Multi-scale structures of porous media and the flow prediction

• Published in: Journal of natural gas science and engineering Vol. 21; pp. 986 - 992
• Main Authors: Lei, G., Dong, P.C., Wu, Z.S., Gai, S.H., Mo, S.Y., Li, Z.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.11.2014
• Subjects: Lognormal distribution; Mathematical modeling; Microstructure; Multi-scale; Relative permeability; Mathematical modeling; Relative permeability; Multi-scale; Microstructure; Lognormal distribution
• ISSN: 1875-5100
• DOI: 10.1016/j.jngse.2014.10.033

For the same porous media, the pore structures on different scales and the corresponding fluid flow have different features. The pore structure ultimately affects the fluid flow property. So the study of multi-scale pore structure of the given sample is important for oil/gas reservoir engineering. In this paper, the lognormal distribution characteristics of the multi-scaled porous media have been described and the analytical expressions for capillary pressure and relative permeability for each scaled porous media are developed based on the lognormal distribution function. It is shown that the pore-throat size distribution density functions of the sample in different analysis scales are lognormal. The predictions of capillary pressure for higher scaled porous media conform to the trend of variation with the available experimental data at lower mercury saturation. However, the variation trend of predictions for lower scaled porous media is in agreement with experimental data only at higher mercury saturation. Compared to the fractal model, our new model for relative permeability has a wider tolerance for changes of pore-throat radius distribution. Our model is also well suitable for those non-fractal porous media, for which the fractal model is not applicable. The predictions of relative permeability by the proposed model are all consistent with experimental data. The effects of irreducible wetting fluid saturation, lognormal distribution parameters α and σ on the relative permeability also have been discussed. •We proposed an analytical model for capillary pressure and relative permeability for multi-scaled porous media.•The pore-throat distribution functions of the porous media in different analysis scales are lognormal.•The complete capillary pressure curve contains the entire pore-throat size information.•Predicted capillary pressure has similar trend with experimental data.•The effects of structural parameters on relative permeability are discussed in detail.