Coal Layers Research Articles

Research on Solidification Layer Detection in Coal Transportation Process Based on Improved YOLOv8 Algorithm

Railway transportation is one of the main modes of long-distance coal transportation, and it inevitably causes environmental pollution during the transportation process. In order to improve the environment along the railway and increase the utilization rate of coal resources, this paper proposes a detection algorithm for the scattered coal solidification layer during transportation based on the YOLOv8 model and designs an intelligent recognition model suitable for coal solidification layer detection devices by combining fluorescence detection methods. Through experimental analysis, we found that the model meets the requirements of practical detection and can play a crucial role in environmental protection, with high practical application value.

Application and Research of Multi-Scale Dynamic Diffusion Permeability Model in Different Coal Ranks

The spatial scale of coal mining and rock layer control is distributed between 10-10 and 107, spanning 17 orders of magnitude. There are multi-scale pore cracks from millimeter to micro and nanometers in the coal, and the pore size can reach one million times, which makes the coal permeability also show a multi-scale characteristics of millions and time. For the permeability of the coal seam, it is necessary to test and analyze the distribution of micro and nano pores and cracks in the coal [1]. CBM mining is accompanied by the dynamic change of adsorption pressure in coal and the complex deformation of multi-scale heterogeneous structure of coal, and the multi-scale deformation feature of pore fissure structure plays an important role in the transport of methane [2]. However, existing studies focus on treating coal as a homogeneous isotropic medium, without considering the influence of coal multiscale pore structure on permeability. The variation of heterogeneous degree of coal structure with structural scale and its influence on dynamic diffusion and permeability are rarely reported. Li Zhiqiang et al. [3] conducted an experimental-model-mechanism study of CBM gas micro-nano series multi-scale dynamic diffusion permeability. On this basis, the dynamic diffusion and permeability of different coal scales.

Geological engineering double sweet spot evaluation of thin coal seam reservoirs based on facies control: A case study of tight sandstone gas in the Shenfu block of the Ordos Basin

Abstract The development of thin coal layers within the Shenfu tight sandstone reservoirs significantly impacts the control of hydraulic fractures over the actual sweet spots, leading to considerable inter-well production variability. This paper establishes a connection between individual well sweet spots and block sweet spots through a refined lithofacies model and conducts a comprehensive double sweet spot secondary optimization in conjunction with the characteristics of thin coal layer development. The research findings indicate the following: Class I sweet spots ≥0.46, 0.37≥ Class II sweet spots <0.46, 0.3≥ Class III sweet spots <0.37; fractures will be captured by the coal layer if the thin coal layer is more than 5 m away from the perforation point or if the coal layer thickness exceeds 3 m; the secondary sweet spot optimization can eliminate the influence of thin coal layers and establish a three-dimensional comprehensive double sweet spot model suitable for the study area.

Study on the force chain characteristics with coal dust layer and the three-body contact stiffness

To explore the influence of the meso-mechanical behaviors of the wet coal dust layers on the contact stiffness of mechanical bonding surfaces, a three-body contact model incorporating an interface with wet coal dust was constructed based on breakage theory. The model considered the mechanical surface morphology and contact characteristics of the wet coal dust. The force chain evolution laws of the wet coal dust layer were elucidated under the effects of gap filling and the cover layer, and the bearing characteristics of the three-body contact bonding surfaces were revealed by quantitative analyses of the number, length, collimation coefficient, and coordination number of the force chains within the wet coal dust layer. Finally, the three-body normal contact stiffness under various preload forces was computed and experimentally validated. The results demonstrate that the external load transfer path of the three-body contact bonding surfaces was from mechanical surface (macroscopic stress) to wet coal dust layer (mesoscopic force chains) and then to mechanical surface (peaks and valleys). The interactions among these three elements contributed to transforming the distributions of the macroscopic stresses and mesoscopic force chains to the locations at the peaks and valleys of the mechanical surface. Among them, the proportion of short force chains in the wet coal dust layer increased from approximately 0.8%–91%, while the proportion of long force chains exhibited an opposite changing trend. The force chain collimation coefficient initially increased and subsequently stabilized, reaching a maximum value of 0.93. A large number of broken, small particles in the wet coal dust layer mainly served to fill the gaps among large particles. The maximum relative error between the experimental and simulated values on the three-body contact stiffness is 7.26%, indicating that the simulation results can be an approximate substitute for the experimental results with a certain degree of accuracy and practicality. The research results are of great significance for understanding the contact characteristics of mechanical surfaces containing particulate media.

