minerals decreases, and a higher Young’s modulus of the minerals results in a greater ultimate permeability ratio. Evolution of the effective diffusion coefficient for the organic matter is controlled by multiple components. A negative correlation exists between mineral grain size and the creep effects, indicating that larger grain sizes result in smaller creep magnitudes during gas production. The Young’s modulus of inorganic matter is inversely correlated with the diffusion coefficient, while an increase in the Young’s modulus in the organic matter corresponds to a higher diffusion coefficient. The proposed model complements the traditional continuum dual-medium method and provides a clearer understanding of the interactions between minerals during gas depletion behavior.Document Type: Original articleCited as: Cheng, W., Guo, Y., Cui, G., Elsworth, D., Tan, Y., Pan, Z. Impact of micro-scale characteristics of shale reservoirs on gas depletion behavior: A microscale discrete model. Advances in Geo-Energy Research, 2025, 15(2): 143-157. https://doi.org/10.46690/ager.2025.02.0
The effects of clay minerals on imbibition in shale reservoirs: A review
Get PDFThe imbibition process plays a crucial role in the development of shale reservoirs, particularly during the volume fracturing and water injection development phases. This process significantly influences the production capacity of shale and also serves as a essential parameter for assessing reservoir performance. Clay minerals contribute to the formation of numerous micro-pores and micro-fractures, exhibit strong plasticity and are prone to swelling. The unique structures and properties of clay minerals have a profound impact on shale imbibition. This review analyzes the effects of clay minerals on imbibition from different perspectives, finding that the effect is closely related to the total amount of clay minerals, as well as to specific mineral types and content. Clay minerals exhibit a dual impact on imbibition, which can either facilitate imbibition by promoting micro-fractures formation or hinder it by reducing pore throats and migrating to block flow paths due to swelling. While capillary action is usually considered the main mechanism for fluid displacement during the imbibition, the osmotic pressure formed by clay minerals can also serve as a driving force for imbibition, positively contributing to shale oil and gas recovery. This review aims to provide a comprehensive understanding of the role of clay minerals on the imbibition, providing a theoretical foundation and practical guidance for future research and efficient development of shale reservoirs.Document Type: Invited reviewCited as: Wang, L., Wang, H., Xia, X., Zhao, F., Masoodi, R., Xia, Y. The effects of clay minerals on imbibition in shale reservoirs: A review. Capillarity, 2025, 14(1): 13-22. https://doi.org/10.46690/capi.2025.01.0
Molecular insights into two-phase flow in clay nanopores during gas hydrate recovery: Wettability-induced multiple pathways of water lock formation
Get PDFA comprehensive understanding of the intricate water/gas two-phase flow in sedimentary pores is essential for accurately predicting gas production following the in-situ dissociation of natural gas hydrates, as it is crucial for optimizing resource extraction strategies. This study constructed three typical clay slit nanopore models with distinct wettability characteristics – hydrophilic, relatively hydrophobic, and Janus hybrid-wettability – and used molecular dynamics simulations to investigate the spatial distribution and transport dynamics of two-phase fluids under varying water saturation conditions. The results revealed a significant negative correlation between water saturation and gas relative permeability. When water saturation reaches a critical threshold, the water lock effect occurs, blocking gas flow. Pore wettability plays a key regulatory role in water/gas phase dynamics via influencing the formation pathways of water locks. In relatively hydrophobic pores, weaker solid-water interactions promote the rapid clustering of water molecules, forming water locks, while hydrophilic surfaces enable water lock formation through gradual thickening of the liquid film. In Janus pores with low water saturation, strong electrostatic interactions between oppositely charged pore walls facilitate the formation of discrete water bridge networks, maintaining “gas windows” that allow gas flow, although these windows eventually close as saturation increases. The lower the water saturation, the more favorable it is for gas transport; in contrast, hydrophilic pores exhibit higher gas transport efficiency. Our findings provide valuable molecular-scale insights into how wettability governs multiphase flow transport, offering a theoretical foundation for reservoir modification and seepage control in natural gas hydrate recovery.Document Type: Original articleCited as: Fang, B., Zhang, Z., Zhang, Q., Guo, G., Jiang, J., Ning, F. Molecular insights into two-phase flow in clay nanopores during gas hydrate recovery: Wettability-induced multiple pathways of water lock formation. Advances in Geo-Energy Research, 2025, 17(1): 17-29. https://doi.org/10.46690/ager.2025.07.0
Evaluation of the cross-scale mechanical behavior and fracability of deep shales: How innovations benefit the exploitation of deep resources
Get PDFDeep/ultra-deep oil and gas resources are abundant at vertical depths of more than 3,500 m, which is an important succeeding field for future oil and gas exploitation. However, a lack of understanding of the multi-scale mechanical behavior of deep reservoirs under in situ conditions, as well as an insufficiently accurate prediction of engineering sweet spots, restricts the effectiveness of hydraulic fracturing in deep shale gas exploitation. In this study, the application of cross-scale rock mechanics, digital rock core modeling, and machine learning in characterizing reservoir geomechanical properties and assessing engineering sweet spots was summarized. The challenges and future development directions of the above research elements were explored. To achieve efficient deep-resource exploitation, it’s essential to clarify the mechanical behavior of shales with different mineral compositions at micro- and macro-scales. Numerical models incorporating mineral spatial heterogeneity were developed to analyze the multifactorial synergistic mechanism influencing shale brittle failure. Finally, intelligent fracability prediction methods for deep shale were proposed to accurately identify engineering sweet spots. The research findings have identified the key research and development directions for deep-resources development from a rock mechanics perspective.Document Type: PerspectiveCited as: Zhao, G., Guo, Y., Yang, C., Chang X., Zhang X. Evaluation of the cross-scale mechanical behavior and fracability of deep shales: How innovations benefit the exploitation of deep resources. Advances in Geo-Energy Research, 2025, 17(2): 91-94. https://doi.org/10.46690/ager.2025.08.0
