Linking Fractal Theory to a Fully Coupled Coal Deformation and Two-Phase Flow Multiphysics: The Role of Fractal Dimensions

Jianwei Tian, Jishan Liu, Derek Elsworth, Yee-Kwong Leong, Wai Li

Research output: Contribution to journalArticlepeer-review

7 Citations (Scopus)

Abstract

The fractal nature of coal pore sizes affects both coal absolute and relative permeabilities. Previous studies have demonstrated the significant role of coal absolute permeability models in evaluating coal gas extraction, but the role of relative permeability models remains unknown. In this study, the fractal theory was employed to derive new relative permeability models. These new models are verified against the relative permeability data available in the literature. The verified permeability models are used to fully couple coal deformation and two-phase flow during coalbed methane extraction. The degenerated fully coupled model was verified against data obtained from another commercial simulator. The verified model was applied to conduct a series of sensitivity studies of gas production to fractal dimensions. The results show that the larger fractal dimension suggests higher residual water saturation, which compromises the relative permeability correspondingly. The larger fractal parameter facilitates gas recovery although the capillary pressure is enhanced accordingly. Absolute permeability rebounds with the decline of pore pressure, indicating that the dominant factor for gas production transforms from relative permeability in the early stage to absolute permeability in the later stage.

Original languageEnglish
Pages (from-to)12591-12605
Number of pages15
JournalEnergy & Fuels
Volume36
Issue number20
DOIs
Publication statusPublished - 20 Oct 2022

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