Отправлено: 17.02.19 06:47. Заголовок: Снова извилистость (и какая мудреная!) ;-(

Lefki Germanou, Minh Tuan Ho, Yonghao Zhang, Lei Wu

Intrinsic and apparent gas permeability of heterogeneous and anisotropic ultra-tight
porous media

Journal of Natural Gas Science and Engineering

Abstract
Accurate prediction of unconventional gas production requires deep understanding of the permeability of
complex rock samples. Several predictive expressions of permeability, which include either simplifications of
the porous media structure or the flow mechanisms, have been proposed recently. The main objective of this
research is to quantify the impact of solid matrix complexity on both intrinsic and apparent permeability.
To this end, numerous two-dimensional random porous media structures are constructed using the quartet
structure generation set algorithm. Parametric and statistical analysis reveals the importance of the specific
surface area of pores, tortuosity, heterogeneity and degree of anisotropy. Special focus is given to the direc-
tional dependency of the permeability on isotropic and anisotropic geometries, considering the great impact
of anisotropy on the laboratory evaluation of permeability data and the anisotropic nature of shale rocks.
Simulation results, for the same value of porosity, clearly indicate the drastic improvement of permeability
due to the reduction of specific surface area of pores and their height to width ratio. This suggests that
rock matrix complexity has significant impact on permeability and should not be neglected while forming
permeability formulations for porous media. Finally, the results of the apparent permeability, obtained by
solving the gas kinetic equation, are taken into consideration to demonstrate the enhancement ratio, slip
factor and their correlation with the aforementioned parameters. Semi-analytical expressions for intrinsic
and apparent permeability, considering continuum and slip flow respectively, are derived. The proposed
formulations, suitable for both isotropic and anisotropic structures, have the advantage of not entailing any
numerical or experimental data as input.

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Авторы вводят связь извилистости с произведением степени размеров зерен на логарифм пористости