TY - JOUR
T1 - Comparative study of nanoscale pore structure of Lower Palaeozoic marine shales in the Middle-Upper Yangtze area, China
T2 - Implications for gas production potential
AU - Wang, Yang
AU - Zhu, Yanming
AU - Liu, Shimin
AU - Chen, Shangbin
AU - Zhang, Rui
N1 - Funding Information:
The authors would like to thank the financial support of the Fundamental Research Funds for the Central Universities (no. 2017CXNL03) and National Science and Technology Major Project (2017ZX05035004‐002).
Publisher Copyright:
Copyright © 2017 John Wiley & Sons, Ltd.
PY - 2018/11/1
Y1 - 2018/11/1
N2 - The Lower Cambrian Niutitang and Lower Silurian Longmaxi shales in the Middle-Upper Yangtze area are considered the primary shale gas units targeted for development in China. To shed some light on the difference in nanopore structures between Niutitang and Longmaxi shales, systematic comparative investigations were conducted using various techniques, including geochemical analyses, field emission scanning electron microscopy (FE-SEM), high-pressure mercury intrusion porosimetry (MIP), and low-pressure N2/CO2 adsorption techniques. The results show that both Niutitang and Longmaxi shales have high total organic carbon (TOC) content and complex mineral compositions. The porosity of Longmaxi shales is higher than that of Niutitang shales, with an average value of 3.26% and 2.04%, respectively. Interestingly, for both shale formations, the mesopores (2–50 nm) are the major contributors to pore volumes, whereas the specific surface area is dominated by micropores (<2 nm). For the mesopore size distributions (PSDs) calculated from the N2 adsorption, the Longmaxi shales have a dominant pore size ranging from 10 to 60 nm. In contrast, there are more fine mesopores (2–8 nm) in the Niutitang shales. Furthermore, we found that numerous nanoscale pores are well-developed within graptolite-derived organic matter (OM) in the Longmaxi shales. These interconnected graptolite periderm pore systems may not only provide a storage space for both adsorbed and free gas but also serve as pathways for gas transport. The Niutitang shales developed relatively fewer OM pores with smaller diameters, lower OM surface porosity, and lower connectivity compared to the Longmaxi shales. The differences in OM pore structure partly explain why there is a large production difference between these two formations.
AB - The Lower Cambrian Niutitang and Lower Silurian Longmaxi shales in the Middle-Upper Yangtze area are considered the primary shale gas units targeted for development in China. To shed some light on the difference in nanopore structures between Niutitang and Longmaxi shales, systematic comparative investigations were conducted using various techniques, including geochemical analyses, field emission scanning electron microscopy (FE-SEM), high-pressure mercury intrusion porosimetry (MIP), and low-pressure N2/CO2 adsorption techniques. The results show that both Niutitang and Longmaxi shales have high total organic carbon (TOC) content and complex mineral compositions. The porosity of Longmaxi shales is higher than that of Niutitang shales, with an average value of 3.26% and 2.04%, respectively. Interestingly, for both shale formations, the mesopores (2–50 nm) are the major contributors to pore volumes, whereas the specific surface area is dominated by micropores (<2 nm). For the mesopore size distributions (PSDs) calculated from the N2 adsorption, the Longmaxi shales have a dominant pore size ranging from 10 to 60 nm. In contrast, there are more fine mesopores (2–8 nm) in the Niutitang shales. Furthermore, we found that numerous nanoscale pores are well-developed within graptolite-derived organic matter (OM) in the Longmaxi shales. These interconnected graptolite periderm pore systems may not only provide a storage space for both adsorbed and free gas but also serve as pathways for gas transport. The Niutitang shales developed relatively fewer OM pores with smaller diameters, lower OM surface porosity, and lower connectivity compared to the Longmaxi shales. The differences in OM pore structure partly explain why there is a large production difference between these two formations.
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U2 - 10.1002/gj.3075
DO - 10.1002/gj.3075
M3 - Article
AN - SCOPUS:85056855534
VL - 53
SP - 2413
EP - 2426
JO - Geological Journal
JF - Geological Journal
SN - 0072-1050
IS - 6
ER -