Research on comprehensive CBM extraction technology and its applications in China's coal mines

Wang, Haifeng; Wang, Chenghao; Wang, Wei; Xu, Rui

doi:10.1016/j.jngse.2014.05.025

Cited by 69 publications

(49 citation statements)

References 5 publications

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“…The permeability and gas flow pattern of coal play significant roles in controlling methane production of coal reservoirs [1,2]. The permeability of coal is greatly affected by the degree of damage, which is related to the deformation of coal [3,4].…”

Section: Introductionmentioning

confidence: 99%

Stress and Damage Induced Gas Flow Pattern and Permeability Variation of Coal from Songzao Coalfield in Southwest China

Cao

2016

Energies

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Abstract:The permeability of coal is a critical parameter in estimating the performance of coal reservoirs. Darcy's law describes the flow pattern that the permeability has a linear relationship with the flow velocity. However, the stress induced deformation and damage can significantly influence the gas flow pattern and permeability of coal. Coals from Songzao coalfield in Chongqing, southwest China were collected for the study. The gas flow velocities under different injection gas pressures and effective stresses in the intact coal and damaged coal were tested using helium, incorporating the role of gas flow pattern on the permeability of coal. The relationships between the flow velocity and square of gas pressure gradient were discussed, which can help us to investigate the transformation conditions of gas linear flow and gas nonlinear flow in the coal. The results showed that the gas flow in the intact coal existed pseudo-initial flow rate under low effective stress. The low-velocity non-Darcy gas flow gradually occurred and the start-up pressure gradient increased in the coal as the effective stress increased. The gas flow rate in the damaged coal increased nonlinearly as the square of pressure gradient increased under low effective stress. The instability of gas flow caused by high ratio of injection gas pressure over effective stress in the damaged coal contributed to the increase of the gas flow rate. As the effective stress increased, the increase of gas flow rate in coal turned to be linear. The mechanisms of the phenomena were explored according to the experimental results. The permeability of coal was corrected based on the relationships between the flow velocity and square of gas pressure gradient, which showed advantages in accurately estimating the performance of coal reservoirs.

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Section: Introductionmentioning

confidence: 99%

Stress and Damage Induced Gas Flow Pattern and Permeability Variation of Coal from Songzao Coalfield in Southwest China

Cao

2016

Energies

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“…In 2015, total CBM production reached 18 billion m 3 , of which 13.6 billion m 3 was extracted underground, as shown in Figure 2. Underground gas extraction has an important role to play in the development of CBM resource in China [10][11][12]. It is well known that CBM extraction is strongly influenced by coal seam permeability, but seam permeability is low in most mining areas in China (10 −4 -10 −3 mD).…”

Section: Introductionmentioning

confidence: 99%

Research on Hydraulic Technology for Seam Permeability Enhancement in Underground Coal Mines in China

Cheng

Xia

et al. 2018

Energies

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Abstract:Coalbed methane (gas) is a high quality and clean resource, but it also causes disasters in coal mines in China. The low permeability of coal seams is the main reason that developing coalbed methane (CBM) as an energy resource is difficult, so increasing coal seam permeability is the key to CBM development in China. In this paper, the principal techniques for seam permeability enhancement are presented. The paper focuses on hydraulic technology for seam permeability enhancement (HTSPE), which is considered an economic and highly efficient technology for seam permeability enhancement. The process of HTSPE development is reviewed and the current status of the theories behind HTSPE and the technology and equipment for its use are summarized. The goal is to identify the gaps in HTSPE research and the problems in its implementation. In the future, integration and diversification of the technologies along with on-board intelligence and miniaturization may be the trends for the equipment. Finally, it is shown that tree-shaped borehole fracturing can be used to develop CBM in underground coal mines. This study could be used as a valuable example for other coal deposits being mined under similar geological conditions.

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“…Coal-bed methane (CBM), a potential natural gas resource, is abundant in Chinese coal seams. Pre-extracting gas before coal mining can control gas emissions and has a positive influence on economic development and the environment [7].…”

Section: Introductionmentioning

confidence: 99%

Damage Effects and Fractal Characteristics of Coal Pore Structure during Liquid CO2 Injection into a Coal Bed for E-CBM

Wei

et al. 2018

Resources

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Pore structure has a significant influence on coal-bed methane (CBM) enhancement. Injecting liquid CO 2 into coal seams is an effective way to increase CBM recovery. However, there has been insufficient research regarding the damage effects and fractal characteristics of pore structure at low temperature induced by injecting liquid CO 2 into coal samples. Therefore, the methods of low-pressure nitrogen adsorption-desorption (LP-N 2 -Ad) and mercury intrusion porosimetry (MIP) were used to investigate the damage effects and fractal characteristics of pore structure with full aperture as the specimens were frozen by liquid CO 2 . The adsorption isotherms revealed that the tested coal samples belonged to type B, indicating that they contained many bottle and narrow-slit shaped pores. The average pore diameter (APD; average growth rate of 18.20%), specific surface area (SSA; average growth rate of 7.38%), and total pore volume (TPV; average growth rate of 18.26%) increased after the specimens were infiltrated by liquid CO 2 , which indicated the generation of new pores and the transformation of original pores. Fractal dimensions D 1 (average of 2.58) and D 2 (average of 2.90) of treated coal samples were both larger the raw coal (D 1 , average of 2.55 and D 2 , average of 2.87), which indicated that the treated specimens had more rough pore surfaces and complex internal pore structures than the raw coal samples. The seepage capacity was increased because D 4 (average of 2.91) of the treated specimens was also higher than the raw specimens (D 4 , average of 2.86). The grey relational coefficient between the fractal dimension and pore structure parameters demonstrated that the SSA, APD, and porosity positively influenced the fractal features of the coal samples, whereas the TPV and permeability exerted negative influences.

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Research on comprehensive CBM extraction technology and its applications in China's coal mines

Cited by 69 publications

References 5 publications

Stress and Damage Induced Gas Flow Pattern and Permeability Variation of Coal from Songzao Coalfield in Southwest China

Stress and Damage Induced Gas Flow Pattern and Permeability Variation of Coal from Songzao Coalfield in Southwest China

Research on Hydraulic Technology for Seam Permeability Enhancement in Underground Coal Mines in China

Damage Effects and Fractal Characteristics of Coal Pore Structure during Liquid CO2 Injection into a Coal Bed for E-CBM

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