scholarly journals Experimental Study of the Characteristic Changes of Coal Resistivity during the Gas Adsorption/Desorption Process

2018 ◽  
Vol 2018 ◽  
pp. 1-7 ◽  
Author(s):  
Zengchao Feng ◽  
Chen Wang ◽  
Dong Dong ◽  
Dong Zhao ◽  
Dong Zhou
Keyword(s):  
Gas Adsorption ◽  
Gas Content ◽  
Resistivity Change ◽  
Adsorption Experiment ◽  
Desorption Process ◽  
Continuous Adsorption ◽  
Gas Desorption ◽  
Original Figure ◽  
Adsorption Desorption ◽  
The Relationship

To study the influence of gas adsorption-desorption on the resistivity of coal, the resistivity changes in conditions of continuous adsorption/desorption and isovolumetric adsorption/desorption were tested by high-precision resistance measurement, and the relationship between coal resistivity and gas content was investigated. The results show that gas adsorption/desorption has obvious effects on the resistivity of coal. Similar behavior was observed both in continuous adsorption/desorption and in isovolumetric adsorption/desorption experiments. The coal resistivity decreased gradually at the very beginning and then tended to stabilize as the gas adsorption capacity increased; in the process of gas desorption, the resistivity demonstrated a linear relationship with gas content. When comparing resistivities for the different adsorption modes, it was found that, for the same gas content in each mode, the resistivity change in the isovolumetric adsorption experiment was more obvious than in the continuous adsorption experiment. Also, the coal resistivity in the isovolumetric experiment differed further from the original figure when the desorption ended. The results are significant for predicting gas content in the coal mining process.

scholarly journals Gas Desorption of Low-Maturity Lacustrine Shales, Trassic Yanchang Formation, Ordos Basin, China

2018 ◽  
Vol 10 (1) ◽  
pp. 688-698 ◽  
Author(s):  
Bojiang Fan ◽  
Xiangzeng Wang ◽  
Liang Shi
Keyword(s):  
Shale Gas ◽  
Gas Adsorption ◽  
Ordos Basin ◽  
Isotopic Fractionation ◽  
Gas Content ◽  
Gas Generation ◽  
Desorption Process ◽  
Yanchang Formation ◽  
Gas Desorption ◽  
Process Gas

AbstractRecent exploration activities on Triassic Yan-chang Formation has indicated significant potential for shale-gas resources. Even though some areas have been put into pilot production, challenge exists in effectively determining shale-gas content, whichmake it difficult to estimate reserve and forecast production. This is primarily due to the low maturity of the shale and complicated relationships between oil, water and gas. However, studies on the gas generation and accumulation of low-maturity shales are lacking in the literature and previous desorption experiments did not consider the effects of oil and water. In this study, eight core samples are used to run the gas-desorption experiment. Shale-gas composition and isotopic fractionation data are analyzed to provide insights on gas adsorption, expulsion and accumulation processes in the Yanchang Formation. The experiment results indicate that the overall methane content decreases (from 68.8% to 58.9%), heavy hydrocarbon-gas content (from 20.30% to 36.12%) and δ13C1 increase (from -51.43% to - 34.63%) during the desorption process. Gas yield reached up to 3.89 m3/t shale, and the content of lost gas can account for more than 20% of total desorbed gas during the coring process. The recoverable shale gas content is estimated to be 80% of the total gas-desorption volume. Desorbing the rest 20% requires extra heating under much higher temperature.

scholarly journals Experimental research on desorption characteristics of gas-bearing coal subjected to mechanical vibration

2020 ◽  
Vol 38 (5) ◽  
pp. 1454-1466
Author(s):  
Xuexi Chen ◽  
Liang Zhang ◽  
Maoliang Shen
Keyword(s):  
Coalbed Methane ◽  
Gas Adsorption ◽  
Mechanical Vibration ◽  
Particle Diameter ◽  
Reference Value ◽  
Desorption Rate ◽  
Gas Desorption ◽  
Adsorbed Gas ◽  
Vibration Parameters ◽  
Adsorption Desorption