Wetting permeability of surface active agent droplets impacting on a layer of coal dust

The wetting and penetration of the coal dust layer by liquid droplet is crucial for suppressing coal dust. A combination of experimental and simulation methods was employed to investigate the impact of surfactant concentration, droplet velocity, and particle size on the penetration properties and their underlying mechanisms. Droplet impact wetting experiments were employed to evaluate their dynamic wetting behavior on the coal dust layer. The experimental results show that increasing the impact velocity of droplets is advantageous for enhancing the maximum dimensionless wetting length. Increasing the surfactant concentration can expedite the droplet reaching maximum dimensionless wetting volume in the dust layer. The larger the particle size of coal dust, the shorter time required for droplet to reach maximum wetting volume. The research results provide a theoretical basis for selecting and efficiently applying surfactants in treating coal dust.

Slake durability indices of shales from the Batu Arang Beds, Selangor Darul Ehsan

The Eocene to Oligocene Batu Arang Beds outcrop within an approximately triangular basin covering some 15 km2 and comprise stiff, structureless clays to well laminated and fissile shales inter-bedded with fine to coarse sandstones and several coal layers. The shales are often silty and even sandy and contain abundant carbonaceous material. The coal mostly occurs as thin laminae, though two thick seams, mined by open-cast and under-ground methods from 1915 to 1960, are found in the eastern part of the basin. To determine the weatherability characteristics of the shales, three samples (A, B and C) were collected at the western wall, and one sample (D) at the eastern wall, of an open-cast shale pit. Samples A and D are located some 10 m, and 5 m, below the ground surface, whilst samples B and C are 10 m, and 16 m, stratigraphically below sample A. Samples A, B and C, and D have average dry unit weights of 16.64, 14.49, and 15.40, kN/m3 and average apparent porosities of 26.2%, 35.7% and 31.7%, respectively. Slake durability indices of all samples for one standard cycle of wetting and drying (Id1) are between 98.3% and 99.3%, and for two standard cycles (Id2), between 96.7% and 98.9%. Durability indices for three standard cycles (Id3) are between 95.1% and 98.2%, and for four standard cycles (Id4), between 93.3% and 97.6%. The indices lead to the conclusion that the shales are of high to extremely high durability and suitable for use as highway embankment or construction material. The high durability classification is supported by recent excavations at an overburden dump where relatively fresh shale blocks with little disaggregation or disintegration are exposed even after being buried for 78 to 85 years.

Numerical investigation of mechanical responses and failure features of coal measure strata using combined finite-discrete element method

Investigating the mechanical responses and failure features of the deep coal measure strata (CMS) is essential for designing hydraulic fracturing treatments and preventing geological dynamic hazards in underground engineering. In this paper, a three-dimensional CMS model is established by the combined finite-discrete element method (FDEM). The mechanical properties, stress evolutions and failure features of the CMS with different lithological combinations (sandstone-coal-sandstone (SCS), sandstone-coal-mudstone (SCM) and mudstone-coal-mudstone (MCM)) and thickness ratios are investigated under the uniaxial compressive condition. Results indicate that the SCS combination exhibits the highest uniaxial compressive strength (UCS) and elastic modulus, followed by the SCM and MCM combinations. The mechanical properties of the CMS are predominantly determined by the softer coal layer. The mechanical contrasts in elastic modulus and Poisson’s ratio between adjacent layers cause the generation of additional compressive stress in the softer layer and additional tensile stress in the stiffer layer. Therefore, the softer coal layer exhibits the shear-dominated failure pattern while the stiffer sandstone/mudstone layer displays the tensile-dominated failure pattern in the CMS. Furthermore, as the thickness ratio of the coal layer increases, the UCS, elastic modulus, and interfacial constraint stress decrease in the CMS. Additionally, the UCS and stress–strain relationship in the post-peak stage exhibit the noticeable size effect, whereas the mechanical behaviors in the pre-peak stage and the ultimate fracture patterns show the opposite. The elastic modulus and interfacial constraint stress obtained by the FDEM simulation match well with those calculated by theoretical models. The key findings of this paper can provide fundamental understanding and reliable parameters for multi-scale geomechanical modeling in petroleum and mining engineering.

