摘要
目的探究页岩低至纳米级孔隙中气体渗流能力以及分析扩散对总质量通量的贡献。方法先由Kn数划分流动区域,求得各区域对应扩散系数作为系统的扩散系数,然后将其代入气体在纳米孔隙介质中的扩散和渗流方程,最终求出相应的质量通量和视渗透率并分析孔隙半径大小和气体种类对它们的影响。结果页岩储层中气体扩散主要处在过渡扩散和Fick扩散区域;视渗透率与达西渗透率的比值以及扩散质量通量占总质量通量百分比都随孔隙半径的减小而增加;甲烷的扩散能力强于乙烷。结论页岩扩散系数的计算,如果只用Knudsen扩散系数模型会使计算结果偏大;考虑了扩散和滑脱效应后,在储层一般的温压条件下,甲烷在页岩纳米级孔隙中的视渗透率值为10-6μm2级,而非10-9μm2级。
Aim In order to characterize the flow ability of gas flow in pore of shale as low as nanoscale, and ana- lyze the contribution of diffusion to total mass flux. Methods The flow region was determined by Kn number first- ly, taking the diffusion coefficient of the flow region as the diffusion coefficient of system, then substituting it into the equation of gas diffusion and flow in nano-porous media, finally calculated the apparent permeability and mass flux , analyzed the impact of the pore radius and gas kinds. Results A new calculation model of diffusion coeffi- cient, total mass flux and of apparent permeability of shale gas were obtained. The diffusion of gas in shale was mainly in the transition diffusion and Fick diffusion region ; the ratio of the apparent permeability of considering the diffusion and slippage effect to Darcy permeability and the diffusion mass flux to total mass flux increased with the decreasing of the pore radius ; the diffusion ability of the methane is stronger than ethane gas. Conclusion The cal- culation results of the diffusion coefficient by Knudsen diffusion model only may make the coefficient bigger; con- sidering the diffusion and slippage effect, the apparent permeability of nanoscale pore of shale is 10-6μm2 level, not 10-9μm2 level in general temperature and pressure of reservoir.
出处
《西北大学学报（自然科学版）》
CAS
CSCD
北大核心
2013年第1期75-80,88,共7页
Journal of Northwest University（Natural Science Edition）
基金
中国石油科技创新基金资助项目(2012D-5006-0203)
关键词
页岩气
扩散类型
扩散系数
扩散通量
视渗透率
：shale gas
diffusion type
diffusion coefficient
diffusion flux
apparent permeability
