scholarly journals Mechanism of Increasing the Permeability of Water-Bearing Coal Rock by Microwave Steam Explosion

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-13
Author(s):  
Qi Qi ◽  
Weiming Guan ◽  
Xin Li ◽  
Yanyan Ge ◽  
Senlin Nan ◽  
...  
Keyword(s):  
Coalbed Methane ◽  
Steam Explosion ◽  
Ideal Gas ◽  
Gas Pressure ◽  
Water Evaporation ◽  
Heating Process ◽  
Extraction Technology ◽  
Heated Sample ◽  
Coal Rock ◽  
Water Contents

Microwave heating of water-bearing coal can promote pore water evaporation. The pores are broken under the action of steam pressure, increasing the permeability of the coal. This study is aimed at investigating the mechanism of permeability improvement of water-bearing coal rock by microwave steam explosion. First, a microwave oven was used to irradiate and heat five groups of coal rock with different water contents; the NMR test was then conducted on the heated sample. Second, the internal vapor pressure and temperature changes during the heating process were obtained through the T-connector for samples with different water contents. Finally, a numerical experiment was used to explore the deformation characteristics of pores under three filling conditions. The experimental results showed that the total porosity increased significantly when the water content of coal increased from 0% to 8%, while the permeability increased by nearly 4.78 times. The extreme value of gas pressure inside the sample showed an increasing trend. The gas pressure and temperature were in line with the equation of state for an ideal gas during the rising phase. Numerical experiments showed that the pore boundary shrunk inward under vacuum conditions, and compressive stress appeared at the tip. The saturated humid air and liquid water conditions expanded the pore boundaries outward and caused tensile stress at the tip, with the latter being nearly 2.3 times larger than the former, making it more conducive to the development of pores. The findings of this study can be used as a reference value for the expansion of coalbed methane extraction technology.

Elementary derivation of the ideal gas pressure

1975 ◽  
Vol 43 (1) ◽  
pp. 109-110
Author(s):  
Mitja Kregar
Keyword(s):  
Ideal Gas ◽  
Gas Pressure ◽  
Elementary Derivation ◽  
The Ideal

scholarly journals Coupled Effects of Stress, Moisture Content and Gas Pressure on the Permeability Evolution of Coal Samples: A Case Study of the Coking Coal Resourced from Tunlan Coalmine

Water ◽  
2021 ◽  
Vol 13 (12) ◽  
pp. 1653
Author(s):  
Guofu Li ◽  
Yi Wang ◽  
Junhui Wang ◽  
Hongwei Zhang ◽  
Wenbin Shen ◽  
...  
Keyword(s):  
Moisture Content ◽  
Coalbed Methane ◽  
Gas Permeability ◽  
Axial Stress ◽  
Gas Pressure ◽  
Pressure Curve ◽  
Permeability Evolution ◽  
Confining Stress ◽  
Qinshui Basin ◽  
Gas Seepage

Deep coalbed methane (CBM) is widely distributed in China and is mainly commercially exploited in the Qinshui basin. The in situ stress and moisture content are key factors affecting the permeability of CH4-containing coal samples. Therefore, considering the coupled effects of compressing and infiltrating on the gas permeability of coal could be more accurate to reveal the CH4 gas seepage characteristics in CBM reservoirs. In this study, coal samples sourced from Tunlan coalmine were employed to conduct the triaxial loading and gas seepage tests. Several findings were concluded: (1) In this triaxial test, the effect of confining stress on the permeability of gas-containing coal samples is greater than that of axial stress. (2) The permeability versus gas pressure curve of coal presents a ‘V’ shape evolution trend, in which the minimum gas permeability was obtained at a gas pressure of 1.1MPa. (3) The gas permeability of coal samples decreased exponentially with increasing moisture content. Specifically, as the moisture content increasing from 0.18% to 3.15%, the gas permeability decreased by about 70%. These results are expected to provide a foundation for the efficient exploitation of CBM in Qinshui basin.

