构造变形对烟煤级构造煤微孔-中孔的作用

Effects of tectonic deformation on micropore-mesopore of bituminous deformed coal

  • 摘要: 煤作为一种复杂的天然多孔性固体物质,其纳米级孔隙对煤层气的储集和运移有着重大影响。我国受成煤盆地多期次构造运动影响,煤层普遍发育不同破坏类型的构造煤,构造煤纳米级孔隙结构在构造变形作用下发生重要变化,这一变化不仅影响着煤层瓦斯的储集和赋存状态,同时也对煤与瓦斯突出预测和煤层气开采具有重要意义。采集首山一矿和义安矿不同变形程度构造煤样品,基于低温液氮吸附(2~50 nm)和二氧化碳吸附(<2nm)实验,利用多重分形理论分析了构造变形对煤的微孔-中孔结构的影响。结果表明煤样微孔和中孔均具有多重分形特征,微孔广义分形维数谱宽D10-~D10+和奇异指数α0随变形程度的增加整体递增,中孔则先降低后增加。弱变形阶段,微孔信息维数D1和赫斯特指数H逐渐降低而多重分形奇异谱谱宽Δα逐渐增加,中孔D1和H逐渐增加而Δα逐渐降低。强变形阶段,微孔D1,H和Δα均没有发生明显变化,中孔D1和H明显降低,Δα明显增加。分析构造煤孔隙特征与煤体破坏强度的关系,弱变形阶段,构造变形作用导致煤的微孔结构趋于复杂,孔隙连通性较差,中孔结构趋于简单,归因于官能团脱落以及应力作用下部分中孔结构的收缩。强变形阶段,微孔结构差异依然较强,中孔结构差异则由弱变强,这与强构造应力作用下形成大量的分子间孔、缺陷以及气孔有关。

     

    Abstract: Coal is a complex natural porous solid substance and its nano-scale pore has a significant impact on the stor- age and migration of coalbed methane. Influenced by multi-stage tectonic movements in coal-forming basins in China, different types of deformed coal are widely developed in coal seams,and the nano-pore structure changes greatly under the action of tectonic deformation. This change not only affects the state of gas reservoir and occurrence in coal seams, but also has a significant impact on coal and gas outburst prediction and coalbed methane extraction. Samples of de- formed coal with different deformation degrees in Shoushan No. 1 and Yi’an Mines were collected. Based on the exper- iments of low temperature liquid nitrogen adsorption (2-50 nm) and carbon dioxide adsorption (

     

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