Novel Dynamic Multiscale Model of Apparent Diffusion Permeability of Methane through Low-Permeability Coal Seams

2021 ◽  
Author(s):  
Zhiqiang Li ◽  
Jiansong Peng ◽  
Lin Li ◽  
Lingling Qi ◽  
Wai Li
Keyword(s):  
Multiscale Model ◽  
Diffusion Permeability ◽  
Low Permeability ◽  
Coal Seams ◽  
Apparent Diffusion

scholarly journals Micropore Structure and Fractal Characteristics of Low-Permeability Coal Seams

2018 ◽  
Vol 2018 ◽  
pp. 1-15 ◽  
Author(s):  
Guang-zhe Deng ◽  
Rui Zheng
Keyword(s):  
Fractal Dimension ◽  
Electron Microscope ◽  
Scanning Electron Microscope ◽  
Coal Seam ◽  
Linear Relationship ◽  
Surface Area ◽  
Pore Volume ◽  
Low Permeability ◽  
Coal Seams ◽  
Scanning Electron

With the raw coal from a typical low-permeability coal seam in the coalfield of South Junger Basin in Xinjiang as the research object, this paper examined six kinds of coal samples with different permeabilities using a scanning electron microscope and a low-temperature nitrogen adsorption test that employed a JSM-6460LV high-resolution scanning electron microscope and an ASAP2020 automatic specific surface area micropore analyzer to measure all characteristic micropore structural parameters. According to fractal geometry theory, four fractal dimension calculation models of coal and rock were established, after which the pore structure characteristic parameters were used to calculate the fractal dimensions of the different coal seams. The results show that (1) the low-permeability coal seam in the coalfield of South Junger Basin in Xinjiang belongs to mesoporous medium, with a certain number of large pores and no micropores. The varying adsorption capacities of the different coal seams were positively correlated with pore volume, surface area, and the mesoporous surface area proportions, from which it was concluded that mesopores were the main contributors to pore adsorption in low-permeability coal seams. (2) The raw coal pore fractal dimension had a negative linear relationship to average pore size, a positive linear relationship with total pore volume, total surface area, and adsorption capacity, and a positive correlation with the mesoporous surface area proportion; that is, the higher the fractal dimension, the larger the pore volume and surface area of the raw coal. (3) The permeability of the low-permeability coal seam had a phase correlation with the micropore development degree; that is, the permeability had a phase negative correlation with the pore distribution fractal dimension, and there was a positive correlation between permeability and porosity. These results are of theoretical significance for the clean exploitation of low-permeability coal seam resources.

COAL SEAM DEGASIFICATION IN QUEENSLAND UTILISING HYDRAULIC FRACTURING WITH FOAM—A CASE HISTORY

1981 ◽  
Vol 21 (1) ◽  
pp. 137
Author(s):  
B. Wilkinson ◽  
L. Barro
Keyword(s):  
Gas Flow ◽  
Gas Production ◽  
Low Permeability ◽  
Gas Flow Rate ◽  
Coal Seams ◽  
Flow Rates ◽  
Coal Deposits ◽  
Early Production ◽  
Design Calculations ◽  
Gas Bearing

Vast reserves of gas-bearing coal deposits are located in Queensland. Owing to the extremely low permeability and porosity of the coal, very low gas flow rates are normally encountered. In an effort to enhance the gas production to economic quantities and to degasify the coal to provide a safer mining environment, four experimental wells were drilled into coal seams near Blackwater, Queensland.Based on extensive laboratory testing of coal samples, computerised fracture design calculations were performed to determine a suitable stimulation programme. The wells were hydraulically fractured with up to 15 000 US gal of foamed stimulation fluid containing 75 per cent nitrogen. To prop open the induced fracture system, 15 000 lb of sand was pumped with the foam. The maximum concentration was eight pounds of 20-40 mesh sand per gallon of fluid. Gas production from the unstimulated wells was too low to measure. Early production data soon after the fracturing suggested a gas flow rate of approximately 50 Mcf/D.

COALBED METHANE RESOURCES IN THE PERMIAN OF EASTERN AUSTRALIA AND THEIR TECTONIC SETTING

1993 ◽  
Vol 33 (1) ◽  
pp. 161 ◽  
Author(s):  
S. Miyazaki ◽  
R.J. Korsch
Keyword(s):  
Coalbed Methane ◽  
Tectonic Setting ◽  
Temporal Distribution ◽  
Low Permeability ◽  
Burial History ◽  
Coal Seams ◽  
Methane Drainage ◽  
Eastern Australia ◽  
Permian Coal ◽  
Coal Measures

