Coalbed Methane Content Research Articles

Problems in the development of high-rank CBM horizontal wells in the Fanzhuang–Zhengzhuang Block in the Qinshui Basin and countermeasures

Coal reservoirs in the Qinshui Basin are characterized by high thermal evolution degree, low permeability, low reservoir pressure, lower gas saturation and strong heterogeneity, so its coalbed methane (CBM) development is quite difficult. In this paper, the development practice of high-rank CBM horizontal wells in the Fanzhuang–Zhengzhuang Block was analyzed in terms of geological and engineering factors to clarify the productivity influencing factors, suitable geological conditions and potential tapping countermeasures of multi-lateral horizontal wells. It is shown that the reasons for the low development efficiency of multi-lateral horizontal wells are divided into three types. The first one is geological factor, such as encountering low CBM content areas or faults. The second is engineering factor, such as drilling fluid plugging, drilling collapse, drainage collapse and dust coal blockage. The third is the combination of both factors. It is concluded that encountering low CBM content areas and faults, collapse and blockage are the main reasons for the low production of multi-lateral horizontal wells in the Zhengzhuang–Fanzhuang Block, with the CBM content higher than 20 m3/t, the ratio of critical desorption pressure and reservoir pressure higher than 0.7 and vitrinite reflectance (Ro) higher than 3.8. The prerequisite for an open-hole horizontal well in this area to produce CBM at a high rate is that the well lies in the tensile stress zone. Finally, the countermeasures to tap the potential of some inefficient wells were put forward. First, the inefficient wells which are blocked with dust coal or collapsed in the later stage should be stimulated based on classifications. And second, it is necessary to explore new types of horizontal wells so as to deal with borehole collapse and continue the operation in the later stage by using tree-like roof horizontal wells, single-lateral horizontal wells with casing or screen completion and fish-bone horizontal wells.

Analysis of coalbed methane occurrence in Shuicheng Coalfield, southwestern China

This article is the result of authors’ long-term efforts to evaluate the occurrence of coalbed methane (CBM) for CBM exploration and coal gas disaster prevention in Shuicheng Coalfield (SCC). A relatively large program of exploratory drilling to determine the content of CBM, geological surveys and laboratory experiments, including coal proximate analysis, coal physical properties analysis and methane adsorption were conducted. The results show that the coals from the SCC contain 21.42–41.34% volatile, 0.24–1.44% moisture and 6.27–38.1% ash yield, with coal porosity in the range of 5.97–14.89%. The type of coal structure ranges from II to IV. The sedimentary characteristics, tectonic evolution, geological structure, coal reservoir conditions and hydrodynamics were studied via geological surveys, field research and laboratory tests. The relationships between these factors and gas content are explained and analyzed in this present paper. The formation of the Shuicheng coal basin was formed under the control of the Ziyun fracture and the Luoping fracture. Ejective folds and synclines that evolved from inverted geological structures in the stage of Yanshan movement affect CBM occurrence. Folds generated in coal bearing strata play an important role in methane accumulation in the period of Himalayan movement. A positive relationship is observed between gas content and coal burial depth, coal thickness, and hydrodynamics. CBM easily concentrates because of the separation between coal bearing strata and Maokou enrich aquifer. We divide the SCC into three methane geological units, the Ertang syncline unit, the Dahebian syncline unit and the Xiaohebian syncline unit. Furthermore, gas content spatial distributions were predicted in the SCC. The probability of CBM exploration was evaluated based on coal permeability and gas flow attenuation coefficient. These research results could contribute to CBM exploration and coal gas disaster prevention in the SCC.

The Use of a Unipore Diffusion Model to Describe the Kinetics of Methane Release from Coal Spoil in the Longwall Environment

Abstract The unipore methane diffusion model based on the solution of the second Fick’s law describes effectively the kinetics of methane release from coal grains. The knowledge of the model describing the kinetics of methane release from coal, the coalbed methane content, the sorption isotherm, the effective diffusion coefficient and the coal particle size distribution, enables the calculation of the volume of methane which is released from the coal spoil as a function of time. These assumptions became the basis for building the software that enables the analysis of methane emissions from coal during the longwall mining. Simulations were performed to determine the temporal and spatial methane inflow to the longwall. The share of methane emission from coal grains (taking into account both the emission kinetics and mass participation) of various classes has been analyzed. The results of the analysis showed that the methane from the small grains, in particular less than 0.1 mm in size, prevails. The mass fraction of these grains in the total weight does not exceed 5%. For the typical parameters determining the mining, geological and technological conditions of methane emissions at different moments of time and position of the longwall were determined.

