张和伟,申建,李可心,等. 不同煤组成与分布差异传热特征及其机理[J]. 煤炭学报,2023,48(6):2519−2529. DOI: 10.13225/j.cnki.jccs.2023.0203
引用本文: 张和伟,申建,李可心,等. 不同煤组成与分布差异传热特征及其机理[J]. 煤炭学报,2023,48(6):2519−2529. DOI: 10.13225/j.cnki.jccs.2023.0203
ZHANG Hewei,SHEN Jian,LI Kexin,et al. Differential heat transfer characteristics and mechanism of different coal composition and distribution[J]. Journal of China Coal Society,2023,48(6):2519−2529. DOI: 10.13225/j.cnki.jccs.2023.0203
Citation: ZHANG Hewei,SHEN Jian,LI Kexin,et al. Differential heat transfer characteristics and mechanism of different coal composition and distribution[J]. Journal of China Coal Society,2023,48(6):2519−2529. DOI: 10.13225/j.cnki.jccs.2023.0203

不同煤组成与分布差异传热特征及其机理

Differential heat transfer characteristics and mechanism of different coal composition and distribution

  • 摘要: 储层热诱导改造方法是提高煤层气单井产量的有效手段,其中不同煤组成与分布的传热差异性是煤储层热改造工程亟需解决的关键基础问题。以保德王家岭煤矿烟煤为对象,基于煤样宏观描述−显微镜−CT成像相结合的多尺度观测方法,精准识别并表征了显微组分空间分布特征。采用均匀平板加热−热成像采集实验系统表征了不同宏观煤岩类型样品动态传热过程,结合实验数据与热力学定律定量表征了显微组分热物性特征,揭示了显微组分组成与分布的差异传热机理。结果表明,传热过程中半亮煤温度呈双峰分布,暗淡煤呈单峰态,2者温度跨度均先减小后增大,半亮煤温度跨度显著宽于暗淡煤;镜煤+亮煤与暗煤+丝炭的占比越接近其温度差异越显著;根据温差演变特征将传热过程划分为快速升温、增速减缓、波动升温和动态平衡4个阶段。显微组分分布与温度展布对应关系显示,热传递受控于显微组成及其分布,矿物充填惰质组升温最快,形成高温区,惰质组一般形成次高温区,镜质组升温最慢呈低温态;此外,镜质组增温速率及平衡时温度与惰质组距离成反比。热物性定量分析显示,矿物充填惰质组具有较大的导热系数和热扩散系数,因而其传递热扰动的速度最快,达到热平衡用时最少,惰质组次之,镜质组最慢。热作用后煤中新生裂隙主要发育于镜质组中,多沿惰质组与镜质组交联处开裂,半亮煤裂缝热改造效果明显强于暗淡煤,是热改造优质目标。

     

    Abstract: The reservoir stimulation method of thermal induction is effective for improving the production of coalbed methane well, in which the heat transfer difference of coal composition and distribution is the key and fundamental problem to be solved urgently in coal reservoir thermal stimulation project. Taking the bituminous coal in the Wangjialing Coal Mine of Baode as an example, this paper accurately identified and characterized the spatial distribution characteristics of maceral based on the multi-scale observation method combining macro-description, microscopy-CT imaging of coal sample. The dynamic heat transfer process of coal with different lithotypes were characterized by uniform plate heating and thermal imaging acquisition experiment system. The thermal properties of macerals were quantitatively characterized by experimental data combining with the laws of thermodynamics to reveal the differential heat transfer mechanisms of maceral composition and distribution. The results show that in the heat transfer process, the temperature of semi-bright coal presents a bimodal state, while that of dull coal presents a unimodal state. The temperature span of both decreases first and then increases, and the temperature span of semi-bright coal is significantly wider than that of dull coal. The closer the proportion of vitrain + clarain and durain + fusain is, the more significant the temperature difference is. According to the evolutionary characteristics of temperature difference, the heat transfer process can be divided into four stages: rapid temperature rise, slow growth, fluctuating warming and dynamic equilibrium. The correspondence between the distribution of maceral components and the temperature spreading shows that the heat transfer is controlled by maceral composition and distribution. The inertinite filled with mineral is heated up the fastest to form a high-temperature zone, the inertinite generally forms a sub-high-temperature zone, and the vitrinite is heated up the slowest to a low-temperature state. In addition, the heating rate of the vitrinite and the temperature at equilibrium are inversely proportional to the distance of the inert group. The quantitative analysis of thermal properties shows that the mineral-filled inertinite has larger thermal conductivity and diffusion coefficient, thus its speed of transferring thermal perturbation is the fastest and takes the least time to reach thermal equilibrium, the inertinite is the second and the vitrinite is the slowest. The new fissure in coal after the thermal process mainly develops in vitrinite, and cracks mostly along the cross linking of inertinite and vitrinite. The thermal effect of crack reform in semi-bright coal is obviously stronger than that in dull coal, therefore the semi-bright coal is the high quality target of thermal reform.

     

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