Engineering practice of underground heat injection-enhanced gas extraction in low-permeability coal seams

ABSTRACT

The heat injection mechanism for improving gas desorption, coal seam gas pressure, and coal seam permeability in the Yangquan mining area was investigated via theoretical analysis. This analysis was conducted to address the problems of poor permeability, difficult gas extraction, and low extraction efficiency of 15# coal seam. An underground heat injection-enhanced gas extraction technology was proposed; accordingly, a heat injection-enhanced gas extraction system was developed and appropriate extraction methods were devised. The findings of an industrial test on 15# coal seam in the coal mine show that the proposed technology not only increased the amount of gas extracted but also halved the extraction time and realized efficient gas extraction. Two mature underground heat injection-enhanced gas extraction methods were established. These methods have similar gas production principles in that the gas production speed and gas concentration in the heat injection stage are relatively low, while the average degree of improvement in the extraction stage after heat injection can reach more than 50 times. The average degree of improvement in gas production speed and gas concentration after the second heat injection is greater than that after the first.

KEYWORDS:

• Low-permeability coal seam
• heat injection-enhanced gas extraction
• rapid extraction
• alternate heat injection
• cyclic heat injection

Acknowledgments

This work was supported by the National Natural Science Foundation of China (Young Scientist’s Fund No. 12102293).

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was supported by the National Natural Science Foundation of China [12102293].

Notes on contributors

Linjie Hu

Linjie Huis is a Ph.D. candidate at Taiyuan University of Technology, main engaged in coalbed methane recovery.

Zengchao Feng

Zengchao Feng is a professor at Taiyuan University of Technology. He is engaged in teaching and research in the fields of mining engineering and rock mechanics.

Dong Zhou

Dong Zhou is an associate professor at Taiyuan University of Technology, mainly engaged in the exploration and development of coalbed methane.

Xing Wang

Xing Wang is a Ph.D. candidate at Taiyuan University of Technology, specializing in coalbed methane recovery.

Dong Zhao

Dong Zhao is an associate professor at Taiyuan University of Technology, mainly engaged in the exploration and development of coalbed methane.