scholarly journals Induction of Changes in Internal Gas Pressure of Bulky Plant Organs by Temperature Gradients

1990 ◽  
Vol 115 (2) ◽  
pp. 308-312 ◽  
Author(s):  
Kenneth A. Corey ◽  
Zhi-Yi Tan
Keyword(s):  
Bath Temperature ◽  
Ideal Gas ◽  
Gas Pressure ◽  
Temperature Gradients ◽  
Maximum Pressure ◽  
Plant Organs ◽  
Ideal Gas Law ◽  
Increasing Temperature ◽  
Pressure Changes

Water manometers were connected to fruits of tomato (Lycopersicon esculentum Mill.) and pepper (Capsicum annuum L.), and then fruits were submerged in water baths providing initial temperature gradients between fruit and water of 0 to 19C. Apple (Malus domestics Borkh.) fruits, carrot (Daucus carota L.) roots, witloof chicory (Cichorium intybus L.) roots, rhubarb Rheum rhabarbarum L.) petioles, and pokeweed (Phytolacca americana L.) stems were subjected to water bath temperature gradients of 5C. Internal partial vacuums developed in all organs within minutes of imposing the gradients. The maximum partial vacuums in tomato and pepper fruits increased with increasing temperature gradients. Uptake of water accompanied changes in internal pressure reaching maxima of 17% (w/w) and 2% (w/w) of pepper and tomato fruits, respectively, after 22 hours. Maximum pressure changes achieved in bulky organs deviated from those predicted by the ideal gas law, possibly due to concomitant changes in gas pressure upon replacement of intercellular spaces with water and dissolution of CO2. Partial vacuums also developed in pepper fruits, rhubarb petioles, and pokeweed stems following exposure to air 15C cooler than initial organ temperatures. Results point to the role of temperature gradients in the transport of liquids and gases in plant organs.

Effect of Process Parameters on the Adsorption of Chromium VI on a Packed Bed Column (PBC) using Vetiver (Vetiveria zizanioides)

2021 ◽  
Vol 25 (12) ◽  
pp. 53-59
Author(s):  
Pejavara Narayana Gururaj ◽  
Kulathooran Ramalakshmi ◽  
Sureshkumar Sujithra ◽  
Ravichandran Shalini
Keyword(s):  
Process Parameters ◽  
Oxygen Demand ◽  
Packed Bed ◽  
Heating Process ◽  
Tannery Effluent ◽  
Vetiveria Zizanioides ◽  
Experimental Conditions ◽  
Heated Sample ◽  
Packed Bed Column ◽  
Chromium Vi

The objective of this study is to evaluate the different process parameters on adsorption of chromium VI on a packed bed column using Vetiver (Vetiveria zizanioides) and to examine the effect of pH, Chemical Oxygen Demand (COD) and Biological Oxygen Demand (BOD) at a constant contact time of 10 minutes at a temperature of 40 ºC under two experimental conditions namely, tannery effluent with and without microwave treatment. The results revealed that microwave heating process had a higher impact on chromium (VI) adsorption than normal heating process. The pH values of microwave treated sample were found to be 6.65±0.65 when compared to normal heated sample where the pH was 4.62±0.72 when compared to the initial pH of effluent found to be 3.47±0.58. Further, a threefold reduction in BOD and COD values was observed in microwave treated vetiver sample which was around 86.73±1.43 and 107.90±2.82 mg/l respectively when compared to normal heated sample (250±1.45 and 200±2.65 mg/l respectively) and untreated effluent (780±2.53 and 920±3.86 mg/l respectively) which indicated the reduction of chromium VI present in the effluent water. It was also observed that the metal adsorption capacity of the vetiver powder and the adsorption characteristics were positively correlated with the FTIR and SEM analysis which confirmed the presence of chromium (VI) on the surface of vetiver.

scholarly journals Model development and analysis of coal permeability based on the equivalent characteristics of dual-porosity structure