Study on the rigid-discrete coupling effect of scraper conveyor under different chain speed-load conditions

The complexity of the underground environment in coal mines often leads to varying load conditions during the operation of the scraper conveyor, which can affect the lifespan of its components and result in unnecessary energy consumption. A test platform for the scraper conveyor was constructed based on the similarity theory to measure torque, speed, chain tension, and scraper acceleration during transportation. A DEM-MBD model of the scraper conveyor was developed and validated through transport tests and similarity theories to analyze the rigid-discrete coupling effect under different chain speed-load conditions. The results revealed a stratification phenomenon and a Brazilian fruit effect in the movement of coal. The average velocity of the upper and lower coal layers gradually increased during the transportation, while the difference between them gradually decreased. As the load increased, the stacking density and height of coal between scrapers also increased, leading to a higher force exerted on the scraper and chain. As the chain speed increased, the stacking density and height of coal between scrapers decreased, along with a decrease in the force applied to the scraper and chain. The formation of three-body wear necessitates a specific positional condition. When the scraper (chain)- coal-deck plate (chute liner) forms a particle stagnation state, severe wear occurs on the parts. This study provides a foundation for analyzing the transport mechanism of scraper conveyor from the particle perspective, offers a simulation reference for analyzing the mechanical and tribological characteristics of the line pan and scraper chain, and serves as a guideline for the future development of transportation state monitoring and the optimization and enhancement of components under different working conditions.

Optimization of the Layer Location of Extraction Wells Based on the Unpressurized Gas Transport Law.

Protective layer mining is one of the most effective measures to control outbursts of coal seam gas in coal mines. Accurately grasping the overlying rock movement and pressure-relief gas migration patterns under protective layer mining conditions is a prerequisite for efficient surface coalbed methane extraction; it is the basis for green emission reduction in coal mines. A physical model was established using the Ji15-33200 working face of Pingmei Shi Mine as the research object, and a method combining theoretical calculation and numerical simulation was used to obtain the overlying rock movement. In situ stress distribution characteristics of the stope after the upper protective layer was mined to explore the upper protective layer migration rules of pressure-relief gas after mining. On this basis, the location and layer of surface coalbed methane production wells was determined. The research results show that the coal and rock formations on the floor of the goaf experienced a deformation process of compression → expansion → rebalance during the mining process; the stress changes of the overlying and underlying coal strata in the goaf have experienced a process of increasing → decreasing → rebalance; and gas migrates upward through the fissure zone in the coal layer and slowly diffuses in other microfissure areas. When the pressure reaches a certain value, it is enriched in the crack development area and the upper part of the fissure zone; combined with the relevant geological conditions of the study area, it was determined that the upper part of the roof of the Ji16-17 coal seam is a gas-rich area. By comparing three mining vertical wells at different positions in the horizontal direction, it was found that the extraction effect was significant in the "O″ ring, near the excavation face.

