Gas Extraction Effect Research Articles

Molecular insight into the diffusion/flow potential properties initiated by methane adsorption in coal matrix: taking the factor of moisture contents into account.

Coal seam permeability is one of the key parameters affecting coalbed methane (CBM), and plays an important role in resource evaluation and regional selection. To fully explore the diffusion/flow potential properties initiated by methane adsorption beneath diverse moisture contents (1-5%) in coal molecules. The pore size distribution and methane adsorption capacities were discussed based on Monte Carlo (MC) and molecular dynamics (MD) methods. The potential properties of diffusion/flow induced by methane adsorption were investigated using the maximum absolute adsorption capacities as benchmark. The variation patterns of the pore structure were analyzed using SEM scanning experiment to verify the results of simulation analysis. It is found that the free pores facilitate methane molecular adsorption and increase adsorption spaces; the skeleton pores restrict the flow and transport of water molecules. Reduction values in surface free energies increase at different temperatures, and released heat diffusion coefficients and permeabilities for methane molecules drop as moisture contents increase. Interestingly, however, enhancements in temperatures increase the methane molecular diffusion coefficients. The lower the activation energies, the easier they are to diffuse. Sufficiently, the optimum conditions for gas drainage of coal seam are at temperature of 293K and moisture content of 5%, indicating greater contributions to gas pressure relief for coal seam. By comparing the results of molecular simulation and SEM scanning, trend of change is basically the same. Moreover, it is explored that hydraulic measure was the most significant to the CBM stimulation technology through field engineering application. This research is expected to provide guidance for facilitating the effectiveness of gas extraction for coal seam.

Study on the influence mechanism of air leakage on gas extraction in extraction boreholes

Borehole leakage is an important cause of gas extraction failure. In order to study the influence mechanism of borehole leakage on gas extraction, the borehole air leakage mode was studied, and a mathematical model was established to describe the borehole air leakage of the gas extraction. In addition, this paper also analyzed the change rules of borehole air leakage and gas extraction effect at different borehole sealing depth, negative extraction pressure, degree of fracture development and borehole sealing quality. Research shows that: (1) The hole sealing depth has a certain influence on the borehole air leakage and the gas extraction effect. As the hole sealing depth increased, the borehole air leakage gradually decreased. Moreover, the net amount of gas extraction gradually decreased, but the gas extraction concentration increased to some extent, and the increasing range gradually decreased. The reasonable sealing depth of this coal seam was 9∼10 m. (2) The negative pressure of borehole extraction has little influence on borehole air leakage and gas extraction. With the increase of the negative extraction pressure, the gas extraction net amount and borehole air leakage both increased, but the gas extraction concentration decreased. In the later stage of the gas extraction, the negative pressure can be properly reduced to improve the gas extraction effect. (3) The borehole sealing quality has a great influence on the borehole air leakage and gas extraction effect. With the improvement of the sealing quality, the coal-rock permeability gradually decreased. Moreover, the borehole air leakage significantly reduced, and the gas extraction concentration increased significantly. Therefore, attention should be paid to the selection and improvement of sealing materials and sealing techniques in the actual production so that the airtightness and sealing quality of the hole sealing section can be improved.

Optimization of the Plastic Area of a Borehole Based on the Gas Extraction Effect and Its Engineering Application

Gas extraction is most commonly used to control gas disasters in coal mines. The distribution of the plastic zone around a borehole and the sealing quality are key factors affecting gas extraction. In this paper, the plastic zone was simulated by COMSOL, and a theoretical equation of the plastic zone radius was derived. In addition, an antispray hole equipment and the “two plugging and one injection” sealing technology were proposed. The results show that a larger borehole pore size corresponds to a larger plastic zone and larger range of pressure relief of the borehole. The error between the calculated and simulated plastic zone radii is within 1%, and the modified equation is applicable to Puxi mine. The loss and harm caused by borehole spraying are reduced by applying antispray hole equipment. By applying the “two plugging and one injection” sealing technology and phosphogypsum-based self-produced gas expansion paste material to block the borehole, the sealing quality is improved and an accurate gas mixing flow, pure flow, and concentration were obtained. As the plastic zone enlarges, the gas extraction flow gradually increases with, but the relative variation of flow first increases and subsequently decreases. Considering the safety and economy of construction, the optimal radius of the plastic zone is 64.9 mm.

