Ma Shujun, Wang Zhaofeng, Yue Jiwei, An Fenghua, Chen Haidong
School of Safety Science and Engineering, Henan Polytechnic University, Jiaozuo, Henan, 454000, China.
MOE Engineering Center of Mine Disaster Prevention and Rescue, Jiaozuo, Henan, 454000, China.
Heliyon. 2024 Jul 6;10(14):e34207. doi: 10.1016/j.heliyon.2024.e34207. eCollection 2024 Jul 30.
When the drilling core method is used to determine the coalbed gas content, the cutting heat generated by the core bit cutting coal will increase the core tube temperature, and the excessively high core tube temperature will have an heating effect on the coal core, which will accelerate the coal core gas desorption rate and increase the gas loss amount. The generation of cutting heat of core bit and the measurement of core tube temperature are the basis for grasping the gas desorption law of coal core and projecting the amount of gas loss. Firstly, the self-developed core tube temperature measurement device was used to conduct on-site core temperature measurement experiments at different cutting speeds. Then, the cutting temperature of core bit was solved by establishing thermodynamic model for cutting coal and heat transfer model of cutting edge. Finally, based on the thermal conductivity characteristics of the core tube, the core tube temperature at different cutting speeds was simulated, and the simulated temperature was compared with the on-site measured temperature to verify the reliability of the model. The results show that when coring in primary structural coal, the temperature change trend of core tube wall temperature measurement point at different cutting speeds is basically consistent, the temperature measurement point at the front end of the core tube mainly goes through a relatively stable period in the drilling process, a sharp rising period in the cutting process, a slow rise and cooling period in the withdrawal process. However, the temperature measurement point at the back end of the core tube wall mainly goes through a relatively stable phase and a slowly increasing phase. The temperature rise of the core bit and the core tube wall are significantly positively correlated with the cutting speed. When coring in hard coal seam and the core depth is not large, the cutting heat generated by the core bit and the coal body is the dominant factor for the temperature rise of the core tube. The core tube wall temperature calculated using the model matches well with the field measured temperature, and the error is small, which fully shows that the coring thermodynamic model is feasible. This study provides a basis for further research on the dynamic distribution characteristic of coal core temperature during coring, which is of profound significance to calculate the gas loss and coalbed gas content.
采用钻芯法测定煤层气含量时，岩芯钻头切割煤体产生的切削热会使岩芯管温度升高，过高的岩芯管温度会对煤芯产生热作用，加速煤芯瓦斯解吸速率并增加瓦斯损失量。岩芯钻头切削热的产生及岩芯管温度的测定是掌握煤芯瓦斯解吸规律、推算瓦斯损失量的依据。首先，利用自行研制的岩芯管温度测量装置，在不同钻进速度下进行现场岩芯温度测量实验。然后，通过建立煤体切削热力学模型和刃口传热模型求解岩芯钻头的切削温度。最后，基于岩芯管的导热特性，模拟不同钻进速度下的岩芯管温度，并将模拟温度与现场实测温度进行对比，验证模型的可靠性。结果表明，在原生结构煤中取芯时，不同钻进速度下岩芯管壁测温点的温度变化趋势基本一致，岩芯管前端测温点在钻进过程中主要经历相对稳定期、切削过程中的急剧上升期、提钻过程中的缓慢上升及冷却期。而岩芯管后端管壁测温点主要经历相对稳定阶段和缓慢上升阶段。岩芯钻头及岩芯管壁温度升高与钻进速度呈显著正相关。在硬煤层取芯且岩芯深度不大时，岩芯钻头与煤体产生的切削热是岩芯管温度升高的主导因素。利用该模型计算得到的岩芯管壁温度与现场实测温度吻合较好，误差较小，充分表明取芯热力学模型可行。该研究为进一步研究取芯过程中煤芯温度动态分布特征提供了依据，对计算瓦斯损失量和煤层气含量具有重要意义。