Dependence of Radiance of Burning Coal Bed on Ash Formation and Dew Condensation

Abstract In this study, coal samples with different moisture contents were prepared using a drying and humidification system. Coal samples were placed in a crucible and ignited using a heating wire, to which power was applied during coal combustion. The combustion radiance of coal samples with three moisture contents (0, 20, and 50%) was measured using a narrow-angle radiometer at three temperatures (10, 25, and 50 °C). A numerical simulation model was developed to predict the unsteady radiation characteristics of a coal layer burning on one-dimensional planar plates. The unsteady energy balance equation and radiative transfer equation were solved using the semi-implicit Runge–Kutta method and discrete ordinates method. In addition, the effect of dew condensation on the radiance was investigated. The greatest reduction in radiance was observed during the burning of the high-moisture coal. Furthermore, the effect of ash (converted from coal) on radiance was examined. The results demonstrated that certain changes in the optical properties during the burning of coal to ash can alter the absorption as well as anisotropic scattering, and thereby the radiance, as combustion proceeds.

Reservoir rock typing assessment in a coal-tight sand based heterogeneous geological formation through advanced AI methods

Geoscientists now identify coal layers using conventional well logs. Coal layer identification is the main technical difficulty in coalbed methane exploration and development. This research uses advanced quantile–quantile plot, self-organizing maps (SOM), k-means clustering, t-distributed stochastic neighbor embedding (t-SNE) and qualitative log curve assessment through three wells (X4, X5, X6) in complex geological formation to distinguish coal from tight sand and shale. Also, we identify the reservoir rock typing (RRT), gas-bearing and non-gas bearing potential zones. Results showed gamma-ray and resistivity logs are not reliable tools for coal identification. Further, coal layers highlighted high acoustic (AC) and neutron porosity (CNL), low density (DEN), low photoelectric, and low porosity values as compared to tight sand and shale. While, tight sand highlighted 5–10% porosity values. The SOM and clustering assessment provided the evidence of good-quality RRT for tight sand facies, whereas other clusters related to shale and coal showed poor-quality RRT. A t-SNE algorithm accurately distinguished coal and was used to make CNL and DEN plot that showed the presence of low-rank bituminous coal rank in study area. The presented strategy through conventional logs shall provide help to comprehend coal-tight sand lithofacies units for future mining.

Delineation of Coal Identification Using Inversion Microtremor and Borehole at PT X

Coal is a natural resource composed of organic and inorganic materials. The potential of coal is one of the national and world resources. Microtremor method is a geophysical exploration method that utilises microseismic waves to identify the presence of hydrocarbons. Microtremor data processing is processed first using Geopsy software to obtain the H/V curve which will then be processed using Hv-Inv software to obtain the Vs value. Microtremor data is correlated with data from the borehole, the coal seam thickens to the southwest. Similarly, with the correlation results of other microtremor cross sections, the cross section shows that the coal seam is thickened and continuous to the west or southwest. This is further strengthened by the existence of boreholes as a correlation of coal Vs value data in the range of 613.37 m/s-887.70 m/s. Other constituent materials such as soil,claystone, sandstone, carboneseus. Based on the Vs value of the 1D model, it is known that the research area shows the distribution of coal at a depth of 53.5-76 metres. The coal layer in the study area is bituminous to sub-bituminous coal.

The Overview of Indonesia Coal Bed Methane Resources

Coal Bed Methane (CBM) is generated by coal layers, there is a preceding process, which is the formation of coal (coalification). Coalification begins with the burial of organic material originating from plants. The burial, lasting hundreds of millions of years, results in increasing temperatures and pressures, causing physical and chemical changes to the organic material. Methane gas, the largest component of CBM, is formed. Two processes: biogenic and thermogenic. In the early stages of coalification, biogenic methane gas is produced as a byproduct of the activities of decomposing microorganisms (anaerobic bacteria), similar to what occurs in the decomposition of organic waste. Only about 5 to 20 percent is stored within coal. There are four mechanisms for gas storage in coal: absorption, adsorption, free gas, and gas dissolved in water. Among these four mechanisms, adsorption is the most significant, accounting for 98 percent of the stored CBM in a combined system of micropores (coal matrix) and cleats. Coal Bed Methane resources in Indonesia can be found across South Kalimantan, East Kalimantan, Sumatra, and Java.