Analysis and prediction of gas recovery from abandoned underground coal mines in China

Mine closures will be especially widespread in eastern China. However, Because of relatively high residual coal-bed methane content, the abandoned coal mine methane (ACMM) reserves of China are huge, and from a greenhouse gas control perspective it is preferable that they be developed and utilized, rather than allowed to vent to the atmosphere. The exploitation and development of ACMM in China is still in its infancy, with theory and practice undergoing rapid development. Four factors are particularly influential on design of ACMM recovery strategies. The first factor is what may be termed the "enrichment space", which reflects the final state of the strata after completion of longwall extraction and subsequent strata settlement, and is here defined as the region between the outer, limit of stress relief and the limit of the extracted panels. Quantitative analysis of the components of gas mixtures recovered from the enrichment space can be tracked using stable carbon isotope techniques. The second factor is the permeability field surrounding the abandoned mine voids. The thick mudstones that commonly overlie the coal seams serve to confine the water and gas within the enrichment space and old mine voids. The geometry of these confining layers can be confirmed by seismic reflection or other geophysical methods, which can reveal the extent of the zone affected by fracture development. On this basis, models of methane movement in abandoned mines can be constrained, allowing valuable predictions of availability of ACMM resources under different mining and post-closure drainage conditions.

Nonlinear relationships between coalbed methane release, natural methane content and kinematic parameters of cutting picks of shearers

It has been found that the rated and actual data on methane emission in production headings in some Kuzbass mines disagree. The air and gas control shows that actual methane emission from broken coal is much less than the rated data when a coal shearer has high advance velocity and production output. The authors demonstrate the connection between an average diameter of broken coal fragment, shearer advance velocity and drum rotation speed using Darcy’s law of flow and Langmuir’s adsorption equation. It is found that methane emission from broken coal and natural coalbed methane content relate nonlinearly and that the relationship of absolute methane emission, shear advance velocity and production output has an extremum.

CBM Reservoir Rock Physics Model and Its Response Characteristic Study

The rock physics model of coalbed methane (CBM) reservoir is significant for the study of CBM content. However, because of the adsorption and dissociation of the CBM reservoir, it is difficult to establish models. In addition, the studies on rock physics modeling of the CBM reservoir are scarce. This paper proposes the basic modeling process. First, the coal rock minerals and methane in adsorbed state are used to calculate elastic parameters of coal rock matrix. Then, the differential equivalent medium model is used to get elastic parameters of the dry rock skeleton. The free methane is mixed with water, and finally the Gassmann equation is applied to obtain elastic parameters of the CBM reservoir model. The study on the CBM reservoir rock physics model’s response characteristics has found that there is a sensitive negative correlation between CBM content and P-wave velocity and density. The higher CBM content goes with larger absolute values of intercept, gradient, and seismic amplitude, because their seismic attributes are more sensitive to higher CBM content, whereas the response characteristics are opposite with the lower CBM content. The relationship among the CBM content and absolute values of intercept, gradient, and seismic amplitude in the real data of Qinshui Basin is largely consistent with the response characteristics of the established rock physics model, indicating that the CBM reservoir rock physics model proposed in this paper has a certain feasibility, and the response characteristics of its intercept, gradient, and seismic amplitude are more sensitive to predicting CMB reservoirs.

Systematic Division of Coalbed Methane-Enriched Units

Division of coalbed methane (CBM)-enriched units primarily depends on the analysis of the main controlling factors of CBM occurrence. The main controlling factors analyzed in this article are sedimentary sequences related to the forming and alteration of CBM, tectonic movement, and burial and hydrocarbon-generation histories. The parameters were measured for independent quantities such as CBM content, gradient, coefficient of extraction difficulty and geological structure complexity. Correlation analysis was conducted between the measured parameters of CBM-bearing systems and the main controlling factors. When the controlling factors are sedimentary sequences and the sedimentary systems tract, the division of CBM-enriched units is based on the coal-forming environment, coal mass distribution and coal characteristics. When the controlling factor is the tectonic matching between the orefield, mining area and mining wells, the division of CBM-enriched units is based on tectonic movement. When burial and hydrocarbon-generation histories are the controlling factors, the division of CBM-enriched units is based on metamorphic traits.

