致密多孔介质气体运移机理  

Gas Transport Mechanism in Tight Porous Media

作　　者：刘圣鑫 钟建华[1,2] 刘晓光 李勇[1] 邵珠福 刘选 

机构地区：[1]中国石油大学(华东)地球科学与技术学院,山东青岛266580 [2]中国科学院广州地球化学研究所,广东广州510640

出　　处：《天然气地球科学》2014年第10期1520-1528,共9页Natural Gas Geoscience

基　　金：中国地质科学院地质力学研究所项目"柴达木盆地东部石炭系页岩气资源潜力评价研究"(编号:1212011221045)资助

摘　　要：气体在致密多孔介质中的运移受多种因素的影响,如孔隙结构、气体的赋存方式、温度和压力等。地层压力大,气体密度高,应属于稠密气体;另外,在页岩、煤岩、致密砂岩等多孔介质中发育了丰富的纳米级孔隙,使气体的运移机制极为复杂。详细研究了气体在致密多孔介质中的运移机理,并引入稠密气体理论,通过计算分子平均自由程,发现直径大于2nm的孔隙中,压力大于1.135MPa时(76.85℃),气体不会发生Knudsen型扩散,Fick型扩散和表面扩散可能是主要的扩散方式;并得到Knudsen渗透率修正因子随压力增加而减小,随温度的升高而增加,随孔隙半径的减小而增加,在较小孔隙中温度的影响更显著;气体从小孔扩散至大孔和裂缝系统是多种扩散机制的结果,孔隙的大小、气体的赋存方式和压力直接关系到气体的运移机理。对比分析Klinkenberg渗透率和Knudsen渗透率修正因子,发现Knudsen渗透率模型是更精确的渗透率模型,Klinkenberg渗透率修正因子可以看作是Knudsen渗透率修正因子的一级修正。Gas transport mechanism in tight porous media is influenced by many factors,such as the pore structure and gas occurrence form,temperature and pressure,etc.In addition,the shale,coal,tight sandstone are enriched in nanopores,which makes the gas transport mechanism very complex.This study investigated the migration mechanism of gases in density of porous medium,and introduced the dense gas that is under great formation pressure and has high gas density.By calculating the molecular average free path,it is found that free path Fick diffusion and surface diffusion may be the main ways of gas when the pressure is greater than 1.135MPa（76.85℃）.The Knudsen correction factors of permeability decreased with increasing pressure increased,or with increasing pore radius,but increased with increasing temperature.Gas spreads from pore to hole and fracture system is a result of various diffusion.Pore size and gas occurrence mechanism directly affect gas diffusion mechanism.Knudsen permeability model is a more accurate permeability model though the comparison between Klinkenberg and Knudsen permeability correction factor,and Klinkenberg permeability correction factor can be regarded as the Knudsen permeability correction factor＇s first-order correction.

关 键 词：Knudsen数 渗透率修正因子 Enskog稠密气体理论 滑脱效应 

分 类 号：TE122.1[石油与天然气工程—油气勘探]