Numerical Study on the Characteristics and Control Method of Coal Leakage between Supports in Integrated Mining of Extremely Loose and Soft Coal Seams

Extremely loose and soft coal seams, with a Platts coefficient of less than 0.3, are easy to break in the process of integrated mechanized roof coal mining and are prone to spilling and piling up between the hydraulic supports, which is a safety hazard for the movement of equipment. The coal particles must be cleaned up manually, resulting in reduced resource recovery rates and lower mining face efficiency. To effectively mitigate and control the problem of coal spillage accumulation amidst hydraulic supports, this study utilizes discrete element numerical simulation to examine the characteristics of block size distribution and the spilling process during the crushing of highly loose and soft top coal. By taking into account various parameters associated with shelf spacing, this research identifies key factors for controlling arching and self-stopping phenomena in top coal particles. The study findings suggest that the uppermost coal layer undergoes significant fragmentation during the integrated mining process of loosely packed and soft coal seams, resulting in a higher probability of coal leakage issues observed near the rack’s coal wall side and at the end of the roof control area. The key factors contributing to the self-arresting of spilled coal particles include inherent characteristics of the coal body, particle diameter, and stand spacing. In this specific mine under investigation, an arch formation naturally occurs to prevent further leakage when the distance between stands is less than eight times the diameter of particles, and after process correction, the average time saving for a single shift of manual floating coal cleaning at the working face is about 2 h, and the proportion of time saving is more than 50~75%.

Research on intelligent identification algorithm of coal and rock strata based on Hilbert transform and amplitude stacking

AbstractThe high precision identification of coal–rock layers is a significant challenge in intelligent mining. There is a large amount of electromagnetic noise and metal reflector signals in the full space detection environment of mining roadway, which makes it hard to distinguish the reflected waves at interface from a set of echo signals generated by the interface due to the similar amplitudes among them. So the method of identifying layers solely based on amplitude characteristics has poor stability and accuracy in coal mining environments. This paper proposes a method for identifying coal–rock layers based on Hilbert transform and tracking–scanning–stacking technology. There are two steps to achieve the recognition of air–coal–rock interfaces. First, by analysing the instantaneous amplitude spectrum obtained from the Hilbert transform, the first extreme point that is always the maximum value within a wavelength range is determined as the rough position of the air–coal interface. To solve the problem of recognition errors caused by noise and energy dispersion, the density difference method is used to remove discrete points. Second, the precise position of the air–coal interface is determined by tracking the extreme points within the 1.5 wavelength range around the rough position, and using the amplitude stacking method to quantitatively analyse and compare the degree of energy concentration. The data between zero time and the reflected waves at the air–coal interface is removed to avoid the impact of them on the recognition of the coal–rock interface. Results of physical model experiments and actual coal mine experiments show that this method yields better results and has high stability compared to conventional recognition method. Moreover, the average relative thickness errors are 4.5% for air layer and 4.2% for coal layer.

Comparative research on the pipe-soil frictional resistances of circular and rectangular pipe sections during trenchless pipe jacking.

