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With the increase of mining depth, the gas management problem in coal and gas outburst mine is more prominent. At the same time, gas is used as a clean resource to mine together with coal which is to realize the simultaneous extraction of coal and gas more practical significance. The relation between coal mining and gas extraction is mutually reinforcing and restricting. It is of great theoretical significance and application value to study simultaneous extraction of coal and gas technique optimization. The Qidong Coal Mine of the Wanbei Coal and Electricity Group is a coal and gas outburst mine. The spacing of the coal seam is small, the occurrence conditions are complex, and the mining is difficult. This study used theoretical analysis, numerical simulation, and engineering analogy to investigate the coordinated mining technology of coal and gas in outburst coal seams. [ABSTRACT FROM AUTHOR]

Among surface mining methods, strip mining is a widely used technique for extracting mineral resources. This method is suitable for most near-surface stratiform sedimentary deposits and has historically been linked to surface mining of deposits such as coal, phosphates, and other natural substances. Given the significant economic interest that strip mining represents, it is in the best interest of mining companies to exploit as much of the reserves as possible using this technique, as it offers many advantages compared to open-pit or underground methods, particularly regarding safety and ore recovery rates. Today, the exploited deposits have become deeper, making the strip mining process more complex. Hence, there is a need for certain adaptations and the introduction of new techniques to address these geological conditions that threaten the feasibility of this method. This article explores the challenges that strip mining faces in contexts of thick overburden and subsequently presents the various techniques proposed by researchers worldwide aimed at overcoming these difficulties. The paper is based on an in-depth review of existing literature that deals with case studies of open-cast mines in different contexts. The examination of various approaches and techniques used for optimizing exploitation under thick overburden conditions by strip mining, along with their limitations, is presented. [ABSTRACT FROM AUTHOR]

Coal is the cheapest source of energy. It is much cheaper than nuclear and petroleum. However, spontaneous combustion is inherent in coal seams that lead to fires at their place of storage. Therefore, early detection is required to ensure safety. This article aims to develop an intelligent system for the classification of coal seams based on their spontaneous heating on the Internet of Things (IoT) paradigm. It utilizes an artificial intelligence (AI) approach by utilizing a two-stage neural network architecture to render an accurate and robust categorization of coal samples. Three commonly available proximate analysis parameters of the coal samples have been used as input to this system. These inherent parameters are found to be sufficient to classify coal samples into different categories according to their combustion susceptibility. Three publicly available datasets are involved in the assessment purpose. Our proposed method has outperformed previous approaches. The coal seams classification results agree with the real field experiences. [ABSTRACT FROM AUTHOR]

We investigated the distribution patterns and evaluated the average contents of trace elements in the k7 seam of the Karaganda coal basin in Central Kazakhstan. This paper presents the results of studying the geochemistry of 34 elements in 85 samples of the k7 seam. The study employed a suite of advanced high-resolution analytical methods, including atomic emission spectrometry with inductively coupled plasma (ICP–OES) and mass spectrometry with inductively coupled plasma (ICP–MS), along with their processing and interpretation. It was determined that the concentrations of trace elements in the k7 seam are primarily associated with lithophile elements, revealing high concentrations of Li, V, Sc, Zr, Hf, and Ba. Additionally, increased concentrations of Nb, Ta, Se, Te, Ag, and Th were observed compared to the coal Clarke. Specific Nb(Ta)–Zr(Hf)–Li mineralization accompanied by a group of associated metals (Ba, V, Sc, etc.) was identified. The study revealed lateral and vertical heterogeneity of the rare elements' distributions in coals, attributed to the formation dynamics of the coal basin. A correlation between Li and Al2O3 with a less positive relationship with K2O suggests the affinity of certain elements (Li, Ta, Nb, and Ba) to kaolinite. Clay layers showed increased radioactivity, with Th—13.2 ppm and U—2.6 ppm, indicating the possible presence of volcanogenic pyroclastic rocks characterized by radioactivity. Taken together, these data reveal the features of the rock composition of the source area, which is considered a mineralization source. According to geochemical data, it was found that the source area mainly consists of igneous felsic rocks, indicating that the formation occurred under conditions of a volcanic arc. This study's novelty lies in estimating the average trace elements in the k7 seam, with elevated concentrations of certain elements that suggest promising prospects for industrial extraction from coals and coal wastes. These findings offer insights into considering coal as a potential source of raw material for rare metal production, guiding the industrial processing of key elements within coal. The potential extraction of metals from coal deposits, including from dumps, holds significance for industrial and commercial technologies, as processing critical coal elements can reduce disposal costs and mitigate their environmental impact. [ABSTRACT FROM AUTHOR]

