Lithofacies types, reservoir characteristics and silica origin of marine shales: A case study of the Wufeng formation–Longmaxi Formation in the Luzhou area, southern Sichuan Basin
Shale, which is a fine-grained sedimentary rock, differs in reservoir quality (RQ) and completion quality (CQ) as the result of variations in its mineral and organic-matter compositions. The RQ and CQ directly affect shale gas exploitation. Therefore, classification of the lithofacies types of shale...
| Main Authors: | , , , , , , |
|---|---|
| Format: | Article |
| Language: | English |
| Published: |
KeAi Communications Co., Ltd.
2022-08-01
|
| Series: | Natural Gas Industry B |
| Subjects: | |
| Online Access: | http://www.sciencedirect.com/science/article/pii/S2352854022000523 |
| _version_ | 1797286327533699072 |
|---|---|
| author | Shuyan Wang Ling Man Shiqian Wang Lei Wu Yiqing Zhu Yi Li Yifan He |
| author_facet | Shuyan Wang Ling Man Shiqian Wang Lei Wu Yiqing Zhu Yi Li Yifan He |
| author_sort | Shuyan Wang |
| collection | DOAJ |
| description | Shale, which is a fine-grained sedimentary rock, differs in reservoir quality (RQ) and completion quality (CQ) as the result of variations in its mineral and organic-matter compositions. The RQ and CQ directly affect shale gas exploitation. Therefore, classification of the lithofacies types of shale, analysis of the reservoir differences of different lithofacies, and identification of the superior shale lithofacies with the best RQ and CQ are important for decisions on well placement, targeting the “sweet spot” zone and optimizing the expected ultimate recovery of a shale gas well. In this study, several methods including microscopic observation of thin sections, X-ray diffraction analysis, core analysis and elemental geochemistry were used to investigate the lithofacies types, reservoir characteristics and silica origin of the marine shales of the Wufeng Formation–Longmaxi Formation (WF Fm.–LMX Fm.) in the Luzhou area, southern Sichuan Basin, China. The lithofacies characteristics exhibit marked differences through the WF–LMX shale succession. Specifically, the lower gas-bearing zone (LMX-1) is mainly composed of siliceous shales and siliceous–argillaceous mixed shales, whereas the upper gas-bearing zone (LMX-4) mostly contains argillaceous shales and argillaceous–siliceous mixed shales. The lower shale gas reservoirs have a higher silica content and lower clay and carbonate contents than the upper zones, and thus superior petrophysical qualities. The upper part of the WF Fm. (WF-2) and the lower part of the LMX Fm (LMX-1, LMX-2) are rich in bio-chemical authigenic silica, whereas the silica minerals of other intervals are mainly derived from allochthonous terrigenous material. The siliceous shales and siliceous–argillaceous mixed shales with a biogenic quartz content greater than 40% have the best RQ and CQ and are the most promising lithofacies for shale gas in the Luzhou area. Although the upper gas-bearing zones represented by LMX-4 are also good shale gas reservoirs, the RQ, CQ and gas content are generally worse than those of the lower gas-bearing zones because of the silica origin and lithofacies types; thus, extracting shale gas from the upper zones would be a greater challenge. |
| first_indexed | 2024-03-07T18:16:40Z |
| format | Article |
| id | doaj.art-42c04b433e994383acde9bcd730e97e9 |
| institution | Directory Open Access Journal |
| issn | 2352-8540 |
| language | English |
| last_indexed | 2024-03-07T18:16:40Z |
| publishDate | 2022-08-01 |
| publisher | KeAi Communications Co., Ltd. |
| record_format | Article |
| series | Natural Gas Industry B |
| spelling | doaj.art-42c04b433e994383acde9bcd730e97e92024-03-02T07:30:17ZengKeAi Communications Co., Ltd.Natural Gas Industry B2352-85402022-08-0194394410Lithofacies types, reservoir characteristics and silica origin of marine shales: A case study of the Wufeng formation–Longmaxi Formation in the Luzhou area, southern Sichuan BasinShuyan Wang0Ling Man1Shiqian Wang2Lei Wu3Yiqing Zhu4Yi Li5Yifan He6Exploration Division of PetroChina Southwest Oil & Gasfield CompanyExploration and Development Research Institute of PetroChina Southwest Oil & Gasfield CompanyShale Gas Research Institute of PetroChina Southwest Oil & Gasfield Company; Corresponding author.Shale Gas Project Management Department of CNPC Chuanqing Drilling Engineering Co., LtdShale Gas Research Institute of PetroChina Southwest Oil & Gasfield CompanyShale Gas Research Institute of PetroChina Southwest Oil & Gasfield CompanyShale Gas Research Institute of PetroChina Southwest Oil & Gasfield CompanyShale, which is a fine-grained sedimentary rock, differs in reservoir quality (RQ) and completion quality (CQ) as the result of variations in its mineral and organic-matter compositions. The RQ and CQ directly affect shale gas exploitation. Therefore, classification of the lithofacies types of shale, analysis of the reservoir differences of different lithofacies, and identification of the superior shale lithofacies with the best RQ and CQ are important for decisions on well placement, targeting the “sweet spot” zone and optimizing the expected ultimate recovery of a shale gas well. In this study, several methods including microscopic observation of thin sections, X-ray diffraction analysis, core analysis and elemental geochemistry were used to investigate the lithofacies types, reservoir characteristics and silica origin of the marine shales of the Wufeng Formation–Longmaxi Formation (WF Fm.