页岩微孔结构及其对气体传质方式影响

页岩复杂的孔隙结构对页岩气赋存状态、储量计算以及多尺度传质具有重要影响。运用压汞和氮气吸附法测定了页岩孔隙结构参数，基于不同孔径中的气体努森数，分析了孔隙尺度与页岩气传质方式的关系。结果表明:页岩压汞孔喉分布曲线呈现明显的三峰特征，直径小于100nm的纳米孔占页岩基块总储渗空间的80%~95%；页岩纳米孔平均直径为3.78~10.09nm，纳米孔具有巨大的BET比表面，77%~99%的比表面集中分布于孔径小于10nm的纳米孔内；基于气体动力学理论，在页岩多尺度孔隙中，页岩气的传质方式可划分为无滑脱渗流、存在滑脱渗流、过渡流动以及分子扩散，孔隙尺度控制着气体的传质方式；在页岩气藏开采的不同时期，不同孔隙尺度中的气体传质方式是动态变化的；在气藏开采中后期，页岩孔隙尺度是影响气体扩散类型和扩散系数的重要因素。 

Micro-pore Structure of Gas Shale and Its Effect on Gas Mass Transfer

The pore structures of gas shale have great significance to understand gas storage mechanisms,estimation of initial gas in-place and deliverability of multi-scaled pores.The micro-pore structure has been investigated through mercury injection capillary pressure (MICP) and nitrogen adsorption method.Then,the effect of pore diameter on shale gas mass transfer modes was analyzed in pores based on Knudsen number.The MICP results show that there are three peaks in pore-throat size distribution curves,and up to 90% of the total pore volumes are located in nanopores with pore diameter less than 100nm.Nitrogen adsorption analysis indicates that average diameter for nanopores ranges from 3.78nm to 10.09nm and 77% to 99% of the total BET surface areas mainly come from pores with size in diameter less than 10nm.Based on the theory of molecular dynamics,the modes of gas-transport controlled by pore dimension are summarized as four types: non-slip percolation,slip percolation,transition flow,and diffusion.The gas flow types in pores are variable during different development stages.And gas diffusion type and diffusivity within shale pores are greatly influenced by pore size at middle-late stage of shale gas reservoir.