多尺度孔隙介质视渗透率模型

The model for apparent permeability in Multi-scale porous medium

为研究页岩气在多尺度孔隙介质中的渗流率表征,以及分析各种流动状态对渗透率的贡献。基于页岩储层孔径分布特征,利用Kundsen数对流动状态进行划分,建立气体分子在多孔介质中的渗透率理论计算模型,分析了孔隙流体压力与渗透率的关系以及不同流动状态对渗透率的贡献。模型研究表明:多孔介质渗透率受气体达西流、滑脱流、Fick扩散流、过渡扩散流及Kundsen扩散流的影响;气体流动状态受流体压力和孔径分布决定,流体压力降低导致气体在多孔介质中的流动状态发生改变;随着储层流体压力降低,过渡扩散流对渗透率贡献增加,页岩储层渗透率增大。储层流体压力低于1 MPa时,Kundsen扩散流对渗透率贡献逐渐增大,渗透率迅速增加。

To investigate the permeability characterization of shale gas in multi-scale of porous media, analyse the contribution of permeability of the various flow state. The gas molecule permeability calculation model in the porous medium established according to the pore size distribution characteristics of shale reservoir and utilize Kundsen number in dividing flow state, analyzed the relationship between the pore fluid pressure and permeability,and the contribution of different flow state on the permeability. Results show that the porous medium permeability is affected by darcy flow, slip flow, Fick diffusion flow, transition flow and Kundsen diffusion flow. Gas flow state determined by the fluid pressure and pore size distribution in multi-scale of porous media, and fluid pressure lower lead to the change of the state of gas flow. As the reservoir fluid pressure is reduced, the transitional diffusion flow contribution to permeability increase, and apparent permeability increase. When reservoir fluid pressure is lower than 1 MPa, Kundsen diffusion flow contribution to permeability increases gradually, and the apparent permeability increase rapidly.