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Analysis of pore scale fluid migration in a porous medium- application to coal rock seam

Ji Youjun (State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation, Southwest Petroleum University, Chengdu, China and Department of Mechanical Engineering, University of California, Riverside, California, USA and School of Geoscience and Technology, Southwest Petroleum University, Chengdu, China)
K. Vafai (Department of Mechanical Engineering, University of California Riverside, Riversde, California, USA)

International Journal of Numerical Methods for Heat & Fluid Flow

ISSN: 0961-5539

Article publication date: 7 August 2017

Abstract

Purpose

The purpose of this study is to digitize the porous structure and reconstruct the geometry of the rock by using the image processing software photoshop (PS) and ant colony algorithm coded with compiler Fortran PowerStation (fps) 4.0 based on the microscopic image of a typical rock mass.

Design/methodology/approach

The digital model of the microstructure of the porous coal rock was obtained, and imported into the numerical simulation software to build the finite element model of microstructure of the porous coal rock. Creeping flow equations were used to describe the fluid flow in the porous rock.

Findings

The simulation results indicate that the method utilized for reconstructing the microstructure of the porous coal rock proposed in this work is effective. The results demonstrate that the transport of fluid in a porous medium is significantly influenced by the geometric structure of the pore and that the heterogeneous porous structure would result in an irregular flow of the fluid.

Research limitations/implications

The authors did not experience a limitation.

Practical implications

The existence of the pores with dead ends would hinder the fluid to flow through the coal rock and reduce the efficiency of extracting fluid from the porous coal rock. It is also shown that the fluid first enters the large pores and subsequently into the small pore spaces.

Social implications

The paper provides important and useful results for several industries.

Originality value

Image processing technology has been utilized to incorporate the micro image of the porous coal rock mass, based on the characteristics of pixels of the micro image. The ant colony algorithm was used to map out the boundary of the rock matrix and the pore space. A FORTRAN code was prepared to read the micro image, to transform the bmp image into a binary format, which contains only two values. The digital image was obtained after analyzing the image features. The geometric structure of the coal rock pore was then constructed. The flow process for the micro fluid in the pore structure was illustrated and the physical process of the pore scale fluid migration in the porous coal seam was analyzed.

Keywords

Acknowledgements

This work was financially supported by the open fund project (Grant No. ESP1406) from Ecological Security and Protection Key Laboratory of Sichuan Province (Mianyang Normal University), the open foundation project from State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation of Southwest Petroleum University (Grant No. PLN1131), the open foundation project (Grant No. 2016trqdz02) from Sichuan Key Laboratory of Natural Gas Geology, the project (Grant No. 2014QHZ036) from sail plan of Southwest Petroleum University, the project (No. 2014_3310, 2014_3334) from Work Safety Supervision Bureau of China and open foundation project from State Key Laboratory for Geo Mechanics and Deep Underground Engineering in China University of Mining & Technology (Grant No. SKLGDUEK1308), the major projects of national science and technology (Grant No. 2017ZX05013001-001, 2017ZX05013006-005 and 2017ZX05037001-005). The funding for the extended stay of Dr Ji Youjun at University of California, Riverside to collaborate on this research work is greatly appreciated.

Citation

Youjun, J. and Vafai, K. (2017), "Analysis of pore scale fluid migration in a porous medium- application to coal rock seam", International Journal of Numerical Methods for Heat & Fluid Flow, Vol. 27 No. 8, pp. 1706-1719. https://doi.org/10.1108/HFF-05-2016-0198

Publisher

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Emerald Publishing Limited

Copyright © 2017, Emerald Publishing Limited