Mechanical vibration can induce coal and gas outburst accidents, and can also promote the exploitation of coalbed methane. In this paper, a vibration-adsorption-desorption experiment system was established, the effects of coal sample particle diameter, gas pressure, and vibration frequency on gas desorption were studied. Mechanical vibration can generate a shear force in the adsorbed gas and promote gas desorption, but there are appropriate vibration parameters. Within the range of experimental parameters, the larger the amplitude, the more favorable for gas desorption. The change rules of gas desorption rate and desorption quantity under different conditions are basically the same, showing a power function shape with time increase, and most of the desorption quantity was completed within the first 5 minutes. The gas desorption rate and desorption quantity were positively related to the gas adsorption pressure. The results have great reference value for preventing gas outbursts and promoting gas exploitation.

scholarly journals Coal Anisotropic Sorption and Permeability: An Experimental Study

Processes ◽  
2018 ◽  
Vol 6 (8) ◽  
pp. 104 ◽  
Author(s):  
Yulong Chen ◽  
Xuelong Li ◽  
Bo Li
Keyword(s):  
Experimental Study ◽  
Gas Adsorption ◽  
Great Influence ◽  
Flow Characteristics ◽  
Volumetric Strain ◽  
Bedding Plane ◽  
Gas Production ◽  
Desorption Process ◽  
Bedding Angle ◽  
Adsorption Desorption

Knowledge of the bedding plane properties of coal seams is essential for the coalbed gas production because of their great influence on the inner flow characteristics and sorption features of gas and water. In this study, an experimental study on the anisotropic gas adsorption–desorption and permeability of coal is presented. The results show that during the adsorption–desorption process, an increase in the bedding plane angle of the specimen expands the length and area of the contact surface, thereby increasing the speed and quantity of adsorption and desorption. With an increase in the bedding angle, the number of pores and cracks was found to increase together with the volumetric strain. The evolution of permeability of coal heavily depended on stress–strain stages. The permeability decreased with the increase of stress at the initial compaction and elastic deformation stages, while it increased with the increase of stress at the stages of strain-hardening, softening and residual strength. Initial permeability increased with increasing bedding angle.

Experimental Study on Gas Pressure Effects on Gas Desorption Characteristic of Coal Seam

2013 ◽  
Vol 318 ◽  
pp. 367-370 ◽  
Author(s):  
Lin Chao Dai ◽  
Da Yong Lu ◽  
Zhen Liu
Keyword(s):  
Coal Seam ◽  
Gas Adsorption ◽  
Experimental System ◽  
Gas Pressure ◽  
Pressure Effects ◽  
Gas Content ◽  
Equilibrium Pressure ◽  
Gas Desorption ◽  
Exploitation And Utilization ◽  
The Impact

To further explore the impact of gas pressure on gas desorption and flowing law, the gas desorption experimental system designed autonomously is used to carry out studies on gas desorption experiment under different gas pressures. By data fitting, the relationship between gas desorption quantity and time is obtained and also established the model for gas desorption. The results show that: the gas desorption quantity curves is "The first half rises sharply, the latter half segment is gently rising and eventually becomes stabilized", and when the gas adsorption equilibrium pressure is the greater, the gas desorption amount is greater. And the formula can describe the gas desorption law well, the correlation coefficient R2 is above 0.97. The study provides an important theory reference to coal and gas outburst prediction, coal seam gas content prediction and its exploitation and utilization.

Analysis of Antireflection and Outburst Prevention Mechanism on Hydrofracture Technology in Soft Coal Seam

2014 ◽  
Vol 556-562 ◽  
pp. 597-602
Author(s):  
Yi Lei ◽  
Wen Bin Wu
Keyword(s):  
Mechanical Properties ◽  
Coal Seam ◽  
Gas Adsorption ◽  
Coal Extraction ◽  
Phase Flow ◽  
Two Phase ◽  
Soft Coal ◽  
Gas Desorption ◽  
Soft Coal Seam ◽  
Adsorption Desorption

