期刊封面

更多>>

Online System Service

更多>>

About the Journal

更多>>
Journal:
Coal Geology & Exploration
Establishment year:
1973
 
Periodicity:
Biomonthly
Supervised by:
Xi’an Research Institute Co. Ltd., China Coal Technology and Engineering Group Corp.
Sponsored by：
Xi’an Research Institute Co. Ltd., China Coal Technology and Engineering Group Corp.
Editor-in-chief:
 DONG Shuning
 
Associate E ditor-in-chief:

 LIU Cheng, James W. LaMoreaux 

 

Executive Editor-in-chief:
JIN Xianglan 

 

ISSN:
1001-1986
CN:
61-1155/P
Web:
www.mdkt.cbpt.cnki.net

Download Center

更多>>

2025年01期目次

  • Coal mining-induced composite damage to geological bodies and geological guarantee against damage reduction

    WANG Shuangming;SUN Qiang;HU Xin;GENG Jishi;HOU Enke;WANG Shengquan;ZHOU Shutao;SHI Qingmin;YUAN Shihao;CHEN Kai;SONG Shijie;Shaanxi Provincial Key Laboratory of Geological Support for Coal Green Exploitation, Xi'an University of Science and Technology;Geological Research Institute for Coal Green Mining, Xi'an University of Science and Technology;College of Geology and Environment, Xi'an University of Science and Technology;School of Geology and Mining Engineering, Xinjiang University;

    [Objective and Background] Coals have long served as a predominant energy source in China. With an increase in mining scale and intensity in recent years, the correlations between rocks, soils, hydrosphere, and ecological environment in coal mining areas have been strengthened. Given this, there is an urgent need to, from the perspective of Earth system science, understand the coupling relationships and chain characteristics among factors including the movement and deformations of surrounding rocks, rock bursts, coal and gas outbursts, water inrushes, ground subsidence, water and soil erosion, and damage to ecological environments, aiming to achieve safe, green coal mining. [Methods and Results] Based on geological structure control and mining-induced responses of rock mass structure, this study proposes scientific research on composite damage to geological bodies, including content, key issues, and geological guarantee philosophies for damage reduction. Specifically, it is necessary to research the combination relationships of coals, rock water, soils, and ecosphere in coal mining areas, as well as their dynamic response characteristics. This will help analyze the basic geological conditions for the formation of composite damage, ascertain the dynamic evolution characteristics of the geological conditions of various spheres before, during, and after mining under the background of coal development,and establish a dynamic coupling and evolution model of coals, rocks, water, soils, and ecosystems. There is a need to establish a collaborative driving model of the composite damage. This will assist in accurately identifying and quantifying key state parameters of various elements, identifying damage types and their primary controlling factors, and revealing the multi-field coupling response laws to coal mining and the evolution process of composite damage. It is supposed to, based on the correlations between multi-sphere damage under coal mining, pay much attention to the dynamic evolution process of composite damage and corresponding changes in key state parameters and, accordingly, establish a collaborative prediction, monitoring, and prevention system against composite damage in coal mining areas. Furthermore, it is necessary to build five systems and one platform, i.e., a precise exploration system, an intelligent perception system, a rapid interpretation system, a risk assessment system, an engineering loss reduction system, and a comprehensive analysis platform for mining-induced composite damage. These systems and the platform are supposed to scientifically analyze natural factors such as coal burial conditions, rock mass structure conditions, hydrogeological conditions, and ecological conditions, as well as geological information like multi-sphere response laws of rocks, waters, soils, and ecosystems. The purpose is to achieve transparent geological structure conditions, effective evaluation models and methods, optimized coal development models, advanced prediction of risk dynamics, and scientific strategies for geological security.Additionally, research on the geological guarantee against composite damage to coal mine surrounding rocks can provide scientific guidance for damage reduction during coal mining and contribute to green, safe coal mining and ecological protection.

    2025 01 v.53;No.325 [Abstract][OnlineView][Download 8267K]

  • Advances and trends of modern and contemporary research on the geology of coal-measure minerals in China

    QIN Yong;China University of Mining and Technology;

    [Background] Coal-measure minerals(CMMs) play a significant role in ensuring the safe supply of mineral resources in China. Reviewing the advances and trends of research on the geology of CMMs in China holds great historical significance and practical value while potentially providing some insights into subsequent research. [Advances]Based on textual research and the analysis of logical relations, this study generalized the advances in research on the geology of CMMs in China into four aspects.(1) Increasingly improved geological theory system of CMMs: China's classic theoretical system of coal field geology was formed in the second half of the 20th century, and the geological theory system focusing on coals, coal-measure gas, and coal-measure critical metals has been gradually developed since the21st century.(2) Research on the origin and genesis of coals, advancing the international coal geology: The advancements include the development of the new coal metamorphism theory, the discovery of the world's youngest soft lignite,the reveal of late-stage coalification jumps, the establishment of the ordinary organic petrology, and the comprehensive ascertainment of the formation and evolutionary mechanisms of coals.(3) The unique CMM accumulation, distribution,and metallogenic theory: The specific outcomes include the establishment of multiple sedimentary and structural coalcontrolling patterns, the reveal of the fundamental framework of coal accumulation in sea areas, the identification of deposits of various coal-measure critical metals, and the determination of the division schemes for coal-controlling geotectonic units and the metallogenic zones of coal-measure critical metals, and the development of a geological theory system for coalbed methane.(4) Significant achievements in the geological surveys and assessment of special coal resources: Specifically, the methodological system for the geological prediction and assessment of special coal types and high-quality, eco-friendly, and clean coal resources has been developed, the methodological system for the resource potential assessment of tar-rich coals and underground coal gasification has been formed, and the coal resources for related purposes have been preliminarily investigated. [Prospects] The analytical results indicate that major national demands determine the trends of research on the geology of CMMs. It is recommended to focus on four aspects in future geological study: the precise exploration and exploitation of coal resources, the exploration and orderly production of coal-measure gas, the exploration and exploitation of critical metals, and the geological guarantee for in situ fluidized coal mining.Additionally, it is necessary to pay attention to the accumulation mechanisms and resource prediction methods for helium in coal measures.

    2025 01 v.53;No.325 [Abstract][OnlineView][Download 1448K]

  • Connotation, research status, and development directions of clean coal geology in China

    TANG Yuegang;WANG Shaoqing;WANG Xiaoshuai;GUO Xin;WANG Yafeng;XUE Liping;Harold H.Schobert;State Key Laboratory for Fine Exploration and Intelligent Development of Coal Resources, College of Geoscience and Surveying Engineering, China University of Mining and Technology-Beijing;Intelligent Mine Research Institute,Chinese Institute of Coal Science;Yunnan Provincial Key Laboratory of Soil Carbon Sequestration and Pollution Control, Faculty of Environmental Science & Engineering;The EMS Energy Inst

