Natural gas potential of Carboniferous and Permian transitional shales in central Hunan, South China

Research output: Contribution to journalArticlepeer-review

Authors

  • Zhenghui Zhao
  • Jianqiang Tan
  • Yiwen Ju
  • Rongfeng Yang
  • Ping Zhou
  • Yanran Huang
  • Bowen Ning
  • Jisong Liu

Colleges, School and Institutes

External organisations

  • Central South University
  • Chinese Academy of Sciences
  • Hunan University of Science and Technology
  • Hunan Institute of Engineering
  • China Chemical Geology and Mine Bureau

Abstract

The Carboniferous Ceshui formation and Permian Longtan and Dalong formations were deposited in transitional settings preserved in what is now central Hunan Province, South China, as they are potential natural gas plays. In this study, we analysed the total organic carbon (TOC), vitrinite reflectance (Ro), kerogen type, mineralogy, porosity, permeability, and methane adsorption of representative shale samples from these rock units. Our results indicate that TOC content can be as high as 9.2%, with a mean (x̄) of 3.5%. The Permian shale formations were deposited in more strongly reducing environments than the Carboniferous Ceshui shale. The kerogen composition of the Carboniferous Ceshui shale is dominated by Type III, while both of the Permian shales contain primarily Type II kerogens; Ro values range from 1.1% to 2.4% (x̄=1.6%). The organic matter in all the studied shales is in the wet gas window of thermal maturity and is relatively less mature than Lower Palaeozoic marine shales in south China. Mineral compositions are dominated by quartz (x̄=53.8%) and clay (x̄=35.6%), suggesting a high brittleness index. Porosity ranges from 0.5% to 14% (x̄=6.4%), while permeability varies from 0.0026 micro Darcy (mD) to 0.0640 mD (x̄=0.0130 mD). The gas adsorption capacity varies from 1.24 to 4.53 cm3/g (x̄=2.40 cm3/g). Relatively less mature shale samples (Ro<1.5%) have low methane adsorption capacities, regardless of their TOC values. However, the methane adsorption capacity of more mature (Ro>1.5%) shales samples exhibit a positive correlation with TOC content.

Details

Original languageEnglish
Pages (from-to)520-533
JournalJournal of Natural Gas Science and Engineering
Volume55
Early online date18 May 2018
Publication statusPublished - 1 Jul 2018

Keywords

  • lower carboniferous, upper Permian, natural gas, transitional shale, unconventional reservoir, Hunan province

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