T217 The Unconventional Shale Systems: From Source-Rocks to Reservoirs II

Thursday, 29 October 2020
1:30 PM - 5:30 PM
Meeting Rooms

EFFECTS OF THERMAL EVOLUTION OF ORGANIC MATTER ON THE GENESIS OF SHALE GAS AND THE DEVELOPMENT OF ORGANIC MATTER PORES: A CASE STUDY OF MARINE SHALE IN THE UPPER YANGTZE REGION, SOUTH CHINA

Paper number: T217-21
Program: Technical Sessions
Time: 4:45 PM – 4:50 PM

Authors

  • Kun Zhang Presenting Author
    Southwest Petroleum University, Chengdu
  • Xin Ji
    Southwest Petroleum University, Chengdu
  • Xiang Li
    Southwest Petroleum University, Chengdu
  • Peng Yang
    Southwest Petroleum University, Chengdu
  • Jun Peng
    Southwest Petroleum University, Chengdu
  • Xin Wang
    China University of Petroleum, Beijing, Beijing
  • Xin Wang
    China University of Petroleum, Beijing, China, Beijing
  • Zixin Xue
    China University of Petroleum, Beijing, Beijing
  • Ming Wen
    China University of Petroleum, Beijing, Beijing
  • Yizhou Huang
    University of Bristol, Bristol
  • Xiaoxue Liu
    China University of Petroleum, Beijing, Beijing
  • Yiming Yang
    Southwest Petroleum University, Chengdu
  • Yao Zeng
    Southwest Petroleum University, Chengdu

Abstract

The Marine shale in southern China has undergone complex tectonic evolution with high thermal evolution degree. Excessive thermal evolution brings certain risks to shale gas exploration and development. With the advancement of experimental methods, the evolution process of shale reservoirs can be better understood from the the micro-nano scale. This work takes the Ordovician-Silurian Wufeng and the first member of Longmaxi Formation in the Sichuan Basin and Lower Cambrian Niutitang Formation in Outer Margin of the Sichuan Basin to study the impact of maturity upon the genesis of shale gas and development features of the reservoir. A series of geochemical research methods, including TOC, gas component and gas isotope, were adopted to study the impact of different thermal evolution stages of organic matter upon the genesis of shale gas. The nanoscale micro-imaging technique, such as FIB-SEM and FIB-HIM, was used to analyze the development of OM-hosted pores. As shown from the results, when Ro=1.2%~3.5%, the marine shale gas is dominated by the methane and other hydrocarbon gases, since the mixture of cracking gas from liquid hydrocarbons and kerogen-cracking gas cause the carbon isotope reversal. Besides, the pyrobitumen pores characterized by the strong connectivity and storage capacity were primarily developed. When Ro>3.5%, the organic matter is at the graphitization stage. The shale gas is mainly composed by nitrogen at this stage. The nitrogen is originated from the atmosphere and the thermal evolution process, and the OM-hosted pores (pyrobitumen and kerogen pores) characterized by the bad connectivity and storage capacity are developed. Finally, the main component of shale gas, the genesis of shale gas and pattern of OM-hosted pores under different thermal evolution stages of organic matter are summarized, which provides technical support for the exploration and development of shale gas.

Geological Society of America Abstracts with Programs. Vol. 52, No. 6

doi: 10.1130/abs/2020AM-350924

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