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Multi-scale evaluation of mechanical properties of granite under microwave irradiation
Get PDFNowadays, the depletion of shallow resources drives deeper mining operations. Microwave pre-treatment has shown promise for efficient drilling in deep hard rock. While previous studies have confirmed the feasibility of microwave-assisted crushing of hard rocks and analyzed their structural and mechanical property changes at various scales, the microscopic mechanisms behind the evolution of the macro-mechanical parameters of hard rock remain unclear. This study addresses this knowledge gap. At the microscopic scale, the mineral characteristics and the micromechanical properties of minerals (including interfaces) at different sites before and after microwave irradiation were tested in typical hard granites. At the macroscopic scale, the real-time monitoring of mass and surface heating-rupturing characteristics of granite during microwave irradiation was achieved. Meanwhile, acoustic wave and uniaxial compression tests were conducted to explore the evolution of the macroscopic physical and mechanical parameters of granite before and after microwave irradiation. Variability in the mineral structure and mechanical properties accounts for differences in the uniaxial compression strength of granites. To realize the macro-micro linkage, the micro-mechanical parameters of minerals in different granite sections before and after microwave treatment were upscaled. The upscaling results, obtained using the Mori-Tanaka method, closely matched those from uniaxial compression tests, and the upscaling of mineral micro-mechanical parameters in interior samples was found to accurately predict the weakening of macro-mechanical properties of granite. This study provides insights into how microwave irradiation affects the mechanical properties of granite at a microscopic level, offering a quick and efficient method for assessing microwave weakening in deep hard rock and establishing a theoretical foundation for microwave-assisted mechanical drilling in industrial applications.Document Type: Original articleCited as: Gao, M., Bai, Y., Yang, B., Xie, J., Tang, R., Yang, Z., Zhang, Y. Multi-scale evaluation of mechanical properties of granite under microwave irradiation. Advances in Geo-Energy Research, 2025, 15(1): 27-43. https://doi.org/10.46690/ager.2025.01.0
Design and experimental performance evaluation of high-temperature and high-pressure test platform for deep in-situ fidelity coring tools
Get PDFWith the increasing mining depth of mineral resources, the temperature and pressure of the underground environment are also on the rise, which puts forward strict requirements for the performance of fidelity coring tools. To promote the development of such tools, a comprehensive high-temperature and high-pressure test platform for deep in-situ fidelity coring tools was constructed, and its working principle was described in detail. In addition, four key functional modules of the test platform were developed. On the basis of the principle of gas-liquid pressurization and the burst failure criterion of pressure vessel, a mechanical module integrating the functions of pressurization and pressure maintaining was designed. The heating and insulation module was developed by using a U-shaped high-speed heater and electromagnetic induction heating technology. The innovation utilized coil cooling technology to achieve effective cooling and pressure relief. Furthermore, the working performance of the test platform was studied experimentally. The designed test platform could run stably for more than 110 min under test conditions of high pressure and temperature of 140 MPa and 150 ◦C, respectively, and it could maintain a stable pressure and temperature at 200 MPa and 160 ◦C for more than 182 min. Under the high-pressure condition of 220 MPa, the pressure remained stable within 140 min, without any fluid leakage. Therefore, the test platform designed in this study can provide experimental conditions of high pressure and high temperature for the research of fidelity coring tools, which is of great significance for the accurate evaluation and safe exploitation of deep mineral resources.Document Type: Original articleCited as: Huang, W., Li, J., Yang, Y., Liu, Z., Shang, D. Design and experimental performance evaluation of high-temperature and high-pressure test platform for deep in-situ fidelity coring tools. Advances in Geo-Energy Research, 2025, 15(1): 55-67. https://doi.org/10.46690/ager.2025.01.0
Infrared thermal imaging under a macro lens empowers geo-energy exploration and development: Application scenarios and scheme conceptions
Get PDFThis study introduces the potential applications of infrared thermal imaging under a macro lens in the realm of geo-energy. Leveraging disparities in the thermal radiation of objects, this technology captures minute thermal signals from small objects through its macro lens, offering benefits such as straightforward sample preparation, rapid testing, and non-destructive imaging. In the context of static attribute characterization of reservoirs, it facilitates the acquisition of temperature data and the identification of macroscopic geological attributes like lithology via machine learning. It also enables precise characterization of microscopic solid components and fluid distribution, based on variances in thermophysical properties, and aids in determining multidisciplinary properties of rocks. In studies concerning dynamic behavior, it allows for real-time monitoring of structural changes during reservoir heating or cooling, the design of in-situ conversion heating schemes for low-maturity shale oil, tracking of fluid-rock interactions and microbial oil extraction characteristics, and provides dynamic information to optimize extraction schemes in energy development and utilization. Although there are challenges in practical applications, innovative ideas and technological progress are expected to overcome these obstacles, supporting the efficient exploration and sustainable development of geo-energy.Document Type: PerspectiveCited as: Du, S., Bai, L., Zhao, A., Wang, Y. Infrared thermal imaging under a macro lens empowers geo-energy exploration and development: Application scenarios and scheme conceptions. Advances in Geo-Energy Research, 2025, 16(1): 4-7. https://doi.org/10.46690/ager.2025.04.0
