Oil & Gas Geology ›› 2020, Vol. 41 ›› Issue (5): 1060-1072.doi: 10.11743/ogg20200516

• Petroleum Geology • Previous Articles     Next Articles

Characteristics and controlling factors of organic-matter pores in Longmaxi Formation shale, Middle Yangtze Region: A case study of Well YY3

Jian Hong1(), Xuan Tang1,*(), Cong Zhang2, Huang Huang1, Yansheng Shan2, Yuyan Zheng1, Huangchang Xie1   

  1. 1. Key Laboratory of Shale Gas Exploration and Evaluation(Ministry of Land and Resources), China University of Geosciences(Beijing), Beijing 100083, China
    2. Oil and Gas Resource Survey Center of China Geological Survey, Beijing 100083, China
  • Received:2018-08-27 Online:2020-10-28 Published:2020-10-22
  • Contact: Xuan Tang E-mail:lcbhj@qq.com;Tangxuan@cugb.edu.cn

Abstract:

The exploration and development of shale gas in the Jiaoshiba gas field, a major Longmaxi Formation shale gas field in the Upper Yangtze Region, has made great success.However, the resource potential of the formation is still unclear.To this end, the characteristics and controlling factors of organic-matter pores in shale samples from the Well YY3 in the Yongshun area, Hunan Provinces, are analyzed to provide references for the assessment of shale reservoir properties in the formation.The Longmaxi Formation shale from the Well YY3 contains typical marine organic matter, and is characterized by a total organic matter content (TOC) of 0.65%-3.81% (1.87% on average), high-to-over-mature thermal maturity and low porosity (2.06% on average).The pores in the samples were systematically observed under scanning electron microscopy (SEM) after an Argon-ion-polishing treatment.Moreover, the characteristics of organic-matter pores were analyzed with energy spectrum test and JMicro Vision image processing software; and a new characterization method based on SEM images was proposed to describe the pore connectivity.The results show that the Longmaxi Formation shale contains mostly migrated organic matters with well-developed pore systems and native organic matters with under-developed pores.As a whole, the pore growth in organic matters of the shale in the formation is heterogeneous and mainly controlled by the micro-components of organic matters as well as the content of organic carbon and clay minerals, and at higher thermal evolution stages, organic carbon content plays a critical role in the development of pores in organic matters.

Key words: organic-matter pore, organic-matter thin section porosity, shale, Longmaxi Formation, Well YY3, Middle Yangtze Region

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