    [Objective] The exploration and assessment of low-carbon, zero-emission, and maximized utilization of coal resources, emerge as a focus of coal geology in the 21st century. [Research Advances] Based on the research content of coals and coal geology, along with the domestic and international development trends of clean coal technology(CCT),this study defines clean coal geology in the broad and narrow sense. Clean coal geology in the narrow sense focuses on the geological and geochemical issues related to efficiency enhancement and emission reduction in coal processing and utilization. In contrast, clean coal geology in the broad sense emphasizes efficiency enhancement and emission reduction throughout the coal life cycle, involving the exploration, exploitation, and utilization of coals, as well as relevant ecological restoration. This study summarizes the compositions and distributions of beneficial and harmful components in coals and analyzes the geologic factors affecting CCT, which are primarily associated with endogenetic and exogenetic geological processes during coal formation and involve tectonics, metamorphism, volcanic eruption, magmatic intrusion, aeolian-fluvial transport and deposition, redox reactions, and groundwater. Furthermore, this study provides a comprehensive overview of the current status of research on the clean assessment, clean processing, conversion, and utilization of coal resources. Additionally, this study reviews the advances in research on China's clean coal geology, categorizing them into five stages: germination, exploration, maturity, establishment, and expansion. [Issues and Prospects] This study proposes some scientific and technical problems concerning coal formation, organic/inorganic elements, minerals,and clean assessment, positing that future advancements in chemistry, physics, biology, and big data/artificial intelligence(AI) will bring opportunities for the further development of clean coal geology and its applications in large-scale engineering. In the next decade, important research and development directions will include the spatiotemporal distribution of clean coals; the green, intelligent, quality-based combined production of paragenetic and associated minerals like coal gas; clean coal gasification; coal-based novel materials; underground coal-to-chemicals, and ecological restoration.It is advisable to continuously pay attention to the innovative research achievements in these aspects.

    2025 01 v.53;No.325 [Abstract][OnlineView][Download 1740K]

  • Prospects for mine geological work in the intelligence age: Architecture of the intelligent geological guarantee technology system for mine exploitation

    XIA Yucheng;SUN Xueyang;MIAO Lintian;GUO Chen;DU Rongjun;College of Geology and Environment, Xi'an University of Science and Technology;Shaanxi Provincial Key Laboratory of Geological Support for Coal Green Exploitation;Key Laboratory of Coal Resources Exploration and Comprehensive Utilization, Ministry of Natural Resources;

    [Background and Significance] In response to the serious challenges posed by the goals of peak carbon dioxide emissions and carbon neutrality, the intelligentization of coal mines is an inevitable course and a significant sign of the high-quality, sustainable development of the coal industry in the New era. Mine geological work, providing geological foundation and guarantee for underground coal mining, plays an increasingly significant role in the transformation and upgrading of the coal industry for high-quality development. Constructing an intelligent geological guarantee technology system for coal mining by combining mine geology with artificial intelligence(AI) can provide a comprehensive,whole-process geological guarantee for safe, efficient, green, and intelligent coal mining. Therefore, building such a technology system represents the development target and inevitable trend for mine geological work to match the goal of the intelligent construction of coal mines in the new era. The technology system will surely become the novel productivity that boosts the quality and efficiency of mine geological work. [Methods and Results] By exploring the scientific connotation of the technology system, this study preliminarily established the architecture of the technology system.Then, this study systematically sorted the five subsystems of the technology system(i.e., the intelligent management subsystem for fundamental geological survey information, the intelligent prediction and early warning subsystem for geologic hazards in mines, the intelligent monitoring, prediction, and early warning subsystem for ecosystems in mining areas, the intelligent identification subsystem for favorable mining blocks, and the transparent mining face subsystem),as well as their core modules. [Conclusions] Notably, with the constant advancements in technologies for geological explorations and detections, the effectiveness of the technology system depends on the accuracy and reliability of original data, ultimately relying on the number and professional quality of personnel engaged in geological surveys. Therefore, it is necessary to further strengthen the introduction and cultivation of professionals in the field of mining geology.

    2025 01 v.53;No.325 [Abstract][OnlineView][Download 1638K]

  • Gas drainage and utilization in coal mines in China: History, technological advances, and prospects

    LI Guofu;LI Chao;ZHANG Bichuan;XU Yun;WANG Zheng;ZHOU Xianjun;State Key Laboratory of Coal and Coalbed Methane Co-Mining;Yi'an Blue Flame Coal and Coalbed Methane Co-Mining Technology Co., Ltd.;School of Safety Engineering, China University of Mining and Technology;Key Laboratory of In-Situ Property Improving, Mining of Ministry of Education,Taiyuan University of Technology;

    [Objective and Methods] To promote the research and application of gas drainage and utilization technologies for coal mines, this study systematically summarizes the history of China's coal mines transitioning from gas pumping to gas drainage, the accurate and effective gas drainage technologies for typical coal mining areas in China, and the latest applications of technologies related to safe gas gathering and transportation, as well as the utilization of gas with a full range of concentrations. This study aims to provide a reference for accelerating the advancement in gas drainage and utilization technologies for coal mines, achieving methane emission reduction, and helping attain the goals of carbon neutrality and peak carbon dioxide emissions. [Advancement] The period from the 1930s to the 1950s represents the initial stage of gas pumping in coal mines in China. During this period, underground drilling was employed for gas pumping in target coal seams and their upper adjacent strata to ensure mining safety in the Fushun mining area in Liaoning Province, the Yangquan mining area in Shanxi Province, and the Tianfu mining area in Chongqing City. From the1960s to the 1970s, gas pumping while mining was used for the prevention and control of gas overrun and accidents in the Jixi and Shuicheng mining areas in Heilongjiang and Guizhou provinces, respectively, achieving encouraging results.During this period, gas pumping technology for adjacent strata was developed, and methods including hydraulic slotting,controlled pre-splitting blasting, and water jet reaming were tested for coal seams with low air permeability. From the1980s to the end of the 20th century, with a substantial increase in the gas outflow from the mining face, pressure-relief gas was effectively drained using various methods including gas pre-drainage in target coal seams, as well as gas pumping in adjacent strata and goaves. However, this period witnessed slow advancement in gas utilization. Since the beginning of the 21st century, the understanding of gas in coal mines has transitioned from simple disasters to disasters associated with resources, gradually achieving the transformation from gas pumping to gas drainage. In combination with the differences in geological conditions of gas in varying mining areas, three typical gas drainage modes have been formed:the surface-underground combined gas drainage mode through “ four-zone linkage” in the Jincheng mining area in Shanxi Province(the new Jincheng mode), the protective layer mining mode for broken-soft and low-permeability coal seams in the Huainan-Huaibei area in Anhui Province(the Huainan-Huaibei mode), and the hydraulically enhanced permeability mode of the Songzao mining area in Chongqing City(the Songzao mode). Concurrently this period has seen the development and extensive applications of many safe transportation technologies and devices, including water sealing of fire barriers and explosion venting devices, dry flame arresters, and explosion suppression devices through water mist/automatic powder spraying. In terms of gas utilization, many technologies have been researched and applied, involving gas power generation, direct current(DC) oxidation, combustion in porous media, regenerative oxidation, and oxidation by mixing ventilation air methane with low-concentration gas. These technologies provide technical support for the utilization of gas with a full range of concentrations from coal mines. Nevertheless, gas drainage technologies for coal mines are confronted with challenges including poor applicability and high costs, and related gas drainage technologies suffer from low economic feasibility. [Prospects] Gas drainage and utilization technologies for coal mines will focus on the development of the advanced gas pre-drainage technology system for ten-year planning areas, the expansion of the simultaneous extraction of coal and gas mode, the optimization of gas utilization processes from the source, the improvement in the intelligent level of gas drainage pipeline networks, and the implementation of gas utilization projects via government-industry-university-institute collaborations. This will help achieve both the utilization of gas with a full range of concentrations from coal mines and the goals of carbon neutrality and peak carbon dioxide emissions in the coal industry.

