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Drilling rock image segmentation and analysis using segment anything model
Get PDFImage processing and analysis techniques are commonly utilized in various fields such as geology, underwater engineering, environmental conservation, marine resource exploration, and soil and geological assessments, particularly for examining drilling rock samples. However, processing images of rocks drilled underwater is challenging due to the intricate nature of aquatic settings, where factors such as light reflection and refraction, irregular sizes of rocks, and overlapping particles introduce noise, obscure textures, and distort colors in the images. Although improved versions of the mask region-based convolutional neural network have shown promise for quick and accurate analysis of large sets of underwater rock images, these methods can still be affected by inconsistencies in rock appearance, texture, and lighting. To address these issues, a comprehensive approach is introduced using the segment anything model. Our methodology begins with the application of Gaussian filters to reduce noise and smooth images, followed by the deployment of underwater image enhancement. Further, histogram equalization is applied to better the contrast and employ the segment anything model approach for the detailed understanding of rock features by extracting information on rock size and shape. EeEquivalent area circle diameter and axial ratio are used to generate particle size alignment maps and to ascertain shape details. Our approach has achieved an average precision rate of 80.6%, outperforming other strategies and yielding more precise rock information analysis.Document Type: Original articleCited as: Shan, L., Liu, Y., Du, K., Paul, S., Zhang, X., Hei, X. Drilling rock image segmentation and analysis using segment anything model. Advances in Geo-Energy Research, 2024, 12(2): 89-101. https://doi.org/10.46690/ager.2024.05.0
A new pixel-free algorithm of pore-network extraction for fluid flow in porous media: Flashlight search medial axis
Get PDFPore-network models have become a critical tool in the study of fluid flow in geo-energy researches over the last few decades, and the accuracy of pore-network modeling results highly depends on the extraction of pore networks. Traditional methods of pore-network extraction are based on pixels and require images with high quality. Here, a pixel-free method called the flashlight search medial axis algorithm is proposed for pore-network extraction in a continuous space. The search domain in a two-dimensional space is a line, whereas a surface domain is searched in a three-dimensional scenario. Thus, the algorithm follows the dimensionality reduction idea; the medial axis can be identified using only a few points instead of calculating every point in the void space. In this way, computational complexity of this method is greatly reduced compared to that of traditional pixel-based extraction methods, thus enabling large-scale pore-network extraction. Based on cases featuring two- and three-dimensional porous media, the algorithm performs well regardless of the topological structure of the pore network or the positions of the pore and throat centers. This algorithm can also be used to examine both closed-boundary and open-boundary cases. Finally, this algorithm can identify the medial axis accurately, which is of great significance in the study of geo-energy.Document Type: Original articleCite as: Liu, J., Zhang, T., Sun, S. A new pixel-free algorithm of pore-network extraction for fluid flow in porous media: Flashlight search medial axis. Advances in Geo-Energy Research, 2024, 13(1): 32-41. https://doi.org/10.46690/ager.2024.07.0
Brittle minerals, mechanical properties and fracability evaluation of shales
Get PDFThe brittleness of shales is critical to hydraulic fracturing since rock with high brittle minerals are more likely to fracture and maintain open fractures. Shale rocks have a wide range of constituting components, and different minerals display distinct elastic behavior. The microscale measurements of mechanical properties indicate that pyrite has the highest Young’s modulus, followed by quartz and feldspar. Organic matter was commonly recognized as the soft component, and has very low Young’s modulus. Alkaline minerals show similar Young’s modulus values to quartz and feldspar, and can be grouped into brittle minerals. The relative content, source and structure of brittle minerals can affect rock brittleness from multiple scales. Understanding the relationship between mineral compositions and geomechanical properties is beneficial for fracability estimation in engineering applications for shales.Document Type: PerspectiveCited as: Xu, S., Wen, J., Liu, K., Shi, X., Dong, T. Brittle minerals, mechanical properties and fracability evaluation of shales. Advances in Geo-Energy Research, 2024, 14(1): 8-11. https://doi.org/10.46690/ager.2024.10.0
The mechanism of porous reservoir permeability deterioration due to pore pressure decrease