Research and Optimization of Gas Extraction by Crossing-Seam Boreholes from Floor Roadway

Deep coal seams are characterized by large stress, high gas pressure, and low permeability. The gas disaster threatens the safe production of coal mine seriously. Gas extraction by crossing-seam boreholes from floor roadway (GECMBFR) can reduce the pressure and content of coal seam gas, which is the main measure to prevent gas disaster. Considering the Klinkenberg effect, governing equations of gas adsorption/desorption-diffusion, gas seepage, and stress fields within the coal seam are established to form the seepage-stress coupling model. The governing equations are embodied into a finite element driven software to numerically simulate gas migration and fluid-solid coupling law in coal seam. On this basis, the process of gas extraction under different borehole spacings and diameters is simulated. The effects of these two key parameters on coal seam gas pressure, gas content, and gas permeability were analyzed. The borehole spacing and diameter were determined to be 5 m and 0.09 m, respectively. Combined with the actual situation of a mine, the process of gas extraction from floor roadway with different cross-sectional schemes, ordinary drilling boreholes and punching combined drilling boreholes, is comparatively analyzed. The results show that the gas extraction effect by ordinary drilling boreholes is lower than that of the punching combined drilling boreholes, and the extraction is uneven and makes it difficult to meet the standard. Hydraulic punching was carried out, and coal was washed out of the borehole, which expanded the contact area between the borehole wall and coal seam. The coal seam around the punching borehole is unloaded, which improves coal permeability and accelerates gas migration towards the borehole, thus promoting the efficiency of gas extraction. It is more reasonable to use punching combined drilling borehole scheme when implementing the GECMBFR technology.

Invited Perspective: Oil and Gas Development and Adverse Birth Outcomes: What More Do We Need to Know?

Invited Perspective: Oil and Gas Development and Adverse Birth Outcomes: What More Do We Need to Know?

An experimental study on coal damage caused by two-phase displacement of CO2- alkaline solution

Two-phase displacement of CO2- alkaline solution technology was proposed to address the obvious problems existing in the current coal mine gas control technologies, such as the gas enrichment and outburst risk caused by tradition CO2 injection technology, and the poor effect of conventional coal seam water injection technology. In order to investigate the damage characteristics of coal pore structure and permeability caused by two-phase displacement of CO2- alkaline solution, the composition and microstructure of coal after two-phase displacement of CO2- alkaline solution were tested experimentally, and the permeability experiment of two-phase displacement of CO2- alkaline solution was carried out. The results show that the reaction degree and dissolution of CO2-containing coal with alkaline solution are stronger than those with distilled water. The reaming effect of alkaline solution on CO2-containing coal is stronger than that of distilled water, and the two-phase displacement of CO2- alkaline solution has the greatest influence on mesopore and macropore; After two-phase displacement of CO2- alkaline solution, the permeability of coal sample increased by 47.6%–108.6%, and the water content of coal sample increased by 109%. The two-phase displacement of CO2- alkaline solution leads to the secondary development of coal pores, which significantly changes the coal pore structure, increases the permeability and water content of coal body, and thus obviously increases the gas extraction effect to reduce coal seam outburst risk and ensure coal mine safety production.

Experimental Study on Gas Extraction Effect of Conventional Drilling in Coal Mining Face

In order to study the effect of conventional drilling gas extraction technology, combined with the observation results of upward drilling and downlink drilling field test in 81309 working face of Baode Mine. The analysis of field test data shows that under the same gas control effect, the average gas concentration and gas purity of uplink drilling are higher than that of downlink boreholes. In the extraction range, the average pumping concentration of uplink boreholes is 1.134 times higher than that of downlink boreholes, while the average pure gas flow rate of uplink boreholes is 1.296 times higher than that of downlink boreholes. The test results show that the uplink conventional drill Hole has better pumping concentration stability and extraction effect than downlink conventional drilling.

Application research on hydraulic fracturing of cross-layer drilling in Sijiazhuang Coal Mine

The No.15 coal seam of Sijiazhuang Coal Mine belongs to high gas and low permeability coal seam. Hydraulic fracturing, as a technical measure for outburst prevention, is more and more widely used in high gas outburst mines. The influence of hydraulic fracturing high-pressure water on stress and displacement of roadway is analyzed, and the feasibility of hydraulic fracturing is verified. The industrial test of hydraulic fracturing through layers was carried out and the effect of gas extraction was investigated. The average concentration and pure volume of gas extraction unit in the fracturing area were 3.1 times and 5.7 times of those in the non fracturing area, respectively, which verified the permeability increasing effect of hydraulic fracturing measures. Through fracturing test, the extraction effect has been significantly improved. This paper provides important theoretical support and practical basis for hydraulic fracturing under similar conditions.