Variation in maceral composition and gas content with vitrinite reflectance in bituminous coal of the eastern Ordos basin, China

Development of coal petrology is of great importance in both understanding the coal formation and its controlling effect on the coalbed methane content. We report microscopic analyses and field desorption test results of 113 coal samples from epicontinental (lower) and continental (upper) strata in the eastern Ordos basin, China. The maceral group composition shows great variation, and the vitrinite increases from 50% in the north to approximately 75% in the south of the study area, corresponding to the increase of maximum vitrinite reflectance (Ro,max) from 0.5% to 2.5%. Liptinite shows a power function decrease with Ro,max from 0.5% to 1.5%, and the mineral composition is relatively high in low Ro,max samples. The photomicrographs of the same rank coals also exhibit heterogeneity, and the higher Ro,max coals show more compact microstructures. Gas content varies between 2 and 10m3/t and exhibits a sharp increase in areas where Ro,max is about 1.0% demonstrating that the gas content in the middle and south areas is primarily controlled by the preservation conditions. The gas content shows an “increase–decrease” trend with depth increment, with the transition point at 1000m for Ro,max between 0.4% and 1.2%, and 1400m for Ro,max between 1.2% and 2.5%.The relationships between maceral group composition and gas content have also been discussed. The gas content generally shows a positive correlation with the vitrinite percentage, Ro,max and the Langmuir volume. The Langmuir volume increases linearly as with the Ro,max values, while the Langmuir pressure is relatively high in low rank coals. The epicontinental and continental coals do not show a significant difference in the organic compositions, except that the sulfur content of 1.9% in lower coals and 1.0% in the upper coals. Furthermore, the epicontinental coals exhibit relatively better gas preservation and production conditions with higher gas content and Langmuir volumes. Results from the same source coal samples show strong heterogeneity in maceral composition and gas content variations and illustrate the controlling effect of Ro,max on coal petrology and the importance of preservation conditions on gas content.

Degasification possibilities evaluation in Socotá coal mines (Boyacá, Colombia)

In the Socotá area in Boyacá, Colombia, high contents of coalbed methane have been reported. In order to prove it, additional gas measurements were done and different possibilities of degassing were considered. To measure the gas content, the canisters desorption system were used, with control of pressure and temperature, according to the USBM and GRI methodology. Lost, desorbed and residual gases were determined separately, and proximate analyses were also carried out. In some samples the content of gas reached the 100-200 SCF/t. These gas contents have good possibilities for energy production (CBM) by drilling vertical wells to extract it.Those wells would not only produce gas, but would also degas the future underground mining areas. The combination of degasification and ventilation would considerably allow a decrease in the explosions risk. The high coalbed methane content in the area could produce energy for the mining company or commercial gas for the natural gas distribution network. The Socotá area has the ideal conditions for a pilot project, which could be a model for other degasification projects in Colombia.

Effect of lithostatic stress on methane sorption by coal: Theory vs. experiment and implications for predicting in-situ coalbed methane content

Recent research has demonstrated that confining stresses applied to the solid framework of coal can reduce its gas sorption capacity by several percent to perhaps several tens of percent. To evaluate the magnitude of this effect more rigorously in relation to predicting in-situ coalbed methane (CBM) content, a better understanding of the effects of stress on methane sorption by coal is needed. In this paper, a previous thermodynamic model for the effects of stress on CO2 sorption by coal is revised and applied to CH4. The revised model predicts that in-situ CBM content is indeed determined not only by the geological factors generally considered, such as coal rank, coal composition, moisture content and temperature, but also by lithostatic or confining stress, which is usually ignored. This prediction is tested by means of experiments performed on a composite cylindrical sample of Brzeszcze 364 high volatile bituminous coal subjected to 10MPa methane pressure at a temperature of 40°C, varying the hydrostatic stress or confining pressure in the range 11-43MPa. In these experiments, we determined if CH4 was desorbed as confining pressure was increased by subtracting the poroelastic expulsion of CH4 from the total CH4 expelled, assuming the former to equal the gas volume expelled in control experiments performed using Helium. The experimental results show that the equilibrium sorption capacity for CH4 at 10MPa gas pressure and 11MPa confining pressure (1MPa Terzaghi effective stress) was 0.808mol/kgcoal. This was reduced by at least ~6% by increasing the confining pressure to 43MPa (33MPa effective stress), confirming the validity of our model. We apply our model to predict in-situ CBM concentration as a function of coal seam depth for dry, high volatile bituminous coal, assuming a geothermal gradient of 32°C/km. The results indicate a maximum CH4 concentration of ~0.76mol/kgcoal at a burial depth of ~900m, which is ~3% lower than conventional predictions. This reduction is minor but helps to explain why gas saturation is generally lower than expected from conventional sorption measurements on unconfined coal powders. More importantly, our results confirm that there is an intimate coupling between in-situ stress, strain and sorption in coal that needs to be considered in developing gas-enhanced CBM strategies.

