中文摘要：

根据多孔介质中气体分子的扩散形式，结合页岩气储层多尺度分布的结构特点，分析了页岩储集空间中页岩气的扩散机理，包括：有机干酪根中溶解气的扩散和纳米孔隙中游离气的扩散。其中纳米孔隙中游离气的扩散又根据克努森（腼）数的不同分为Knudsen扩散、Fick扩散和过渡扩散。根据Fick第二定律，建立了干酪根中溶解气扩散模型，给出了纳米孔隙中3种扩散机理扩散系数的计算方法。分析了压缩性对气体平均自由程计算的影响，重点讨论了温度、压力、孔隙直径以及气体压缩性等对纳米孔隙中扩散机理选择的影响。得出：不同扩散机理的选择对扩散能力的影响不可忽略，实际计算中必须根据Knudsen数，选取相应扩散机理对应的扩散系数。

英文摘要：

According the diffusion forms of the gas molecules in the porous media and combining with the structural characteristics of the multi-scale distribution in the shale gas reservoirs, the diffusion mechanisms of the shale gas in the reservoir space are analyzed, including the diffusions of the dissolved gas in the organic kerogen and the free gas in the nano-pores. And moreover, according to the differences of Knudsen number （Kn） , the later diffusion is di- vided into the following three diffusions： Knudsen, Fick diffusion and transitional diffusions. Based on the second Fick＇s law, the diffusion model of the dissolved gas in the kerogen is established; and furthermore the calculating means of the diffusion coefficients of the aforementioned three kinds of the diffusion mechanisms are presented. The effects of the compressibility of the gas on the calculation of its mean free path are analyzed. And furthermore the effects of the temperature, pressure, pore diameter, gas compressibility and so forth on the selection of the diffusion mechanisms are mainly focused. As a result, the influences of the choice of the different diffusion mechanisms on the diffusion capacity cannot be neglected, in the actual calculation, the diffusion coefficients corresponding to the diffusion mechanisms must be the selected according to Knudsen numbers.