Study on the Sedimentary Environments and Its Implications of Shale Reservoirs for Permian Longtan Formation in the Southeast Sichuan Basin
Marine–continental transitional shale is one of the most promising targets for shale gas exploration in the Lower Yangtze region. To investigate the sedimentary environments and the regularity of the enrichment of the Longtan shale, multiple techniques including core and thin-section observations, g...
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| Format: | Article |
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MDPI AG
2023-05-01
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| Series: | Minerals |
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| Online Access: | https://www.mdpi.com/2075-163X/13/5/689 |
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| author | Yana Chen Xuewen Shi Hao Xu Qian Cao Xiangyang Pei Wei Wu Linqi Wang Xue Yang |
| author_facet | Yana Chen Xuewen Shi Hao Xu Qian Cao Xiangyang Pei Wei Wu Linqi Wang Xue Yang |
| author_sort | Yana Chen |
| collection | DOAJ |
| description | Marine–continental transitional shale is one of the most promising targets for shale gas exploration in the Lower Yangtze region. To investigate the sedimentary environments and the regularity of the enrichment of the Longtan shale, multiple techniques including core and thin-section observations, geochemical and elemental analyses, X-ray diffraction, scanning electron microscopy (SEM), and low-pressure nitrogen adsorption (LPNA) were used to analyze the sedimentology, mineralogy, and pore structure of the Longtan shale. The core descriptions and thin-section observations showed that the Longtan shale was deposited in marine–delta transitional environments including delta-front, shore swamp, mixed tidal flat and shallow shelf environments. The Sr/Cu, V/Cr, CIA, EF (Mo), EF (U), and other major and trace element results indicated warm and moist climates and water-reducing conditions in the Longtan period. Both the climate and water conditions were favorable for organic matter production and preservation. The geochemical results showed that the Longtan shale was in the overmature stage (Ro values ranging from 2.4% to 3.57%) and that the average total organic carbon (TOC) content was 5.76%. The pore system of the Longtan shale consisted of inorganic pores with a small number of organic pores and microfractures. The porosity and specific surface area were mainly affected by the TOC and clay mineral contents. An effective combination of brittle mineral particles, organic matter, and clay minerals provided the necessary conditions for pore preservation. The organic pores, intergranular pores in clay minerals, and brittle mineral pores formed the main network system for the Longtan shale. In summary, the lithological combinations, organic geochemistry, and pore structure system were all affected by the sedimentary environments. |
| first_indexed | 2024-03-11T03:27:11Z |
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| institution | Directory Open Access Journal |
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| language | English |
| last_indexed | 2024-03-11T03:27:11Z |
| publishDate | 2023-05-01 |
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| record_format | Article |
| series | Minerals |
| spelling | doaj.art-31eae75e818c4cf68c652d5cc9ab1f5f2023-11-18T02:37:10ZengMDPI AGMinerals2075-163X2023-05-0113568910.3390/min13050689Study on the Sedimentary Environments and Its Implications of Shale Reservoirs for Permian Longtan Formation in the Southeast Sichuan BasinYana Chen0Xuewen Shi1Hao Xu2Qian Cao3Xiangyang Pei4Wei Wu5Linqi Wang6Xue Yang7PetroChina Research Institute of Petroleum Exploration & Development, Beijing 100083, ChinaShale Gas Research Center, PetroChina Southwest Oil & Gasfield Company, Chengdu 610051, ChinaState Key Laboratory of Oil and Gas Reservoir Geology and Exploitation, Chengdu University of Technology, Chengdu 610059, ChinaState Key Laboratory of Oil and Gas Reservoir Geology and Exploitation, Chengdu University of Technology, Chengdu 610059, ChinaPetroChina Research Institute of Petroleum Exploration & Development, Beijing 100083, ChinaShale Gas Research Center, PetroChina Southwest Oil & Gasfield Company, Chengdu 610051, ChinaState Key Laboratory of Oil and Gas Reservoir Geology and Exploitation, Chengdu University of Technology, Chengdu 610059, ChinaShale Gas Research Center, PetroChina Southwest Oil & Gasfield Company, Chengdu 610051, ChinaMarine–continental transitional shale is one of the most promising targets for shale gas exploration in the Lower Yangtze region. To investigate the sedimentary environments and the regularity of the enrichment of the Longtan shale, multiple techniques including core and thin-section observations, geochemical and elemental analyses, X-ray diffraction, scanning electron microscopy (SEM), and low-pressure nitrogen adsorption (LPNA) were used to analyze the sedimentology, mineralogy, and pore structure of the Longtan shale. The core descriptions and thin-section observations showed that the Longtan shale was deposited in marine–delta transitional environments including delta-front, shore swamp, mixed tidal flat and shallow shelf environments. The Sr/Cu, V/Cr, CIA, EF (Mo), EF (U), and other major and trace element results indicated warm and moist climates and water-reducing conditions in the Longtan period. Both the climate and water conditions were favorable for organic matter production and preservation. The geochemical results showed that the Longtan shale was in the overmature stage (Ro values ranging from 2.4% to 3.57%) and that the average total organic carbon (TOC) content was 5.76%. The pore system of the Longtan shale consisted of inorganic pores with a small number of organic pores and microfractures. The porosity and specific surface area were mainly affected by the TOC and clay mineral contents. An effective combination of brittle mineral particles, organic matter, and clay minerals provided the necessary conditions for pore preservation. The organic pores, intergranular pores in clay minerals, and brittle mineral pores formed the main network system for the Longtan shale. In summary, the lithological combinations, organic geochemistry, and pore structure system were all affected by the sedimentary environments.https://www.mdpi.com/2075-163X/13/5/689sedimentary faciespore systemLongtan Formationsoutheast Sichuan Basin |
| spellingShingle | Yana Chen Xuewen Shi Hao Xu Qian Cao Xiangyang Pei Wei Wu Linqi Wang Xue Yang Study on the Sedimentary Environments and Its Implications of Shale Reservoirs for Permian Longtan Formation in the Southeast Sichuan Basin Minerals sedimentary facies pore system Longtan Formation southeast Sichuan Basin |
| title | Study on the Sedimentary Environments and Its Implications of Shale Reservoirs for Permian Longtan Formation in the Southeast Sichuan Basin |
| title_full | Study on the Sedimentary Environments and Its Implications of Shale Reservoirs for Permian Longtan Formation in the Southeast Sichuan Basin |
| title_fullStr | Study on the Sedimentary Environments and Its Implications of Shale Reservoirs for Permian Longtan Formation in the Southeast Sichuan Basin |
| title_full_unstemmed | Study on the Sedimentary Environments and Its Implications of Shale Reservoirs for Permian Longtan Formation in the Southeast Sichuan Basin |
| title_short | Study on the Sedimentary Environments and Its Implications of Shale Reservoirs for Permian Longtan Formation in the Southeast Sichuan Basin |
| title_sort | study on the sedimentary environments and its implications of shale reservoirs for permian longtan formation in the southeast sichuan basin |
| topic | sedimentary facies pore system Longtan Formation southeast Sichuan Basin |
| url | https://www.mdpi.com/2075-163X/13/5/689 |
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