Mineral-controlled nm-μm-scale pore structure of saline lacustrine shale in Qianjiang Depression, Jianghan Basin, China

• Published in: Marine and petroleum geology 2019-01, Vol.99, p.347-354
• Main Authors: Zhang, Yuxiang, Hu, Qinhong, Long, Shengxiang, Zhao, Jianhua, Peng, Nyujia, Wang, Haitao, Lin, Xiang, Sun, Mengdi
• Format: Article
• Language: English
• Subjects: Pore structure; Qianjiang; SANS; Shale
• ISSN: 0264-8172
• DOI: 10.1016/j.marpetgeo.2018.10.016

The pore structure of the saline lacustrine shales in the Eq3 unit of the Qianjiang Formation was characterized for pore space of μm-nm scales through a combined study of mercury injection capillary pressure (MICP) and small/ultra-small angle neutron scattering (SANS and USANS). X-ray diffraction (XRD) and total organic carbon (TOC) content tests, as well as field emission-scanning electron microscopy (FE-SEM) imaging, are also employed to obtain the mineralogical composition, organic richness, as well as the general pore types and sizes of the selected Qianjiang shale samples. In these samples, three major rock types are identified: (1) silica-rich carbonate mudstone; (2) carbonate/siliceous mudstone; and (3) salt. The porosity, as well as pore size and pore-throat size distributions, generated from both SANS/USANS and MICP techniques indicate a porous rock matrix and well-connected pore networks in the two mudstone rock types. Meanwhile, an averaged TOC of around 3.5 wt% for Eq3 unit exhibits a good quality for oil generation potential. This study primarily provides new insights into the pore structure of the Qianjiang shales across a wide measurable range for both pore and pore-throat sizes, and correlates the pore structure and mineral compositions at different scales. •Pore structure of the saline lacustrine shales of the Qianjiang Formation was characterized.•A combined study of SANS/USANS measurement and MICP analysis was employed.•A porous rock matrix and well-connected pore network were found for silica-rich carbonate and carbonate/siliceous mudstone.•Qianjiang shales have a wide measurable pore size range which correlates to mineral compositions at different scales.