Get PDFThis study investigates the causes of permeability decline in porous reservoirs under decreasing reservoir pressure by comparing laboratory experiments with well test data. Well tests indicate a greater sensitivity of permeability to pressure changes in reservoir formations compared to laboratory conditions and for this remain unclear. Field studies of permeability changes in northern Perm oil fields were conducted alongside laboratory experiments on core permeability under pressure. Results showed that highly permeable samples exhibited the greatest decline in permeability during elastic deformations, with reductions of 6% for limestones and 20% for sandstones. The relationship between permeability and purely elastic deformations for both rock types was accurately described by a power law. By comparing coefficients from field and lab studies, the mechanism of permeability decline in field conditions was established. A model incorporating elastic and plastic deformations of porous reservoirs was developed. The model considers the localization of plastic deformations in horizontal and vertical low-permeability deformation bands. Findings indicate that highly permeable formations are more susceptible to deformation band formation, particularly in thicker layers. The decrease in permeability was found to correlate strongly with the formation thickness, likely due to the formation of transverse deformation bands in pore layers.Document Type: Original articleCite as: Kozhevnikov, E., Turbakov, M., Riabokon, E., Gladkikh, E., Guzev, M., Qi, C., Li, X. The mechanism of porous reservoir permeability deterioration due to pore pressure decrease. Advances in Geo-Energy Research, 2024, 13(2): 96-105. https://doi.org/10.46690/ager.2024.08.0
Experimental and numerical simulation technique for hydraulic fracturing of shale formations
Get PDFHydraulic fracturing is crucial for extracting shale oil and gas. This technique involves creating fractures in rock formations to enhance reservoir development efficiently. Due to the complexity of shale rock, it is important to conduct multiscale investigations into the fracturing process. Despite extensive research, the technology for deep-underground shale hydraulic fracturing continues to advance as it moves deeper underground. This paper explores the existing technical challenges of shale fracturing, review the current status of physical experiments and numerical simulations, and highlight the importance of multiscale numerical simulation methods. Meanwhile, an integrated approach to optimizing fracturing designs for field cases is introduced. Finally, this paper summarizes the challenges and opportunities in shale hydraulic fracturing, aiming to provide fresh insights into the advancements of hydraulic fracturing technology.Document Type: PerspectiveCited as: Huang, L., Liao, X., Fan, M., Wu, S., Tan, P., Yang, L. Experimental and numerical simulation technique for hydraulic fracturing of shale formations. Advances in Geo-Energy Research, 2024, 13(2): 83-88. https://doi.org/10.46690/ager.2024.08.0
Integration of large-scale underground energy storage technologies and renewable energy sources
Get PDFLarge-scale underground energy storage technology uses underground spaces for renewable energy storage, conversion and usage. It forms the technological basis of achieving carbon peaking and carbon neutrality goals. In this work, the characteristics, key scientific problems and engineering challenges of five underground large-scale energy storage technologies are discussed and summarized, including underground oil and gas storage, compressed air storage, hydrogen storage, carbon storage, and pumped storage. This perspective provides valuable theoretical and technical guidance for the construction and development of large-scale underground energy storage, further promoting the utilization of renewable energy and the realization of the “double carbon target” in China.Document Type: PerspectiveCited as: Ji, W., Wan, J., Li, J., Chen, S., Ma, H., Yu, H. Integration of large-scale underground energy storage technologies and renewable energy sources. Advances in Geo-Energy Research, 2024, 14(2): 81-85. https://doi.org/10.46690/ager.2024.11.0
Failure patterns in layered gas-storage systems
Get PDFThe underground storage of gases, such as CO2 and H2, in the porous media is a critical component for achieving carbon neutrality and economical energy storage. While previous research has predominantly focused on gas injection in one piece of uniform porous media, and gravity is often neglected, the reality is that natural storage formations are typically multi-layered porous systems. An in-situ gas injection apparatus based on high resolution micro-CT was utilized to investigate gas injection behaviors and failure patterns in layered porous media systems. The system includes a reservoir layer and a cap layer, where both capillarity and permeability are meticulously controlled. Our findings reveal that all cases experience cycles of a pressure built-up period and a sudden pressure release when a barrier, either capillarity or effective stress, is overcome. Drainage conditions within the layered system significantly impact both the volume of gas trapped and the failure patterns observed. Effective stress analyses show that the key determinants of failure patterns are capillarity, effective stress, and excess pore fluid pressure, affected by pore size, cap layer thickness, gas injection rate and permeability. Five distinct failure patterns are categorized: capillary invasion, fracture opening, integral uplifting, local heaving, and violent liquefaction-based on two dimensionless parameters. This work provides new insights into understanding the gas injection dynamics in layered porous media.Document Type: Original articleCited as: Guo, Z., Gao, X., Wu, H., Liu, L., Lei, L. Failure patterns in layered gas-storage systems. Advances in Geo-Energy Research, 2024, 12(3): 183-193. https://doi.org/10.46690/ager.2024.06.0
Rock physical evolution and microscopic flow mechanism of massive energy replenishment in tight oil reservoirs
