Numerical investigation of temperature distribution and thermal damage of heterogeneous coal under liquid nitrogen freezing

Haifei Lin, Botao Li, Shugang Li, Lei Qin, Zongyong Wei, Pei Wang and Rongwei Luo

Energy, 2023, vol. 267, issue C

Abstract: As a new water-free fracturing fluid, liquid nitrogen (LN2) has been widely studied and applied in coalbed methane (CBM) production. The heterogeneity of the reservoir has a significant effect on the mechanical strength, heat transfer and damage form of coal. Herein, a thermal-mechanical-damage (TMD) model was proposed based on the damage mechanics and micro-element theories. The numerical results indicated that the surface temperature of the coal sample experienced a rapid drop when the coal sample first came into contact with LN2. Low-temperature and high thermal stress regions were generated on the surface of the specimen. As the LN2 freezing time increased, the low-temperature and high thermal stress regions gradually expanded into the specimen's interior. The temperature and stress changes in coal samples showed three main stages: stage I (the first 200 s) was a rapid cooling stage, stage II (200–4000 s) was a slow cooling stage, and stage III (after 4000 s) was a stable temperature stage. A higher initial coal sample temperature led to more significant instantaneous thermal stress, more serious damage and weaker mechanical properties. The findings would provide a theoretical basis for the LN2 fracturing in CBM extraction.

Keywords: LN2 freezing; Heterogeneity; TMD coupling Model; Temperature evolution; Thermal stress (search for similar items in EconPapers)
Date: 2023
References: View references in EconPapers View complete reference list from CitEc
Citations: View citations in EconPapers (3)

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Persistent link: https://EconPapers.repec.org/RePEc:eee:energy:v:267:y:2023:i:c:s036054422203479x

DOI: 10.1016/j.energy.2022.126592

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