Unidirectional apparent diffusion-permeability model of gas in matrix micro-pores of low permeability coal seam

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.

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Research and practice on fluctuation water injection technology at low permeability coal seam

Safety Science ◽

10.1016/j.ssci.2011.08.021 ◽

2012 ◽

Vol 50 (4) ◽

pp. 851-856 ◽

Cited By ~ 65

Author(s):

Wei-min Cheng ◽

Wen Nie ◽

Gang Zhou ◽

Yanbin Yu ◽

Youying Ma ◽

...

Keyword(s):

Coal Seam ◽

Water Injection ◽

Low Permeability ◽

Research And Practice ◽

Injection Technology

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Study on the stress relief and permeability increase in a special low-permeability thick coal seam to stimulate gas drainage

Energy Sources Part A Recovery Utilization and Environmental Effects ◽

10.1080/15567036.2019.1602211 ◽

2019 ◽

Vol 42 (8) ◽

pp. 1001-1013 ◽

Cited By ~ 2

Author(s):

Rong Zhang ◽

Yuanping Cheng ◽

Liang Yuan

Keyword(s):

Coal Seam ◽

Stress Relief ◽

Low Permeability ◽

Gas Drainage ◽

Thick Coal Seam ◽

Permeability Increase

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Experimental Study on Deep Borehole Pre-Cracking Blasting of Drilling through Strata at Low Permeability Seam

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.868.339 ◽

2013 ◽

Vol 868 ◽

pp. 339-342

Author(s):

Jian Liu ◽

Qian Le

Keyword(s):

Coal Seam ◽

Control Area ◽

Low Permeability ◽

Gas Extraction ◽

Test Results ◽

Deep Borehole ◽

Coal Seam Gas ◽

Gas Concentration ◽

Working Face ◽

Outburst Coal Seam

In the process of roadway excavation in the low permeability outburst coal seam, with drilling through strata in the bottom drainage roadway extracting coal seam gas of control area. In order to improve extraction effect, the method that deep borehole pre-cracking blasting is used to increase the permeability of coal in the drilling through strata seam segment is proposed. The calculation formula on crushing circle and crack circle radius of deep borehole pre-cracking blasting are derived, and the effective loosening radius of blasting is calculated in theory, the research achievements are applied to field test, the test results show that deep borehole pre-cracking blasting permeability improvement technology is carried out in the drilling through strata of the low permeability outburst coal seam, the permeability of coal seam is improved by 180 times, the gas extraction scalar is raised by 8-10 tomes, during the process of roadway excavation, gas concentration of the working face is 0.2%-0.3%, and tunneling footage is increased by 2 times.

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Assessment of NPV Uncertainty on Heterogeneous Reservoirs during Polymer Flood

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.448-453.4033 ◽

2013 ◽

Vol 448-453 ◽

pp. 4033-4037 ◽

Cited By ~ 1

Author(s):

Kyung Wan Yu ◽

Byung In Choi ◽

Kun Sang Lee

Keyword(s):

Net Present Value ◽

Water Saturation ◽

Polymer Flooding ◽

Water Flooding ◽

Low Permeability ◽

Oil Viscosity ◽

Permeability Model ◽

Heterogeneous Reservoirs ◽

Polymer Flood ◽

Porosity And Permeability

This study shows net present value (NPV) distribution by considering uncertainties in porosity, oil viscosity, water saturation, and permeability for polymer flood with Monte Carlo simulation. For high and low average permeability conditions, differences of NPV between polymer flooding and water flooding have been investigated. According to results both average NPV and range of NPV distribution tend to increase with porosity and permeability in all cases. Although water saturation and oil viscosity affect NPV, they are not important parameters that conclude uncertainty of NPV under the conditions considered in this study. For high permeability model which has Dykstra-Parsons coefficient (DP) as 0.72 and porosity as 0.3088, Monte Carol simulations for polymer flood show that 50th percentile (P50) of NPV is 352.81 M$. If porosity is decreased from 0.3088 to 0.1912, the P50 is also decreased 63.8 %. The reduction of NPV during polymer flooding in low permeability reservoirs are almost 40 % higher than that of water flood. These differences come from polymer adsorption and permeability reduction that easily occurs in low permeability zone. The procedure has proven to be useful tool to generate probability distribution of NPV when polymer flood is selected as a tertiary flood process.

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Study on Methods of Exploring the Loosening Radius of Deep-Hole Controlling Blasting

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.734-737.650 ◽

2013 ◽

Vol 734-737 ◽

pp. 650-655

Author(s):

Wen Qing Zhang ◽

Jian Liu

Keyword(s):

Theoretical Analysis ◽

Coal Seam ◽

Gas Flow ◽

Critical Factor ◽

Field Investigation ◽

Flow Index ◽

Low Permeability ◽

Deep Hole ◽

Deep Borehole ◽

Outburst Coal Seam

Deep borehole controlling blasting is one of the most popular methods which used to improve permeability of low permeability and highly gassy coal seam. Proper interval between blasting hole is the critical factor. On this paper, the theory and insufficiency of each method are discussed by theoretical analysis and field investigation. The result shows that, because of the complexity of outburst coal seam, the measuring result got by different methods is relative and declinational. We need to make a right choice according to the actual demand. And the method of gas flow index is quickly, visual and reliable, which to be worth paying the utmost attention to.

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