Saturation-functions models in CO2-brine system: A comparative study
Get PDFCO2 injections into deep saline aquifers create a multiphase flow system within the porous media. In this context, relative permeability and capillary pressure, as saturation functions, are key parameters that control flow dynamics, simulation accuracy, and operational decisions. Since various models have been proposed for the saturation functions, this study aims to assess the existing models and investigate which model performs best under different circumstances. To this end, we first gathered a comprehensive data set to evaluate the existing models. Following that, the nonlinear fitting of experimental data was used to obtain the parameters of each model. Finally, the root-mean-square error and correlation coefficients were used to assess the accuracy of the fit. Based on the results of capillary pressure analysis, the models can be classified into two main categories. The first category includes models with power-law behavior suitable for homogeneous formations (single curvature), such as Brooks-Corey, Li-Horne, Lambda, Thomeer, Leverett J-function, and modified J-function models. The second category includes Van Genuchten, Kosugi, Skelt-Harison, Johnson, and Jing-Van Wunnik, which can be applied to homogeneous and heterogeneous formations (capture more than one curvature). Regarding relative permeability, the L.E.T., Chierici, Van Genuchten, and Corey models exhibit comparable performance across all scenarios. Corey offers simplicity with minimal parameters, while Van Genuchten provides more adaptability for complex data sets with more physically based parameters.Document Type: Original articleCited as: Faramarzi, M., Tabatabaei, S. M., Sedaee, B., Attari, N., Panahi, S. A. Saturation-functions models in CO2-brine system: A comparative study. Capillarity, 2025, 14(2): 35-52. https://doi.org/10.46690/capi.2025.02.0
Borehole full-waveform inversion of monopole logging in slow formations: Insights for shear-wave velocity profiling
Get PDFSlow formations, characterized by shear-wave velocities lower than those of the borehole fluid, present significant challenges for shear-wave velocity estimation using monopole acoustic logging, primarily due to the absence of critically refracted shear waves. To address this limitation, a borehole full-waveform inversion framework is proposed in this paper, which employs low-frequency monopole excitation to exploit the sensitivity of Stoneley waves to shear velocity. The elastic wave equation is reformulated in cylindrical coordinates as a recurrent neural network structure within a deep learning framework, allowing automatic differentiation for efficient gradient computation without adjoint-state methods. Numerical experiments reveal that while high-frequency monopole data can accurately recover compressional-wave velocities, they fail to resolve shear-wave velocities due to weak Stoneley energy in the high-frequency data. In contrast, strong low-frequency Stoneley waves enable robust and reliable shear-wave inversion. An inversion workflow is further proposed, in which an initial shear-wave velocity model is derived by applying a velocity ratio to the inverted compressional-wave model and subsequently refined through inversion of low-frequency monopole data. The proposed approach yields high-accuracy shear velocity profiles in the near-wellbore region and remains effective under complex geological conditions, including small-scale anomalies and ultra-slow formations. These results highlight the critical role of Stoneley waves in monopole-based inversion and offer a practical solution for estimating the shear-wave velocities of slow and unconsolidated formations.Document Type: Original articleCited as: Xu, S., Liu, Y., Zou, Z., Liu, Y. Borehole full-waveform inversion of monopole logging in slow formations: Insights for shear-wave velocity profiling. Advances in Geo-Energy Research, 2025, 17(1): 82-90. https://doi.org/10.46690/ager.2025.07.0
Investigating rock properties and fracture propagation pattern during supercritical CO₂ pre-fracturing in conglomerate reservoir
Get PDFCarbon dioxide pre-fracturing has shown high application potential in improving oil recovery in conglomerate reservoirs. However, the influence of CO₂ on the physical properties of reservoir rock and its diffusion behavior within the reservoir matrix have not been systematically studied. This paper integrates CO₂-saturated water soaking experiments, true triaxial fracturing experiments and field-scale tests to demonstrate that CO₂ soaking induces quartz reduction and clay mineral increase, leading to a decrease in porosity and mechanical strength. Clay-cemented conglomerates experience a greater loss in compressive strength and a higher reduction in permeability compared to calcareous-cemented counterparts under identical CO₂ soaking. In the horizontal principal stress direction, CO₂ fracturing achieves a greater fracture penetration depth than slickwater fracturing or CO₂ pre-injection followed by slickwater fracturing. CO₂ pre-fracturing reduces breakdown pressure by 15%-5% and increases fracture complexity. Field tests confirm a reduction in injection pressure and improved effective stimulation. However, dnarrower fracture width and higher tortuosity may limit proppant transportation.Document Type: Original articleCited as: Zhou, H., Yan, T., Trivedi, J., Wang, B., Zhou, F. Investigating rock properties and fracture propagation pattern during supercritical CO₂ pre-fracturing in conglomerate reservoir. Advances in Geo-Energy Research, 2025, 17(2): 95-106. https://doi.org/10.46690/ager.2025.08.0
Pore-scale investigation of the effects of wetting phase re-imbibition on gas capillary trapping in porous media
