Sedimentary environment and organic matter accumulation of Wufeng-Longmaxi shales, southwest Yangtze Plate, China: Insights from geochemical and petrological evidence
ABSTRACT: Upper Ordovician–Lower Silurian Wufeng-Longmaxi Formation is the most developed strata of shale gas in southern China. Due to the complex sedimentary environment adjacent to the Kangdian Uplift, the favorable area for organic-rich shale development is still undetermined. The authors, there...
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KeAi Communications Co., Ltd.
2024-10-01
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| Series: | China Geology |
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| Online Access: | http://www.sciencedirect.com/science/article/pii/S2096519224001459 |
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| author | An-kun Zhao Dong Wang Qian Zhang Zi-hui Lei Qian Yu Di Zhang Ye-xin Zhou |
| author_facet | An-kun Zhao Dong Wang Qian Zhang Zi-hui Lei Qian Yu Di Zhang Ye-xin Zhou |
| author_sort | An-kun Zhao |
| collection | DOAJ |
| description | ABSTRACT: Upper Ordovician–Lower Silurian Wufeng-Longmaxi Formation is the most developed strata of shale gas in southern China. Due to the complex sedimentary environment adjacent to the Kangdian Uplift, the favorable area for organic-rich shale development is still undetermined. The authors, therefore, focus on the mechanism of accumulation of organic matter and the characterization of the sedimentary environment of the Wufeng-Longmaxi Shales to have a more complete understanding and new discovering of organic matter enrichment and favorable area in the marginal region around Sichuan Basin. Multiple methods were applied in this study, including thin section identification, scanning electron microscopy (SEM) observations and X-ray diffraction (XRD), and elemental analysis on outcrop samples. Five lithofacies have been defined according to the mineralogical and petrological analyses, including mudstone, bioclastic limestone, silty shale, dolomitic shale, and carbonaceous siliceous shale. The paleo-environments have been reconstructed and the organic enrichment mechanism has been identified as a reduced environment and high productivity. The Wufeng period is generally a suboxic environment and the early Longmaxi period is a reducing environment based on geochemical characterization. High dolomite content in the study area is accompanied by high TOC, which may potentially indicate the restricted anoxic environment formed by biological flourishing in shallower water. And for the area close to the Kangdian Uplift, the shale gas generation capability is comparatively favorable. The geochemical parameters implied that new favorable areas for shale gas exploration could be targeted, and more shale gas resources in the mountainbasin transitional zone might be identified in the future. |
| format | Article |
| id | doaj-art-4e9005a1fbd54117892844f5692973c9 |
| institution | Kabale University |
| issn | 2589-9430 |
| language | English |
| publishDate | 2024-10-01 |
| publisher | KeAi Communications Co., Ltd. |
| record_format | Article |
| series | China Geology |
| spelling | doaj-art-4e9005a1fbd54117892844f5692973c92025-08-20T03:28:41ZengKeAi Communications Co., Ltd.China Geology2589-94302024-10-017474776110.31035/cg2022074Sedimentary environment and organic matter accumulation of Wufeng-Longmaxi shales, southwest Yangtze Plate, China: Insights from geochemical and petrological evidenceAn-kun Zhao0Dong Wang1Qian Zhang2Zi-hui Lei3Qian Yu4Di Zhang5Ye-xin Zhou6Chengdu Center of China Geological Survey, Ministry of Natural Resources, Chengdu 610081, China; Key Laboratory of Sedimentary Basin and Oil and Gas Resources, Ministry of Natural Resources, Chengdu 610081, ChinaChengdu Center of China Geological Survey, Ministry of Natural Resources, Chengdu 610081, China; Key Laboratory of Sedimentary Basin and Oil and Gas Resources, Ministry of Natural Resources, Chengdu 610081, China; Corresponding author: (Dong Wang); (Qian Zhang)Chengdu Center of China Geological Survey, Ministry of Natural Resources, Chengdu 610081, China; Key Laboratory of Sedimentary Basin and Oil and Gas Resources, Ministry of Natural Resources, Chengdu 610081, China; Corresponding author: (Dong Wang); (Qian Zhang)Key Laboratory of Sedimentary Basin and Oil and Gas Resources, Ministry of Natural Resources, Chengdu 610081, China; The College