Study of the Law of Hydraulically Punched Boreholes on Effective Gas Extraction Radius under Different Coal Outputs

Hydraulic punching technology has recently developed into an effective pressure relief measure and permeability enhancement method for soft and low permeability coalbeds. Different coal outputs directly affect the shape and size of boreholes as well as the effective extraction radius. Taking the Zhongmacun mine as an example, the influence of different coal outputs and different extraction periods on effective extraction radius was analyzed and studied through field tests and numerical simulation. The results show that the increase in coal outputs from hydraulic punching can improve the effective extraction radius of the boreholes. For example, when the gas extraction reaches 90 days, with a coal output of 0.5 t/m, 1.0 t/m, and 1.5 t/m, the effective extraction radius is 3.08 m, 3.46 m, and 3.83 m, respectively. The difference in gas extraction effect of different coal output boreholes increases significantly with the extension of the extraction time, but the speed of growth gradually decreases, which is consistent with the conclusions obtained on-site. This result has important practical significance for optimizing the technical parameters of hydraulic punching, guiding the accurate layout of extraction and drilling, and enhancing the effect of gas control in mines.

Liquid CO 2 high‐pressure fracturing of coal seams and gas extraction engineering tests using crossing holes: A case study of Panji Coal Mine No. 3, Huainan, China

Owing to the low coal permeability coefficients and poor gas extraction efficiencies associated with the extraction of coal in the Huainan coal mining area, the aim of this study was to design, for the first time, a high-pressure low-temperature liquid CO2 (LCO2) pump for engineering tests with respect to the fracturing of coal seams and the improvement of CH4 recovery in China. To reasonably calculate the initiation pressure for the coal seam fracturing as well as the gas flow parameters, theoretical analysis with field testing were integrated in the design. In addition, considering the interim gas extraction standard, the gas extraction equivalent radius based on this standard was calculated. The test results revealed a maximum LCO2 pressure of 20.6 MPa, which surpasses the theoretical maximum pressure (19.5 MPa) required for the fracturing of coal seams. During the entire gas extraction process, the CO2 concentrations in boreholes K1 and K3 decrease exponentially with time, showing attenuation coefficients of 0.0205 and 0.0231, respectively. The attenuation coefficients of the three attenuation stages of the original coal seam gas flow rate were 0.0314, 0.2142, and 0.1198, which were higher than those corresponding to the test area. The CH4 concentration in boreholes K1 and K3 in the test area were both higher than that in the original coal seam, and the maximum CH4 flow rates in these boreholes were 1.31- and 1.72-fold higher than that in the original coal seam, respectively. The comparative analysis of CH4 concentrations and flow rates indirectly showed an improvement in the permeability of the coal seam. Further, a quantitative equivalent gas extraction evaluation method based on LCO2 fracturing of coal seam and gas displacement was proposed. Furthermore, based on a comprehensive evaluation, the effective displacement radius caused by the LCO2 fracturing test was 9 m, with a displacement efficiency of 23.95%, and a displacement volume ratio of 0.21. This method offered the possibility of realizing the quantitative evaluation of the LCO2 injection amount and the gas extraction effect, and provides a basis for optimizing the LCO2 fracturing of coal seams as well as the gas extraction process.

Borehole diameter shrinkage rule considering rheological properties and its effect on gas extraction.

