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GSA Annual Meeting in Indianapolis, Indiana, USA - 2018

Paper No. 23-13
Presentation Time: 9:00 AM-5:30 PM

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


ZHANG, Kun1, SONG, Yan2, JIA, Chengzao3, JIANG, Zhenxue4, JIANG, Shu5, HUANG, Yizhou6, WEN, Ming7, LIU, Tianlin4, LIU, Xiaoxue8 and WANG, Xin9, (1)Energy & Geoscience Institute, University of Utah, Salt lack, UT 84108, (2)Research Institute of Petroleum Exploration and Development, Beijing, 100083, China, (3)Research Institute of Petroleum Exploration and Development, No.20, Xueyuan Road, Haidian District, Beijing, 100083, China, (4)Unconventional Natural Gas Institute, China University of Petroleum (Beijing), No.18, Road Fuxue, District Changping, Beijing, 102249, China, (5)Energy & Geoscience Institute, University of Utah, Salt Lake City, UT 84108, (6)China University of Petroleum (Beijing), State Key Laboratory of Petroleum Resources and Prospecting, No.18, Road Fuxue, District Changping, Beijing, 102249, China, (7)China University of Petroleum (Beijing), State Key Laboratory of Petroleum Resources and Prospecting, Beijing, 102249, China, (8)China University of Petroleum, Beijing, 102249, China; China University of Petroleum (Beijing), Unconventional Natural Gas Institute, No.18, Road Fuxue, District Changping, Beijing, 102249, China, (9)China University of Petroleum (Beijing), Unconventional Natural Gas Institute, Beijing, 102249, China

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.

Session No. 23--Booth# 35

T34. Unconventional Energy Resources (Posters)
Sunday, 4 November 2018: 9:00 AM-5:30 PM
Halls J-K (Indiana Convention Center)
Geological Society of America Abstracts with Programs. Vol. 50, No. 6
doi: 10.1130/abs/2018AM-320243
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