Pipe jacking is a trenchless construction method to achieve forward tunneling and efficient construction of underground structure simultaneously without extensive surface excavation. In the process of pipe jacking construction, the jacking force provided by the hydraulic jacking equipment must overcome the frontal resistance of the cutter head and the frictional resistance between the pipe sections and formation at the same time. In particular, the pipe-soil frictional resistance increases with the increases of jacking distance, buried depth, pipe diameter and the complexity of jacking trajectory. Therefore, it is very important to correctly estimate jacking force in trenchless jacking engineering practice for the smooth implementation of pipe jacking, operation risk and comprehensive cost control. Firstly, the stress states of jacking circular and rectangular pipe sections in the soil are analyzed, and the key influencing factors of their pipe-soil frictional resistance are obtained respectively. Then, the pipe-soil frictional resistance of jacking the circular and rectangular pipe sections with the same external surface area in the dry sandy soil and coal granular layer are tested separately by using the self-developed multifunctional experimental apparatus during trenchless pipe jacking. The results show that the pipe-soil frictional resistances of jacking circular and rectangular pipe sections in the coal granular layer are always smaller than that in the sandy soil under the same experimental conditions, and the corresponding fitting calculation equation of pipe-soil frictional resistances are obtained respectively. Meanwhile, the modified calculation methods of the above pipe-soil frictional resistances are proposed respectively based on the relationship between the lateral pressure coefficient K and the buried depth of pipe section H. Moreover, the disturbed area of soil in the upper part of jacking circular pipe section presents an arc distribution, while the disturbed area of soil in the upper part of jacking rectangular pipe section presents a slightly concave distribution. Due to the different disturbance conditions of soil around the pipe section, the lateral pressure coefficient K should be corrected in the calculation equations of pipe-soil frictional resistance of jacking circular and rectangular pipe sections based on the discrete element numerical simulation analysis by EDEM software. Finally, the pipe-soil frictional resistances obtained by different methods in the sandy soil are compared and analyzed. The calculated values of the modified theoretical calculation method are very close to the experimental test values, while the other methods are smaller than the experimental test values, which makes the rationality of the modified theoretical calculation method of pipe-soil frictional resistance is verified, and some suggestions are also put forward for the value of some coefficients in the relevant empirical estimation equations. The above research achievements systematically compared the states of pipe-soil frictional resistances of jacking circular and rectangular pipe sections based on different research methods, especially for the correct evaluation of jacking force during trenchless pipe jacking, they could provide some valuable references and effective guidance for the subsequent research, engineering practice and further development of trenchless pipe jacking technology.

Study on the gas outburst control effect of goaf on the neighboring working face: Case study of Pingmei No.4 Mine

AbstractAs coal mining depth increases, there is a corresponding increase in both ground stress and gas pressure, leading to a higher incidence of coal and gas outburst accidents. To investigate the stress distribution law and gas release degree of the adjacent coal body within the goaf of the outburst coal seam, and to acquire an understanding of the impact range of the large mining face goaf on the stress of the coal seam, this study employed theoretical analysis and numerical simulation to analyze the impact and scope of the goaf on the adjacent coal body, and measured the gas content of the coal seam. The findings indicated that following the completion of mining on the working face, there was a redistribution of stress in the coal and rock layers within 40 m of the goaf, with the stress concentration phenomenon observed at a distance of 2.6 m from the goaf. Affected by the stress relief effect of mining, the stress, gas content, and other related factors have been studied in detail by researchers. Affected by the stress relief effect of mining, the stress, gas content, and gas pressure of the surrounding rock near the goaf in the coal seam are significantly reduced. The research results verify that tunneling along the goaf is an effective method to prevent coal and gas outbursts and improve stoping efficiency.

Precise detection of coal and gangue based on natural γ-ray

To address the technical limitations of automatic coal and gangue detection technology in fully mechanized top coal caving mining operations, the low radiation level radioactivity measurement method is utilized to assess the degree of coal-gangue mixture in top coal caving process. This approach is based on the distinguishing radiation characteristics of natural γ-rays between coal and gangue. This study analyzed the distribution characteristics of natural γ-rays in coal and rock layers of thick coal seams and the applicability of this method, introduced the basic principle of coal-gangue detection technology based on natural γ-ray, developed the test system about automatic coal-gangue detection, studied the radiation characteristics of coal and gangue, proposed determination model of the coal-gangue mixed degree, combined with the time sequence characteristics of the top coal’s releasing flow and the energy spectrum characteristics of different layers of rock, realized the precise coal-gangue detection technology in complex structure thick coal seam with multiple gangue. Field tests were conducted in Lilou, Xiaoyu and Tashan Coal Mine. The test results were well corroborated with the research results and achieved the expected results, which laid the foundation for the field application of intelligent coal mining.