On the example of the Alardinskaya mine, the problem of underground mining of seams prone to spontaneous combustion and rock bumps in the conditions of the Kondomsky geological and economic region of the Kuznetsk coal basin is considered. The contradictions in the requirements of regulatory documents for the width of the inter-panel coal pillars in the mining of seams with longwalls in conditions of endogenous fire hazard and in the mining of seams that are dangerous due to geodynamical phenomena are discussed. These contradictions impede the safe mining of seams using traditionally used layouts with the danger of spontaneous combustion of coal and rock bumps. A mining-geomechanical model is presented, which is used for numerical three-dimensional simulation of the stress-strain state of a rock mass with various layouts for longwall panels using the finite element method. The results of the numerical analysis of the stress state of the rock mass immediately before the rock bump are presented, and the main factors that contributed to its occurrence during the mining of the seam are established. A dangerous degree of stress concentration in the coal seam near the leading diagonal entries is shown, especially in conditions of application of abutment pressure from the edge of panels’ gob. The analysis of the features of stress distribution in the inter-panel pillar at different widths is carried out. Recommendations for improving the layout for the development and mining of coal seams that are prone to spontaneous combustion and dangerous in terms of rock bumps in the conditions of Alardiskaya mine have been developed. The need for further studies of the influence of pillars for various purposes, formed during the mining of adjacent seams, on the stress-strain state of previously overmined and undermined seams is shown.

Germanium - rare element, it is a raw material of multipurpose usage and it is included in the list of "critically important minerals" confirmed by the European Commission. The mineral base of Ukraine is characterized by considerable reserves of accompanying germanium and prospects of its development during the complex mining development of coal deposits. Purpose of the work is to study the origin of germanium in the course of the geological history of the formation of coalbearing deposits and to establish the law-governed nature of its distribution as the element-admixture in coal of the Lviv-Volyn Basin. Germanium in coal of Lviv-Volyn Basin is present in samples of the coal ash in all coal seams the Lower and Middle Carboniferous. The concentration of germanium for the seams v6, n7, n8, n9 в, n9 was analyzed in the Chervonohrad geologicalindustrial region (Mezhyrichanske and Zabuzke fields). The article analyzes and constructs a map of germanium concentrations for coal of the seam v6 for the Chervonohrad geological-industrial region of Lviv-Volyn Basin. Along the lateral of the seam one can fix the rise in the concentration in the edge zones of paleopeatbog. Such distribution is explained by the mechanism of sorption accumulation of Ge in the organic mass of peats in the areas of increased water-mineral supplying. Data received while executing prospecting in the Lyubelske field of Lviv-Volyn Basin were analyzed. Coal of the seams п7 в, п8 в, п9, b1 of the Lyubelska-3 site that is planned from burning with the energy purposes, simultaneously may be used as source of germanium. At stratigraphic interval of the upper alluvial-lacustrine-marshy-lagoonal subformation of the Carboniferous formation of the Lviv-Volyn Basin (Bashkirian stages) the coal of the South-Western coal-bearing region (the Lyubelske field) is more germanium-bearing than coal from the Chervonohrad geological-industrial region (Mezhyrichanske and Zabuzke fields). The uneven distribution of germanium concentration is characteristic of the coal seams of the Lviv-Volyn Basin. The wave-like character of the distribution of concentrations is caused by the process of sedimentation which is subordinated to consedimentary movements that influenced the water regime of paleopeatsbogs, lithological and facies changing of the coalbearing deposits as a whole. [ABSTRACT FROM AUTHOR]