The Bowen and Sydney Basins in eastern Australia contain vast coal resources which provide a source for coalbed methane. Through studies of the spatial and temporal distribution of the sedimentary packages, the structural geometry and tectonic setting of the sedimentary packages, and the maturation and burial history, the Australian Geological Survey Organisation (AGSO) is mapping the distribution and structural styles of the sources of methane, in particular, the Late Permian coal measures. AGSO's results from the Bowen Basin show at least two distinctly different structural styles of potential targets for coalbed methane drainage: on the Comet Ridge, the Permian coal measures are essentially subhorizontal and tectonically undisturbed, whereas in the western Taroom Trough, the coal measures are folded into a series of anticlines, each of which occurs above a thrust fault which in turn forms part of an imbricate thrust fan. Both of these styles occur at depths of less than 1000 m.Calculations by the Bureau of Resource Sciences (BRS) indicate that the inferred coalbed methane resources-in-place are 62 trillion cubic feet (1760 billion m3) for Australia, in which the Bowen and Sydney Basins are currently the only potential provinces of coalbed methane. The low permeability of the coal seams hinders attempts to utilise this vast amount of energy resources.Further exploration is necessary to delineate commercially feasible areas. This delineation is the only process that will be able to determine demonstrated coalbed methane resources.

scholarly journals Experimental Study on Adsorption Pore Structure and Gas Migration of Coal Reservoir Using Low-Field Nuclear Magnetic Resonance

2020 ◽  
Vol 2020 ◽  
pp. 1-9
Author(s):  
Jiazhuo Li ◽  
Penghui Guo ◽  
Wenhao Xie ◽  
Jiaqi Chu ◽  
Zhiqiang Yin ◽  
...  
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Pore Structure ◽  
Methane Adsorption ◽  
Gas Pressure ◽  
Low Permeability ◽  
Coal Seams ◽  
Low Field ◽  
Tectonic Coal

For the quantitative recognition and characterization of the flow characteristics of polymorphism coalbed gas in tectonic coal, experiments on pore morphology, pore diameter distribution, and methane adsorption law in outburst tectonic coal were carried out by field emission scanning electron microscopy and low-field nuclear magnetic resonance. The results revealed abundant round and dense “pyrolysis pores” in outburst tectonic coals, most of which were adsorption and seepage pores, with micropores accounting for 78.2%. Most pores were independent and formed the network pore space for gas enrichment and migration in outburst tectonic coal. The transverse relaxation time (T2) of methane adsorption in tectonic coal and crushed outburst tectonic coals presented three peaks, namely, adsorption, drifting, and free peaks. The isolation of nanopores and micropores revealed lower adsorption capacity of outburst tectonic coal than that of crushed outburst tectonic coal. The gas staged adsorption of raw coal with outburst tectonic low-permeability was observed. Under low gas pressure, the T2 spectral peak area of methane adsorption increased remarkably, whereas that of desorbed methane increased slightly. As gas pressure was increased to a certain numerical value, the increment of methane adsorption decreased and tended to reach equilibrium. This finding reflected that methane adsorption tended to be saturated after gas pressure reached a certain value, but desorbed methane in isolated micropores increased quickly. The quantitative recognition and characterization of pore structure and gas adsorption in tectonic low-permeability outburst coal seams based on low-field magnetic resonance imaging provide an experimental method for gas exploitation in coal seams and the study and control of coal and gas outburst mechanism.

The Preventing Coal and Gas Outburst Technology of Middle Distance and Low Permeability and Upper Protective Layer

2013 ◽  
Vol 690-693 ◽  
pp. 3059-3067 ◽  
Author(s):  
Guo Wei Dong
Keyword(s):  
Protective Layer ◽  
Mining Area ◽  
Coal And Gas Outburst ◽  
Low Permeability ◽  
Control Effect ◽  
Coal Seams ◽  
Gas Outburst ◽  
Protection Layer ◽  
And Control ◽  
Layer Control

Protective layer mining is the main regional measures for control coal and gas outburst . According to the defects of the preventing coal and gas outburst technology of middle distance and low permeability and upper protective layer in western Shuicheng mining area, the coal seams coal and gas outburst original danger are analyzed and protective layer is choosed initially using gas geological theory,the choice upper protective layer feasibility is analyzed using protection layer theory. the preventing coal and gas outburst technology of middle distance and low permeability and upper protective layer control effect is studied by numerical simulation and spot investigation. The conclusions from this research：the preventing coal and gas outburst technology of middle distance and low permeability and upper protective layer can decrease coal and gas outburst prediction index and control coal and gas outburst; the coal seams coal and gas outburst original danger can be preliminarily evaluated and the evaluation result can provide the basis for protective layer choice; the preventing coal and gas outburst technology of middle distance and low permeability and upper protective layer can be applied in western marine-continental transitional facies coal measure strata.

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