工程科学学报，第40卷，第2期：136-143,2018年2月 Chinese Journal of Engineering,Vol.40,No.2:136-143,February 2018 DOI:10.13374/j.issn2095-9389.2018.02.002;http://journals.ustb.edu.cn 基于微观机理的页岩气运移分析 张鹏伟12)，胡黎明2)☒，温庆博2) 1)清华大学水利水电工程系，北京1000842)清华大学水沙科学与水利水电工程国家重点实验室，北京100084 ☒通信作者，E-mail:gehu@tsinghua.edu.cn 摘要认识气体在页岩孔隙中的运移机理对页岩气开采具有重要的科学意义.页岩作为一种致密岩石，孔隙尺寸分布主要 集中在几纳米到百纳米之间，小孔隙尺寸与气体的平均分子自由程在同一个数量级，气体与孔隙边壁的碰撞对流动起到控制 作用.本文针对页岩气开采过程中孔隙中气体流动过程，建立了考虑气体滑移、Knudsen扩散，Langmuir等温吸附、孔隙压缩等 过程的多场耦合控制方程.分析了流态变化对滑移效应的影响，得到了考虑滑移效应的临界孔径，并针对实际中不同页岩储 层有机质含量的差异，分析了解吸机制对页岩气产气率、产气量的贡献.研究还表明孔隙压缩性对产气率影响显著，通过考虑 开采过程中孔隙压缩，可以更真实地反映页岩气运移过程. 关键词滑移流动；孔隙压缩；Knudsen扩散；Langmuir等温吸附；页岩气 分类号TU42 Micro-mechanism analysis of shale gas migration ZHANG Peng-wei2).HU Li-ming,WEN Qing-bo) 1)Department of Hydraulic Engineering,Tsinghua University,Beijing 100084,China 2)State Key Laboratory of Hydroscience and Engineering,Tsinghua University,Beijing 100084,China Corresponding author,E-mail:gehu@tsinghua.edu.cn ABSTRACT For shale gas exploitation,it is scientifically essential to clarify the mechanism of gas flow in nanopore media.Shale is a kind of tight rock,whose pore size mainly ranges from several nanometers to dozens of nanometers.Since it is of the same magnitude as the gas molecular mean free path,the collision between the gas molecular and pore surface is not negligible for gas flow and results in the failure of Darcy's law when describing this low permeability reservoir gas flow mechanism.In order to clarify the micropore gas flow mechanism and the real extraction process of shale gas,a multiphysics governing equation was established,which combines slip flow,Knudsen diffusion,Langmuir isotherm adsorption,and pore compressibility.The effect of different flow regimes on slip flow was analyzed,and the threshold pore size was obtained with consideration of the slippage effect.Then,the contribution of desorption to gas production rate and gas output was clarified based on the organic content of disparate shale samples.The results indicate that the gas production rate is sensitive to pore compressibility,and it is more reasonable to simulate the gas flow process when considering pore compressibility. KEY WORDS slip flow;pore compressibility;Knudsen diffusion;Langmuir isotherm adsorption;shale gas 页岩气作为一种非常规天然气资源，在北美的 页岩气在低渗透储层中的运移机理研究对于页 成功开采极大缓解了美国紧迫的能源现状.我国的 岩气科学开采具有重要意义.页岩是一种非常致密 页岩气初步勘探结果表明，其可开采储量与美国大 的岩石，其渗透率一般为10-18~10-1m2[3],孔隙尺 致相当1-2] 寸主要分布在几纳米到百纳米之间4].此时，气体 收稿日期：2017-05-06 基金项目：请华大学自主科研计划资助项目(TH720161080101):国家自然科学基金资助项目(41372352)工程科学学报,第 40 卷,第 2 期:136鄄鄄143,2018 年 2 月 Chinese Journal of Engineering, Vol. 40, No. 2: 136鄄鄄143, February 2018 DOI: 10. 13374 / j. issn2095鄄鄄9389. 2018. 02. 002; http: / / journals. ustb. edu. cn 基于微观机理的页岩气运移分析 张鹏伟1,2) , 胡黎明1,2)苣 , 温庆博1,2) 1) 清华大学水利水电工程系, 北京 100084 2) 清华大学水沙科学与水利水电工程国家重点实验室, 北京 100084 苣 通信作者, E鄄mail: gehu@ tsinghua. edu. cn 摘 要 认识气体在页岩孔隙中的运移机理对页岩气开采具有重要的科学意义. 页岩作为一种致密岩石,孔隙尺寸分布主要 集中在几纳米到百纳米之间,小孔隙尺寸与气体的平均分子自由程在同一个数量级,气体与孔隙边壁的碰撞对流动起到控制 作用. 本文针对页岩气开采过程中孔隙中气体流动过程,建立了考虑气体滑移、Knudsen 扩散、Langmuir 等温吸附、孔隙压缩等 过程的多场耦合控制方程. 分析了流态变化对滑移效应的影响,得到了考虑滑移效应的临界孔径,并针对实际中不同页岩储 层有机质含量的差异,分析了解吸机制对页岩气产气率、产气量的贡献. 研究还表明孔隙压缩性对产气率影响显著,通过考虑 开采过程中孔隙压缩,可以更真实地反映页岩气运移过程. 关键词 滑移流动; 孔隙压缩; Knudsen 扩散; Langmuir 等温吸附; 页岩气 分类号 TU42 收稿日期: 2017鄄鄄05鄄鄄06 基金项目: 清华大学自主科研计划资助项目(THZ20161080101); 国家自然科学基金资助项目(41372352) Micro鄄mechanism analysis of shale gas migration ZHANG Peng鄄wei 1,2) , HU Li鄄ming 1,2)苣 , WEN Qing鄄bo 1,2) 1) Department of Hydraulic Engineering, Tsinghua University, Beijing 100084, China 2) State Key Laboratory of Hydroscience and Engineering, Tsinghua University, Beijing 100084, China 苣 Corresponding author, E鄄mail: gehu@ tsinghua. edu. cn ABSTRACT For shale gas exploitation, it is scientifically essential to clarify the mechanism of gas flow in nanopore media. Shale is a kind of tight rock, whose pore size mainly ranges from several nanometers to dozens of nanometers. Since it is of the same magnitude as the gas molecular mean free path, the collision between the gas molecular and pore surface is not negligible for gas flow and results in the failure of Darcy爷s law when describing this low permeability reservoir gas flow mechanism. In order to clarify the micropore gas flow mechanism and the real extraction process of shale gas, a multiphysics governing equation was established, which combines slip flow, Knudsen diffusion, Langmuir isotherm adsorption, and pore compressibility. The effect of different flow regimes on slip flow was analyzed, and the threshold pore size was obtained with consideration of the slippage effect. Then, the contribution of desorption to gas production rate and gas output was clarified based on the organic content of disparate shale samples. The results indicate that the gas production rate is sensitive to pore compressibility, and it is more reasonable to simulate the gas flow process when considering pore compressibility. KEY WORDS slip flow; pore compressibility; Knudsen diffusion; Langmuir isotherm adsorption; shale gas 页岩气作为一种非常规天然气资源,在北美的 成功开采极大缓解了美国紧迫的能源现状. 我国的 页岩气初步勘探结果表明,其可开采储量与美国大 致相当[1鄄鄄2] . 页岩气在低渗透储层中的运移机理研究对于页 岩气科学开采具有重要意义. 页岩是一种非常致密 的岩石,其渗透率一般为10 - 18 ~ 10 - 21 m 2 [3] ,孔隙尺 寸主要分布在几纳米到百纳米之间[4鄄鄄5] . 此时,气体