Get PDFMassive energy replenishment presents a practical approach to increase and maintain the formation pressure in tight oil reservoirs. However, the evolution of rock physical properties after this process remains unclear, posing challenges to further elucidate the related microscopic flow mechanism. In the current work, we designed a physical method that uses online nuclear magnetic resonance to simulate the life cycle of “injection, soaking, and production” in massive energy replenishment. The rock physical properties evolution and pore-scale flow mechanism are analyzed by quantitative and visualization methods. Additionally, the influence of injection volume and production pressure difference on oil recovery is clearly defined. The findings suggest that the primary evolution of microscopic pore structure during massive energy replenishment involves microfractures and micropores, promoting the involvement of more pore throats in the flow. However, the flow capacity increase varies at different locations, with a higher increase observed at the inlet than at others. The increase in pseudo-permeability exhibits exponential growth with the injection volume, and its inflection point positively correlates with initial permeability. Massive water huff and puff significantly enhances oil recovery by increasing the pore pressure and flow channels. The apparent energy enhancement and accumulation effect during soaking facilitates oil drained by imbibition to migrate towards the macropores at the outlet in abundance and being enriched. The inflection point of the increase in the recovery degree can be realized by a small pressure difference in production. Importantly, however, considering the carry-over and extrusion effect of injected water on oil droplets, a combination of flooding and soaking is essential to mobilize the fluid in micro-mesopores.Document Type: Original articleCited as: Dou, Z., Yang, Z., Dong, C., Li, H., Wang, Y., Hou, H. Rock physical evolution and microscopic flow mechanism of massive energy replenishment in tight oil reservoirs. Advances in Geo-Energy Research, 2024, 14(1): 49-63. https://doi.org/10.46690/ager.2024.10.0
MicroGraphNets: Automated characterization of the micro-scale wettability of porous media using graph neural networks
Get PDFThis study introduces MicroGraphNets, a deep learning framework for automating the microscopic characterization of wettability in porous media using graph neural networks. The framework predicts rock surface roughness, fluid/fluid interfacial curvatures, and contact angles at 3-phase contact lines from segmented multiphase micro-computed tomography images. This is achieved by converting these images into sets of surface and interfacial points, with their intersection defining the 3-phase contact line points. Specialized geometrical training graphs are constructed from these points to predict each property, leveraging surface and interfacial normal vectors as input features for constructing surface and interfacial graphs. To address the unique challenge that arises from the coexistence of all phases around 3-phase contact lines, distinct node types assigned to each phase were embedded as node features for constructing contact angle graphs. To predict the properties, the framework employs a message-passing graph neural network with three modules: an encoder for initial feature embeddings, a processor for aggregating neighboring embeddings and propagating messages, and a decoder for final property prediction. This approach effectively captures node and edge relationships, facilitating accurate regression of surface and interfacial properties. Validation includes testing on unseen samples and a synthetic droplet test against analytical solutions. Time-resolved analysis was performed to demonstrate the scalability and efficiency of the framework on large datasets. MicroGraphNets demonstrates superior accuracy and efficiency compared to traditional deep learning methods, showcasing its potential for predicting microscopic surface and interfacial properties of porous media.Document Type: Original articleCite as: Alzahrani, M. K., Shapoval, A., Chen, Z., Rahman, S. S. MicroGraphNets: Automated characterization of the micro-scale wettability of porous media using graph neural networks. Capillarity, 2024, 12(3): 57-71. https://doi.org/10.46690/capi.2024.09.0
Gas adsorption behavior in shale reservoirs: Insights from molecular scale
Get PDFAdsorbed gas confined in nanopores is a significant component of shale gas, and understanding the mechanisms of gas adsorption in shale nanopores is crucial for enhancing shale gas recovery and carbon dioxide geological sequestration. Due to the nanoscale pore sizes, complex pore structures, and diverse mineral types, adsorption experiments have a limited capacity to elucidate the microscopic mechanisms of gas adsorption. Compared to expensive adsorption experiments, molecular simulation methods can not only simulate reservoir in-situ conditions but also reveal the adsorption mechanisms from the molecular scale perspective. This work provides a brief review for the characteristics of methane adsorption in shale inorganic minerals and organic matter. Additionally, the competitive adsorption behavior of methane and carbon dioxide in shale is introduced to clarify the potential of shale reservoirs for carbon dioxide geological storage. Finally, the challenges faced by molecular simulation methods in gas adsorption research are discussed.Document Type: PerspectiveCited as: Xia, X., Jiao, X., Li, J., Shen, W., Xia, Y., Wang, H. Gas adsorption behavior in shale reservoirs: Insights from molecular scale. Capillarity, 2024, 13(3): 68-72. https://doi.org/10.46690/capi.2024.12.0