Sequence Stratigraphic Characteristics and Organic Matter Enrichment of Wufeng-Longmaxi Formation in Northwestern Hunan—
  A Case Study of Well XY-3

doi:10.11867/j.issn.1001-8166.2021.077

Advances in Earth Science ›› 2021, Vol. 36 ›› Issue (10): 1026-1038. doi: 10.11867/j.issn.1001-8166.2021.077

Sequence Stratigraphic Characteristics and Organic Matter Enrichment of Wufeng-Longmaxi Formation in Northwestern Hunan— A Case Study of Well XY-3

Bing ZHANG ¹ ^, ² ^, ³( ), Shuheng TANG ¹ ^, ² ^, ³( ), Zhaodong XI ¹ ^, ² ^, ³, Donglin LIN ¹ ^, ² ^, ³, Yapei YE ¹ ^, ² ^, ³

^1.School of Energy Resources，China University of Geosciences （Beijing），Beijing 100083，China
^2.Key Laboratory of Marine Reservoir Evolution and Hydrocarbon Enrichment Mechanism，Ministry of Education，Beijing 100083，China
^3.Beijing Key Laboratory of Unconventional Natural Gas Geological Evaluation and Development Engineering，Beijing 100083，China

Received:2021-05-06 Revised:2021-07-19 Online:2021-10-10 Published:2021-11-19
Contact: Shuheng TANG E-mail:2106190036@cugb.edu.cn;tangsh@cugb.edu.cn
About author:ZHANG Bing (1995-), male, Anqing City, Anhui Province, Master student. Research areas include unconventional gas geology. E-mail: 2106190036@cugb.edu.cn
Supported by:
the National Science and Technology Major Project "Assessment on the enrichment law and key targets of shale gas in Sichuan Basin and its periphery"(2017zx05035)

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Bing ZHANG, Shuheng TANG, Zhaodong XI, Donglin LIN, Yapei YE. Sequence Stratigraphic Characteristics and Organic Matter Enrichment of Wufeng-Longmaxi Formation in Northwestern Hunan— A Case Study of Well XY-3[J]. Advances in Earth Science, 2021, 36(10): 1026-1038.

The marine black shale from Wufeng Formation of Upper Ordovician to Longmaxi Formation of Lower Silurian is widely developed in Northwest Hunan， with large thickness， high thermal evolution and relatively moderate buried depth， which has a good prospect for shale gas exploration and development. In order to study the stratigraphic sequence characteristics of Wufeng-Longmaxi Formation in Northwest Hunan， based on the wavelet transform of GR logging curve of Well XY-3， combined with element geochemical characteristics， organic matter abundance， graptolite type and lithologic characteristics， the sequence framework of Wufeng-Longmaxi Formation in the study area is established， and the characteristics of differential enrichment of organic matter in the sequence framework are discussed. The results show that the Wufeng-Longmaxi Formation of Well XY-3 is divided into two third-order sequences： SQ-1 and SQ-2， and the four system tracts are TST1， HST1， TST2 and HST2 respectively. However， the abundance of organic matter in HST1 and HST2 system tracts is relatively low， and the average TOC is 0.89% and 0.26%. The deposition was in an oxidizing environment with relatively high deposition rate， high paleoproductivity and relatively high terrigenous input；the abundance of organic matter in TST1 and TST2 system tracts is relatively high， and the average TOC is 1.46% and 1.35%. It was deposited in a poor oxidation environment with relatively small deposition rate， high paleoproductivity and less terrigenous clastic input. Compared with the organic rich horizons exposed in Wufeng-Longmaxi Formation in Changning and Jiaoshiba areas at the same time， the organic rich interval of Well XY-3 in Northwest Hunan was in an environment with relatively strong oxidation and relatively high paleoproductivity. Under the condition of relatively low deposition rate， the deposition thickness and organic matter abundance of organic rich shale are obviously low. The research results provide guiding significance for shale gas exploration and development in Northwest Hunan.

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