Coalbed Methane Drainage Research Articles

Optimization design of stress relief coalbed methane surface well in a high-gas mine

Coalbed methane drainage through surface wells has become increasingly important in high-gas mines. Surface wells are prone to different types of deformations and failures owing to mining-induced effects. In this paper, a displacement and deformation model was established for the overlying strata. Three forms of deformation and failure of the surface well casing was proposed, namely shearing, stretching, and uneven extrusion. Moreover, the mathematical model functions for the S-type shear deformation, delamination tensile deformation, and non-uniform extrusion of the surface well were established. In the Shanxi Coal Group Yue Cheng Mine, coalbed methane drainage at the surface well was conducted on the mining-affected area to achieve good effects. The YCCD-04 well without a local protective device was deformed and damaged, and the dynamic deformation and failure of the surface well was detected using a well imager. The YCCD-02 surface well with a local protective device showed good mining and gas drainage, which verified the effectiveness of the local protective device; the coalbed methane drainage time of this surface well was 35 months, and the cumulative coalbed methane drainage volume extracted was 1.3 × 107 m3. Simultaneously, the problem of gas control in the working face was solved, thereby ensuring the safety of coal mining and achieving good social as well as economic benefits.

Gas-liquid permeability of propped fracture with retained coal fine particles in coalbed methane reservoirs

Coal fine particles are easily retained in the propped fractures during hydraulic fracturing and CBM (coalbed methane) extraction, which seriously affects the gas–liquid permeability. In this paper, gas–liquid permeability test experiments of propped fractures under different retained coal fine particles concentration were conducted. The results showed that the retained coal fines discharge rate (Rd) and gas/liquid effective permeability (Kge/Kwe) decreased with the increase of the closure stress. As the gas–liquid ratio increased, the Rd of the propped fractures with retained coal fine particles decreased. The Kwe decreased significantly while Kge increased slightly, yet the gas/liquid effective permeability loss rate (lw/lg) rose. As the retained coal fine particles concentration in the propped fractures increased, both the Rd and Kge/Kwe decreased monotonously. When the retained coal fine particles concentration reached 10%, changing the gas–liquid ratio and.closure stress exerted little effect on the gas/liquid effective permeability. In addition, the lg/lw was inversely proportional to Rd within the propped fractures with retained coal fine particles. The research results are of guiding significance for optimizing the CBM extraction system, solving the problem of low gas–liquid permeability caused by retained coal fine particles, and promoting the smooth drainage of CBM.

Geological and Geochemical Responses to Productivity of CBM Wells in the Baiyang River Block of the Southern Junggar Basin, China

The southern Junggar Basin, Xinjiang, has abundant coalbed methane (CBM) resources. Currently, the Baiyang River development pilot test area (BYR block for short) in the Fukang east block has achieved large-scale CBM development, but the productivity characteristics and its controlling factor are still unclear. Based on the field production data of the BYR block and experimental tests, this paper summarizes the gas and water production characteristics and presents the analysis results of the geological and geochemical responses to the productivity of CBM wells. The productivity of CBM wells in the BYR block was generally characterized as medium-to-low yield. The productivity was jointly controlled by the burial depth, structure condition, thickness and number of co-production coal seams, and hydrogeological conditions. The gas production first increased and then decreased with the increase in the burial depth of the coal seam, and a burial depth between 750 and 1000 m was the most beneficial to increasing the gas production due to the good gas preservation conditions and suitable permeability and stress conditions. The total thickness of the co-production coal seams had a positive effect on the productivity of gas wells, but the productivity was also affected by the number of co-production coal seams and interlayer interference. In the BYR block, the co-production of the nos. 41 and 42 coal seams was the most favorable combination form for CBM drainage. The productivity of CBM wells had a good response to the Na+, K+ and HCO3− concentrations but a poor response to δD-H2O and δ18O-H2O. Based on the concentrations of the main ions and TDSs of the coal seam water, a productivity response index δ* was established, and there was a good positive correlation between the productivity and δ*.

