深部煤层CO_2置换CH_4过程中煤岩特性变化研究

Research progress of coal rock properties change in the process of CO_2 replacement CH_4 in deep coal seam

综述了在高压条件下CO2置换CH4过程中煤岩特性变化的试验及模型等方面的研究进展,分析注入CO2后煤岩特性变化对煤岩结构、渗透率及CH4产量的影响,指出我国深部煤层CO2置换CH4过程中煤岩特性变化的研究方向.分析表明,由于CO2较CH4具有更强的可吸附性,CO2置换CH4过程中煤基质发生吸附膨胀,应力、应变同时增大,造成渗透率下降,初期CH4产量较低,随着CH4气体解吸量的不断增大,开采一段时间后CH4产量将大幅度增加,这种煤岩特性变化规律及CH4产量变化特征与现场试验结果具有很好的一致性.

Deep coal bed methane resources in China are very rich,but they have not been mined with a large scale because of the technology cost.The emergence of CO2 injection-production technology makes it possible to develop the deep coal bed methane.Finding out the relationship of the coal rock property change during the process of CO2 injection/replacement in a deep coal seam to be a theoretical foundation for the exploitation of deep coal bed methane,the experiments and model research achievements of changes in coal characteristics during the process of CO2 injection/replacement under high pressure are summarized;the effects of changes in coal,the rock characteristics after the injection of CO2 on coal structure,permeability,and CH4 gas production are analyzed,and the research direction of coal rock properties change in the process of CO2 injection/replacement CH4 in deep coal seam are pointed out.The result indicates that： as CO2 has a stronger adsorption than CH4,the coal matrix becomes swelling and the stress and strain have great changes when the CO2 replacement the CH4,resulting in that the permeability decreased,and that the initial CH4 production became low.But with the CH4 gas desorption continuous increases,the CH4 production mining will increase substantially after a period.This variation of coal properties and the variation of CH4 production have a good consistency with the results of field test.