页岩纳米级孔隙气体流动特征　　

Gas flow characteristics in shales nanopores

郭为 熊伟 高树生 刘洪林

GUO Wei XIONG Wei GAO Shusheng LIU Honglin

中国科学院渗流流体力学研究所，河北廊坊　065007 中国石油勘探开发研究院廊坊分院，河北廊坊　065007

Institute of Porous Fluid Mechanics Chinese Academy of Sciences, Lang fang 065007, China Research Institute of Petroleum Exploration and DevelopmentLang fang, Lang fang 065007, China

页岩气在孔隙中的流动规律是评价页岩气产能的基础，而气体流动规律与页岩的孔隙大小密切相关。通过液氮等温吸附对昭通地区龙马溪组以及五峰组页岩的孔隙进行研究发现，该地区页岩孔隙大小主要分布在4~6 nm。利用Kn数和Beskok-Karniandakis方程计算了页岩的表观渗透率，分析了压力、温度以及吸附作用对气体流动规律的影响：在直径小于10 nm的孔隙中，气体表观渗透率与达西渗透率的比值高达30，气体的吸附会缩小页岩的孔径，吸附层的存在会使得孔径小于10 nm的孔隙表观渗透率与达西渗透率的比值增大。温度与压力都会影响Kn数，从而影响气体的表观渗透率和页岩吸附层厚度。在不考虑吸附层的影响下，压力升高，页岩表观渗透率下降，温度升高，表观渗透率稍有变化，变化不明显；考虑吸附层影响下，页岩表观渗透率与达西渗透率之比与不考虑吸附时表观渗透率与达西渗透率之比随压力降低或温度上升呈下降趋势。

Gas flow characteristics directly influence the productivity of shale gas reservoir and production evaluation. And shale gas flow characteristics are directly related to the pore distribution of shale. Pore sizes of 4-6 nanometers were mainly found in Long maxi and Wufeng shales formations of Zhao tong area using nitrogen isothermal adsorption. The calculation of apparent permeability of shale is made by using Kn number and Beskok-Karniandakis equation. The influence of temperatures, pressure and gas adsorption to the gas flow characteristics was analyzed. The ratio of apparent permeability to Darcy permeability reaches as much as 30 in the nanopores with diameter less than 10 nm. Gas adsorption layer will reduce pore diameters, the apparent permeability of pores with diameter less than 10 nm increases as the adsorption layer increases. The apparent gas permeability of nanopores is relevant to Kn number which is affected by temperature and pressure. Without considering of adsorption layer, the gas apparent permeability decreases as pressure increases and temperature increases. The ratio of apparent permeability to Darcy permeability with the consideration of adsorption layer and without consideration adsorption layer increases as the pressure increases and the temperature decreases.