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Mechanism of organo-nickel co-enrichment in marine black shale
Get PDFOrganic matter and metal elements are commonly co-enriched in marine black shales. However, the element types vary among different shales and the relevant mechanisms of organo-metal co-enrichment are still unclear. The super-enrichment of organic matter and nickel in the ore bed of Early Cambrian marine black shale of southern China provides an ideal opportunity to investigate this mechanism. Herein, to clarify the coenrichment mechanism of organic matter and , the laminated structure of this ore bed was characterized and the geochemical and mineralogical proxies of different laminae were analyzed. The results indicated that there are four types of laminae in this ore bed, namely, siliceous laminae, calcareous laminae, clay minerals laminae, and organic-rich laminae. Clay minerals laminae and organic-rich laminae were deposited under anoxic environments, while siliceous laminae were deposited under strong oxidizing to anoxic environments. Neither organic matter nor are distributed homogeneously in the ore bed; organic matter is mainly concentrated in organic-rich laminae, while is largely enriched in clay minerals laminae. Clay minerals and organic matter have strong adsorption capacity for , and the adsorption capacity of clay minerals (such as illite) for is stronger than that of organic matter. Hydrothermal events and terrestrial input are key factors affecting the paleoenvironment and laminated structure during the deposition of the ore bed. Although organic matter and are co-enriched in the ore bed, their enrichment stages and conditions vary according to the geochemical differences among laminae.Document Type: Original articleCited as: Xia, P., Hao, F., Yang, C., Tian, J., Fu, Y., Wang, K. Mechanism of organo-nickel co-enrichment in marine black shale. Advances in Geo-Energy Research, 2024, 13(1): 10-21. https://doi.org/10.46690/ager.2024.07.0
Experimental and numerical study of the water-in-oil emulsions in porous media
Get PDFIn different industries and environments, water-in-oil emulsions are complicated mixtures of multiple phases. They are useful for enhanced oil recovery, petroleum refining, and oil spill remediation. The behavior and properties of water-in-oil emulsions through porous media depend on several factors, such as interfacial tension, contact angle, and oil viscosity. In this work, modeling of water-in-oil emulsions was performed using COMSOL Multiphysics and validated using experimental data. The utilized experimental method included a T-junction microfluidic device to visualize and measure how the water droplets in water-in-oil emulsions differ in size, shape, and displacement. A sensitivity analysis was conducted to evaluate the impacts of interfacial tension, contact angle, oil and water channel size, and oil viscosity on the water and oil droplet sizes, distribution, and mobility in porous media. The results show the effects of water salinity, flow rates, and asphaltenes on the interfacial tension and water droplet size in water-in-oil emulsions using a T-junction microfluidic device. The size of droplets water-in-oil emulsions is influenced by the water’s salinity, the interfacial tension between water and oil, and the flow rate within each phase. The optimal water droplets were obtained by the seawater diluted two times (SW#2), and the droplet shape and breakup were influenced by the shear rate, reynolds number and weber number. The rates of flow affect the shaping and division of droplets, while the suggested modeling approach can precisely depict the behavior and structure of water-in-oil emulsions within porous media. The findings of this research provide valuable insights for optimizing the performance and efficiency of water-in-oil emulsion processes.Document Type: Original articleCited as: Zarin, T., Aghajanzadeh, M., Riazi, M., Ghaedi, M., Motealeh, M. Experimental and numerical study of the water-in-oil emulsions in porous media. Capillarity, 2024, 13(1): 10-23. https://doi.org/10.46690/capi.2024.10.0
Pore scale modeling of fluid transport in complex reservoirs: Multi-scale digital rock construction, flow experiments and simulation methods
Get PDFThe heterogeneities of complex reservoirs are expressed in terms of multi-scale pore structure, different pore type and multiple occurrence mode. Fluid transport mechanisms notably differ from that in conventional sandstone reservoir. Conventional core scale experimental methods are not applicable to complex reservoirs because of nanoscale pore size and strong heterogeneity. Investigating pore scale fluid flow is the key to reveal flow mechanisms while the current pore scale modelling framework fails to consider the multi-scale structure, multiphase fluid-rock interaction and confined phase change. This work leverages the recent advances in pore scale modeling methods of fluid transport in complex reservoirs. The developing trend of multi-scale digital rock construction, flow experiments and simulation methods are elaborated in detail. The mentioned pore scale modeling methods in this work form the future research paradigm for understanding fluid transport mechanisms in complex reservoirs.Document Type: Current minireviewCited as: Song, W., Liu, F., Li, Y., Yang, Y. Pore scale modeling of fluid transport in complex reservoirs: Multi-scale digital rock construction, flow experiments and simulation methods. Capillarity, 2024, 11(3): 81-88. https://doi.org/10.46690/capi.2024.06.0
Accurate structural characterization of nanopores in coal by cryo-FIB-SEM
