煤基质中甲烷扩散特征及其对气井产能的影响

发布时间：2018-05-14 21:55

本文选题：煤层气 + 高煤阶煤　；参考：《地球科学》2017年08期

【摘要】：扩散是煤层甲烷运移的关键环节之一,而目前有关煤层中甲烷扩散特征的认识并不充分.以沁水盆地南部高煤阶煤层气藏为例,应用微纳渗流力学理论分析了煤基质中气体扩散模式及定量表征参数;应用Simed软件开展了扩散性能对不同煤体结构煤层气排采规律的影响数值研究.结果表明:煤层甲烷的扩散受化学势梯度的驱动,产气过程中体相扩散、努森扩散和构型扩散模式并存且呈动态变化;甲烷扩散性能受气体温度、压力、气体种类、水分以及基质孔隙结构共同影响,基质孔隙吸附甲烷会改变微孔孔径并影响扩散路径的空间形态;煤基质中甲烷的扩散是非热力平衡过程,扩散系数是吸附量的函数.基于拟稳态扩散的数值研究表明,扩散性能强弱对于长期累计产气量几乎没有影响,而对短期产气速率具有较大的影响;扩散性能弱的,产气速率峰值较低,但峰值之后的一段时间内产气速率相对较高;与高渗煤层相比,低渗构造煤层的产气速率对吸附时间常数更敏感.
[Abstract]:Diffusion is one of the key links of methane migration in coal seams, but the characteristics of methane diffusion in coal seams are not well understood at present. Taking the high-rank coalbed methane reservoir in the southern Qinshui Basin as an example, the gas diffusion model and quantitative characterization parameters in coal matrix are analyzed by using micro-nano percolation mechanics theory. The effect of diffusivity on coal bed methane (CBM) production with different coal structure was studied by Simed software. The results show that the diffusion of methane in coal seam is driven by the chemical potential gradient, the mass diffuses in the gas production process, the Knudsen diffusion model and the configuration diffusion mode coexist and change dynamically, the methane diffusion performance is affected by the gas temperature, pressure, gas type, The adsorption of methane by matrix pore will change the pore size of micropore and affect the spatial morphology of diffusion path, and the diffusion of methane in coal matrix is a non-thermal equilibrium process, and the diffusion coefficient is a function of adsorption capacity. The numerical study based on quasi-steady diffusion shows that the diffusion performance has little effect on the long-term cumulative gas production, but has a great effect on the short-term gas production rate, while the diffusion performance is weak, the peak value of the gas production rate is lower. However, the gas production rate is relatively high in the period after the peak value, and the gas production rate of the low permeability structure coal seam is more sensitive to the adsorption time constant than that of the high permeability coal seam.
【作者单位】：中国地质大学构造与油气资源教育部重点实验室;山西晋城无烟煤矿业集团有限责任公司煤与煤层气共采国家重点实验室;中国矿业大学地球科学与测绘工程学院;
【基金】：“十三五”国家科技重大专项(Nos.2016ZX05067001,2016ZX05043-001) 国家自然科学基金项目(No.41372163) 山西省煤层气联合研究基金资助项目(Nos.2015012014,2014012001) 山西省煤基重点科技攻关项目(Nos.MQ2014-1,MQ2014-12) 湖北省自然科学基金项目(No.2014CFB169)
【分类号】：TE37

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