    2025 01 v.53;No.325 [Abstract][OnlineView][Download 2050K]

  • Impacts of coal fracture roughness and aperture on the seepage of injected water:An experimental study

    WANG Gang;CHEN Xuechang;CHEN Hao;LONG Qingming;LIU Yixin;Mining Disaster Prevention and Control-Ministry of State Key Laboratory Breeding Base, Shandong University of Science and Technology;College of Safety and Environmental Engineering, Shandong University of Science and Technology;State Key Laboratory of Gas Disaster Detecting, Preventing, and Emergency Controlling, CCTEG Chongqing Research Institute;

    [Objective] Water injection into coal seams is recognized as a critical technical measure for dust removal and the prevention and control of coal and gas outbursts and rock bursts in coal mines. The effectiveness of this measure is significantly influenced by the morphological characteristics of fractures, such as their roughness and aperture. [Methods] This study prepared coal samples containing fractures with different roughness and apertures using sandpaper and polyimide tape, calculated the fracture roughness parameters accurately using a confocal laser scanning microscope(CLSM), and tested the seepage rate of fractured coal samples. [Results and Conclusions] The results indicate that the roughness of a coal profile can be characterized using the surface height deviation(H_a), the maximum surface height(H_z), and the fractal dimension(D_s) of the 3D morphology. The seepage rate of coals decreased exponentially with an increase in Ha, Hz, and D_s. As the profile roughness increased from 4.69 to 18.43, the seepage rate of fractures decreased by up to 84.42%. In the case where fracture apertures ranged from 60 to 90 μm, the fracture roughness exhibited the most significant blocking effect on seepage. With a further increase in the fracture aperture, the blocking effect of roughness elements began to weaken, with the fracture aperture dominating the seepage process. The seepage rate of coals increased exponentially with an increase in the fracture aperture. As the fracture aperture increased from 30 μm to 150 μm,the seepage rate of fractures increased 355.88 times at most. Through a deep exploration into the relationships of the fracture aperture and roughness with seepage rate, this study determines the key mechanisms underlying the impacts of the fracture aperture and roughness on water injection into coal seams. The results suggest that it is necessary to fully consider the morphological characteristics of fractures in water injection practices. Proper water injection methods should be selected based on different fracture apertures and roughness to enhance the water injection efficiency effectively.

    2025 01 v.53;No.325 [Abstract][OnlineView][Download 2137K]

  • Fracture-seepage characteristic zones of the overburden of extra-thick coal seams:Evolutionary patterns and their engineering applications

    KONG Xiangguo;ZHAO Tianshuo;LIN Haifei;ZHAO Pengxiang;WANG Xu;CAI Yuchu;JI Pengfei;HE Di;LI Ke;XU Chuanyu;College of Safety Science and Engineering, Xi'an University of Science and Technology;Key Laboratory of Western Mine Exploitation and Hazard Prevention, Ministry of Education, Xi'an University of Science and Technology;Beijing Anke Xingye Science and Technology Co., Ltd.;Shaanxi Binchang Xiaozhuang Mining Co., Ltd.;

    [Objective and Methods] Given that the overburden's structure significantly influences pressure relief gas extraction, this study aims to explore the gas migration patterns of the overburden of thick coal seams during coal seam mining. To this end, this study analyzed the evolutionary patterns of the fracture morphology and seepage capacity of the overburden using physical similarity simulation experiments. Accordingly, this study investigated the mechanisms behind the evolution of fracture-seepage characteristic zones of the overburden of extra-thick coal seams and proposed a method for identifying fracture-seepage characteristic zones of the overburden. Using this method, this study conducted gas extraction along the experimental mining face based on directional boreholes. [Results and Conclusions] The results indicated that the bed separation and fracture density of the central part of the overburden were 47% and 31%, respectively, of those of its two sides, indicating that both indicators were low in the central part and high on the two sides.In the early stage of mining, the fracture-seepage characteristics of the overburden displayed synchronous spatial distributions. With the further advancement of the working face, the overburden was affected by mining to varying degrees,gradually displaying evolutionary zoning. Specifically, the central part of the overburden exhibited significantly weaker fracture-seepage characteristics than the surrounding areas, with these characteristics of the two sides gradually weakening with an increase in the horizon. The overburden manifested fracture ratios, fracture entropy, connectivity coefficients, and permeability ranging from 1.0% to 8.5%, from 0.15 to 0.90, from 0.10 to 0.65, and from 6.34×10-9 m~2 to7.78×10~(-7) m~2, respectively. Based on the impacts of the fractures and seepage capacity of the overburden on gas migration, the overburden can be divided into four zones: a low-elevation turbulence zone, a medium-elevation compaction zone, a medium-elevation transition zone, and a high-elevation constant flow zone. Based on the spatiotemporal evolution patterns of the fracture ratios, fracture entropy, connectivity coefficients, and permeability of these zones, this study developed an evolution model and identification flowchart for the fracture-seepage characteristic zones of the overburden of extra-thick coal seams. The analysis of the evolution model reveals that the medium-elevation transition zone and the high-elevation constant current zone were the dominant horizons for gas extraction, with the vertical distances of boreholes designed ranging from 6 m to 25 m. The changes in the pure gas flow extracted from boreholes can be divided into three stages: the initial fluctuation, rapid growth, and slow drop stages. The mining along the mining face yielded methane volume fractions of less than 1%, suggesting encouraging effects in the engineering practice. This verifies the feasibility of the proposed method and the rationality of directional borehole arrangement. The results of this study will provide some theoretical guidance for the optimization of borehole parameters for gas extraction and the gas control of coal seams.

    2025 01 v.53;No.325 [Abstract][OnlineView][Download 3013K]

  • China's CBM exploration and production and associated technological advancements: A review and reflections

    YE Jianping;China National Offshore Oil Co., Ltd.;

    [Objective and Methods] Based on extensive scientific and technical literature and technical data on coalbed methane(CBM) exploration and production projects, this study conducted a comparative analysis of the development process and latest advances in China's critical technologies for CBM exploration and production and reviewed the CBM exploration and production history of this country over the past three decades. Accordingly, this study discussed the theoretical and technical challenges in CBM exploration and production and proposed future development directions. [Advances] The results indicate that the insights into conversion between adsorbed and free deep CBM prove to be a significant theoretical understanding. The breakthroughs in the ideological understanding of exploration and production, as well as the innovative applications of near-bit geosteering drilling technology and multistage volume fracturing technology for horizontal wells, elevate China's deep CBM production to a higher level. Recent years have seen major advances in the accumulation mechanisms and modes of deep CBM, assessment methods for CBM exploration and production, and knowledge about CBM production regularity. The geology-engineering integration serves as an effective method for the prediction and assessment of play fairways, well deployment, and the research and development of adaptive technologies. Presently, the most advanced comprehensive technology system for CBM production consists of the deployment of cluster horizontal well groups, the deployment of horizontal well groups combined with vertical and directional well groups, the multistage volume fracturing of horizontal wells, and the intelligent dewatering and CBM production using rodless lifting. Furthermore, the efficient CBM production of thin coal seams suggests a breakthrough in the lower limit of coal seam thickness for CBM production and the discovery of new target layers for CBM production.China's CBM production focuses primarily on CBM reservoirs dominated by adsorbed gas and those bearing both adsorbed and free gas. The two major CBM reservoir types differ significantly in gas accumulation mechanisms and the technologies and philosophies for CBM exploration and production. [Prospects] It is recommended that the future CBM exploration and production in China should center on four fields. Specifically, deep CBM will be the primary target for future CBM exploration and production and technological research, and it is necessary to intensify and accelerate the exploration and production of deep CBM resources in platform-type sedimentary basins such as the Ordos, Junggar,Turpan-Hami, Tarim, and Sichuan Basins. Large-scale production of moderately deep CBM is identified as an important direction. Shallow CBM, acting as the “ballast stone” for the development of the CBM industry, is supposed to keep continued stable production and serve as the replacement for current CBM resources. Additionally, CBM in low-rank coal reservoirs is a potential target for CBM exploration and production.