Study on Breakage Characteristics and Anti-Breakage Theory for Pressure-Relieved CBM Drainage by Surface Wells in Coalbed Groups Covered by Super-Thick Pedosphere

During the mining of highly gassy and low-permeability coalbed groups, massive pressure-relieved desorbed coal bed methane (CBM) is stored in the fracture zone and in the gob under the impact of mining activities. Surface wells can cross the fracture zone and the gob to drain a large amount of highly concentrated pressure-relieved CBM. CBM drainage by surface wells is an effective technology for disaster control. However, it is difficult to drill or maintain surface wells in the mining disturbance zone and overlying strata in the gob. The keyisto prevent the surface wells in the mining disturbance zone from being broken and to keep the whole surface wells unblocked. This study adopted a variety of research methods, including similar-material simulation in laboratory, numerical simulation, onsite monitoring and industrial tests. Specifically, the strata structure of surface wells for pressure-relieved CBM drainage was explored, and the characteristics of roof strata movement and stress redistribution under coalbed group mining were analyzed. Besides, positions where the surface wells are prone to breakage were found. Furthermore, based on the mechanical analysis and breakage characteristics of surface wells, the anti-breakage principle of “resistance and dodge” and the surface well completion and protection method of “upper stop and lower leak” were proposed. The proposed theory and method were then applied to pressure-relieved CBM drainage surface wells in a coalbed group covered by the super-thick pedosphere in the Huainan Coal Field. The application results indicate that the proposed theory and method succeeded in solving the breakage of surface wells and realizing the smooth transport of CBM product. The surface wells can completely resist the mining disturbance, achieving an average single-well pure CBM production of 2.71 million m3, an average service period of 482 d, and a maximum pure CBM production of 4.32 million m3.

Study on the Movement of Pulverized Coal Particles in Fractal Fracture Network.

Coalbed methane (CBM) exploitation is a complex multiphase flow process. With the development of CBM extraction technology, it is recognized that the migration of reservoir fluid in the fracture network is affected by the matrix fracture structure, fracture width, and pulverized coal particles plugging, therefore the fluid-particle coupling problem has received increasing attention. In this paper, six groups of fracture models with different fractal dimensions are established using the Weierstrass-Mandelbrot function, and the fluid-particle coupling phenomena in fractures with different roughness and aperture are simulated using an immersed boundary-lattice Boltzmann method (IB-LBM), by comparing the numerical simulation results with the theoretical analysis, it is proved that the IB-LBM numerical method has high accuracy and effectiveness. The effects of fractal dimension, particle size, and particle concentration on the plugging effect were investigated. The results show that the plugging effect on the fracture is enhanced with the increase of the pulverized coal particles content. When the concentration and size of pulverized coal particles are the same, the migration path of pulverized coal particles in complex fractures is more tortuous and more likely to be plugged. It may lead to a shift in the main seepage network of the fracture and the formation of new seepage channels. The research in this paper provides a data basis for the formation and plugging pattern of pulverized coal particles in coal seam fractures, which can provide a basis for the control of pulverized coal particles concentration in CBM drainage.

The strength characteristics and competitive failure mechanism of primary coal-rock combination considering interface damage quantity

The strength and failure characteristics of primary coal-rock combinations are essential in coal-rock dynamic hazards prevention and coalbed methane drainage. Current studies simplify the primary coal-rock interface as smooth, which is inconsistent with the fact that there is a complex structure at the actual primary coal-rock interface. To study the influence of actual primary coal-rock interfaces on the strength and failure characteristics of primary coal-rock combinations, large primary coal-rock combinations from the Shendong Baode coal mine were collected, processed into standard samples, and scanned by industrial CT to reconstruct the 3D model of the primary coal-rock combinations interface. The probability density function of interface microelement inclination angle was statistically obtained, and the progressive damage model of the interface was established based on the density function. Then, uniaxial compression tests with acoustic emission localization were conducted on primary coal-rock combinations with different interface inclination angles. Finally, the competitive failure mechanism was used to analyze the influence of interface damage quantity on the strength characteristics and failure mode of the primary coal-rock combination. The results show that the primary coal-rock combination interface has a complex microstructure, and the inclination of the interface microelements is right-skewed distributed between 0 and 90°, with a plurality of 16°, conforming to the Rayleigh-Beta joint distribution. The coal and interface competed for the damage quantity of the primary coal-rock combination under uniaxial compression. As the interface inclination increased, the interface damage quantity increased, but the strength and energy density decreased, and the main damage gradually changed from the coal to the interface.