Fast evaluation of the coalbed methane content of coal viewed as an element leading to improvement in exploitation conditions

Abstract Methane, as a co-occurring compound, can be found in the majority of coal basins all over the world. The knowledge of methane content is a basic piece of information used in balancing and describing a given coal seam, in conducting safe exploitation – with methane hazards and methane and rock outburst hazards in mind – as well as in less common procedures, such as coal seam fracturing and methane extraction, or storing carbon dioxide in off-balance coal seams. The author of the present paper outlines a thoroughly modified desorbometric method used to analyze the coal-methane system. The research object, in underground conditions, is the full process of releasing methane from coal, which makes it possible to determine gas losses, the desorbable methane content, and the effective diffusion coefficient. This type of research can be conducted in less than 24 hours due to the reduction of the grain fraction of the analyzed bore dust. The thorough research in underground conditions was preceded by a model analysis of the simultaneous impact of the desorbable methane content in coal and the effective diffusion coefficient upon the value of the desorption indensity index. The influence of a grain fraction on the kinetics of methane release from coal was described, and the 0.20–0.25 [mm] grain fraction was selected. The choice of this particular fraction made it possible to register the full process of methane release from coal, in the assumed time. An original methodology of performing underground measurements was presented, together with an instrument used to perform these measurements. The underground research involved measuring the desorbable methane content according to the presented original methodology, which was done simultaneously with an analysis of the coalbed methane content carried out by means of the bore dust method, an analysis of desorption intensity, and an analysis of the technical parameters of coal. The results point to a substantial discrepancy between the desorbable methane content in coal and the coalbed methane content measured by the bore hole method in compliance with the Polish standard. The mean relative percentage error for 17 measurements was 6.5%. The author provided an example concerning using the effective diffusion coefficient in explaining substantial differences in the desorption intensity index for two samples characterized by the similar coalbed methane content.

Method for Determining the Coalbed Methane Content with Determination the Uncertainty of Measurements

AbstractMethane has a bad influence on safety in underground mines as it is emitted to the air during mining works. Appropriate identification of methane hazard is essential to determining methane hazard prevention methods, ventilation systems and methane drainage systems. Methane hazard is identified while roadways are driven and boreholes are drilled. Coalbed methane content is one of the parameters which is used to assess this threat. This is a requirement according to the Decree of the Minister of Economy dated 28 June 2002 on work safety and hygiene, operation and special firefighting protection in underground mines. For this purpose a new method for determining coalbed methane content in underground coal mines has been developed. This method consists of two stages - collecting samples in a mine and testing the sample in the laboratory. The stage of determining methane content in a coal sample in a laboratory is essential. This article presents the estimation of measurement uncertainty of determining methane content in a coal sample according to this methodology.

Prediction of coalbed methane content based on uncertainty clustering method

An analysis of factors that influence coalbed methane content showed that seven factors had a major influence: coal thickness, methane concentration, vitrinite reflectance, permeability, cracks, and sealing conditions hydrodynamic conditions were selected as criterion indexes. The prediction model of coalbed methane content was built based on the uncertainty measure theory. Data from six regions in the central and southern Qinshui Basin were used as the training sample. The sample mean was set as the cluster centers, and the index weight was determined by information entropy theory. Calculation of the multi-index comprehensive measure of the sample showed that the sample was classified according to the minimum uncertainty measure distance principle, which was used to predict coalbed methane content. The research results show that: the obtained level by the prediction method is consistent with the practical level, the predictive value is basically consistent with the actual value, coalbed methane content prediction method based on uncertainty measure theory is reliable and practical, as well as showing a new way for the prediction and evaluation of coalbed methane content in the future.

