热解无烟煤三维裂隙重构及定量表征研究

Research on Reconstruction and Quantitative Characterization of Three-dimensional Cracks in Pyrolysis Anthracite

以晋城无烟煤为研究对象,利用μCT225 kVFCB扫描系统,在不同温度下对晋城无烟煤进行CT扫描,研究不同温度下裂隙发育状况。基于AVIZO三维可视化重构技术,对煤样内部裂隙进行提取。对单个裂隙进行了定量分析,对比了不同温度下热破裂和热解对裂隙发育的影响。实验结果表明:200℃时,微裂隙扩展形成长度L>1000μm的裂隙,在不同温度作用下,无烟煤孔裂隙的致裂原因不同;在常温300℃时,裂隙2发育剧烈,主要由热破裂引起,随着温度的升高无烟煤内部发生热解反应,裂隙发育主要受热解作用影响;400℃时,最大裂隙体积减小;600℃时,温度对裂隙发育影响最大,裂隙1和3相互连通扩展,同时次生裂隙生成。根据长度L的不同,晋城无烟煤内部裂隙分为3类:1μm<L<100μm;100μm≤L<1000μm;L≥1000μm.在不同温度作用下,综合单裂隙提取主裂隙面张量方向不同;随着温度的升高裂隙沿层理方向发育较快,其中在300℃与600℃时,裂隙空间发育最为显著。温度越高,三维裂隙体积变大,空间相互连通,渗透性增大,为煤层气抽采提供了高渗透性通道。

In order to study the effect of temperature on the permeability of anthracite coal cracks,Jincheng anthracite coal was used as the research object,and the pyrolysis CT scan of Jincheng anthracite coal under different temperatures was performed by using the μCT225 kVFCB scanning system.On the basis of AVIZO three-dimensional visualization reconstruction technology,the internal cracks of coal samples were extracted.The single crack was analyzed separately,the main crack surface of the crack was constructed,and the effects of thermal cracking and pyrolysis on the development of crack at different temperatures were compared and analyzed.The research results show that:at 200℃ micro-cracks develop into cracks with a length of L>1000μm.Under different temperatures,they affect the development of the cracks.Low temperature mainly affects the individual cracks 2,and a cracking phenomenon occurs with increasing temperature.Under the action of high temperature,cracking goes through the cracks 1 and 3 to expand and develop,meanwhile the formation and penetration of secondary cracks occurs.At different temperatures and according to the length L,there are three main types of internal cracks in Jincheng anthracite,which are 1μm<L<100μm,type I;100≤L<1000μm,type II;and L≥1000μm,type III.Under the effect of different temperatures,the direction of the main crack surface tensor extracted by a single crack is different;as the temperature increases,crack develops faster in the direction of bedding.Especially,the development of the crack space is most significant at 300℃ and 600℃.At higher temperature,the fissures are interconnected and the permeability is increased,which provides a high permeability channel for coalbed methane extraction.