T23 Unconventional Energy Resources (Posters)

Sunday, 4 November 2018
9:00 AM - 5:30 PM
Halls J-K

ENRICHMENT MECHANISM OF MARINE SHALE GAS IN ANTICLINES: A CASE STUDY OF THE SOUTHERN SICHUAN BASIN AND XIUWU BASIN IN THE YANGTZE REGION

Paper number: T23-13
Program: Technical Sessions
Time: 9:00 AM – 5:30 PM

Authors

  • Kun Zhang Presenting Author
    University of Utah, Salt lack, UT
  • Xin Wang
    Unconventional Natural Gas Institute, Beijing
  • Yan Song
    Research Institute of Petroleum Exploration and Development, Beijing
  • Chengzao Jia
    Research Institute of Petroleum Exploration and Development, Beijing
  • Zhenxue Jiang
    China University of Petroleum (Beijing), Beijing
  • Shu Jiang
    University of Utah, Salt Lake City, UT
  • Yizhou Huang
    State Key Laboratory of Petroleum Resources and Prospecting, Beijing
  • Ming Wen
    State Key Laboratory of Petroleum Resources and Prospecting, Beijing
  • Tianlin Liu
    China University of Petroleum (Beijing), Beijing
  • Xiaoxue Liu
    Unconventional Natural Gas Institute, Beijing

Abstract

The study of tectonics is one of the important aspects of shale gas preservation，which is vital for understanding the gas enrichment mechanism of marine shale reservoir in anticlines. In this study, triaxial unloading tests, permeability tests perpendicular and parallel to the bedding plane, FIB-HIM tests and inclusion analyses are carried out with real drilling data to characterize the shale gas enrichment factors of Upper Ordovician and the Lower Silurian shales in the Yangtze region. The mechanism of marine shale gas enrichment in anticlines is studied through aspects of the angle of the limbs and the burial depth. For anticlines with adjacent synclines, the migration pattern of shale gas is investigated through the aspects of dynamics, channels and processes of migration. This study reveals that a limb angle of greater than 120°has a relatively good condition for shale gas preservation, while limb angles of less than 70° indicate relatively poor conditions. Also, this study suggests that extensive and dense fractures will form at a certain depth range and horizontal stress field during the process of uplift, resulting in the large loss of shale gas. The regression equation of the fractured depth (H) and the horizontal stress (S) is proposed as H = 15.404S-754.41 (with a correlation coefficient R² = 0.6834). The bedding plane and the organic pores will provide the migration pathways for natural gas. With the existence of both anticlines and contiguous synclines, shale gas leaks through fractures resulted from extrusion along the anticline and the uplift effect. In addition, driven by differences in the formation pressure coefficients, shale gas is capable of migrating in a short-distance stairs-type style from synclines to the adjacent anticlines. The deeply buried syncline is suggested to have favorable conditions for shale gas enrichment. Thus, the optimal well positions should be placed in the deeper syncline with an allowance for the drilling cost.

Geological Society of America Abstracts with Programs. Vol. 50, No. 6

doi: 10.1130/abs/2018AM-320243

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