Quantitatively evaluating the CBM reservoir using logging data

In order to evaluate coal bed methane (CBM) reservoirs, this paper select five parameters: porosity, permeability, CBM content, the coal structure index and effective thickness of the coal seam. Making full use of logging and the laboratory analysis data of a coal core, the logging evaluation methods of the five parameters were discussed in detail, and the comprehensive evaluation model of the CBM reservoir was established. The #5 coal seam of the Hancheng mine on the eastern edge of the Ordos Basin in China was quantitatively evaluated using this method. The results show that the CBM reservoir in the study area is better than in the central and northern regions. The actual development of CBM shows that the region with a good reservoir has high gas production—indicating that the method introduced in this paper can evaluate the CBM reservoir more effectively.

Quantitative study of the macromolecular structures of tectonically deformed coal using high-resolution transmission electron microscopy

Tectonic deformations damage the macrostructure and impact the macromolecular structures of coal. In this study, high-resolution transmission electron microscopy (HRTEM) was applied to observe the macromolecular structures of six different types of tectonically deformed coal, and quantitative analyses were conducted by using image analysis algorithms to extract the images of lattice fringes to obtain the following three structural parameters: fringe length, fringe tortuosity and fringe separation. The results show that coal rank has an important influence on the macromolecular structures of coal, and this effect varies with different stages of metamorphism. For weak tectonically deformed coal, increases in coal rank indicate an increase in fringe length and decrease in fringe separation and fringe tortuosity. The increments in the fringe separation and fringe length first increase and then decrease, and the maximum values occur during the evolution from mid metamorphic stage to high metamorphic stage. Fringe tortuosity shows a gradually decreasing trend. Tectonic deformation also has an important influence on the macromolecular structure of coal, and this effect varies with different stages of coal rank. With decreases of tectonic deformation, fringe length is increased and fringe separation and tortuosity are decreased; however, the impact of tectonic deformation on the macromolecular parameters of low-rank coal is stronger than that of the mid-rank coal. The impacts of tectonic deformation on the nanoscale pores, coal methane adsorption capacity and coalbed methane contents of low-rank coal are higher than those of the mid-rank coal.

Well type and pattern optimization method based on fine numerical simulation in coal-bed methane reservoir

Coal-bed methane (CBM) is a precious clean energy. A reasonable well type and pattern design is the premise and the key to effective development of coal-bed methane. In this paper, a set of optimization method is presented which includes a fine CBM numerical model with the combina tion of the isothermal adsorption test results. Different Langmuir curves and adsorption–desorption time are corresponding to different grids in the model. The model has advantages over previous models in terms of the CBM reservoir structural characteristics and permeability anisotropy. As in most of CBM mining area, the structural characteristics are so complex that a combination of vertical and U-shaped wells is the best choice to achieve optimum production of gas. To optimize the pattern and spacing between vertical wells, different types of coal-bed cleats pressure drop rules are in consideration. Based on the CBM content in the reservoir, the distribution of different well types can be determined. The optimization method above has been applied in one pilot area in QinDuan Block, China. The result shows that combination of U-shaped and vertical wells in a diamond well pattern will provide the best CBM production scenario. In this diamond well pattern, the optimum well spacing along the long and short diagonals is 350 and 300 m, respectively. The degree of reserve recovery was predicted to up to 56.63 % after 30 years of production.

A quantification prediction model of coalbed methane content and its application in Pannan coalfield, Southwest China

This study analyzed the influential factors of CMC including quantitative and qualitative indexes. In order to predict CMC (coalbed methane content) accurately in advance during exploration stage with limited data in Pannan coalfield, Southwest China, the prediction models of CMC (coalbed methane content) were established using quantification theory on the foundation of limited data obtained from the exploratory bores. The application result based on prospecting bores in MaYi coalmine confirms that the widely applied one-dimension linear regression prediction method of CMC in engineering in China can't fully reflect the storage law of CMC. It was found that the cover depth of coal seam may not be the only cardinal affecting element, other quantitative indexes and factors referring to qualitative indexes are also have close relation to CMC. The prediction model of CMC with and without considering qualitative indexes were established on the foundation of quantification theory, and the results of quantification prediction model considering both quantitative and qualitative factors of CMC are in good agreement with the initial records of CMC. This means that more indexes including quantitative ones and qualitative facets must be carefully considered in the prediction of CMC. F-test value and VIF suggest that quantification prediction model considering both quantitative and qualitative indexes that influence CMC is more comprehensive and accurate than traditional methods.