Methane drainage from coal seams is a complex process. Quantification of the geological and microstructural characteristics of the coal matrix is of utmost importance to assess the migration of methane for the success of methane drainage from coal seams. This research makes a comprehensive assessment of the methane drainage potential of two gassy coal seams of the Moonidih colliery of the Jharia coalfield. Various geological and microstructural characteristics of the coal seams, viz. chemical and petrographical compositions, pore structure, cleat morphology, and permeability, have been investigated. Both the coal seams are identified as type III kerogen, which fall within the gas-prone range reaching the thermogenic methane generation peak. The vitrinite, inertinite, and liptinite content varied in the range of 78.35–84.78%, 13.82–17.88%, and 0–0.47% for the XV seam, and 55.76–68.45%, 29.65–37.53%, and 0.8–0.89% for the XVI seam, respectively. The micropore specific surface area (SSA) and micropore volume, respectively, are determined as 17.084 m2/g and 0.0252 cm3/g for the XV seam and 15.141 m2/g and 0.0216 cm3/g for the XVI seam. The Brunauer–Emmett–Teller (BET) surface area and Barrett-Joyner-Halenda (BJH) mesopore volume are determined as 0.75 m2/g and 0.00307 cm3/g, respectively, for the XV seam and 0.66 m2/g and 0.003273 cm3/g, respectively, for the XVI seam. The XV seam coal was found to be less porous (13.92%) than the XVI seam (15.76%). SEM image analysis revealed that the cleats are more developed in the XV seam; consequently, it possesses greater permeability (0.896 mD) than the XVI seam (0.274 mD). Owing to its favourable geological and microstructural properties, the XV seam is more suitable for methane drainage. [ABSTRACT FROM AUTHOR]

In order to study the effect of freezing and thawing of liquid nitrogen on the mechanical and seepage characteristics of coal rock with different water content values, conventional triaxial loading tests on freeze–thawed coal samples with different water content values were carried out using non-contact digital image processing technology. The research results showed that with the same water content, the peak strength of a liquid nitrogen freeze–thawed coal sample was smaller than that of a non-freeze–thawed coal sample, and the Poisson's ratio was larger than that of the non-freeze–thawed coal sample; compared with the non-freeze–thawed coal sample, the strain fluctuation and concentration in the stages of compression density, elasticity, yield, and damage were weakened after freeze–thawing by liquid nitrogen, but the local stress concentration was more obvious; the non-freeze–thawed coal sample mainly showed single shear damage, and the damage fissures were inclined fissures with small openings. The higher the water content, the more obvious the tensile damage; with the increase in water content, the permeability of non-freeze–thawed coal samples showed a linear decreasing trend, and the permeability of coal samples was 0.03 × 10–3 μm2 when the water content reached 9%. The permeability of freeze–thawed coal samples showed a non-linear increasing trend, and the higher the water content under the effect of expansion, the faster the permeability growth rate; the permeability of coal samples could reach 6.30 × 10–3 μm2 when the water content was 9%. The results of the study can provide a theoretical guidance for gas permeation enhancement in deep low-permeability coal seams. [ABSTRACT FROM AUTHOR]