    2025 01 v.53;No.325 [Abstract][OnlineView][Download 1357K]

  • Key experimental technologies and their development directions for the exploration and production of deep coalbed methane

    YAN Xia;XU Fengyin;XIONG Xianyue;WANG Feng;LI Chunhu;ZHANG Jiyuan;XU Borui;CHENG Qianhui;HU Xiong;ZHU Xueguang;LIANG Wei;YUAN Pu;FENG Yanqing;WEI Zhenji;China United Coalbed Methane National Engineering Research Center Co.Ltd.;PetroChina Coalbed Methane Company Limited;State Key Laboratory of Deep Oil and Gas, China University of Petroleum (East China);School of Petroleum Engineering, China University of Petroleum (East China);

    [Objective] Deep coalbed methane(CBM) production enjoys advantages including rapid gas shows, high single-well yield, and continuous resource distribution, which establish deep CBM as a significant target for reserve growth and production addition of natural gas. However, the exploration and production of deep CBM are still confronted with many technical challenges, and there is a lack of studies on key experimental technologies related to the geological characteristics and engineering assessment of deep CBM reservoirs, the occurrence characteristics and production mechanisms of gas and water, the formulation of production systems, and methods for enhanced CBM recovery. [Advances in Research] Given the characteristics of deep coal seams and CBM, this study identifies four challenges in the exploration and exploitation of deep coal seams: the collection of large coal samples, the high-temperature, high-pressure, and high-stress in-situ conditions, high-precision characterization and desorption of sub-nano-to nano-scale micropores, and the accurate determination of gas content. Furthermore, this study systematically analyzes the advances and challenges in experimental technologies for deep coals, involving the characterization of multi-scale pores and fractures,the assessment of absorption and gas-content properties, the mechanic characteristics and fracture propagation patterns of coals, and the dynamic patterns of fluid occurrence and production post-fracturing. [Prospects] This study posits seven development directions for deep CBM production and in-situ coal conversion experiments:(1) Clear, direct observation techniques for micropores(< 2 nm) in deep coal seams with ultra-low porosity and permeability, full-scale pore size splicing technology for multiscale pore structure characterized by abundant micropores, a few mesopores, and many macropores, and assessment techniques for pore-fracture connectivity.(2) Isothermal adsorption test technologies for raw coals considering the effects of deep coal seam wettability, fracturing fluid invasion, and high total dissolved solids(TDS) under high-temperature, high-pressure in-situ conditions;(3) Sealed coring devices and in-situ pressure-retaining coring technologies featuring high pressure retaining success rates, heat preservation rates, and traceable gas volume.(4) Nanoscience-based assessment technologies for gas and water occurrence in micropores in deep coal seams under high-temperature and high-pressure multi-field coupling, and experimental technologies for desorption, diffusion, and seepage across nano-micro-millimeter scales.(5) Techniques for developing and testing multifunctional mechanical experiment equipment applicable to in-situ conditions of deep coal seams featuring high stress, low modulus of elasticity,and high Poisson's ratio.(6) Experimental techniques for the purpose of enhancing CBM recovery of deep coal seams,including reservoir stimulation(microwaves, laser, and electric heating), stimulation for permeability enhancement(electromagnetic pulses, pulsed ultrasonic waves, and controlled shockwaves), displacement via CO2 injection, and mechanical pulsation with supercritical CO2.(7) Experimental techniques for in-situ coal conversion and utilization, including pyrolysis, underground coal gasification(UCG), geothermal utilization, and CO2 geological storage. Analyses reveal that there is an urgent need to establish the standards and regulations for the operational procedures of these experimental technologies, as required by objective demand for the exploration and production of deep CBM. These experimental technologies aim is to achieve environment protection, permeability enhancement, desorption promotion, and CO2 storage, thus providing vital support for the efficient production and utilization of deep CBM and coals and helping attain the goals of peak carbon dioxide emissions and carbon neutrality.

    2025 01 v.53;No.325 [Abstract][OnlineView][Download 1860K]

  • Critical technologies and geology-engineering integration practices for deep CBM production in the Yanchuannan CBM field

    CHEN Zhenlong;WANG Yunhai;LIU Xiao;CUI Bin;YANG Song;LI Xin;FANG Qilong;East China Oil and Gas Company,SINOPEC;Linfen Coalbed Methane Company,SINOPEC;Key Laboratory of Deep Coalbed and Methane Exploration and Development,SINOPEC;

    [Objective and Methods] This study introduces the adjustments for coalbed methane(CBM) production in the Yanchuannan CBM field-the first deep CBM field in China. Deep CBM production in this CBM field faces challenges including strong heterogeneity of reservoirs, single arrangement mode of production well patterns, low applicability of conventional hydraulic fracturing, excessively long conventional production cycles, and a high proportion of inefficient wells. To address these challenges, a production capacity construction model for efficient deep CBM production of the field was developed through in-depth geology-engineering integration. [Results and Conclusions] The results indicate that the production capacity construction process of the Yanchuannan CBM field has undergone three stages: largescale production capacity construction, addressing technological challenges, and technological innovations and their popularization. [Results and Conclusions] The following achievements were obtained:(1) The geological understanding of four critical indicators for the selection of optimal geological-engineering “sweet spots” and efficient CBM production.(2) The concept of fracturing through effective propping and key supporting technologies for reservoir stimulation.(3)The optimal and fast production technologies characterized by four stages, three pressures, and three aspects of control.Based on these achievements, the average cycle for acquiring gas shows was shortened from 240 d to 30 d, and the single-well production was significantly enhanced, with the daily gas production of directional and horizontal wells reaching 2.0×104 m3 and 6.5×104 m3, respectively. The deep CBM reservoirs in the Yanchuannan CBM field exhibit strong heterogeneity, causing difficulties with effective production. Given this, the work philosophy that consolidates overall deployment, implementation in batches, integrated assessment and construction, and rolling production capacity construction was developed for production capacity construction. Adhering to this work philosophy, the production capacity construction was performed through continuous assessment and adjustment of geological-engineering sweet spots and timely optimization of production schemes to effectively avoid the co-occurrence of a substantial number of inefficient wells. This increased the fulfillment rate of production capacity from the initial 84% to 100%, suggesting significantly enhanced economic effects. Based on the concept of geology-engineering integration and the full life cycle of gas reservoir development that consists of well emplacement, well drilling and completion, reservoir stimulation, well tests and production, and gathering, transportation, and processing, the following outcomes were obtained:(1) Rational well spacing that matches reserves, well patterns, and fracture networks, increasing single-well producing reserves by 30% to 50%.(2) The optimal well drilling and completion technology focusing on speed increase and cost reduction, improving the drilling speed by 34%.(3) The low-pressure gathering and transportation technology involving high-and low-pressure gathering and transportation, three-stage pressurization, and inter-station connection, reducing the platform investment by 10.8% and the land use by 20%. The geology-engineering integration practices in the Yanchuannan CBM field provide technical support for the deep CBM industry, holding great demonstration and promotion significance.