Grout Ground Leakage Caused by the Development of Separation Layer in a Case Study of Muduchaideng Coal Mine

A lot of grout ground leakage occurred during Muduchaideng coal mine separation layer grout work, resulting in serious pollution. To find the mechanism of grout leakage, this paper carried out indoor experiments and on-site measurements. Through the indoor scale model test, the deformation of overburden stratum was captured, which reflected that the horizontal shear band developed at the depths of 289.67–322.48 m, 386.42–431.18 m, and 474.95–524.07 m. Then, these positions were verified through on-site drilling. It was found that the mud slurry consumption increased, the water level dropped, and the borehole wall was seriously deformed in these disturbed positions. Therefore, the reason for this grout leakage was that the overlying separation layer continued to develop upwards, and the borehole was destroyed in the location where the separation layer developed. Then, the grout pipeline was destroyed, and some grout flew towards the ground surface along the pipeline and the borehole wall. This article reveals a kind of grout ground leakage phenomenon in a case study of Muduchaideng coal mine, which can provide a warning for engineering projects.

Source apportionment of methane emissions from the Upper Silesian Coal Basin using isotopic signatures

Abstract. Anthropogenic emissions are the primary source of the increase in atmospheric methane (CH4) levels. However, estimates of anthropogenic CH4 emissions still show large uncertainties at global and regional scales. Differences in CH4 isotopic source signatures δ13C and δ2H can help to constrain different source contributions (e.g., fossil, waste, agriculture). The Upper Silesian Coal Basin (USCB) represents one of the largest European CH4 emission regions, with more than 500 Gg CH4 yr−1 released from more than 50 coal mine ventilation shafts, landfills, and wastewater treatment plants. During the CoMet (Carbon Dioxide and Methane Mission) campaign in June 2018 methane observations were conducted from a variety of platforms including aircraft and cars to quantify these emissions. Besides the continuous sampling of atmospheric methane concentration, numerous air samples were taken from inside and around the ventilation shafts (1–2 km distance) and aboard the High Altitude and Long Range Research Aircraft (HALO) and DLR Cessna Caravan aircraft, and they were analyzed in the laboratory for the isotopic composition of CH4. The airborne samples downwind of the USCB contained methane from the entire region and thus enabled determining the mean signature of the USCB accurately. This mean isotopic signature of methane emissions was -50.9±0.7 ‰ for δ13C and -226±9 ‰ for δ2H. This is in the range of previous USCB studies based on samples taken within the mines for δ13C but more depleted in δ2H than reported before. Signatures of methane enhancements sampled upwind of the mines and in the free troposphere clearly showed the influence of biogenic sources. We determined the source signatures of individual coal mine ventilation shafts using ground-based samples. These signatures displayed a considerable range between different mines and also varied for individual shafts from day to day. Different layers of the USCB coal contain thermogenic methane, isotopically similar to natural gas, and methane formed through biogenic carbonate reduction. The signatures vary depending on what layer of coal is mined at the time of sampling. Mean shaft signatures range from −60 ‰ to −42 ‰ for δ13C and from −200 ‰ to −160 ‰ for δ2H. A gradient in the signatures of subregions of the USCB is reflected both in the aircraft data and in the ground samples, with emissions from the southwest being most depleted in δ2H and emissions from the south being most depleted in δ13C, which is probably associated with the structural and lithostratigraphic history of the USCB and generation and migration processes of methane in the coal. The average signature of -49.8±5.7 ‰ in δ13C and -184±32 ‰ in δ2H from the ventilation shafts clearly differs from the USCB regional signature in δ2H. This makes a source attribution using δ2H signatures possible, which would not be possible with only the δ13C isotopic signatures. We assume that the USCB plume mainly contains fossil coal mine methane and biogenic methane from waste treatment, because the USCB is a highly industrialized region with few other possible methane sources. Assuming a biogenic methane signature between and −320 ‰ and −280 ‰ for δ2H, the biogenic methane emissions from the USCB account for 15 %–50 % of total emissions. The uncertainty range shows the need of comprehensive and extensive sampling from all possible source sectors for source apportionment. The share of anthropogenic–biogenic emissions of 0.4 %–14 % from this densely populated industrial region is underestimated in commonly used emission inventories. Generally, this study demonstrates the importance of δ2H-CH4 observations for methane source apportionment in regions with a mix of thermogenic and biogenic sources and, especially in our case, where the δ13C signature of the coal mine gas has a large variability.