Purpose: develop an engineering method for determining sulfur in mineral impurities to predict the hazardous properties of mine seams in mining operations. Methodology: The research methodology and the development of the method are based on a close correlation dependence of the sulfur content in the combustible part of the fuel on the total sulfur for coals of almost all mine seams of the Donetsk and Lvov-Volyn basins. The ratios between the organic mass and mineral impurities are characterized by the yield of ash. The ratio of ash content of reservoir and enriched samples, as well as information about the content of total sulfur and sulfur in the combustible part, make it possible to estimate the sulfur content in mineral impurities by calculation. All the initial data necessary for the development of the method were established experimentally by standard methods over several decades and are given in the reference and regulatory documents on the consumer qualities of coals. Results: The percentage of total sulfur for the entire set of considered coal seams can either exceed the sulfur content in the combustible part of the fuel or vice versa. The difference between the content of total sulfur and its presence in the combustible part of the fuel is, in the first approximation, a criterion for assessing the possible sulfur content in the conditionally non-combustible part of the fuel. Negative values of the criterion indicate the predominant sulfur content in the combustible part, and positive values, in the conditionally non-combustible (mineral) impurities. Based on the available initial experimental data on the content of total sulfur in the combustible part of the fuel, the yield of ash from reservoir and enriched samples, dependencies are proposed for calculating the sulfur content in conditionally non-combustible components. Between the calculated values of the sulfur content in the conditionally non-combustible part and the proposed criterion, correlations are considered for seven sets of coal seams. The formation of the populations was done taking into account the possible influence of enrichment processes and positive or negative values of the proposed criterion. Based on the analysis of empirical dependences of the considered sets of coal seams, the necessary conditions were established for obtaining the most reliable results of the calculated determination of sulfur in conditionally non-combustible (mineral) impurities of fossil coals. Scientific novelty: For the first time, empirical dependences of the sulfur content in conditionally non-combustible (mineral) impurities were established according to the proposed criterion. Practical value: The results are necessary to improve the regulatory framework for the safety of mining operations in terms of predicting the manifestation of hazardous properties of coal seams due to the presence of sulfur varieties.

Rare earth elements (REEs) are considered to be one of the most important metal raw materials, and coal seams are one of the potential sources of REEs. As a low-molecular-weight organic acid, oxalic acid has a strong ability to migrate and dissolve minerals. The coal seam is formed by herbaceous plants and contains more oxalic acid, which may affect the enrichment and transport of REEs during coal formation. Based on the provenance minerals and enrichment carriers of REEs in the coal seam, granite and its weathered minerals (plagioclase, kaolinite, montmorillonite, and quartz) were selected for oxalic acid leaching experiments, to clarify the activation ability of oxalic acid for REEs in coal seams. Experimental results have shown that oxalic acid dissolves minerals and leads to the dissolution and migration of REEs. The higher the concentration of oxalic acid, the stronger the dissolution ability. Each element has a similar dissolution ability in high-concentration oxalic acid solutions, while the ionic radius and electronegativity can cause abnormal distribution of individual elements. The REE dissolution ability in different minerals is controlled by the crystal structure, and the re-adsorption of minerals inhibits the dissolution of REEs in low-concentration oxalic acid solutions. In addition, comparative analysis of REE distribution characteristics in natural water shows that the dissolution and migration of REEs are complexly affected by many factors in addition to pH and fluid environment. Therefore, the activation effect of oxalic acid on REEs in coal seams needs to be further studied. [ABSTRACT FROM AUTHOR]

The yield of volatile substances during the thermal decomposition of coals and the oxygen content in the organic mass do not unambiguously characterize both the types of coals according to the expected reduction, and the manifestations of the hazardous properties of coal seams during mining. To establish the true reasons for the change in the properties of coal seams in the process of metamorphic transformations and the appearance of a tendency to the emergence of hazardous properties, it is necessary to take into account the change in the ratio between all the main components of the organic mass (carbon, oxygen, hydrogen, sulfur and nitrogen) and is not limited to considering the content of only oxygen and total sulfur. It has been proved that the different oxygen content in the organic mass with the same degree of metamorphic transformations of coal seams is not a consequence of their reduction, but is associated with a different initial ratio between the main components at the previous stages of coal formation. The research methodology is based on the statistical processing of known experimental data obtained for almost all coal seams in the Donbass and the Lviv-Volyn basin. The conducted studies have shown a great multifactorial influence of metamorphic processes, both on the change in the elemental composition of the combustible (organic) mass of the initial substance, and on its physical and mechanical properties. It is not possible to characterize such a range of changes in the composition and properties of fossil coals during the metamorphism of coal seams, as it is presented in regulatory documents, with practically one indicator - the release of volatile substances during thermal destruction of fuel. This indicates the need to improve the regulatory framework for the safe conduct of mining operations. When making the necessary adjustments, it is proposed to take into account the established features of changes in the elemental composition and properties of coals during metamorphic transformations of coal seams.