    2025 01 v.53;No.325 [Abstract][OnlineView][Download 2126K]

  • An analytical method for the desorption superposition effect in commingled production of coalbed methane and its application:A case study of the Xiaotun mine field in western Guizhou Province,China

    GUO Chen;JI Yan;ZHAO Chenyi;LU Lingling;YU Xinhang;GAO Junzhe;LI Houqiang;ZHANG Xuyang;WANG Xiang;HE Hongbin;ZHANG Runhan;College of Geology and Environment, Xi'an University of Science and Technology;Shaanxi Provincial Key Laboratory of Geological Support for Coal Green Exploitation;Geological Research Institute for Coal Green Mining, Xi'an University of Science and Technology;Department of Geology, Northwest University;Aerophoto Grammetry and Remote Sensing Bureau, China National Administratio

    [Objective] The commingled production of coalbed methane(CBM) serves as a significant means to increase single-well production. However, production practices reveal that the commingled production of CBM exhibits complex and varied effects and controlling factors, facing technical challenges of identifying gas-producing contributions, predicting gas-producing potential, and optimizing pay interval combinations. The superposition of desorption for gas production among different coal seams determines whether high CBM production can be achieved using commingled production. [Methods] This study proposed an analytical method for the desorption superposition effect in the commingled production of CBM, involving determining desorption sequences, analyzing the superposition of desorption intervals and the matching of desorption stages, and predicting well-controlled desorption capacities. The proposed method was applied to the Xiaotun mine field in western Guizhou Province, China. [Results and conclusions] The results indicate that coal reservoirs in the Xiaotun mine field feature high adsorption capacities, low gas saturation, and low critical desorption pressures. The CBM pay intervals can be categorized into the upper and lower desorption systems. The upper desorption system manifested a desorption sequence of the No.6 upper, No.7, No.6 middle, and No.6 lower coal seams,while the lower desorption system displayed a desorption sequence of the No.34 and No.33 coal seams. Using changes in the working fluid during the production process as an indicator, this study analyzed the desorption processes of coal seams during the commingled production of CBM. The analytical results reveal that the synchronous desorption of the No.6 upper, No.7, No.6 middle, and No.6 lower coal seams can be achieved within a working fluid of 45 m and the synchronous desorption of the No.33 and No.34 coal seams can be gained within a working fluid of 92 m. Isothermal adsorption curves discovered the matching of the coal seams' desorption stages. The low critical desorption pressures allowed various coal seams to directly enter the sensitive desorption stage after desorption, suggesting high desorption efficiency and effective matching. This creates favorable conditions for high CBM production. However, limitations like insufficient pressure drop space and long drainage periods impose high requirements for coal seam stimulation and CBM production. The well-controlled desorption capacities and their time-varying curves indicate that gas desorption capacities peaked in the case of the synchronous desorption of all pay intervals within the respective desorption systems. In this case, the upper and the lower desorption systems yielded well-controlled desorption capacities of 378.09×10~4 m~3(daily average: 4.20×10~4 m~3) and 199.11×10~4 m~3(daily average: 1.08×10~4 m~3), respectively. Both desorption systems demonstrated satisfactory desorption superposition effect, each forming a favorable pay interval combination for the commingled production of CBM. The proposed method will provide a reference for identifying gas-producing contributions,predicting gas-producing potential, and optimizing pay interval combinations for the commingled production of CBM.

    2025 01 v.53;No.325 [Abstract][OnlineView][Download 1886K]

  • A key technology for synergistic backfilling of coal-based solid waste and high-salinity wastewater

    DONG Shuning;YU Shujiang;DONG Xingling;ZHANG Buqin;GUO Xiaoming;WANG Xiaodong;WANG Kai;ZHU Shibin;WU Boqiang;LIU Lei;CCTEG Xi'an Research Institute (Group) Co., Ltd.;Coal Mine Hazard Prevention and Control National Key Laboratory;Shaanxi Key Laboratory of Prevention and Control Technology for Coal Mine Water Hazard;Beijing Symgreen Environmental Technology Group Co., Ltd.;Feny Co., Ltd.;

    [Background and Objective] Limited by locations, as well as economic and technical levels, most of the coalbased solid waste is still accumulated in the form of open-air landfills without treatment, thus occupying large quantities of land resources and causing secondary pollution to the environment. The proper treatment and reduction of high-salinity wastewater(e.g., high-salinity mine water and high-salinity water from the coal chemical industry) represent a key link in the achievement of zero liquid discharge. However, existing technologies for high-salinity wastewater treatment are generally confronted with issues such as great initial investment and high operation costs of the treatment engineering. [Methods] This study developed a technology for the synergistic treatment of coal-based solid waste and high-salinity wastewater(also referred to as solid-liquid synergistic waste backfilling). Specifically, high-salinity water, rather than ordinary water and additives such as early strength agent, and solid waste cementitious materials-used to replacing part of cement, were mixed while stirring to produce filling paste, which was then pumped to the underground goaves of coal mines. To analyze the feasibility of this technology, this study investigated the mechanical properties and potential environmental impacts of filling paste prepared using coal-based solid waste and high-salinity wastewater from a certain coal mine in the Ningdong coal base in Ningxia. The mechanical properties, microstructures, and heavy metal leaching characteristics of the solidified filling paste were analyzed using the uniaxial compressive strength(UCS) test, scanning electron microscopy(SEM), and inductively coupled plasma-mass spectrometry(ICP-MS). [Results and Conclusions] The results indicate that the strength of all the solidified filling paste increased over time but gradually decreased with an increase in the quantity of mineral powders added and a decrease in the proportion of cementitious materials. Notably,after some time, all filling paste prepared using high-salinity water as mixing water exhibited 3-day strength exceeding0.5 MPa, meeting the minimum requirements specified in Technical specification for coal mine gangue-based solid waste filling(NB/T 11432-2023). Their 14-day strength reached 3.38-5.99 MPa, satisfying the requirements of various scenarios in most coal mine filling. The assessment results obtained using Nemerow's pollution index and extraction toxicity tests indicate that the leachate from the solidified filling paste exhibited a comprehensive pollution index of heavy metals of 0.25, rated as “Safety” according to the grading criteria for comprehensive pollution assessment. The leaching test results of the solidified filling paste indicate that the primary pollutant concentrations in the leachate all fell below the requirements of Class III water standard specified in Identification standards for hazardous wastes-Identification for extraction toxicity(GB 5085.3-2007) and Standard for groundwater quality(GB/T 14848-2017). Therefore,the technology for synergistic treatment of coal-based solid waste and mine high-salinity water can meet the relevant standards in the assessment of mechanical properties and environmental stability. This technology enables the recyclable,low-cost, and full quantitative utilization of coal-based solid waste and high-salinity water, enjoying significant economic and ecological benefits. The results of this study will provide technological support for the construction of waste-free mines, mining cities, and chemical industry.