Get PDFThe structural characteristics of nanopores are known to significantly affect the wetting effect in coal seam water injection. Currently, the three-dimensional characterization of nanopores in coal relies mainly on digital images, whereas poor image resolution and segmentation methods pose significant challenges. Therefore, using coal samples from Wudong Coal Mine in China as an example, cryo-focused ion beam scanning electron microscopy (cryo-FIB-SEM) and deep learning segmentation methods were implemented to accurately characterize the nanopores and water distribution. In the obtained pore structure, the number of isolated pores was higher than that of connected pores, while the volume of connected pores was significantly larger than that of isolated pores, comprising the key path and storage space for external water to enter the coal body. The water content of isolated pores mainly depends on the permeability of the coal matrix. The connectivity of single pores can be characterized by the coordination number, whose increase leads to the number of pores exponentially decreasing. The connectivity of pore clusters depends on the number of internal branches. The number of branches in the pore cluster increases exponentially with the increasing total length, total volume and average radius of the cluster, and the connectivity is correspondingly enhanced. The increase in pore size enhances the shape factor, surface area and connectivity of pores while reducing tortuosity, which in turn facilitates coal wetting. The accurate characterization of coal nanopores in this study helps to scientifically evaluate the effect of coal seam water injection, highlighting the importance of increased pore size and improved pore connectivity for enhanced water injection effectiveness.Document Type: Original articleCited as: Wang, G., Chen, X., Wang, G., Zhang, H., Wang, J., Xu, H. Accurate structural characterization of nanopores in coal by cryo-FIB-SEM. Advances in Geo-Energy Research, 2024, 14(3): 187-200. https://doi.org/10.46690/ager.2024.12.0
Geomechanical properties of hydrate-bearing strata and their applications
Get PDFNatural gas hydrate is an alternative potential energy source that contributes to depressurizing the pressure of energy supply and environmental pollution in the future. Field hydrate production has a close association with geological risks. In this regard, accurate estimation of strength and deformation properties is crucial to risk prevention and control during hydrate development. However, the geomechanical properties of hydratebearing sediments and their applications remain unclear. Herein, this work provides a comprehensive summary of studies on the mechanical characteristics of hydrate-bearing sediments and their applications in field trials. It starts with the main research methods, including laboratory tests, constitutive modeling, and numerical simulations, followed by the effects of clay content, hydrate distribution, and morphology on mechanical properties. Besides, typical applications of geomechanical parameters are examined and discussed. Finally, the challenges and perspectives of mechanical studies on hydrate-bearing sediments are presented, which is favorable for the evaluation and control of geological risks during hydrate exploration and development.Document Type: PerspectiveCited as: Dong, L., Liu, X., Gong, B., Li, Y. Geomechanical properties of hydrate-bearing strata and their applications. Advances in Geo-Energy Research, 2024, 11(3): 161-167. https://doi.org/10.46690/ager.2024.03.0
Artificial intelligence-based investigation of fault slip induced by stress unloading during geo-energy extraction
Get PDFSeismic events triggered by stress unloading during geo-energy extraction activities have become a key focus in both seismological research and engineering safety. This study presents a novel application of waveform neural networks, combining unsupervised and supervised learning techniques to classify and characterize fractures in laboratory-induced seismic events. Initially, A neural network model was initially developed that is capable of extracting time-frequency features from waveforms through unsupervised training on 1.2 million Acoustic Emission waveforms. Subsequently, this model was fine-tuned using a labeled dataset obtained from Brazilian split and uniaxial compression tests. The final result was a highly accurate model, achieving an accuracy rate of 97.6%. By applying this refined model, insights have been gained into the complex fault slip behaviors induced by geo-energy extraction activities. Our findings reveal that fluid infiltration at the onset triggers low-energy, shear-induced fractures in low-stress fault regions, which then escalate into tensile fractures during critical sliding in high-stress areas. Key precursors to fluid-induced seismicity have been identified, providing a major advance in early seismic hazard detection. These insights are essential for monitoring and early warning of induced seismicity during geo-energy extraction activities. Our work contributes significantly to improving the safety and efficiency of geo-energy extraction, including geothermal, shale gas, and conventional hydrocarbon production.Document Type: Original articleCited as: Song, Z., Qian, Y., Mao, Y., Chen, X., Ranjith, P. G., Deng, Q. Artificial intelligence-based investigation of fault slip induced by stress unloading during geo-energy extraction. Advances in Geo-Energy Research, 2024, 14(2): 106-118. https://doi.org/10.46690/ager.2024.11.0
Design of passive insulation system and optimization of thermal insulation material for deep in-situ condition-preserved coring