2019 ◽  
Vol 17 (2) ◽  
pp. 313-327
Author(s):  
Haijun Guo ◽  
Kai Wang ◽  
Yuanping Cheng ◽  
Liang Yuan ◽  
Chao Xu
Keyword(s):  
Coalbed Methane ◽  
Model Development ◽  
Gas Pressure ◽  
Dual Porosity ◽  
Permeability Evolution ◽  
Evolution Law ◽  
Fracture Width ◽  
Coal Permeability ◽  
Porosity Structure ◽  
Gas Seepage

Abstract Mining is a dynamic fracture process of coal and/or rock. The structural failure of coal bodies will change the coal matrix-fracture characteristics and then affect the distribution characteristics of the coalbed methane (CBM). Because of the structural complexity of coal, the coal matrices and fractures will be assumed to the geometries with rule shapes when the gas seepage characteristics in coals are analyzed. The size of the simplified geometries is the equivalent scale of dual-porosity coal structures (i.e. the equivalent fracture width and equivalent matrix scale). In this paper, according to the reasonable assumptions with regarding to dual-porosity coal structures, a new coal permeability evolution model based on the equivalent characteristics of dual-porosity structure (ECDP model) was built and the effect of the equivalent characteristics of dual-porosity structure on the coal permeability evolution law was analyzed. It is observed that if the initial fracture porosity is constant and the equivalent matrix scale increases, the range in which the permeability of coal rises with rising gas pressure increases; if the equivalent fracture width decreases and the equivalent matrix scale is constant, the range in which the permeability of coal rises with rising gas pressure decreases. The ECDP model is more suitable for revealing the evolution law of the coal permeability when large deformations occur in the coal bodies and/or the coal structure is damaged irreversibly, especially during enhancing CBM recovery.

scholarly journals Experimental Investigation on Mechanics and Seepage Characteristics of Tectonic and Intact Coal Containing Gas

2020 ◽  
Vol 10 (20) ◽  
pp. 7290
Author(s):  
Chaolin Zhang ◽  
Enyuan Wang ◽  
Jiang Xu ◽  
Shoujian Peng
Keyword(s):  
Coalbed Methane ◽  
Triaxial Compression ◽  
Coal Mines ◽  
Gas Pressure ◽  
Extraction Time ◽  
Gas Extraction ◽  
Effective Measure ◽  
Pressure Stage ◽  
Tectonic Coal ◽  
Seepage Characteristics

Coalbed methane is a double-edged sword with two attributes of energy and hazard in coal mines. Gas drainage is the most direct and effective measure for gas recovery and disaster prevention in coal mines, which is seriously affected by the mechanics and seepage characteristics of coal. In this work, we experimentally simulated the triaxial compression and gas depletion processes using both tectonic coal and intact coal. The mechanics and seepage characteristics of tectonic and intact coal under the coupling effect of stress and gas pressure were analyzed and compared. The results show that during the triaxial compression, the damage stress and peak stress of tectonic coal is only half that of intact coal, while their compaction stress or residual stress are almost the same. Meanwhile, the permeability recovery value after tectonic coal failure is very limited, even smaller than that of intact coal, although its primary permeability is much larger than that of intact coal. On the contrary, the permeability recovery value after intact coal failure is more than twice of its primary permeability. During the gas depletion, the rebound gas pressure of tectonic coal is smaller than that of intact coal, and the permeability of tectonic coal is one order of magnitude larger than that of intact coal before the gas pressure drops to 2 MPa. The broken of tectonic coal and the low permeability of intact coal may be the two principal reasons. Therefore, in the tectonic coal area, the gas extraction time at high gas pressure stage should be stabilized, while in the intact coal area, the gas extraction time at low gas pressure stage should be increased, and the coal permeability enhancement measures should be combined to achieve the goal of high and stable production of coalbed methane.

