TY - JOUR
T1 - Pore network extraction for shale gas flow in nanoporous media
AU - Yi, Zhixing
AU - Hu, Shouzhi
AU - Wu, Songtao
AU - Ma, Jingsheng
AU - Gao, Jian
AU - Yuan, Yahui
N1 - Funding Information:
This study is supported by the National Natural Science Foundation (Grant No. 41572109 ), the CNPC Science and Technology Project (Grant No. 2016B-03 , 2019E-26 ), and the National Science and Technology Major Project of China (Grant No. 2017ZX05046 ), and UK NERC (Grant NE/R018022/1 ). We gratefully thank Prof. Yongbiao Wang, Prof. Wenbin Jiang, Prof. Mian Lin, Prof. Martin J. Blunt, Dr. Haishan Li, Dr. Tang Wang, and Dr. Yawen Cui for beneficial discussions. The APN simulator and shale sample can be obtained from the corresponding author upon request.
Publisher Copyright:
© 2021 Elsevier Ltd
Copyright:
Copyright 2021 Elsevier B.V., All rights reserved.
PY - 2021/4
Y1 - 2021/4
N2 - Most of pore network models were originally designed for conventional porous media (e.g. sandstone), where pore size is at micron-scale and the dominant flow is Darcy-flow. However, those models could be inapplicable for shale (a typical unconventional porous media), since plenty of nanopores exist therein and therefore the non-Darcy effects can no longer be ignored. In this contribution, the details of shale gas flow were analyzed, and it was found that flow resistance could be misestimated by previous models. For this reason, we propose a pore network model that takes into account the influences of non-Darcy effects on pore structure. In the model, pore/throat radius and throat length are not constant but change with pressure, which is distinguishable from previous models where parameters are independent of pressure. The proposed model and previous models are defined as apparent pore network (APN) and intrinsic pore network (IPN), respectively. A shale sample, imaged by focused ion beam-scanning electron microscope, was used to extract APN and IPN, and then, their network structures were compared in the terms of throat length and throat radius. Under different pressure conditions (ranging from 0.1MPa to 48MPa) and image resolutions (5nm, 10nm, 20nm, 50nm, and 100nm), shale gas flow was simulated through APN and IPN, respectively. Numerical results show that apparent permeability is likely to be erroneously predicted by IPN, while APN provides a relatively reasonable solution.
AB - Most of pore network models were originally designed for conventional porous media (e.g. sandstone), where pore size is at micron-scale and the dominant flow is Darcy-flow. However, those models could be inapplicable for shale (a typical unconventional porous media), since plenty of nanopores exist therein and therefore the non-Darcy effects can no longer be ignored. In this contribution, the details of shale gas flow were analyzed, and it was found that flow resistance could be misestimated by previous models. For this reason, we propose a pore network model that takes into account the influences of non-Darcy effects on pore structure. In the model, pore/throat radius and throat length are not constant but change with pressure, which is distinguishable from previous models where parameters are independent of pressure. The proposed model and previous models are defined as apparent pore network (APN) and intrinsic pore network (IPN), respectively. A shale sample, imaged by focused ion beam-scanning electron microscope, was used to extract APN and IPN, and then, their network structures were compared in the terms of throat length and throat radius. Under different pressure conditions (ranging from 0.1MPa to 48MPa) and image resolutions (5nm, 10nm, 20nm, 50nm, and 100nm), shale gas flow was simulated through APN and IPN, respectively. Numerical results show that apparent permeability is likely to be erroneously predicted by IPN, while APN provides a relatively reasonable solution.
KW - Apparent permeability
KW - Apparent pore network
KW - Intrinsic pore network
KW - Shale gas
UR - http://www.scopus.com/inward/record.url?scp=85099842890&partnerID=8YFLogxK
U2 - 10.1016/j.marpetgeo.2020.104896
DO - 10.1016/j.marpetgeo.2020.104896
M3 - Article
SN - 0264-8172
VL - 126
JO - Marine and Petroleum Geology
JF - Marine and Petroleum Geology
M1 - 104896
ER -