Contents lists available at ScienceDirect International Journal of Coal Geology journal homepage: www.elsevier.com/locate/coal Quantitative characterization of pore connectivity using NMR and MIP: A case study of the Wangyinpu and Guanyintang shales in the Xiuwu basin, Southern China Fenglin Gao a,b,c , Yan Song a,b,d, ⁎ , Zhuo Li a,b , Fengyang Xiong e , Lei Chen a,b,c , Xinxin Zhang f , Zhiyuan Chen a,b,c , Joachim Moortgat e a State Key Laboratory of Petroleum Resources and Prospecting, China University of Petroleum, Beijing 102249, China b Unconventional Natural Gas Institute, China University of Petroleum, Beijing 102249, China c Unconventional Oil & Gas Cooperative Innovation Center, China University of Petroleum, Beijing 102249, China d Research Institute of Petroleum Exploration and Development, Beijing 100083, China e School of Earth Sciences, The Ohio State University, Columbus, OH 43210, USA f Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China ARTICLE INFO Keywords: Wangyinpu and Guanyintang shales Pore size distribution Pore connectivity Stratification Pore morphology ABSTRACT Pore connectivity is one of the most important characteristics of shale reservoirs because it significantly impacts the effective pore space, the fluid migration, and the gas production. In this work, pore connectivity and its primary controlling factors were investigated using a combination of field emission-scanning electron micro- scopy (FE-SEM), focused ion beam-scanning electron microscopy (FIB-SEM), mercury intrusion porosimetry (MIP), and nuclear magnetic resonance (NMR). The results show that using the difference between NMR and MIP is a reliable method to characterize pore connectivity. NMR pore size distribution (PSD) curves converted from T 2 spectra, and MIP PSD curves were observed to have consistent shapes. The amplitude of NMR PSD curves is higher than that of MIP PSD curves for S-group pores (< 200 nm), while the relationship is opposite for L-group pores (200 nm–10 μm), which may be due to the permeability of shale. A low permeability allows a smaller amount of mercury to intrude into the small pores. Based on experimental results, the pores of 8–20 nm make a contribution of 5%–11% to pore connectivity, whereas the pores of 200–700 nm are mainly interparticle pores and microfissures, contributing from 38% to 72% of pore connectivity. Stratification and pore morphology in the Lower Cambrian Wangyinpu and Guanyintang shales in the Xiuwu Basin are the two critical influencing factors of pore connectivity. The pore connectivity of well-laminated shale is higher than that of less-laminated shale. The laminated structures are usually composed of argillaceous and siliceous lamina, which tend to give rise to fissures during hydrocarbon generation or under confining stress. As a result, the pores around the microfissures are more likely to be communicating. Shales with the structure of uniformly distributed organic and inorganic minerals have the best pore connectivity. Both the interparticle pores and microfissures between organic matter and inorganic minerals or between inorganic minerals can effectively connect organic pore networks and greatly improve the pore connectivity. 1. Introduction The success of shale gas exploration and development in the United States encourages other countries with large proven reserves of shale gas to adopt similar technologies to satisfy increasing energy demands. Because its reserves and production of conventional oil and gas has plateaued in the past decade. China has gradually shifted its energy paradigm from conventional to cleaner natural gas resources, especially shale gas (Jia et al., 2012; Zou et al., 2012). It is reported that the total technically recoverable shale gas resource in China reaches 25.08 tril- lion cubic meters (Zhang et al., 2011; C.G.S., 2014). At present, China has established several national research areas to better understand the storage mechanisms of shale gas, such as Sichuan Jiaoshiba, Changning Weiyuan, and Yuannan Zhaotong Area. Those national research areas include both shale plays that are capable of commercial production and uncommercial shale plays for comparison. https://doi.org/10.1016/j.coal.2018.07.007 Received 12 March 2018; Received in revised form 16 July 2018; Accepted 18 July 2018 ⁎ Corresponding author. E-mail address: songyanbsy@126.com (Y. Song). International Journal of Coal Geology 197 (2018) 53–65 Available online 19 July 2018 0166-5162/ © 2018 Published by Elsevier B.V. T