On the basis of analysis of mining plans and field studies at mines of JSC SUEK-Kuzbass, it is shown that in conditions of increasing the size of excavation columns during the development of flat-lying coal seams the stress-strain state of the rock mass along the workings length changes significantly. The necessity of predicting the stress-strain state at the design stage of the workings timbering standards, as well as subsequent monitoring of the workings roof state and its changes in the mining operations using video endoscopes, is noted. The results of numerical studies of the stress-strain state of the rock mass during the development of excavation sites by three workings for various combinations of width of the pillars between the workings for mining-geological and mining-technical conditions of the “Taldinskaya-Zapadnaya-2” mine are provided. The stresses in the vicinity of the three workings are compared with the values obtained during the development of the excavation sites by double drift. A set of recommendations on the choice of the location of the workings, the width of pillars, timbering standards that ensure the stable condition of the workings throughout the entire service life at the minimal losses of coal in the pillars is presented.

Seismic profiling in a coal seam enables the determination of anomalous changes in the P-wave velocity compared to reference velocity at a specific mining depth, indicating potential stress changes. This information can improve the coal exploitation processes in advance at greater depths, especially in seismic hazard areas. This study aims to update the empirical mathematical formula for calculating reference P-wave velocities in coal seams by including new data measured at greater depths. The research was performed at the Zofiówka Coal Mine in the geological and mining conditions of the Upper Silesian Coal Basin in Poland. The analysis involved the study of 276 velocity values including 24 new velocity values measured at depths ranging from 704 to 1073 metres in the period 2009-2024. Through regression analysis, the standard model was modified. The new model provides more reliable velocity anomaly calculations and accurately reflects the geomechanical conditions at greater depths in the Zofiówka Coal Mine. The calculation procedure can be utilised to develop velocity models for various geological and geomechanical conditions in underground mines that exploit coal seams at continuously increasing depths., Competing Interests: Declarations. Competing interests: The authors declare no competing interests., (© 2025. The Author(s).)

Once a coal seam has been weathered and oxidized, the quality of the coal is lost and the coal resources are wasted. At the same time, new risks are introduced to the safe operation of the coal mine. Therefore, it is critical to determine the extent of the weathered and oxidized zone in the coal seam. This paper depicts the electromagnetic characteristics of the weathered and oxidized zone of coal seams, briefly introduces the method of detection by transient electromagnetic method (TEM) and the data processing steps, and performs the numerical simulation for the simplified resistivity model of weathered and oxidized zone in a coal seam. It is observed that after the coal seam has been weathered and oxidized, the electromagnetic characteristics (secondary field potential and resistivity) will be dramatically affected, namely high secondary field potential and low resistivity. For experimental verification purposes, this study selects the test project of the Shixin Minefield in Shanxi, China as an example, and the accuracy for the detection of the weathered and oxidized zone of the coal seam using TEM is successfully verified. [ABSTRACT FROM AUTHOR]

An effective and safe operation for sequestration of CO2 in coal seams requires a clear understanding of injection-induced coupled hydromechanical processes such as the evolution of pore pressure, permeability, and induced caprock deformation. In this study, CO2 injection into coal seams was studied using a coupled flow-deformation model with a new stress-dependent porosity and permeability model that considers CO2-induced coal softening. Based on triaxial compression tests of coal samples extracted from the site of the first series of enhanced coalbed methane field tests in China, a softening phenomenon that a substantial (one-order-of-magnitude) decrease of Young's modulus and an increase of Poisson's ratio with adsorbed CO2 content was observed. Such softening was considered in the numerical simulation through an exponential relation between elastic properties (Young's modulus and Poisson's ratio) and CO2 pressure considering that CO2 content is proportional to the CO2 pressure. The results of the numerical simulation show that the softening of the coal strongly affects the CO2 sequestration performance, first by impeding injectivity and stored volume (cumulative injection) during the first week of injection, and thereafter by softening mediated rebound in permeability that tends to increase injectivity and storage over the longer term. A sensitivity study shows that stronger CO2-induced coal softening and higher CO2 injection pressure contribute synergistically to increase a significant increase of CO2 injectivity and adsorption, but also result in larger caprock deformations and uplift. Overall, the study demonstrates the importance of considering the CO2-induced softening when analyzing the performance and environmental impact of CO2-sequestration operations in unminable coal seams. © 2017 Society of Chemical Industry and John Wiley & Sons, Ltd.

