Pore-scale modeling of pore structure properties and wettability effect on permeability of low-rank coal

Xiangjie Qin ¹Jianchao Cai ¹Gang Wang²

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作者信息

1. State Key Laboratory of Petroleum Resources and Prospecting,China University of Petroleum,Beijing 102249,China
2. State Key Laboratory of Mining Disaster Prevention and Control Cofounded by Shandong Province and the Ministry of Science and Technology,Shandong University of Science and Technology,Qingdao 266590,China
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Abstract

Permeability is a key parameter for coalbed methane development.Although the absolute permeability of coal has been extensively studied,wettability and pore structure properties continue to challenge the microscopic description of water-gas flow in coal.For this purpose,we reconstructed the microstructures of low-rank coal using micro-computed tomography(micro-CT)images.Pore geometry and pore-throat parameters are introduced to establish a relationship with absolute permeability.A dual-porosity pore network model is developed to study water-gas displacement under different wetting and pore structure properties.Results show that absolute permeability is significantly affected by pore geometry and can be described using a binary quadratic function of porosity and fractal dimension.Water-gas relative perme-ability varies significantly and the residual gas saturation is lower;the crossover saturation first decreased and then increased with increasing porosity under hydrophobic conditions.While the water relative permeability is lower and a certain amount of gas is trapped in complex pore-throat networks;the crossover saturation is higher under hydrophilic conditions.Models with large percolating porosity and well-developed pore networks have high displacement efficiency due to low capillary resistance and avoidance of trapping.This work provides a systematic description of absolute permeability and water-gas relative permeability in coal microstructure for enhanced gas recovery.

Key words

Micro-CT/Permeability/Wetting condition/Pore structure properties/Water-gas flow

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基金项目

National Natural Science Foundation of China(51934004)

National Natural Science Foundation of China(51974176)

Natural Science Foundation for Distinguished Young Scholars of Shandong Province(ZR2020JQ22)

Youth Science and Technology Innovation of Shandong Province(2019KJH006)

Special Funds for Taishan Scholar Project(TS20190935)

出版年

2023

矿业科学技术学报(英文版)

中国矿业大学

矿业科学技术学报(英文版)

CSTPCDCSCD北大核心EI

影响因子：1.222

ISSN：2095-2686

参考文献量4

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