Dynamic behavior of gas pressure and optimization of borehole length in stress relaxation zone during coalbed methane production

Fuel ◽  
2018 ◽  
Vol 233 ◽  
pp. 816-824 ◽  
Author(s):  
Chaolin Zhang ◽  
Jiang Xu ◽  
Shoujian Peng ◽  
Qixian Li ◽  
Fazhi Yan ◽  
...  
Keyword(s):  
Stress Relaxation ◽  
Dynamic Behavior ◽  
Methane Production ◽  
Coalbed Methane ◽  
Gas Pressure ◽  
Relaxation Zone ◽  
Coalbed Methane Production

Non-uniform Distributions of Gas Pressure and Coal Permeability in Coalbed Methane Reservoirs Induced by the Loess Plateau Geomorphology: A Case Study in Ordos Basin, China

2019 ◽  
Vol 29 (3) ◽  
pp. 1639-1655
Author(s):  
Qingquan Liu ◽  
Peng Chu ◽  
Congmeng Hao ◽  
Yuanping Cheng ◽  
Haifeng Wang ◽  
...  
Keyword(s):  
Loess Plateau ◽  
Coalbed Methane ◽  
Ordos Basin ◽  
Gas Pressure ◽  
The Loess Plateau ◽  
Coal Permeability ◽  
Uniform Distributions

scholarly journals CBM exploration: Permeability of coal owing to cleat and connected fracture

2021 ◽  
pp. 014459872110571
Author(s):  
Zhigang Du ◽  
Yawen Tao ◽  
Xiaodong Zhang ◽  
Wuxiu Ding ◽  
Qiang Huang
Keyword(s):  
Coalbed Methane ◽  
Gas Pressure ◽  
Molecular Flow ◽  
Target Area ◽  
Reservoir Pressure ◽  
Gas Migration ◽  
Fracture Permeability ◽  
Klinkenberg Effect ◽  
Linear Flow ◽  
Cbm Production

Coalbed methane (CBM) resources cannot be efficiently explored and exploited without a robust understanding of the permeability of fracture-size heterogeneities in coal. In this study, two sister coal samples were imparted with pre-developed cleat and connected fractures, and the permeability of the coal samples was measured under different conditions of controlled confining and gas pressures. Furthermore, the implications of the results for CBM exploration and exploitation were discussed. The permeability of coal with cleat development ranged from 0.001–0.01 mD, indicating ultra-low permeability coal. The gas migration in this coal changed from a linear flow to a non-linear flow, with the increase in gas pressure (>1 MPa). Thus, the permeability of the coal initially increased and then decreased. However, the Klinkenberg effect does not exist in this ultralow-permeability coal. For the coal sample with connected fracture, permeability ranged from 0.1–10 mD, which is larger by hundred orders of magnitude than that of the sample with cleat. For this coal, with a decrease in gas pressure (<1 MPa), the Klinkenberg effect significantly increased the permeability of the coal. With an increase in the applied confining pressure, both the Klinkenberg coefficient and permeability of the coal presented a decreasing trend. It is suggested that field fracture investigation is a prerequisite and indispensable step for successful CBM production. The coal beds that cleat network is well conductive to the connected fracture can be an improved target area for CBM production. During CBM production, a variety of flow regimes are available owing to the decrease in CBM reservoir pressure. In particular, under the low CBM reservoir pressure and low in situ geo-stress conditions, the gas migration in the CBM reservoir with connected facture development exhibits remarkable free-molecular flow. Thus, the reservoir permeability and predicted CBM production will be enhanced.

Ideal gas pressure bath: a method for applying hydrostatic pressure in the computer simulation of nanoparticles

2006 ◽  
Vol 104 (22-24) ◽  
pp. 3709-3715 ◽  
Author(s):  
M. Grünwald ◽  
C. Dellago
Keyword(s):  
Computer Simulation ◽  
Hydrostatic Pressure ◽  
Ideal Gas ◽  
Gas Pressure
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