The low-frequency strong reflection of coal seams always makes the gas detection of the adjacent gas reservoir difficult in a tight sandstone reservoir. An adaptive decomposition processing approach is introduced in this study to inspect the ability to target the weak seismic response of the gas reservoirs interfered by the adjacent coal seams. The variational mode decomposition (VMD)–based highlight volumes extraction approach is used to better detect the weak seismic response of the gas reservoirs concealed by the adjacent strong reflection of coal seams in a tight sandstone reservoir. The amplitudes above the average and peak frequency volumes are extracted from each intrinsic mode functions after VMD for gas detection. Field data examples show that the VMD highlights the weak seismic responses of the geological and stratigraphic information and hydrocarbon-related contents. The results obtained from the VMD-based highlight volumes extraction approach are in close agreement with previous logging interpretations and the drilling information of wells, and the lateral extent of hydrate-bearing strata is estimated with increased accuracy. When the influence of the strong reflection amplitudes caused by the coal seams is not suppressed, the characterization of the weak seismic responses in the reservoirs would prevent the detection of gas or overestimate the lateral distribution of the gas strata. The adaptive decomposition processing methodology has the ability to detect the weak seismic responses in reservoirs interfered or concealed by adjacent coal seams and yields a better hydrocarbon-related interpretation.

The characteristic stages of metamorphic transformations of mines are established according to the increase in the elemental content of carbon and changes in other components of organic matter. Stages of metamorphism transformations with an average carbon content of more than 93.6% can significantly differ in properties due to the unpredictability of the ratio between the components of organic matter. At these stages, even a minimal difference between the components can be the reason for the emergence of new properties of the coal seams. As the influence of the processes of metamorphism increases, the boundaries of the stages, determined by the percentage of carbon, narrow. The established stages of the transformation of reservoirs in terms of the individual proportion of the components in carbonization practically do not differ from the boundaries of the stages determined by the elemental composition of organic matter. It is noted that the average carbon content at the stages of seam metamorphism, determined by the yield of coke, in most cases does not coincide with the ranges of changes in the average carbon content, established by the individual content of the components or their share in carbonization. The inconsistency of the boundaries in the stages of seam metamorphism makes it unacceptable to use the coke yield as the main criterion for assessing the conversion of coal and even more so the manifestation of hazardous properties of coal seams. [ABSTRACT FROM AUTHOR]

In the article, the authors talk about ways to improve the quality of core sampling from methane coal seams in the Kuznetsk coal basin. Core sampling is carried out at the exploration wells of Naryksko-Ostashinskaya square. Methane extraction is carried out to remove gas from coal seams. Moreover, gas can be used as unconventional energy sources. Thus, safety at coal mining facilities increases, and we receive additional income for the sale of gas to end consumers. To develop a technology for extracting gas from coal seams, core sampling is carried out, and the results obtained are analyzed. Further adjustments are made to the extraction technology, the selection of technological equipment is carried out. Drilling is carried out in the following sequence: initially, a vertical well with core sampling is performed, and then a multi-hole well is drilled with a large face deviation. As a result of experimental core selection and development of improved equipment, core removal was increased from 77% to 100%.