Research and application of dual tube gas lift technology in coal bed methane well

ABSTRACT Coal bed methane (CBM) is a gas resource associated with and symbiotic with coal, which refers to the hydrocarbon gas stored in the coal seam, with methane as the main component, which belongs to unconventional natural gas. The development and utilization of CBM has the effect of achieving multiple things in one fell swoop: clean energy, commercialization can produce huge economic benefits. At present, rod pump, screw pump and other lifting technologies commonly used in CBM drainage and production have poor adaptability, short pump inspection period, and it is difficult to enter horizontal section in horizontal well. Aiming at this problem, a new method of efficient CBM lifting is proposed by adopting dual-pipe gas lift technology. In this paper, the basic principle of double tube gas lift is analyzed, the optimization design of gas injection volume, coiled tubing size and coiled tubing running depth is carried out, and the field technology application of vertical and horizontal Wells is carried out. The results show that the dual tube gas lift technology has good adaptability in the deliquification of CBM, and the field application has achieved good production results. After the process modification, gas production of CBM Wells increases continuously, while water production decreases gradually, with the maximum gas rate exceeding 2400 m3/d. According to the latest production data, well L31 has been in steady production for more than 9 months, with an average gas rate of 1294.56 m3/d, which greatly exceeds the capacity before the transformation. Because there are no moving parts in the wellbore, the pump inspection period is greatly improved, and it has the potential to be widely applied in CBM.

Anisotropic Evolution of Effective Stress and Pore Pressure during Coalbed Methane Drainage

Summary The anisotropy and dynamic variation in permeability of gas-adsorbing coals have a significant influence on fluid flow behavior in the cleat system. The assumption of a constant anisotropy coefficient (the ratio between permeability components in orthogonal directions) has been traditionally made to simplify the seepage-stress coupling analytical model. In this approach, the pressure drop of the coalbed is separated into desorption and nondesorption areas. To evaluate the effective stress, pore pressure, permeability distribution, and variable anisotropy coefficient more accurately, analytical formulas were developed that consider elastic mechanics and methane sorption. The results show that the anisotropy coefficient can be dynamic when cleat compressibility anisotropy exists. Pressure contours are a set of ellipses that increase in eccentricity from the near-wellbore area to the pressure drop boundary, leading to corresponding anisotropy changes in effective stress and permeability. The gas desorption-related matrix shrinkage effect causes a discontinuous pressure drop gradient at the boundary between desorption and nondesorption areas, resulting in nonsmooth pressure drop curves. The pressure gradient difference changes with the radius of the desorption area and is nonisotropic, with the high-permeability direction showing a greater difference than the low-permeability direction. These results indicate that the dynamic anisotropy coefficient has a significant impact on coalbed drainage and extraction. Compared to previous mathematical models, which assumed permeability isotropy or constant anisotropy coefficient in cleat systems, the proposed model provides a more accurate method to evaluate pressure and permeability distribution.

Evolutionary Model and Experimental Validation of Gas-Bearing Coal Permeability under Negative Pressure Conditions.

Coal bed methane drainage is the main approach to lower risks of coal seam while raising the efficiency in natural resource utilization. The negative pressure used for extraction in coal mines is largely determined empirically due to a lack of experimental research on how coal permeability changes under the combined influence of effective stress and negative pressure. This results in low gas extraction efficiency and concentration. In this paper, to study the effect law of complex stress and extraction on coal permeability during coal and gas co-mining, a test system was specially designed to determine the gas flow and coal permeability of coal samples under different stress paths and negative pressure conditions in the lab. The study analyzed the correlation between coal permeability, effective stress, and negative pressure and subsequently developed a permeability evolution model for gas-bearing coal under negative pressure conditions. The results showed that the permeability of coal increases with the increase in negative pressure and decreases with the increase in effective stress; the permeability of coal can be abruptly changed by changes in stress loading patterns; the established model of permeability evolution of gas-bearing coal can better reflect the correlation between permeability, effective stress, and negative pressure. The research outcomes offer a valuable theoretical foundation for the efficient extraction and utilization of methane in coal mines.