To study the shrinkage rule of borehole diameter and its effect on gas extraction, a visco-elastoplastic model for boreholes considering strain softening and the dilatancy characteristic was established to obtain the expressions of the coal stress, variation in diameter, and pressure relief range. The stress distribution and pressure relief effect of the boreholes in soft and hard coal seams were comparatively analyzed. The shrinkage rule of the borehole diameter was studied. The reasons for the rapid reduction in the extraction concentration of the borehole in soft coal seams were described. A technology of improving the gas extraction effect in soft coal seams was developed. The research results showed that the radius of the plastic softening zone is 0.405 m for a borehole in a soft coal seam and 0.224 m for that in a hard coal seam. This indicates that the borehole in a soft coal seam has a better pressure relief effect. The boreholes in both hard and soft coal seams will incur a shrinkage phenomenon; however, the soft coal seam has low strength and a weak ability to resist damage, and thus the surrounding coal will have a more intense creep deformation, leading to an instability failure during a short period of time and thus, a blocking of the extraction channel, thereby causing a rapid reduction in the gas extraction concentration. The borehole in a hard coal seam also shows a shrinkage phenomenon, but remains in a stable state without a blockage; thus, high-concentration gas can be extracted from this borehole for a long period of time. The geo-stress and coal strength are the two main factors controlling the amplitude of borehole shrinkage. From an increase in stress, the borehole in a hard coal seam shows a more intense creep deformation in a deep mine, which may lead to blockage. The key to improving the gas extraction effect in soft coal seams is to maintain a smooth extraction channel. The full screen pipe is installed through the drill pipe to retain an extraction channel, leading to an average gas extraction increase from 0.043 m3/min to 0.12 m3/min, an increase of 2.77 times. These research results are consistent with actual production, and can provide theoretical guidance for determining the gas extraction parameters.

SHALE OIL AND THE ENVIRONMENT IN AUSTRALIA: THE SEARCH FOR BALANCE

And the world. Its economy is largely dependent on the export of raw materials; a positive commodities trade balance ensured the stability of the country's economy over the past three decades. The country has significant reserves of shale oil and gas, which allows for expanding Australia's export potential. The extraction of shale resources is fraught with a number of difficulties, including financial, which do not always have obvious consequences for both the economy and the environment. This article is aimed at assessing the possibility of extracting shale oil and gas without significant harm to the Australian environment and society. In Australia, social and environmental effects are very closely related, as are social and economic effects; that is why the authors investigate a set of interactions. The authors analyze the dynamics of export and import of hydrocarbons by Australia in order to identify the economic effect of the start of oil shale production in 2011. In addition, the authors reveal the dynamics of carbon dioxide emissions, as one of the key elements of environmental pollution after the start of active shale oil production in Australia, according to the expert community. It is also pointed out that the negative consequences of shale extraction are not only in the form of increased CO2 emissions, but also through a complex interaction with the natural environment. The authors propose using an econometric approach to the analysis of the advantages and disadvantages of the development of shale oil in the country. Based on the obtained results, the authors conclude that the positive effects of shale oil and gas extraction for the country’s economy do not outweigh the negative effects for the environment, and propose considering shale reserves as a strategic resource for recovering from crises and currently performing extraction in the test mode.

Modeling air leakage around gas extraction boreholes in mining-disturbed coal seams

Air leakage is one of the most important factors that affect the underground gas extraction in mining-disturbed coal seams. It was demonstrated that the gas concentration in most in-seam boreholes decreased to a very low level in a short time. Such a low concentration may lead to secondary disasters such as coal spontaneous combustion, gas explosion and gas combustion. Aiming at this problem, a fully coupled mechanical- composite gas flow (MCF) model was developed to reveal the mechanism of air leakage around the borehole. The reliability of the model was verified by matching the calculating results with gas extraction data monitored in the field. Then, with the MCF model, factors affecting the gas extraction effect were systematically investigated. It was found that the mining-disturbed zone led to an increase of both the gas and air flow rate, but a decrease of the gas concentration in the borehole. Both the gas and air flow rate reduced with an increase of the sealing length of the borehole, while the gas concentration showed an increase trend. The optimal sealing length of the in-seam borehole in Pingmei 8th Mine was identified as 10−14 m. In addition, the attributes of the coal seam itself also have obvious influence on the quality of the gas extracted. The results indicate that both the borehole and the mining-induced fractures around the borehole should be appropriately treated to improve the quality of gas extracted. Therefore, we propose a new sealing method which integrates cement grouting and gel injection. In this method, after the sealing of the gas extraction boreholes, the sodium silicate and ammonium bicarbonate aqueous solutions were mixed and injected into the coal seam. The produced silicone gel could block the mining-induced fractures and the crescent-shaped gap between the sealing material and borehole wall, thus preventing the air leakage. The research results could help to optimize borehole sealing and improve the quality of gas extracted, thus prevent disasters such as coal spontaneous combustion and gas explosion, so as to guarantee the safety of mining and reduce the greenhouse gas emission.