    2025 01 v.53;No.325 [Abstract][OnlineView][Download 2041K]

  • Spatiotemporal evolutionary patterns of the hydrochemistry of Jurassic conglomerate aquifers under the influence of curtain walls

    CHEN Luwang;WU Minghui;HOU Xiaowei;HU Yongsheng;ZHANG Miao;CAI Xinyue;YIN Xiaoxi;SHI Xiaoping;School of Resources and Environmental Engineering, Hefei University of Technology;

    [Objective] Curtain walls, recognized as a primary project for the prevention and control of water disasters in coal mines, will change the dynamic field of groundwater. Furthermore, their dissolution will affect the chemical field of groundwater, leading to variations in its hydrochemical composition. [Methods] This study investigated the Jurassic conglomerate aquifers in the Zhuxianzhuang Coal Mine, Huaibei coal field. Based on the statistics of conventional hydrochemical composition, Piper diagrams, ion combination proportions, and principal component analysis(PCA), this study explored the impacts of curtain walls on the hydrochemistry of the aquifers and determined the spatiotemporal hydrochemical evolutionary patterns under the influence of the curtain walls. [Results and Conclusions] The results indicate that the hydrochemical characteristics differ greatly between inside and outside the curtain walls, with the groundwater inside the curtain walls exhibiting elevated Ca~(2+) and Mg~(2+) concentrations compared to that outside the curtain walls.After the construction of the curtain walls, the hydrochemical processes are dominated by the dissolution of the curtain walls based on the leaching and dissolution of calcite(CaCO_3) and dolomite(CaMg(CO_3)_2), accompanied by varying degrees of pyrite oxidation, alternating adsorption of cations, and desulfurization. Influenced by mining, the dissolution of the curtain walls produces significantly enhanced impacts on groundwater within them, with the dissolution of the northern curtain wall relatively weaker than that of the eastern counterpart. The results of this study will provide theoretical support for the monitoring and protection of curtain walls and the environmental protection of groundwater.

    2025 01 v.53;No.325 [Abstract][OnlineView][Download 2197K]

  • Experimental study of the piezoelectricity of Middle Pleistocene loess in the Weibei region, China

    JING Yanlin;LIU Jie;LIU Qingying;DUAN Xiaoxiao;XIE Na;YANG Dengke;School of Intelligent Science and Engineering, Xi'an Peihua University;School of Civil Engineering, Chang'an University;

    [Objective] Quartz, the piezoelectric material discovered the earliest, has found widespread applications in industry, military fields, and daily life due to its piezoelectricity. The widely distributed loess worldwide is composed primarily of quartz, accounting for 37.0% to 69.9%. However, there is a lack of studies on the piezoelectricity of loess both domestically and internationally. [Methods] This study investigated the Qe2ol loess from the Weibei Loess Tableland in Shaanxi Province as an example to explore the piezoelectricity of loess. The piezoelectric coefficient of the loess was measured, and its piezoelectric voltage under the action of static loading and vibration was investigated using experiments [Results and Conclusions] The results indicate that loess exhibits piezoelectricity. Based on this characteristic,loess can be used for developing piezoelectric cells and conduct piezoelectric power generation. The piezoelectricity of loess is related to its dry density and moisture content rather than its thickness. Loess with lower dry density and higher moisture content exhibits stronger piezoelectricity and a higher piezoelectric coefficient; and vice versa. Under the conditions of natural density and moisture content, loess exhibits a piezoelectric coefficient of 16.1 pC/N. Under the action of static loading, the piezoelectric voltage signals of the loess appeared as a sine wave with regular waveforms, a frequency of 10 MHz, a period of 100 ns, and piezoelectric voltage exceeding 0.6 V. When multiple loess samples were connected in series, the voltage increased cumulatively. Under the action of vibration, the piezoelectric voltage of the loess increased significantly. It variedunder different vibration frequencies and peaked under resonance, with the maximum voltage of a single loess sample exceeding 2.1 V. Investigating the feasibility of replacing traditional car batteries with loess-based piezoelectric cells under the combined action of vibration and upper load is undoubtedly a topic of great interest. Furthermore, research based on the piezoelectricity of loess in loess regions, including soil moisture monitoring,seismic activity monitoring, and predominant period determination, holds great theoretical and practical significance.The results of this study could serve as a valuable reference for these research in loess areas.

    2025 01 v.53;No.325 [Abstract][OnlineView][Download 1886K]

  • Deformations and seepage-induced erosion of fractured rocks in fault under confined settings

    SUN Wenbin;TIAN Dianjin;MA Cheng;XUE Yanchao;YANG Can;ZHU Kaipeng;Shaanxi Key Laboratory of Prevention and Control Technology for Coal Mine Water Hazard;College of Energy and Mining Engineering, Shandong University of Science and Technology;

    [Objective] Most of the mining areas in China have entered the deep mining stage. In this case, the risks of mine water inrushes increase significantly due to the complex deep hydrogeological conditions, a significant increase in the number of hidden disaster-causing factors, and the existence of faults. [Methods] Using a deformation-seepage experiment system for fractured rocks, this study investigated the characteristics of compressive deformations and seepageinduced erosion of fractured rocks in faults. By analyzing the impacts of particle-size distribution combinations, saturation state, and seepage pressure, on the deformation-permeability characteristics of fractured rocks under confined axial compression, this study investigated the time-varying patterns of changes in the particle erosion characteristics, void structure, and seepage parameters of the fractured rock samples. [Results and Conclusions] The results indicate that the peak strain of the fractured rock samples increased with an increase in the Talbot index(n). For samples with the same particle size distribution, those in the water-saturated state exhibited higher incremental strain than those in the dry state.The fitted curves of the lost mass of particles exhibited an exponential growth function with time, with the lost mass being inversely proportional to the confining axial stress. Meanwhile, the mass of secondary particles increased with the axial load. The evolutionary trend of the void rate of the rock samples was closely related to their particle size distributions, with the Talbot index(n) correlating positively with the overall void rate of the samples. Comparison before and after loading and seepage revealed that the fractal dimension(D) was inversely proportional to the value of n and the masses of fine and coarse particles increased and decreased, respectively. Furthermore, the fractal dimension of the rock samples increased significantly after loading and seepage. Macroscopically, the confined water lift within faults can be divided into the initial stage of water lift, the expansion stage of channels for discharging water and sand inrush, and the mature stage of the channels. Microscopically, the lift involves the soaking and softening, dislocation and compression,deformations and cracking, and fragmentation and detachment of rock masses. The findings of this study will provide experimental data and a theoretical basis for research on the evolutionary patterns of water inrush disasters in faults.