Gas and water performance from the full-cycle of coalbed methane enrichment-drainage-output: A case study of Daning-jixian area in the eastern margin of Ordos Basin

Coalbed water (CBW), as a stratigraphic fluid, is stored and transported together with coalbed methane (CBM), and has an important influence on the generation, transport, enrichment and production patterns of CBM. In order to study the interaction mechanism between CBM and CBW in the full cycle of CBM enrichment-drainage-output, we collected CBW samples from typical wells at different production times and development data of CBM wells in Daning-jixian area in the eastern margin of Ordos Basin. According to the geochemical test results of CBW samples and the main parameters of 5# coal seam, the basic characteristics of CBW in the study area were analyzed. Then, the control of hydrochemical field on CBM enrichment, the influence of hydrodynamic field on CBM drainage, and the connection between CBW evolution and gas production were discussed, respectively. The results show that in the low burial depth area of the 5# coal seam in the monoclinic structure, the ion concentration of CBW is higher, and the Cl–Na coefficient, desulfurization coefficient and carbonate equilibrium coefficient are relatively small, making it a relatively enriched area for CBM. CBM production in high hydrodynamic areas has a greater need for drainage and depressurization, and the average daily gas production is relatively small. The evolution in daily gas production and the hydrochemical characteristics of CBW during CBM drainage show a good correlation. Every increase in gas production is accompanied by an increase in TDS and a decrease in Cl–Na​ coefficient, desulfurization coefficient and carbonate equilibrium coefficient in the extracted water.

Hydrogeochemical characteristics and water-rock interaction mechanism of coalbed-produced water in the Linfen mining area, eastern margin of Ordos Basin, China

Linfen mining area is one of the main coalbed methane industrial bases in the eastern margin of Ordos Basin, China. However, there are few studies on the hydrogeochemical characteristics of coalbed-produced water in the area. This article collected water samples from 14 coalbed methane drainage wells and analyzed the ionic concentrations, hydrogen and oxygen isotopes, dissolved inorganic carbon isotopes (δ13CDIC) and trace elements. The results showed that the water of Nos. Five and eight coal seams are both Cl-Na type. The total dissolved solids content was high, ranging from 5011.45 mg/L to 23405.39 mg/L. Hydrogen and oxygen isotope data indicated that the coalbed-produced water in the study area is recharged from atmospheric precipitation. In addition, the HCO3− in the produced water of No. Five coal seam and No. Eight coal seam was negatively correlated with δ13CDIC. The value δ13CDIC in the produced water of No. Five coal seam was heavier than that of No. Eight coal seam. These indicate that microbial degradation occurred more strongly in No. Five coal seam than in No. Eight coal seam. The water-rock interaction in the study area was found to be dominated by cation exchange and dissolution filtration through the relationships between anion and cation.

Experimental Study on Damage Fracture Law of Coal from Solid-Propellant Blasting

The low permeability of coal seams has always been the main bottleneck restricting coalbed methane drainage. In this paper, a coal seam anti-reflection technology with solid-propellant blasting was proposed, and the composition and proportion of the solid propellants were determined based on the principle of oxygen balance. The authors designed a solid-propellant blasting damage fracture experiment of simulation coal, tested the impact pressure on a blast hole wall, measured the ultrasonic wave velocity, explosive strain and crack propagation velocity, and then revealed the blasting damage fracture process and mechanism of coal based on the experimental results and damage fracture mechanics theory. The history curve of impact pressure time can be divided into three processes including the slow pressurization process, dramatic increase process, and nonlinear pressure relief process. The pressure distribution along the whole blasting hole was uneven, and the peak pressure was relatively small, but the pressure action time was long. The damage and fracture process of coal solid-propellant blasting can be divided into two stages including the rapid damage fracture development stage and the stable slow damage fracture development stage. Firstly, the explosion stress wave produced and rapidly accelerated the radial cracks extension; secondly, the cracks slowly expanded over a large area by the combined effects of the high-pressure gases, the gas, and the original rock stress.

Study on Key Parameters for Jet Impacting Pulverized Coal Deposited in Coal-Bed Methane Wells

Cleaning out the pulverized coal deposited at the bottom of a coalbed methane (CBM) well is key to achieving continuous CBM drainage and prolonging the workover period. In this study, Fluent is used in conjunction with the standard k-ε model and the Eulerian-Eulerian model to simulate and analyse jet erosion of deposited pulverized coal particles. The depth and width of the stable erosion pit that is formed by jet-impacting deposited pulverized coal under different conditions are determined and provide a theoretical basis for the cleanout of pulverized coal in the bottom of a CBM well. In this paper, the three parameters of the jet target distance, nozzle diameter and nozzle outlet flow velocity are selected to perform an orthogonal simulation. The change trends in the depth and width of the scouring pit with time are determined. The results show that jet impacting of deposited pulverized coal can be categorised into four stages, periods of rapid growth, stability, jet swing and dynamic stability. A sensitivity analysis shows that the nozzle outlet flow velocity has the strongest influence on the depth of the scouring pit among the selected parameters. The depth of the jet impact pit can reach the maximum depth at t = 3 s, while the width of the impact pit can reach the maximum after t = 7 s. This can provide key design parameters for CBM well pulverized coal impacting operation. It is of great significance for capacity damage control during CBM well workover operation.

