Study on heat transfer effect of high-temperature nitrogen seepage in low-permeability coal

ABSTRACT

High-temperature nitrogen injection into the low permeability coal can be used to improve the efficiency of coalbed methane extraction effectively. In order to study the heat transfer effect of High-temperature nitrogen seepage in low-permeability coal, a coupled hydro-thermo-mechanical model of High-temperature nitrogen injection into coal is established. On this basis, by using COMSOL Multiphysics numerical software to numerically solve the coupled model, the results show that: the higher the High-temperature nitrogen temperature is, the more favorable the heat diffusion of N₂ will be. The High-temperature nitrogen pressure and the initial coal permeability have few effects on the heat transfer. The longer time of High-temperature nitrogen injection is, the greater influence range of heat transfer becomes, but the influence gradually decreases. In addition, the larger borehole diameter is, the greater influence is, but the influence is limited. Under the condition of 4MPa, 100°C and 20 days of heat injection, the gas recovery concentration is up to 98%. The research results can guide the field test of High-temperature nitrogen injection into coal seam.

THE HIGHLIGHTS OF THIS WORK CAN BE PRESENTED AS

1. The N₂ pressure and the initial coal permeability have little influence on the heat transfer

2. The longer time of N2 injection is, the larger effect range of heat transfer becomes

3. The larger borehole diameter is, the more obvious effect of heat transfer is

4. The higher the nitrogen temperature is, the greater the recovered methane concentration is

KEYWORDS:

• CBM extraction
• high-temperature nitrogen injection
• a coupled HTM model
• heat transfer effect
• methane recovery rate

Acknowledgements

The work presented in this paper is financially supported by the Natural Science Foundation of the Jiangsu Higher Education institutions of China (No.22KJD440002); Funded by the Basic Science (Natural Science) Research Project of Colleges and Universities in Jiangsu Province (23KJA620004); the Science and Technology Deputy General Project in Jiangsu Province, China(FZ20220397); the Industry-university -research Cooperation Project in Jiangsu Province, China (BY2022771);the National Natural Science Foundation of China (52004285; 12202353); the Third Level Training Object of the Sixth “333 High-level Talent Training Project” in Jiangsu Province, China; Supported by the Hebei Key Laboratory of Mine Intelligent Unmanned Mining Technology (North China Institute of Science and Technology).

Disclosure statement

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

Author contributions

Conceptualization: Shengcheng Wang: Conceptualization, Methodology, Soft- ware, Writing-original draft preparation. Shanjie Su: Visualization, Investigation, Writing – original draft. Teng Teng& Liu Jia & Lanying Huang: Conceptualization. Haijian Li& Xuan Jiang: Supervision, Writing – review & editing.

Statements and declarations

Conflict of Interest The authors declared that there is no conflict of interest.

Additional information

Funding

The work was supported by the National Natural Science Foundation of China [12202353]; Natural Science Fund for Colleges and Universities in Jiangsu Province [No.22KJD440002]; the Industry-university-research Cooperation Project in Jiangsu Province, China [BY2022771]; the Science and Technology Deputy General Project in Jiangsu Province, China [FZ20220397].