Competitive adsorption and microscopic wetting properties in CO₂-H₂O-rock systems: A review
Get PDFAt the microscopic scale, the competitive adsorption of CO₂ and H₂O alters the inter facial characteristics of rock surfaces, thereby inducing significant deviations between the microscopic wetting properties and macroscopic behaviors, a phenomenon critically impacting unconventional hydrocarbon extraction. Consequently, this paper analyzes the interfacial interactions and microscopic adsorption mechanisms of CO₂ and H₂O on rock surfaces at the molecular level and characterizes the properties of their adsorption layers. Building on this foundation, existing models of competitive adsorption and adsorption energy are summarized, revealing how alterations in interfacial properties affect wettability. Furthermore, the influence of surface energy, surface tension, surface roughness, organic content, and pore structure on the contact angle is discussed, along with the applicability and limitations of contact angle theoretical models. Overall, this paper proposes a method to achieve the accurate characterization of microscopic wetting behavior by incorporating correction coefficients (e.g., adsorption energy, surface roughness) into macroscopic models.Document Type: Invited reviewCited as: Zhang, C., Zhang, Y., Su, Y., Zhang, L., Yu, X. Competitive adsorption and microscopic wetting properties in CO₂-H₂O-rock systems: A review. Capillarity, 2025, 16(3): 61-76. https://doi.org/10.46690/capi.2025.09.0
A more rigorous mathematical model for capillary imbibition of CO2 in shale gas formations
Get PDFAmathematical model was derived in this study to reveal the mechanism of CO2 imbibition in shale formations considering the combined effects of capillary force and viscous force in concave curved triangle pore channels surrounded by different solid materials with different wettability. The model reveals that CO2 imbibition depth is proportional to the square root of CO2 soaking time, square root of the pore size determined by grain size, square root of interfacial tension and cosine of contact angle, and inversely proportional to the square root of CO2 viscosity. Up to three solid wall materials with different contact angles can be considered in the model. Using the average contact angle for the three materials over-estimates the imbibition distance. CO2 imbibition is faster in concave curved triangle pores than in equivalent circular-shaped pores. The dimensionless geometry correction factor is less than unity (α = 0.81). The newly developed imbibition model can be used for predicting the maximum time of imbibition between parallel fractures in multi-fractured shale formations.Document Type: Original articleCited as: Zhang, J., Guo, B., Amponsah, V. N. B. A more rigorous mathematical model for capillary imbibition of CO2 in shale gas formations. Capillarity, 2025, 14(3): 63-71. https://doi.org/10.46690/capi.2025.03.0
A noise-resistant and annotation-free supervoxel-based algorithm for rapid segmentation of multiphase X-ray images
Get PDFThis study introduces a three-dimensional supervoxel segmentation method to accurately separate solid and fluid phases in X-ray images of porous materials, with applications in energy research. Compared with intelligent segmentation algorithms requiring model training, the proposed method operates as a ready-to-use solution with significantly enhanced efficiency. When benchmarked against conventional approaches such as watershed transformation, our technique demonstrates superior segmentation accuracy. Tested on porous rock and gas diffusion layers under varying wettability, it accurately quantifies fluid saturation, interfacial area, curvature, and contact angles—key parameters for enhanced oil recovery, CO2 storage, and hydrogen fuel cells. The proposed three-dimensional segmentation method is noise-resistant and annotation-free, improving both the accuracy and efficiency of segmenting diverse micro-structural material datasets and providing reliable measurements of their geometric characteristics.Document Type: Original articleCited as: Ye, S., Song, X., Ma, Z., Gao, Y., Zhu, L., Zhou, M., Xiao, L., Wen, G., Bijeljic, B., Blunt, M. J. A noise-resistant and annotation-free supervoxel-based algorithm for rapid segmentation of multiphase X-ray images. Advances in Geo-Energy Research, 2025, 16(1): 50-59. https://doi.org/10.46690/ager.2025.04.06
An in-situ low-carbon enhanced oil recovery approach applied in high viscous oil reservoir
Get PDFHigh heat loss, substantial energy consumption, considerable CO2 emission and low thermal utilization efficiency are main challenges in the thermal-based production methods applied in high viscous oil reservoir. To address these limitations while achieving both high oil recovery and reduced carbon footprint, this perspective systematically investigates an enhanced high viscous oil recovery method that integrates in-situ pyrolysis with downhole electric heater. Laboratory experiments and field applications demonstrate that this novel technology offers multiple advantages over conventional thermal-based methods, such as higher thermal utilization efficiency, lower carbon emissions and reduced energy consumption. In this novel technology, with high temperature in the reservoir, inducing pyrolysis and cracking reactions in high viscous oil, significantly reducing oil viscosity and enhancing oil recovery factor. Thereby, this novel method presents a viable, low-carbon, and efficient pathway for future development of high viscous oil resources.Document Type: PerspectiveCited as: Zhou, X., Liu, J., Zhao, Y., Zeng, F., Jiang, Q., Zhang, L. An in-situ low-carbon enhanced oil recovery approach applied in high viscous oil reservoir. Advances in Geo-Energy Research, 2025, 18(3): 291-294. https://doi.org/10.46690/ager.2025.12.0