Get PDFCapillary trapping of the non-wetting phase in porous media is vital for long-term CO2 sequestration and underground gas storage. While injection strategies have received extensive research attention, the pore-scale mechanisms controlling residual gas stability during wetting phase re-imbibition under varying injection directions coupled with buoyancy remain unclear. This study used high-resolution micro-focus X-ray computed microtomography imaging and quantitative analysis to investigate gas trapping in a hydrophilic glass bead pack across multiple capillary numbers. Both downward (gravityaligned) and upward (gravity-opposing) re-imbibition were tested. The results demonstrate that downward injection promotes bubble fragmentation and stabilization, sustaining higher residual saturation, increased populations of small bubbles, and greater specific surface area even under elevated capillary numbers. Upward injection, in which buoyancy aligns with flow, enhances bubble coalescence and mobilization, lowering residual saturation and trapping efficiency. These pore-scale trends highlight the critical interplay of capillary, viscous, and buoyancy forces in shaping gas trapping behavior. The findings of this study provide valuable experimental insights for optimizing injection direction and flow rate, in order to improve long-term CO2 storage security and underground gas storage operations.Document Type: Original articleCited as: Zhang, C., Zhang, K., Yoshida, S., Li, Z., Zhao, W., Suekane, T. Pore-scale investigation of the effects of wetting phase re-imbibition on gas capillary trapping in porous media. Capillarity, 2025, 17(1): 16-26. https://doi.org/10.46690/capi.2025.10.0
Influence of roughness on spontaneous air-water imbibition in fractures: Insights from mathematical model analysis
Get PDFWith the aim to explore the effects of fracture surface roughness on spontaneous imbibition behavior, this study investigates spontaneous air-water imbibition in rough fractures. For this purpose, a mathematical model that comprehensively accounts for fracture surface roughness and gravitational influence is developed. Using the Lambert function, a fully analytical solution for the imbibition height during the spontaneous air-water imbibition process is derived. The results indicate that neglecting fracture surface roughness leads to the overestimation of imbibition rate in model predictions. Moreover, the equilibrium imbibition height is significantly greater than the actual values, which aligns with the experimental observations. As the fractal dimension increases, the rate of imbibition height change decreases, and the imbibition height attained within the same time period is correspondingly reduced. A decrease in contact angle and an increase in interfacial tension both amplify the effect of roughness on imbibition behavior. Additionally, both the equilibrium height and the time required to reach equilibrium decrease with increasing fractal dimension. This research not only deepens the understanding of fluid flow mechanisms in complex fracture networks but also provides essential theoretical support and scientific guidance for engineering applications such as oil and gas extraction.Document Type: Original articleCited as: Cheng, H., Lai, R., Liu, J., Zhao, X., Yuan, Y., Wang, F. Influence of roughness on spontaneous air-water imbibition in fractures: Insights from mathematical model analysis. Capillarity, 2025, 16(3): 87-94. https://doi.org/10.46690/capi.2025.09.03A correction has been applied to this article in: Corrigendum to “Influence of roughness on spontaneous air-water imbibition in fractures: Insights from mathematical model analysis” [Capillarity 2025, 16(3): 87-94]Read correction
Surface acoustic wave manipulation of fluids and suspended particles in microchannels and sessile droplet: A review
Get PDFAcoustofluidic technology enables the precise motion control of microfluids and their suspended matter through microscale flow channels or acoustic streaming mechanisms, featuring multi-functionality, high throughput, dynamic controllability, fast response, high precision, and low energy consumption. In recent years, numerous literatures have reviewed the development of acoustofluidic technology, discussing the acoustic manipulation modes of particles in microfluids and their applications. However, research on the surface acoustic wave-based acoustic manipulation of particles and fluids in different microfluids remains scarce. This paper aims to provide a comprehensive review of this topic, delving into the fundamental principles of surface acoustic wave-based acoustofluidic technology and discussing the latest advancements in this field. First, the basic theory of acoustofluidic technology is introduced along with the forces involved in manipulating particles and fluids, then the advantages and disadvantages of different types of surface acoustic wave devices are reviewed. Microfluids are categorized into two main types: Fluids within microchannels and droplets on open surfaces. The surface acoustic wave-based acoustic manipulation methods for their internal fluids and suspended particles are discussed separately. Subsequently, the advantages and limitations of surface acoustic wave-based platforms in the acoustic manipulation of fluids and particles are analyzed. The work concludes with a summary of the challenges faced by acoustic streaming in the field of fluid and particle manipulation, followed by prospects for the future development of acoustofluidic technology.Document Type: Invited reviewCited as: Peng, L., Zhou, Y., Guan, W., Zhao, F. Surface acoustic wave manipulation of fluids and suspended particles in microchannels and sessile droplet: A review. Capillarity, 2025, 17(1): 1-15. https://doi.org/10.46690/capi.2025.10.0
Enhanced oil recovery via CO₂ flooding in tight reservoirs: A pore-scale analysis
Get PDFCO₂ 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 articleCited 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.2025.08.0