低渗气藏气体渗流滑脱效应影响研究

低渗透气藏储层致密、渗透率极低、以微孔道为主，当气体在低渗孔隙介质中低速渗流时，气体渗流的主要物理特征是具有“滑脱效应”。为此，研究了具有滑脱效应的储层渗透率界限以及孔隙压力条件。通过对苏里格气田32块低渗岩心样品所进行的实验，探讨了低渗气藏天然气渗流规律。研究表明，当努森数介于0.1~1时，气体渗流不遵从克氏方程。实验结果还表明：克氏系数随储层渗透率的增大而减小，当储层渗透率大于0.1×10^-3μm²时，气体滑脱效应可以忽略不计；克氏系数随平均孔隙压力的增大而减小，当孔隙压力大于1.5 MPa时，气体滑脱效应也可以忽略不计。

A STUDY OF SLIPPAGE EFFECT OF GAS PERCOLATION IN LOW PERMEABILITY GAS POOLS

Low permeability gas pools are characterized by tight reservoirs dominated by micro pores and throats. When gas percolates at a low speed in porous medium with low permeability, slippage effect will occur. This paper studies the permeability limits and pore pressure conditions of gas reservoirs with slippage effect. The gas percolation patterns in low permeability gas reservoirs are studied through experiments on 32 tight gas sand core samples of the Sulige Gasfield. When the value of Kn is in the range of 0.1-1, gas percolation does not follow Klinkenberg's theory. Klinkenberg effect constant decreases along with the increasing reservoir permeability and the slippage effect can be neglected when permeability is over 0.1×10-3μm2. Klinkenberg effect constant also decreases along with the increasing the average pore pressure and the slippage effect can be neglected when pore pressure is over 1.5 MPa.