期刊
GONDWANA RESEARCH
卷 126, 期 -, 页码 267-288出版社
ELSEVIER
DOI: 10.1016/j.gr.2023.10.007
关键词
Organic-rich shale; Graptolite biozone; Shale gas; Longmaxi Formation; Lower Silurian; Sichuan Basin
This study investigates the shale quality and shale gas potential in the upper Ordovician to lower Silurian formations in the Sichuan Basin of southern China. The distribution and characteristics of organic-rich shale are analyzed, aiding in the assessment of shale gas potential and identification of sweet spots.
Typical outcrops and shale gas wells from the upper Ordovician (Katian and Hirnantian) Wufeng Formation to the lower Silurian (Rhuddanian) Longmaxi Formation in the Sichuan Basin of southern China were selected to investigate the shale quality and shale gas potential. The chronostratigraphy was studied based on the graptolite biozones and well logging. The sedimentary environment, depositional facies, biostratigraphic distribution, depositional model and lithological characteristics were characterized. Organic-rich shale primarily developed in the late Katian to the early-middle Rhuddanian. Two organic-rich shale depocentres were identified in the southern and eastern-north-eastern Sichuan Basin. The spatial distribution of organic-rich shale of different graptolite biozones was determined and showed gradual migration northwest. The depocentre of the Dicellograptus complexus Biozone to the Cystograptus vesiculosus Biozone was controlled by paleo-uplift and a submarine high. The black shale typically lacks some graptolite biozones, and even if it is fully developed, the thickness of organic-rich shale is thin and has a poor shale gas source potential. The control effect of the graptolite biozone on shale-gasenrichment helps to evaluate the shale-gas-enriched and productive intervals accurately. This study characterises the organic-rich shale distribution in the Sichuan Basin and helps in assessing organicrich shale and identifying sweet spots of shale gas potential. (c) 2023 International Association for Gondwana Research. Published by Elsevier B.V. All rights reserved.
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