Site trials of methane capture from low-concentration coalbed methane drainage wells using a mobile skid-mounted vacuum pressure swing adsorption system

Coalbed methane (CBM) emissions account for a large part of methane (CH4) emission in the fossil energy area, and vacuum pressure swing adsorption (VPSA) is an effective method to recover low-concentration CBM. However, CBM supply can fluctuate in quality or quantity because of the constantly changing geological conditions, thus permanent large-scale factory mode is economically inappropriate. In this work, a highly integrated mobile skid-mounted prototype VPSA system was designed and installed, and site trials of low-concentration CH4 capture were, for the first time, carried out in a coal mine site of Huayang New Material Technology Group Co. Ltd in China. Site trials including breakthrough tests and VPSA experiments were conducted in a fluctuating range of CH4 (16–30%). The effects of flow rate, adsorption pressure, and feed concentration on the separation process were revealed using a breakthrough process, and their effects on the dynamic parameters were also analyzed. After purification, the CH4 content in product gas was increased from 16–30% to 43.3–70.7% which all meet the requirements of 4T grade city gas in China, and maximum CH4 productivity of 43.6 × 10−3 m3/(kg·h) can be achieved. More importantly, multicycle breakthrough tests demonstrated that superhydrophobic zeolite TUTJ-1 is more resistant to the effects of water and has more potential for capturing CH4 under humid conditions than activated carbon.

Fracture propagation mechanism of coalbed methane drainage hole after prefabricated water jet slot fracturing based on J-integral model

Aiming at the method of mining coalbed methane by fracturing with guide groove, the theoretical analysis and numerical simulation method are used to analyze the change law of coal mechanical properties and the crack propagation mechanism after the jet fracture forms the fracture. The results show that there is a failure zone near the center of the jet-forming gap, and there are stress concentration areas on both sides of the gap. There is a more obvious plastic zone at the tip of the crevice, and its shape is a typical ear-like plastic zone. The crack initiation position is more conventional, it is determined by the difference between the stress in the direction parallel to the length of the crack and the direction parallel to the width of the crack; the direction of crack extension depends on the crack initiation position. The comparative analysis shows that it is more reasonable to use elastic–plastic fracture mechanics to calculate the initiation pressure with the crack starts from the tip, and the critical J integral model for the initiation of the crack tip is obtained. The initiation position of guided fracturing is more regular than conventional fracturing, and the initiation pressure of guided fracturing fractures is less than that of conventional fracturing under any stress combination.

Isothermal Desorption Hysteretic Model for Deep Coalbed Methane Development

The adsorption/desorption mechanism of coalbed methane is significant for gas control and coalbed methane exploitation; scholars have done a lot of research on it and generally have confidence in that temperature, pressure, and moisture are central factors affecting the adsorption of coalbed methane. Considering the reduction of recovery efficiency caused by desorption hysteresis in deep coalbed methane drainage, the effects of high reservoir pressure, high gas content, and low permeability on the hysteresis index were analyzed. A desorption hysteresis model based on the combination of dual-porosity media and traditional Langmuir adsorption theory was proposed. By comparing with the four experimental data of Ma et al., the advantages of the new model in fitting desorption data were investigated. Based on the new desorption hysteresis model, the hysteresis index was calculated from the adsorption capacity and desorption capacity under the abandonment pressure. The hysteresis index under different coal sizes and adsorption pressure were calculated, and a good linear relationship was found between the adsorption pressure and the hysteresis index. Through a large number of field production data analysis, the following conclusions are drawn: as the adsorption pressure increases, the hysteresis index enhances; when the coal sample size increases, the hysteresis index also increases. Finally, by comparing experimental data from deep and shallow coal samples, the influence of desorption hysteresis on deep coalbed methane mining was explored. This paper draws the conclusion that although the gas content in deep coalbed methane is considerable, its hysteresis index is also enhanced, which makes coalbed methane development more difficult. The findings of this study can provide theoretical support for coal bed gas control and coal bed methane heat injection mining.