    2025 01 v.53;No.325 [Abstract][OnlineView][Download 1999K]

  • Optical-electrical-acoustic wave multiparameter response characteristics of typical rocks in coal-bearing strata throughout the loading process

    ZHANG Pingsong;LIU Chang;State Key Laboratory for Safe Mining of Deep Coal Resources and Environment Protection, Anhui University of Science &Technology;School of Earth and Environment, Anhui University of Science & Technology;

    [Objective] The deformations and rupture of rocks under loading will cause potential changes in parameters.Dynamic parameter capture assists in characterizing the generation, propagation, and closure processes of fractures,serving as a significant method for assessing rock quality. [Methods] Using a multiparameter test system, this study synchronously acquired strain measured using distributed optic fibers, electrode current, and compressional wave(P-wave)velocities of rock specimens under uniaxial loading. Accordingly, this study determined strength vs. parameter characteristic relationship graphs and parametric tomography results, finely describing the multiparameter spatiotemporal evolutionary characteristics of three typical rocks(i.e., sandstone, limestone, and mudstone) throughout the loading process.[Results and Conclusions] The test results indicate that the time vs. pressure curves were highly consistent with the multiparameter response curves. For the rock specimens, the strain measured using spirally distributed optic fibers exhibited a slow, stable growth in the compression and linear elasticity stages of primary pores but a sudden, rapid growth in the fracture generation and propagation stages. During the tests, the strain measured using distributed optic fibers for sandstone, limestone, and mudstone under critical fracturing were 933×10-6, 401×10-6, and 3 790×10-6, respectively.The electrode current changed minimally in the compression and linear elasticity stages of primary pores, decreased significantly in the fracture generation and propagation stages, and rebounded during fracture closure. In the compression,linear elasticity, and failure stages of primary pores, the P-wave velocities of the sandstone specimen were 4.31 km/s,4.39 km/s, and 1.26 km/s, respectively; those of the limestone specimen were 4.80 km/s, 4.93 km/s, and 3.10 km/s, respectively, and those of the mudstone specimen were 3.65 km/s, 3.57 km/s, and 1.71 km/s, respectively. Based on the energy values of the rock specimens throughout the loading process, this study constructed damage variable D to assess the degrees of damage evolution of the rock specimens. Specifically, the D values of the sandstone specimen experienced gradual increase, decrease, and sudden increase stages; those of the limestone specimen underwent slow increase, rapid increase, stagnation, and sudden increase stages, and those of the mudstone specimen experienced slow increase, rapid increase, and sudden increase stages. This study explored the failure modes of different rock specimens based on the test results of the strain measured using distributed optic fibers. The results of this study will assist in predicting the generation and propagation of secondary fractures, as well as the positions of potential rupture planes, under loading.

    2025 01 v.53;No.325 [Abstract][OnlineView][Download 2991K]

  • Characteristics of Cenozoic volcanic edifices in the Pingnan area, Xihu Sag

    SUN Naiquan;JIANG Donghui;PAN Jie;GAO Yang;PU Renhai;DONG Xinxu;School of Geological Engineering and Geomatics, Chang'an University;Shanghai Offshore Oil & Gas Company,SINOPEC;State Key Laboratory of Continental Dynamics, Northwest University;Department of Geology, Northwest University;School of Mathematics and Computers, Panzhihua University;

    [Significance] Igneous rocks are well-developed in the southern Pinghu slope zone, Xihu Sag, East China Sea Shelf Basin. In this zone, the increased local geotemperature caused by magmatic activity produced significant impacts on the thermal evolution of source rocks and the formation of secondary pores in sandstone reservoirs and also serves as a significant indicator of regional tectonic movements, thus holding great significance for understanding the regional geological history. [Objective and Methods] This study aims to determine the formation stages and distribution patterns of igneous rocks as the cap rocks in the southern Pinghu slope zone. Using previous study results and the data of adjacent areas, as well as 3D seismic data and related attributes, and data from drilling and logs, this study analyzed the types, corresponding strata, and distribution ranges of volcanic rocks in the southern Pinghu slope zone. Furthermore, the formation stages of igneous rocks in the slope zone were explored based on the stratigraphic chronology, the morphologies of volcanic edifices, and the contact relationship between volcanic edifices and surrounding rocks. [Results and Conclusions] The results indicate that the seismic facies of igneous rocks in the Pingnan area can be divided into volcanic vent facies, along with explosive, overflow, and intrusive facies, with mounded and shield volcanic edifices proving the most developed. The magmatic activity in the Xihu Sag can be divided into three stages. Specifically, magmatic activity during the regional Longjing Movement, occurring in the late Miocene, exhibits the highest intensity and widest influence range. Besides, local small-scale tectonic movements occurred in the late depositional stage of the Yuquan Formation and the early depositional stage of the Santan Formation, corresponding to weak magmatic activity with minimal impacts. The Pingnan area contains five lithologic, low-amplitude drape anticline/fault combination traps associated with magmatic activity. The results of this study will provide a reference for future hydrocarbon exploration and production in the southern Pinghu slope zone of the Xihu Sag.

    2025 01 v.53;No.325 [Abstract][OnlineView][Download 3619K]

  • A U-Net-based denoising method for semi-airborne transient electromagnetic data and its application

    LIU Dong;FENG Hao;WANG Yongxin;ZHOU Xiaosheng;YAO Yuhong;SUN Huaifeng;Institute of Geotechnical and Underground Engineering, Shandong University;Guangxi Communications Investment Group CO., Ltd.;Guangxi Longma Expressway Co., Ltd.;Shandong Provincial Communications Planning and Design Institute Group CO., LTD.;

    [Objective and Methods] The semi-airborne transient electromagnetic(SATEM) method, an efficient geophysical exploration technique, has been extensively applied to mineral resource exploration, groundwater surveys, and geothermal resource surveys. However, the collected data are frequently susceptible to noise interference, significantly affecting the accuracy of subsequent data processing and interpretation. To address issues such as residual noise and the loss of effective signals, enhance denoising effects, and reduce the influence of subjective factors, this study proposed a denoising method for SATEM data based on the U-Net deep learning architecture(also referred to as the U-Net-based method) by applying U-Net to SATEM data denoising. In this method, a U-shaped encoder-decoder architecture is employed to automatically learn and extract noise features from the data through an end-to-end training approach. The encoder learns and extracts noise features from data, while the decoder reconstructs the noise features and restores denoised data. By introducing skip connections to the symmetric layers in the encoder and the decoder, the U-Net-based method effectively integrates the low-level features bearing rich spatial information with the high-level features containing semantic information, thus achieving accurate denoising. [Results and Conclusions] Practical calculation cases indicate that the U-Net-based method can improve the signal-to-noise ratio(SNR) of data by approximately 10 dB after denoising, proving significant advantages of denoising SATEM data compared to traditional denoising methods. This method has been employed to denoise the measured data of the No.2 Fenghuang tunnel in the Laibin-Du'an section of the Hezhou-Bama expressway in Guangxi, significantly enhancing the interpretability of the multi-channel diagrams and apparent resistivity images after data denoising. Therefore, the U-Net-based method holds great practical significance for SATEM data denoising, thus providing effective technical support for future geophysical exploration.