Differences in coal bed methane occurrence for different regions of igneous erosion in the Haizi coal mine, Huaibei coalfield, China

Igneous erosion would change the coal bed methane (CBM) occurrence in coal. Based on the different occurrences of magma rock at the II101 and II102 mining areas in the Haizi coal mine of the Huaibei coalfield in China, coal bed methane occurrence in different regions of igneous erosion was studied by collecting and categorizing CBM parameters during the establishment and mining of the II101 and II102 mining areas. The CBM pressure gradient, CBM content, and CBM emission during mining the workface for the II102 mining area with more stable and thicker magmatic rock were larger than those of the II101 mining area. The CBM pressure gradients for the II101 and II102 mining areas were 0.02397 MPa/m and 0.03736 MPa/m, respectively. With increasing depth, the CBM contents of both the II101 mining area and the II102 mining area increased and the CBM content of the II102 mining area was greater than that of the II101 mining area. The absolute CBM emission (AE) gradient and the relative CBM emission (RE) gradients for the II101 mining area were 0.012 m3/min/m and 0.023 m3/t/m, respectively. Additionally, the AE gradient and the RE gradient for the II102 mining area were 0.031 m3/min/m and 0.055 m3/t/m, respectively. Partition management for different regions of igneous erosion should be used.

Investigation on coal seam gas formation of multi-coalbed reservoir in Bide-Santang Basin Southwest China

This paper presents a comprehensive study on the geological characteristics of a multi-coalbed reservoir using coal cores collected from well drilling tests in Bide-Santang Basin, China. The study focuses on the investigation of the coalbed methane (CBM)-bearing property, porosity and permeability, sealability of capping rocks, and groundwater characteristics in coal seams, providing the experimental information on the control function of sequence strata for the coalbed methane. This reservoir is comprised of a large number of coalbeds and exhibits many distinctive geological characteristics of a CBM reservoir, such as high CBM content, complex vertical volatility of CBM content, vertical discontinuous distribution of porosity and permeability, strong sealing capping property and many vertical water-bearing systems, etc. The investigation shows that the unattached multiple superposed CBM-bearing system (UMSCS), which formed the unique multi-coalbed CBM reservoir, can be identified in the study area. Depending on the development scale of vertically unattached CBM-bearing coal seams, the CBM reservoir in the study area can be classified as simple UMSCS and complex UMSCS. The former, typically appearing in Zhuzang syncline and Agong syncline, exhibits the continuity of geological reservoir-forming characteristics in terms of less coal seams, much weaker sealability of capping rocks, higher CBM content, and many vertical water-bearing systems. The latter, typically represented by Shuigonghe syncline and Santang syncline, shows the continuity of geological reservoir-forming characteristics with a large number of coal seams, strong sealing capping property, and reasonably high CBM content. For simple UMSCS reservoirs, a sublevel exploitation method should be adopted for CBM exploitation in order to minimize the effect caused by larger variation of the reservoir energy in different systems. For complex UMSCS reservoirs, one effective way for CBM exploitation is to fracture virtual reservoir (mainly key sandstone member) to depressurize it uniformly and thus achieve large-scale discharging and mining in several adjacent CBM-bearing subsystems.

Research on comprehensive CBM extraction technology and its applications in China's coal mines

One of the primary concerns regarding coal and coalbed methane (CBM) extraction in China is coal mining safety. Based on coal-seam geology and the conditions of CBM occurrence, effective CBM extraction methods should be selected. Comprehensive CBM extraction is achieved by CBM extraction before mining, during mining, and after mining. The methods used for CBM extraction before mining include original coal-seam CBM extraction and pressure-relief coal-seam CBM extraction. The extraction effect is assessed in terms of the residual coal-seam CBM pressure and content. The method used for CBM extraction during coal-seam mining should be selected according to workface ventilation, for which the workface CBM extraction rate is an assessment indicator. CBM extraction after coal-seam mining is performed to extract CBM from sealed goafs and the top fracture zone, which can improve a mine's CBM extraction rate. For comprehensive CBM extraction technology, the mine total return-air CBM volume percentage and the rate of mine CBM extraction are used to measure the effect of comprehensive gas extraction from mines. Herein, the application of various technological approaches to the comprehensive extraction of CBM in coal mining is discussed using the example of the Qinan Coal Mine in the Huaibei mining area, where CBM extraction efforts are notably effective. Recent CBM extraction data and actual outcomes from several mines in China with high levels of CBM are analyzed in detail, with a discussion of existing problems and the presentation of new solutions for CBM extraction. Moreover, this article considers problems such as poor borehole sealing quality, low permeability of coal seams and difficulty in drilling soft coal seams to have restricted the further increase in coal mine gas extraction to a certain extent.