Technological aspects of the development of gas hydrate deposits with the use of carbon dioxide injection

The article is dedicated to the technological peculiarities of natural gas hydrate deposits extraction with using perspective method which consists of introduction of carbon dioxide into the gas hydrate layer removing methane and creating CO2 hydrate. Specific attention is paid to the insufficient efficiency of presently used methods in terms of the economic effect and safety of gas extraction. The complex methodological approach has been used to experimentally determine the optimal pressure of the two gases swap based on the minimal time of the process duration. The rate of the two gases exchange in the reactor has been defined and a new technological solution as to the gas hydrate deposits recovery has been proposed. It is defined that at the pressure being equal to Р = 9 MPa and the temperature Т = +7…+8 ºC, the whole exchange of the guest molecules СН4 for СО2 molecules can be reached in 2 hours. It is established that the gas hydrate crystallisation centres nucleate in about 30 – 35 minutes, after that the crystals continue growing removing methane from the preliminary created hydrate up to the point when about 70 – 80% of the hydrate is filled with СО2 hydrate. The lowest rate of the exchange process took place under the pressure Р = 5 MPa and temperature Т = +7…+8 ºC and resulted in 10 hours. The penetration length of the carbon dioxide jet is established depending on the process duration under the optimal injection pressure of СО2. A new technological scheme is introduced for methane recovery from gas hydrate deposits of the Black Sea with the help of carbon dioxide injection into the hydrate seam.

Influence Factors of Gas Extraction Effect and Residual Gas Content Distribution on Working Face

The influence factors of gas extraction effect and residual gas content after bedding drainage on working face were uncertain, leading to the judge standard of gas extraction effect was not in conformity with the actual extraction situation. The influence zones of gas extraction were divided, according to the goaf and coal pillar of protective layer, including the tectonic belt of working face. The gas extraction parameters and residual gas content were tested, and the gas extraction effect and residual gas content distribution under different influence factors was studied by using Surfer software. The results showed that the concentrated stress under coal pillar made the gas extraction effect reduced greatly. Both the goaf and structural belt had relieving pressure effect on the C7+8 coal seam, but the gas extraction effect was better in the area dominated by the relieved pressure of goaf, while the gas extraction effect was worse in the area dominated by the relieved pressure of structural belt. From large to small, the residual gas content distribution in Area III was greater than that in Area II, greater than that in Area V, greater than that in Area I, greater than that in Area IV.

Does Resource Ownership Matter? Oil and Gas Royalties and the Income Effect of Extraction

We study how subsurface ownership shapes the income effects of oil and gas extraction. For the average US county with growth in extraction from 2000 to 2014, we find that royalty income and its multiplier effect accounted for 70% of the total income gain, with each royalty dollar generating an additional 49 cents of local income. A county where residents own the subsurface captured 28 cents more of each dollar in production than one with absentee ownership. Nationally, oil and gas production increased US personal income in 2014 by $67 billion (0.5%) more than if all royalties accrued abroad. Areas with the same resource abundance can therefore experience contrasting economic outcomes because of differences in ownership.

Hydraulic flushing in soft coal sublayer: Gas extraction enhancement mechanism and field application

AbstractIn China, one or several ultrathin soft coal sublayers are widely developed in the coal seam. Therefore, a method of using hydraulic flushing in soft sublayer to enhance the gas extraction in these particular coal seams is developed in this work. We first established a new fully coupled gas extraction model by combing gas diffusion, gas flow, and a permeability model that considers the effect of stress change and plastic failure. By adopting this model, the gas extraction enhancement mechanism and its main influence factors were studied using the numerical simulation method based on the engineering and geological background in the Yangquan No.5 coalmine. Thereafter, a hydraulic flushing equipment, which could move freely in the underground coalmine, was developed to apply the hydraulic flushing method in soft coal sublayers used in the 8402 working face. Its gas extraction effect was systematically investigated. Our simulation results match well with the field results, suggesting that our model is feasible. Meanwhile, after adopting this method, the gas extraction condition in this coalmine improves significantly. The borehole number decreases by 66.7%, while the gas extraction rate and gas extraction concentration increase by 1.33 times and 3 times, respectively. Moreover, during the coal mining process, the gas adsorption index of drilling cuttings, the quantity of drilling cuttings, and the CH4 concentration also decrease dramatically.