CO2-enhanced coalbed methane (CO2-ECBM) can improve coalbed methane production efficiency and simultaneously alleviate greenhouse gas emissions. In this paper, we integrated TOUGH2 and FLAC3D numerical simulation software to conduct hydro-mechanical coupling analysis for effects of hydrofracturing and secondary fracturing in CO2-ECBM. The simulation results show that the hydrofracturing and secondary fracturing treatments significantly increase the coal seam interconnectivity, enhancing overall injection and production. The reduction of the pore pressure near injection wells can effectively reduce the damage of gas injection well. Moreover, secondary fracturing can even increase cumulative gas production up to 32.5%. In addition to rising fracture density, increasing the fracture length is also considered an efficacious procedure for enhancing permeability in the secondary fracturing process. [ABSTRACT FROM AUTHOR]

Mining a protective layer is an effective way to prevent coal and gas outbursts in underground coal mines; this method has been used widely. However, when mining closely spaced multiple coal seams (CMCS), gas from adjacent coal seams flows into the working face through fractures in the goaf. This is caused by pressure relief and consequently gas overruns occur, a significant problem that negatively affects efficient mine production. This study analyzes the reasons that gas overruns occur at a working face during the mining of CMCS protective layers. A comprehensive gas extraction system coupling a high-level suction roadway and boreholes was introduced and applied to prevent and control gas overruns at the working face. Gas extraction rates and the amount of gas in the air return system were monitored and the results used to evaluate the effectiveness of the system. The results show that gas desorption caused by pressure relief of the adjacent coal seams was the main cause of the gas overruns at the working face. After the system started working, the average extraction rate increased from 2390 m3/d to 16200 m3/d with average gas concentration in the extracted gas rising from 6% to 41.21%. After using the gas extraction system, the average gas concentrations in the tailgate roadway, working face upper corner, and return airway were reduced by 45%, 30%, and 13%, respectively. Gas overrun accidents have apparently been eliminated. At the time of this writing, there have been no new gas overrun accidents. In addition to solving the gas problem, the gas extraction system has allowed average coal production from the working face to increase 46.7% per month and in 9 months, 4.4 million cubic meters of gas, which could be directly used to generate electricity, was extracted. The tests indicated that an appropriately configured high-level gas extraction system in the fractured zone can effectively solve the working face gas overrun problem in mines exploiting CMCS. This study can be used as a valuable example for other coal deposits being mined under similar geological conditions. [ABSTRACT FROM AUTHOR]

Coal measures located in marginal sea basins are important hydrocarbon source rocks. For the purpose of effectively guiding future oil and gas exploration, the characteristics and distribution patterns of coal seams in coal measures of a marginal sea basin are systematically outlined. Coal measures in marginal sea basins can have large thicknesses, but the individual coal seams can be very thin and lack lateral continuity. In the study area, the organic micro-components of the coal are dominated by vitrinite, with very low amounts of inertinite and liptinite. The amount of inorganic microscopic components is large, but with limited drilling results, few cores and thin coal seams, which are easily overlooked during logging activities, a comprehensive analysis of the logging data may improve efficiency in coal-seam identification and thickness determination. The development and distribution of coal seams in marginal sea basins are controlled by various factors, including (1) paleoclimatic and paleobotanic conditions, which could fundamentally limit coal formation, (2) coal-forming sedimentary environmental conditions that may limit the scope of coal-seam development from a macroscopic perspective, and (3) paleotectonic and paleotopographic conditions that define the coal-forming structures. Therefore, the descending and rising cycles of base-levels, along with changes in the growth rates of the accommodation spaces, can be used to determine the horizons that are potentially favourable for coal formation and can also indicate the migration trends of coal-forming environments on the structural plane. Seismic wave impedance inversion methods could be utilised for semi-quantitative assistance for prediction of coal seams. In summary, for models of coal-seam development in marginal sea basins, the grades should be divided according to reliability, and the different reliability levels should be predicted separately. The characteristics of coal seams developed in marginal sea basins are described. The macerals of coals developed in marginal sea basins have been ascertained. A development model and distribution prediction method for coal seams are assessed according to the control factors. A model for the prediction of coal-seam distribution is presented. [ABSTRACT FROM AUTHOR]