Force and Control Measures of Pulverized Coal Migration in Coalbe-d Methane Horizontal Wells

Pulverized coal production is a common problem in the process of coalbed methane drainage and production, which is one of the key factors restricting the continuous stability drainage and production of coalbed methane. The reasons and characteristics of pulverized coal output are summarized. Through a detailed analysis of the migration and stress of pulverized coal in the borehole, the migration of pulverized coal is controlled by the stress conditions of pulverized coal, which causes the migration position of pulverized coal to change. Under the action of total pressure difference ΔF, pulverized coal particles can be divided into three situations: downward inclination, upward inclination and near horizontal migration. Finally, a solution to the control of pulverized coal is put forward from two aspects: the control of drainage and mining system and the selection of drainage and mining equipment. The research shows that continuous stability drainage and mining is the key of drainage and mining system, and controlling the hydrodynamic difference ΔF is the means to control the migration of pulverized coal. Choosing a pump with strong adaptability to pulverized coal is beneficial to coalbed methane drainage and production and increase productivity. Two horizontal wells in Shizhuang South Area 2 were replaced by membrane pumps, and the diaphragm pump system guide cover scheme was adopted. The coalbed methane production increased by about 1000m3/d, and the number of well repair was significantly reduced.

Site Trials of Methane Capture from Low-Concentration Coalbed Methane Drainage Wells Using a Mobile Skid-Mounted Vacuum Pressure Swing Adsorption System

Site Trials of Methane Capture from Low-Concentration Coalbed Methane Drainage Wells Using a Mobile Skid-Mounted Vacuum Pressure Swing Adsorption System

Reservoir characteristics and gas production potential of deep coalbed methane: Insights from the no. 15 coal seam in shouyang block, Qinshui Basin, China

Considering the large burial depth and unclear coalbed methane (CBM) development potential of the No. 15 coal seam in the Shouyang block in the northern Qinshui Basin, this study investigated the characteristics and gas production capacity of deep CBM reservoirs in the No. 15 coal seam based on the analysis of geological characteristics of CBM and the simulation of CBM production capacity. The No. 15 coal seam has a large thickness, strong adsorption capacity, medium gas content, low critical desorption pressure, low reservoir pressure, and a low ratio of critical desorption pressure to reservoir pressure (also referred to as the ratio). Based on the reversible relationship between the adsorption and desorption of CBM, we established an equation expressing the relationship between the gas content and burial depth of the No. 15 coal seam using massive data from gas content tests, isothermal adsorption experiments, and well tests. The analyses of main factors controlling the permeability of deep reservoirs of the No. 15 coal seam and their differences with those of shallow reservoirs indicate that deep CBM reservoirs have significantly low permeability owing to their large burial depth and high in-situ stress despite their favorable coal structure and well-developed fractures. Moreover, this study predicted the gas production characteristics of the No. 15 coal seam through numerical simulations of CBM drainage. The simulation results were similar to the actual gas production results, indicating that the No. 15 coal seam has great gas production potential. The results of this study will provide geological support for predicting the gas content and assessing the development potential of the No. 15 coal seam in the deep part of the northern Qinshui Basin.

A novel sealing material and a bag-grouting sealing method for underground CBM drainage in China

Coalbed methane (CBM) is not only a hazard to underground coal mines and atmospheric environment, but also an unconventional natural gas. The effect of underground CBM drainage is influenced markedly by borehole sealing quality. This research focused on a novel sealing material and a bag-grouting sealing method for CBM drainage. First, based on leakages of underground CBM drainage borehole, a material with dual expansion sources (DE) was proposed. Then, the expansion ratios (by rubber bag method) and the expansion pressures (under small swelling) of a modified cement (MC) and the DE were tested. Next, a bag-grouting sealing method, characterized by a bag-grouting sealing device, was proposed. Slurry can be grouted into the bag-grouting sealing device continuously, then the borehole can be sealed tightly. Finally, engineering test was performed at No.2 coal mine in Huangling mining area. Laboratory test results show that the DE expands fast at initial hydration stage, then continues to expand slowly. Especially, the expansion ratios of the DE are more than 60%, however, the MC tends to shrink after initial expansion. Besides, the expansion pressures of the DE are above 1.3 MPa, which are much greater than those of the MC. Engineering test results show that the effect of the DE and the bag-grouting sealing method is preferable to that of the MC and the traditional “two sealing and one grouting” method. The average methane concentration of the boreholes, sealed by the bag-grouting sealing method with the DE as sealing material, is 40% within 90 days. Besides, the concentration does not decrease drastically.