Effect of gas extraction on the hydrodynamics in a fluidized bed membrane reactor at elevated temperatures

AbstractThis study describes experimental explorations on the effects of gas extraction on hydrodynamics in a pilot‐scalegas fluidized bed membrane reactor (FBMR) at high temperatures. Differential pressure signals were measured at different vertical intervals in bed and were then characterized by multiscale resolution and power spectra analysis. The experimental results showed that the relative amplitude of σr (σ/xav) of pressure signal tended todecrease with the increase of gas extraction fraction.At room temperature, 20% gas extraction caused defluidization at an inlet velocity of 2Umf. However, athigh temperatures the gas extraction simultaneously decreased the magnitude of the low‐frequency components and the numbers of the medium‐ to small‐sized structures, mainly due to the decreased number of small‐sized structures and the integration of bubbles. This effect of gas extraction increased with increase of gas extraction fraction and slightly decreased at higher inlet gas velocities. At elevated temperatures, the D6 sub‐signals (0.781~1.562Hz) possessed the highest wavelet energy distribution percentage of the pressure signals, which meant that the medium‐ to small‐sized bubbles dominated the gas‐solid flow dynamics. Gas extraction was observed to enhance the dominance of the D6 scale components..

Numerical simulation of boreholes for gas extraction and effective range of gas extraction in soft coal seams

AbstractGas disasters are a major factor influencing safe production in mines: Gas extraction can reduce the gas content in coal seams, providing a guarantee of safer production. The parameters for gas extraction are the primary factors influencing the effectiveness thereof. Aiming at the creep properties of soft coal, a fluid‐solid coupling mathematical model considering creep properties of coal was established based on dynamic evolution equation for permeability considering the effects of matrix shrinkage and effective stress. Additionally, by utilizing COMSOL Multiphysics software, the gas extractions from a single borehole and multiple boreholes were calculated. Moreover, the parameters for gas extraction were optimized and applied and tested in field conditions. The result showed the reduction in gas pressure around the boreholes was larger than that from a single borehole when conducting gas extraction from multiple boreholes. The borehole spacing when extracting gas in coal seams by drilling multiple boreholes should be more than twice that of the effective drainage radius. The optimal borehole spacing ranged from 3.2 to 4.2 m for gas extraction lasting 180 d. Numerical simulation was carried out to ascertain the distribution of stress on coal around a roadway. The result revealed that the damage radius of the roadway was 11.8 m, and a reasonable hole‐sealing depth was 12 m. On condition that the borehole spacing during gas extraction from multiple boreholes was 4 m, the reasonable pre‐extraction time was 180 days taking the gas pressure being reduced to <0.74 MPa as a critical point. Furthermore, the gas content, the amount of extracted gas, etc, in a working face after the parameters for gas extraction were optimized were measured. The result suggested that the effect of gas extraction after optimizing parameters conformed to industry standards.

Effects of pore structure and methane adsorption in coal with alkaline treatment

Coal bed methane (CBM) is an important type of clean energy, but it can also result in coal mining disasters. Increasingly more technologies have been applied to improve the effectiveness of gas extraction. Coal contains a large number of organic minerals and inorganic minerals, and some inorganic minerals fill in pores and block the gas seepage. To improve the connectivity of coal pores, chemical methods can be used to change the distribution of the minerals in coal. In this paper, representative bituminous (TY) and anthracite (QC) are used, and an alkaline solution is also used to treat the coal samples. The SEM results show that some minerals in coal can be dissolved in alkaline solution and removed from the pores, thereby changing the distribution of the minerals. According to the LTNA test, the micropore content of coal is changed, especially in the pore size range of 2–5 nm. With the alkaline treatment, the average aperture decreases and the specific surface area increases. Fractal theory was used to analyze the data with relative pressure (P/P0) less than 0.5. The results showed that the fractal dimension of the coal sample increased after the alkaline treatment, which indicated that the micropore content of the coal sample increased due to alkaline erosion. To verify the pores changes, adsorption experiments were carried out to analyse the adsorption capacity of the coal samples. After the alkaline treatment, the maximum sorption capacity and Langmuir-like pressure both increased. CO2 injection is an effective technology to displace CBM, but it easy to leave a great deal of CO2 in coal. The residual CO2 could be reduced by injecting an alkaline solution, and the coal would also be eroded. Based on the results, a new method combining CO2 injection and an alkaline treatment was proposed to improve the effectiveness of the gas control.