Received date: 2012-11-12
Revised date: 2013-03-21
Online published: 2013-10-10
hale gas reservoir pore is very small.Pore radius of domestic and foreign shale mainly concentrates from several nm to twenty nm,and a part of domestic shale pore radius is less than 10nm.There are two main gas sources which are free gas in nano-pore and dissolved gas in kerogen,yielding four mechanisms during production.By researching the four mechanisms which are Knudsen diffusion,gas slippage,Darcy Law and dissolved gas diffusion in kerogen,a cylindrical tube and unidirectional steady seepage flow mathematical model is built to study shale gas permeability and pore pressure.The results show that apparent permeability is much larger than Darcy permeability.The smaller pore diameter is,the larger ratio of the two permeability will be.The ratio will increase by 1 to 2 orders of magnitude while the pore diameter varies from twenty nm to several nm.The smaller the pressure is,the larger the ratio will be.The apparent permeability is also one to two orders greater than Darcy permeability while the pressure lies below 5 MPa.The transient pressure is nonlinear distribution from supply edge to the discharge in nano-pore mainly because Knudsen diffusion in nano-pore gets stronger and depletes more pressure under lower pressure.Diffusion in kerogen has a weak effect on pressure depletion because of such low diffusion flux.
Key words： Shale gas reservoir; Nano-pore; Diffusion; Kerogen; Mathematical model
LI Zhi-feng,LI Zhi-ping,MIAO Li-li,FU Ying-kun,WANG Yang,XIE Shan . Gas Flow Characteristics in Nanoscale Pores of Shale Gas[J]. Natural Gas Geoscience, 2013 , 24(5) : 1042 -1047 . DOI: 10.11764/j.issn.1672-1926.2013.05.1042
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