Get PDFIn order to help establish a new theory of deep rock mechanics and better guide the development of deep engineering, it is crucial to develop a deep in-situ condition preserved coring device capable of obtaining cores while maintaining their original in-situ temperature and pressure conditions. To achieve insulation functionality within a compact design, a passive insulation system must be developed for such coring devices. Considering the size constraints and thermal insulation requirements, a passive thermal insulation system combining a vacuum layer and an insulating material layer has been designed in this work. Epoxy resin was selected as the insulation material due to its high compressive strength and low thermal conductivity. The type and dosage of curing agents, as well as the curing process with epoxy resin, were optimized. The ideal resin achieved a compressive strength of 241.03 MPa and a thermal conductivity as low as 0.25 W/m·K. Additionally, it exhibited excellent thermal stability and a high decomposition temperature. Under high temperature and high-pressure water conditions simulating deep-earth environments, the epoxy resin’s maximum water absorption was below 0.7%. The insulation layer could effectively minimize heat exchange between the core and the external environment by up to 19.01%. These findings provide a significant contribution to the advancement of passive insulation systems for deep in-situ core drilling operations.Document Type: Original articleCited as: Yang, J., Bai, H., He, Z., Yu, B., Xie, H. Design of passive insulation system and optimization of thermal insulation material for deep in-situ condition-preserved coring. Advances in Geo-Energy Research, 2025, 15(2): 99-111. https://doi.org/10.46690/ager.2025.02.03
Evolution of rock pore structure and physical properties due to acidification: Recent advances and future perspectives
Get PDFAcidification is crucial to oil and gas development, which effectively improves reservoir development by reacting acid with some minerals in the rock. There are a large number of minerals that react with acid in carbonate and shale reservoirs. Acidification has a good effect in these two reservoirs, so it is necessary to conduct multi-scale research on the acidification process. This work briefly introduces the evolution characteristics and factors affecting acidification on reservoir pore structure and physical properties, and also analyzes their similarities and differences. Meanwhile, the application status of the acidification method is also discussed. Finally, the challenges and opportunities faced by shale acidification are discussed, aiming to provide new insights into the development of acidizing technology.Document Type: PerspectiveCited as: Zhao, F., Jiao, X., Xia, X., Xu, S., Sun, L., Xia, Y. Evolution of rock pore structure and physical properties due to acidification: Recent advances and future perspectives. Advances in Geo-Energy Research, 2024, 14(3): 238-240. https://doi.org/10.46690/ager.2024.12.0
Intelligent identification of coal fractures using an improved U-shaped network
Get PDFTo address the challenges of coal fracture image recognition, including interference from gangue and multiscale fractures, a multiscale coal fracture segmentation network model to significantly enhance the recognition of coal fracture structures is proposed. The model significantly enhances the recognition of fracture structures based on a U-shaped network architecture and the incorporation of several advanced techniques, including transfer learning, depthwise separable atrous convolutions, and residual modules. Transfer learning, by leveraging pretrained visual geometry group 16-layer network weights, bolsters the feature extraction capabilities of an encoder. Simultaneously, the integration of depthwise separable atrous convolutions and residual modules optimizes a decoder, thereby improving segmentation accuracy and the robust recognition of fractures within images. Experimental results based on qualitative and quantitative data showed that the proposed model surpassed traditional convolutional neural networks, demonstrating proficiency in identifying multiscale fractures in complex coal images. The model was applied to the identification of fractures in roadway surrounding rock boreholes. By extracting fractures from borehole imaging videos and planar diagrams, and conducting cross-validation, the study precisely delineated the fracture distribution. Additionally, to improve coal seam gas extraction efficiency, the grouting and sealing range for cross-layer extraction boreholes was determined.Document Type: Original articleCited as: Wang, D., Li, L., Zhang, H., Li, S., Zhang, F., Xia, Y. Intelligent identification of coal fractures using an improved U-shaped network. Advances in Geo-Energy Research, 2025, 15(2): 129-141. https://doi.org/10.46690/ager.2025.02.0
Study of the pore size influence on infiltration of porous media considering capillary effect
Get PDFThe significance of pore size as a determinant in two-phase flow dynamics is widely acknowledged. However, the micro-scale behavior of flow including pore channel capillary and air-water interface development are not systematically interpreted due to the limitation of test and computation methodologies. In the present study, an investigation was conducted into the impact of varying pore throat widths on the flow of a two-phase fluid. For the investigation, numerical simulations were integrated with microfluidic experimentation to provide a comprehensive analysis. The results indicate that large pore diameters in porous media are associated with accelerated infiltration rates, leading to quicker stabilization. However, an inverse correlation exists between pore throat diameter and seepage area, with larger diameters yielding larger residual air areas. In this investigation, the “queuing effect” was observed across all tests, irrespective of pore throat diameter. Water initially permeated the central region of the pore network, sequentially inducing a breakthrough in adjacent pores. It was found that smaller pore throat diameters necessitated higher breakthrough pressures. Consistently, under unchanged inlet flow rates, narrower channels exhibited greater capillary resistance, impeding water flow. Specifically, for the four models with increasing pore throat widths, the critical capillary resistances are decreasing continuously from 87.6 to 38.2 Pa ultimately.Document Type: Original articleCited as: Lu, Z., Zeng, C., Zhang, Y., Lu, H. Study of the pore size influence on infiltration of porous media considering capillary effect. Capillarity, 2025, 14(1): 1-12. https://doi.org/10.46690/capi.2025.01.0