Base on the hydraulic fracturing field test in soft coal seam, the rule which the cutting quantity is added and the drilling gas desorption index K1 is decreased, is analyzed from the perspective of physical-mechanical properties and adsorption-desorption law is changed, etc. And gas adsorption and desorption law was analyzed using the theory of two-phase flow, to determine the effect after fracturing coal extraction is improved and the main reason for reducing the outburst.

scholarly journals The Relationship between Mining-Induced Stress and Coal Gas under an Optimized Support Scheme: A Case Study in the Guanyinshan Coal Mine, China

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-17
Author(s):  
Tianjun Zhang ◽  
Jiaokun Wu ◽  
Yong Chen ◽  
Hong Ding ◽  
Hongyu Ma ◽  
...  
Keyword(s):  
Gas Pressure ◽  
Gas Content ◽  
Rock Support ◽  
Drill Cuttings ◽  
Coal Gas ◽  
Gas Desorption ◽  
Induced Stress ◽  
Coal And Gas Outbursts ◽  
Residual Gas ◽  
The Relationship

Stress is one of the main factors influencing coal and gas outbursts. The apparent effects of the crustal stress, the structural stress, and the mining-induced stress increase as the depth of mining increases. At present, there have been few studies of the relationship between the comprehensive analyses of the crustal stress, mining-induced stress, and coal gas. The in situ measurement of the relationship between stress-related behaviors and coal gas under the influence of mining was conducted through experimental analysis of surrounding rock support and coal and gas outburst control and optimization of surrounding rock support materials and system construction. The results showed that the mining-induced stress first increased to a peak value, then gradually decreased, and tended to stabilize as the footage progresses. Stress appears at 96 m ahead due to mining; after 57 m of advancing, there is a large increase until it passes through this area. The stress in front of the working face increases linearly, and the increase range is obviously larger than that of the coal body in a certain range on both sides. The support anchoring force gradually decreased and tended to be stable after rapidly increasing to a maximum value. The deep displacement of the roof increased linearly and tended to be stable after reaching an accumulated displacement which can reach 16-28 mm. The residual gas pressure in front of mining operations decreased rapidly, and beyond 15 m on each side of the roadway, it decreased significantly. The residual gas pressure and gas content were consistent with the gas desorption index of drill cuttings due to the influences of gas predrainage and mining. The stress along the direction of the roadway and the residual gas content, the residual gas pressure, and the gas desorption index of drill cuttings conform to the logarithmic functional relationship. The research results provide a basis for the comprehensive prevention and control of coal and gas outbursts from multiple angles considering stress, coal, and gas.

Characterisation of Surat Basin Walloon interburden and overlying Springbok Sandstone: a focus on methane adsorption isotherms, permeability and gas content

2020 ◽  
Vol 60 (2) ◽  
pp. 748
Author(s):  
Syed Shabbar Raza ◽  
Julie Pearce ◽  
Pradeep Shukla ◽  
Phil Hayes ◽  
Victor Rudolph
Keyword(s):  
Adsorption Isotherms ◽  
Gas Adsorption ◽  
Methane Adsorption ◽  
Gas Content ◽  
Coal Seams ◽  
X Ray ◽  
Gas Desorption ◽  
Water Wells ◽  
Temperature And Pressure ◽  
Coal Measures

The Surat Basin in Queensland is one of the world’s premier producers of natural gas from coal seams. We investigate the potential for clay-rich Walloon Coal interburden and the overlying Springbok Sandstone to hold or produce gas. Seventeen core samples were analysed from two wells from intervals within the Walloon Upper Juandah Coal Measures interburden and the Springbok Sandstone. Samples were characterised using high-pressure methane adsorption isotherms, canister gas desorption tests, moisture contents, ash contents, carbon contents, scanning electron microscopy/energy dispersive X-ray spectrometry, X-ray quantitative clay analysis, permeability, helium pycnometry and mercury intrusion porosimetry. Methane adsorption was conducted at 30°C with up to 8 MPa pressure on dried crushed samples. The adsorption capacity of methane at 8 MPa varied from 3 cc/g (calcite-cemented) up to 25 cc/g (standard temperature and pressure equivalent) (coal). Clay-rich interburden samples adsorbed ~5–14 cc/g (dry). The measured isotherms and methane content from canister desorption tests show that appreciable volumes of gas are contained within some portions of interburden and in the overlying Springbok Sandstone. Gas within the interburden likely represents a large volumetric resource, albeit in low permeability rock that restricts direct productivity. The gas adsorption and gas content results for the Springbok Sandstone help to explain field observations of high gas content in some landholder water wells.

