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Multi-scale insights on the threshold pressure gradient in low-permeability porous media


Wang, H and Wang, J and Wang, X and Chan, A, Multi-scale insights on the threshold pressure gradient in low-permeability porous media, Symmetry, 12 Article 364. ISSN 2073-8994 (2020) [Refereed Article]


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Copyright 2020 The Authors. Licensed under Creative Commons Attribution 4.0 International (CC BY 4.0)

DOI: doi:10.3390/sym12030364


Low‐permeability porous medium usually has asymmetric distributions of pore sizes and pore‐throat tortuosity, thus has a non‐linear flow behavior with an initial pressure gradient observed in experiments. A threshold pressure gradient (TPG) has been proposed as a crucial parameter to describe this non‐linear flow behavior. However, the determination of this TPG is still unclear. This study provides multi‐scale insights on the TPG in low‐permeability porous media. First, a semi‐empirical formula of TPG was proposed based on a macroscopic relationship with permeability, water saturation, and pore pressure, and verified by three sets of experimental data. Second, a fractal model of capillary tubes was developed to link this TPG formula with structural parameters of porous media (pore‐size distribution fractal dimension and tortuosity fractal dimension), residual water saturation, and capillary pressure. The effect of pore structure complexity on the TPG is explicitly derived. It is found that the effects of water saturation and pore pressure on the TPG follow an exponential function and the TPG is a linear function of yield stress. These effects are also spatially asymmetric. Complex pore structures significantly affect the TPG only in the range of low porosity, but water saturation and yield stress have effects on a wider range of porosity. These results are meaningful to the understanding of non‐linear flow mechanism in low‐permeability reservoirs.

Item Details

Item Type:Refereed Article
Keywords:threshold pressure gradient, non‐Darcy flow, fractal theory, residual water saturation
Research Division:Engineering
Research Group:Civil engineering
Research Field:Civil geotechnical engineering
Objective Division:Energy
Objective Group:Mining and extraction of energy resources
Objective Field:Oil and gas extraction
UTAS Author:Wang, H (Mr Huimin Wang)
UTAS Author:Wang, X (Professor Xiaolin Wang)
UTAS Author:Chan, A (Professor Andrew Chan)
ID Code:137760
Year Published:2020
Web of Science® Times Cited:3
Deposited By:Engineering
Deposited On:2020-03-03
Last Modified:2020-12-07
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