    2025 01 v.53;No.325 [Abstract][OnlineView][Download 7435K]

  • An intelligent lithology identification method for sandstone and mudstone strata and its applications: A case study of the Jurassic strata in the Lunnan area, Xinjiang, China

    CAI Ming;ZHOU Qingwen;YANG Cong;CHEN Feng;WU Dong;LIN Wang;ZHANG Chengguang;ZHANG Yuanjun;MIAO Yuxin;Key Laboratory of Exploration Technologies for Oil and Gas Resources, Ministry of Education, Yangtze University;College of Geophysics and Petroleum Resources, Yangtze University;Wuhan Safety & Environmental Protection Research Institute Co., Ltd.,Sinosteel;Anhui Provincial Coal Geological Exploration Bureau Third Team;Information Center, CNPC Engineering Technology R&D Company Limited;

    [Objective] Lithology identification lays the foundation for fine-scale reservoir evaluation. However, traditional identification methods generally utilize the interactive relationships between only 2-3 logging parameters, suffering from low utilization rates of logging information and low identification accuracy for strata with small differences in logging responses. This seriously restricts the effects of old well reexamination. The efficient, intelligent CatBoost classification algorithm can fully mine the correlations between multi-source logging information and lithology. [Methods]This study investigated the Jurassic sandstone and mudstone reservoirs in the Lunnan area, Xinjiang, China. Using five logging parameters determined through sensitivity analysis, i.e., natural gamma-ray value, spontaneous potential, deep and shallow resistivity ratio, sonic interval transit time, and density, this study developed an intelligent lithology identification model based on the CatBoost algorithm. The optimized model was employed to deal with actual logging data for lithology identification, and its performance was evaluated using accuracy, precision, and recall and was then compared with the lithology identification results of the random forest(RF) and k-nearest neighbors(KNN) algorithms. [Results and Conclusions] The results indicate that the large-scale lithologies of the Jurassic strata in the Lunnan area include mudstones, sandstones, and conglomerates, with complex fine-scale lithologies. In the identification of the fine-scale lithologies of the target reservoir, the intelligent lithology identification model, established using the CatBoost algorithm and lithology-sensitive logging parameters, yielded an accuracy of 92.64%, significantly higher than that of the random forest model(82.95%) and the KNN model(70.16%). This result demonstrates that the CatBoost model can effectively address of the challenges of lithology identification in the study area. The results of this study will provide a scientific basis for the review and further exploration and development of old wells in the Lunnan area. Besides, these results can serve as a valuable reference for research on methods for fine-scale identification of complex lithologies.

    2025 01 v.53;No.325 [Abstract][OnlineView][Download 2164K]

  • A dehazing and enhancement algorithm for heterogeneous images of underground mining environments in coal mines

    ZHANG Xuhui;XIE Yanbin;YANG Wenjuan;ZHANG Chao;WAN Jicheng;DONG Zheng;WANG Yanqun;JIANG Jie;LI Long;College of Mechanical Engineering, Xi'an University of Science and Technology;Shaanxi Key Laboratory of Mine Electromechanical Equipment Intelligent Monitoring;

    [Objective] In coal mines, the uneven distribution of dust haze and complex illumination conditions caused by underground coal mining and dust removal lead to blurred video images, as well as the loss of information and details. Hence, this study proposed a dehazing and enhancement algorithm for heterogeneous images of underground mining environments. [Methods] Initially, hazy images were segmented into zones with different brightness values, for which the average ambient light intensity of global dark channels was calculated. The calculation results were integrated through weighting with the ambient light of local bright channels, which was obtained using adaptive gamma correction and multiscale Gaussian filtering. Consequently, accurate ambient light intensity estimates were determined. To preserve image details while achieving natural dehazing effects, transmission maps were processed using multiscale fusion correction technology and were then refined using joint bilateral filtering. Afterward, clear hazy images were obtained using the atmospheric scattering model. To further enhance the overall brightness and contrast of the dehazed images,white balance correction was performed. Specifically, images were converted into the hue-saturation-value(HSV) color space. Then, the details and contrast of images were enhanced using the proposed adaptive saturation correction and improved contrast enhancement algorithm, as well as Laplacian sharpening. [Results and Conclusions] Images of typical,actual scenarios were processed using five algorithms: dark channel prior(DCP), maximum reflectance prior(MRP), optimal-scale fusion-based dehazing(OSFD), multiscale fusion – low light image enhancement(MF-LIME), and contrast enhancement and exposure fusion(CEEF). The processing results of these algorithms were those of the proposed algorithm based on multiple indicators. The results indicate that compared to the above novel and excellent algorithms in terms of their optimal indicators, the proposed algorithm exhibited that:(1) The average gradients were approximately twice those obtained by CEEF, suggesting elevated image clarity.(2) The average information entropy decreased by approximately 1% compared to that of MRP, implying more information preserved.(3) The standard deviation increased by approximately 6% on average compared to OSFD, representing improved image contrast.(4) The average fog aware density evaluator(FADE) value by approximately 23% compared to CEEF, implying an effective reduction in the haze Therefore, the proposed algorithm can effectively improve the visual effects and quality of blurred images of underground mining environments in coal mines, exhibiting high utility in engineering.

    2025 01 v.53;No.325 [Abstract][OnlineView][Download 2139K]

  • A deep learning-based method for the intelligent identification of the quantity of coals flushed out during borehole hydraulic flushing

    LI Xiaojun;ZHAO Mingyang;LI Miao;School of Energy Science and Engineering, Henan Polytechnic University;Henan International Joint Laboratory of Coalmine Ground Control;School of Innovation and Entrepreneurship,Henan Polytechnic University;

    [Objective] Given the inaccurate and low-efficiency manual statistics of the quantity of coals flushed out during borehole hydraulic flushing, this study proposed an intelligent identification method that combines YOLOv8n, ResNet34, and PP-OCRv4 algorithms. [Methods] First, the first-level detection was completed using the YOLOv8n algorithm, which, combined with the ResNet34 and PP-OCRv4 algorithms via parallel cascade, was then employed to conduct second-level processing. Through the above processing and in combination with the method for classification status discrimination based on tracking frame numbers, the framework of an algorithm for automatically calculating the quantity of coals flushed out was established. Subsequently, the deformable convolution DCNv2 module was introduced into the C2f module of YOLOv8n to reduce the impacts of point-like strong illumination on feature extraction. Moreover, the default detection head of YOLOv8n was replaced with the Dynamic Head module to strengthen the feature extraction in scale, space, and channel dimensions. The CIoU loss function was replaced with the SIoU loss function to accelerate the matching between prediction and ground truth boxes. Finally, the improved YOLOv8n algorithm was validated using a self-built dataset. [Results and Conclusions] The results indicate that, compared to the original algorithm, the improved YOLOv8n algorithm increased the mean average classification accuracy, recall, and precision by 7.6%, 3.5%, and 6.4%,respectively. This verifies the effectiveness and stability of the improvement strategy for enhancing the model performance. The improved YOLOv8n algorithm was applied to the real-time videos from four drilling sites of borehole hydraulic flushing for gas drainage, yielding respective identification accuracies of 100.0%, 93.3%, 95.7%, and 93.1%,with an average of 95.5%, meeting the accuracy requirements for the automatic identification of coal quantity flushed out during borehole hydraulic flushing. The method for determining the ResNet34 classification status based on tracking frame numbers resolved the problem of unreliable single identification of the classification status. The results of this study provide a technical and practical foundation for the integration of the YOLO series of algorithms with other deep learning techniques and its wide applications. Besides, these results serve as a valuable reference for achieving intelligent advances in complex underground coal mine scenarios such as drilling sites for gas drainage.

    2025 01 v.53;No.325 [Abstract][OnlineView][Download 2529K]