scholarly journals Pore-Scale Lattice Boltzmann Simulation of Gas Diffusion–Adsorption Kinetics Considering Adsorption-Induced Diffusivity Change

Energies ◽  
2020 ◽  
Vol 13 (18) ◽  
pp. 4927 ◽  
Author(s):  
Zhigao Peng ◽  
Shenggui Liu ◽  
Yingjun Li ◽  
Zongwei Deng ◽  
Haoxiong Feng
Keyword(s):  
Coalbed Methane ◽  
Gas Adsorption ◽  
Fluid Velocity ◽  
Gas Diffusion ◽  
Gas Production ◽  
Pore Scale ◽  
Desorption Process ◽  
Gas Diffusivity ◽  
Isotherm Adsorption ◽  
Adsorption Desorption

The diffusion–adsorption behavior of methane in coal is an important factor that both affecting the decay rate of gas production and the total gas production capacity. In this paper, we established a pore-scale Lattice Boltzmann (LB) model coupled with fluid flow, gas diffusion, and gas adsorption–desorption in the bi-dispersed porous media of coalbed methane. The Knudsen diffusion and dynamic adsorption–desorption of gas in clusters of coal particles were considered. Firstly, the model was verified by two classical cases. Then, three dimensionless numbers, Re, Pe, and Da, were adopted to discuss the impact of fluid velocity, gas diffusivity, and adsorption/desorption rate on the gas flow–diffusion–adsorption process. The effect of the gas adsorption layer in micropores on the diffusion–adsorption–desorption process was considered, and a Langmuir isotherm adsorption theory-based method was developed to obtain the dynamic diffusion coefficient, which can capture the intermediate process during adsorption/desorption reaches equilibrium. The pore-scale bi-disperse porous media of coal matrix was generated based on the RCP algorithm, and the characteristics of gas diffusion and adsorption in the coal matrix with different Pe, Da, and pore size distribution were discussed. The conclusions were as follows: (1) the influence of fluid velocity on the diffusion–adsorption process of coalbed methane at the pore-scale is very small and can be ignored; the magnitude of the gas diffusivity in macropores affects the spread range of the global gas diffusion and the process of adsorption and determines the position where adsorption takes place preferentially. (2) A larger Fickian diffusion coefficient or greater adsorption constant can effectively enhance the adsorption rate, and the trend of gas concentration- adsorption is closer to the Langmuir isotherm adsorption curve. (3) The gas diffusion–adsorption–desorption process is affected by the adsorption properties of coal: the greater the pL or Vm, the slower the global gas diffusivity decay. (4) The effect of the gas molecular adsorption layer has a great impact on the kinetic process of gas diffusion–adsorption–desorption. Coal is usually tight and has low permeability, so it is difficult to ensure that the gas diffusion and adsorption are sufficient, the direct use of a static isotherm adsorption equation may be incorrect.

Crystal structures, CO2 adsorption, and dielectric properties of [Cu(ii)2(R-benzoate)4(pyrazine)]∞ polymers (R = m-F, 2,3-F2, m-Cl, and m-CH3)

2014 ◽  
Vol 43 (24) ◽  
pp. 9081-9089 ◽  
Author(s):  
Kiyonori Takahashi ◽  
Norihisa Hoshino ◽  
Takashi Takeda ◽  
Shin-ichiro Noro ◽  
Takayoshi Nakamura ◽  
...  
Keyword(s):  
Dielectric Properties ◽  
Crystal Structures ◽  
Gas Adsorption ◽  
Co2 Adsorption ◽  
Interchain Interactions ◽  
Adsorption Desorption ◽  
The Relationship

The relationship between the interchain interactions and CO2 gas adsorption–desorption properties, and dielectric responses under CO2 desorbed conditions.

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