–LMX Fm.) in the Luzhou area, southern Sichuan Basin, China. The lithofacies characteristics exhibit marked differences through the WF–LMX shale succession. Specifically, the lower gas-bearing zone (LMX-1) is mainly composed of siliceous shales and siliceous–argillaceous mixed shales, whereas the upper gas-bearing zone (LMX-4) mostly contains argillaceous shales and argillaceous–siliceous mixed shales. The lower shale gas reservoirs have a higher silica content and lower clay and carbonate contents than the upper zones, and thus superior petrophysical qualities. The upper part of the WF Fm. (WF-2) and the lower part of the LMX Fm (LMX-1, LMX-2) are rich in bio-chemical authigenic silica, whereas the silica minerals of other intervals are mainly derived from allochthonous terrigenous material. The siliceous shales and siliceous–argillaceous mixed shales with a biogenic quartz content greater than 40% have the best RQ and CQ and are the most promising lithofacies for shale gas in the Luzhou area. Although the upper gas-bearing zones represented by LMX-4 are also good shale gas reservoirs, the RQ, CQ and gas content are generally worse than those of the lower gas-bearing zones because of the silica origin and lithofacies types; thus, extracting shale gas from the upper zones would be a greater challenge.http://www.sciencedirect.com/science/article/pii/S2352854022000523Shale gasMineralogyLithofaciesReservoir qualityElemental geochemistryWufeng shale |
| spellingShingle | Shuyan Wang Ling Man Shiqian Wang Lei Wu Yiqing Zhu Yi Li Yifan He Lithofacies types, reservoir characteristics and silica origin of marine shales: A case study of the Wufeng formation–Longmaxi Formation in the Luzhou area, southern Sichuan Basin Natural Gas Industry B Shale gas Mineralogy Lithofacies Reservoir quality Elemental geochemistry Wufeng shale |
| title | Lithofacies types, reservoir characteristics and silica origin of marine shales: A case study of the Wufeng formation–Longmaxi Formation in the Luzhou area, southern Sichuan Basin |
| title_full | Lithofacies types, reservoir characteristics and silica origin of marine shales: A case study of the Wufeng formation–Longmaxi Formation in the Luzhou area, southern Sichuan Basin |
| title_fullStr | Lithofacies types, reservoir characteristics and silica origin of marine shales: A case study of the Wufeng formation–Longmaxi Formation in the Luzhou area, southern Sichuan Basin |
| title_full_unstemmed | Lithofacies types, reservoir characteristics and silica origin of marine shales: A case study of the Wufeng formation–Longmaxi Formation in the Luzhou area, southern Sichuan Basin |
| title_short | Lithofacies types, reservoir characteristics and silica origin of marine shales: A case study of the Wufeng formation–Longmaxi Formation in the Luzhou area, southern Sichuan Basin |
| title_sort | lithofacies types reservoir characteristics and silica origin of marine shales a case study of the wufeng formation longmaxi formation in the luzhou area southern sichuan basin |
| topic | Shale gas Mineralogy Lithofacies Reservoir quality Elemental geochemistry Wufeng shale |
| url | http://www.sciencedirect.com/science/article/pii/S2352854022000523 |
| work_keys_str_mv | AT shuyanwang lithofaciestypesreservoircharacteristicsandsilicaoriginofmarineshalesacasestudyofthewufengformationlongmaxiformationintheluzhouareasouthernsichuanbasin AT lingman lithofaciestypesreservoircharacteristicsandsilicaoriginofmarineshalesacasestudyofthewufengformationlongmaxiformationintheluzhouareasouthernsichuanbasin AT shiqianwang lithofaciestypesreservoircharacteristicsandsilicaoriginofmarineshalesacasestudyofthewufengformationlongmaxiformationintheluzhouareasouthernsichuanbasin AT leiwu lithofaciestypesreservoircharacteristicsandsilicaoriginofmarineshalesacasestudyofthewufengformationlongmaxiformationintheluzhouareasouthernsichuanbasin AT yiqingzhu lithofaciestypesreservoircharacteristicsandsilicaoriginofmarineshalesacasestudyofthewufengformationlongmaxiformationintheluzhouareasouthernsichuanbasin AT yili lithofaciestypesreservoircharacteristicsandsilicaoriginofmarineshalesacasestudyofthewufengformationlongmaxiformationintheluzhouareasouthernsichuanbasin AT yifanhe lithofaciestypesreservoircharacteristicsandsilicaoriginofmarineshalesacasestudyofthewufengformationlongmaxiformationintheluzhouareasouthernsichuanbasin |