of Literature and Journalism of Sichuan University, Chengdu 610064, ChinaChengdu Center of China Geological Survey, Ministry of Natural Resources, Chengdu 610081, China; Key Laboratory of Sedimentary Basin and Oil and Gas Resources, Ministry of Natural Resources, Chengdu 610081, ChinaChengdu Center of China Geological Survey, Ministry of Natural Resources, Chengdu 610081, China; Key Laboratory of Sedimentary Basin and Oil and Gas Resources, Ministry of Natural Resources, Chengdu 610081, ChinaChengdu Center of China Geological Survey, Ministry of Natural Resources, Chengdu 610081, China; Key Laboratory of Sedimentary Basin and Oil and Gas Resources, Ministry of Natural Resources, Chengdu 610081, ChinaABSTRACT: Upper Ordovician–Lower Silurian Wufeng-Longmaxi Formation is the most developed strata of shale gas in southern China. Due to the complex sedimentary environment adjacent to the Kangdian Uplift, the favorable area for organic-rich shale development is still undetermined. The authors, therefore, focus on the mechanism of accumulation of organic matter and the characterization of the sedimentary environment of the Wufeng-Longmaxi Shales to have a more complete understanding and new discovering of organic matter enrichment and favorable area in the marginal region around Sichuan Basin. Multiple methods were applied in this study, including thin section identification, scanning electron microscopy (SEM) observations and X-ray diffraction (XRD), and elemental analysis on outcrop samples. Five lithofacies have been defined according to the mineralogical and petrological analyses, including mudstone, bioclastic limestone, silty shale, dolomitic shale, and carbonaceous siliceous shale. The paleo-environments have been reconstructed and the organic enrichment mechanism has been identified as a reduced environment and high productivity. The Wufeng period is generally a suboxic environment and the early Longmaxi period is a reducing environment based on geochemical characterization. High dolomite content in the study area is accompanied by high TOC, which may potentially indicate the restricted anoxic environment formed by biological flourishing in shallower water. And for the area close to the Kangdian Uplift, the shale gas generation capability is comparatively favorable. The geochemical parameters implied that new favorable areas for shale gas exploration could be targeted, and more shale gas resources in the mountainbasin transitional zone might be identified in the future.http://www.sciencedirect.com/science/article/pii/S2096519224001459ShalesShale gasSedimentary environmentGraptoliteUpper Ordovician–Lower SilurianOrganic matter accumulation |
| spellingShingle | An-kun Zhao Dong Wang Qian Zhang Zi-hui Lei Qian Yu Di Zhang Ye-xin Zhou Sedimentary environment and organic matter accumulation of Wufeng-Longmaxi shales, southwest Yangtze Plate, China: Insights from geochemical and petrological evidence China Geology Shales Shale gas Sedimentary environment Graptolite Upper Ordovician–Lower Silurian Organic matter accumulation |
| title | Sedimentary environment and organic matter accumulation of Wufeng-Longmaxi shales, southwest Yangtze Plate, China: Insights from geochemical and petrological evidence |
| title_full | Sedimentary environment and organic matter accumulation of Wufeng-Longmaxi shales, southwest Yangtze Plate, China: Insights from geochemical and petrological evidence |
| title_fullStr | Sedimentary environment and organic matter accumulation of Wufeng-Longmaxi shales, southwest Yangtze Plate, China: Insights from geochemical and petrological evidence |
| title_full_unstemmed | Sedimentary environment and organic matter accumulation of Wufeng-Longmaxi shales, southwest Yangtze Plate, China: Insights from geochemical and petrological evidence |
| title_short | Sedimentary environment and organic matter accumulation of Wufeng-Longmaxi shales, southwest Yangtze Plate, China: Insights from geochemical and petrological evidence |
| title_sort | sedimentary environment and organic matter accumulation of wufeng longmaxi shales southwest yangtze plate china insights from geochemical and petrological evidence |
| topic | Shales Shale gas Sedimentary environment Graptolite Upper Ordovician–Lower Silurian Organic matter accumulation |
| url | http://www.sciencedirect.com/science/article/pii/S2096519224001459 |
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