Marine Shale Gas Occurrence and Its Influencing Factors: A Case Study from the Wufeng-Longmaxi Formation, Northwestern Guizhou, China
Organic-rich shales were found in the Ordovician to Silurian Wufeng-Longmaxi Formation in northwestern Guizhou province, China, which has high shale gas content revealed by field measurement. Shale gas occurrence, free gas/sorbed gas ratio, and their influencing factors are crucial for shale gas exp...
Saved in:
| Main Authors: | , , , , , , , |
|---|---|
| Format: | Article |
| Language: | English |
| Published: |
Wiley
2022-01-01
|
| Series: | Geofluids |
| Online Access: | http://dx.doi.org/10.1155/2022/2036451 |
| Tags: |
Add Tag
No Tags, Be the first to tag this record!
|
| _version_ | 1832564892162326528 |
|---|---|
| author | Taotao Cao Hu Liu Anyang Pan Mo Deng Qinggu Cao Ye Yu Yanran Huang Zhenghui Xiao |
| author_facet | Taotao Cao Hu Liu Anyang Pan Mo Deng Qinggu Cao Ye Yu Yanran Huang Zhenghui Xiao |
| author_sort | Taotao Cao |
| collection | DOAJ |
| description | Organic-rich shales were found in the Ordovician to Silurian Wufeng-Longmaxi Formation in northwestern Guizhou province, China, which has high shale gas content revealed by field measurement. Shale gas occurrence, free gas/sorbed gas ratio, and their influencing factors are crucial for shale gas exploitation strategy. Results indicated that the Wufeng-Longmaxi shales are dominated by type I kerogen, with total organic carbon (TOC) and equivalent vitrinite reflectance (eqvRo) of 0.77%–6.98% and 2.37%–2.53%, respectively. The total porosity and permeability are in the range of 1.23%–8.43% and 3×10−4–2.23×10−1 mD, respectively. FE-SEM observation and correlation analysis show shale porosity is dominated by organic matter (OM) pores, followed by interparticle (interP) pores related to brittle minerals. CH4, derived from oil cracking, is the main component of shale gas, but its proportion is lower than that in Fuling and Weiyuan areas, probably due to the weak preservation condition. Desorption gas and lost gas determined by in situ desorption test are 0.42–1.54 cm3/g and 1.9–7.14 cm3/g, respectively, and Langmuir volume (VL) from isothermal adsorption experiment is 1.63–4.78 cm3/g. Shale gas content is positively correlated with micropore volume, mesopore volume and TOC content but negatively correlated with macropore volume and clay mineral content, indicating that methane is preferentially stored in micropores (<2 nm) and mesopores (2–50 nm) related to OMs. By comparing actual total gas content with theoretical gas content, shale gas is considered to exist primarily in sorbed state, and the free gas proportion can increase with increased TOC content, due to that OM pores with larger sizes are also main space for free gas. Combined with the two methods, it can result in accurate calculations of shale gas reserves and free/sorbed gas ratio. Based on this understanding, a model of shale gas occurrence was proposed, which can provide a reference for shale gas exploitation in normal pressure areas. |
| format | Article |
| id | doaj-art-744dd5fec9974e658a66e563291822af |
| institution | Kabale University |
| issn | 1468-8123 |
| language | English |
| publishDate | 2022-01-01 |
| publisher | Wiley |
| record_format | Article |
| series | Geofluids |
| spelling | doaj-art-744dd5fec9974e658a66e563291822af2025-02-03T01:09:53ZengWileyGeofluids1468-81232022-01-01202210.1155/2022/2036451Marine Shale Gas Occurrence and Its Influencing Factors: A Case Study from the Wufeng-Longmaxi Formation, Northwestern Guizhou, ChinaTaotao Cao0Hu Liu1Anyang Pan2Mo Deng3Qinggu Cao4Ye Yu5Yanran Huang6Zhenghui Xiao7School of Earth Sciences and Spatial Information EngineeringShale Gas Evaluation and Exploitation Key Laboratory of Sichuan ProvinceWuxi Research Institute of Petroleum GeologyWuxi Research Institute of Petroleum GeologyWuxi Research Institute of Petroleum GeologySchool of Earth Sciences and Spatial Information EngineeringSchool of Earth Sciences and Spatial Information EngineeringDepartment of GeologyOrganic-rich shales were found in the Ordovician to Silurian Wufeng-Longmaxi Formation in northwestern Guizhou province, China, which has high shale gas content revealed by field measurement. Shale gas occurrence, free gas/sorbed gas ratio, and their influencing factors are crucial for shale gas exploitation strategy. Results indicated that the Wufeng-Longmaxi shales are dominated by type I kerogen, with total organic carbon (TOC) and equivalent vitrinite reflectance (eqvRo) of 0.77%–6.98% and 2.37%–2.53%, respectively. The total porosity and permeability are in the range of 1.23%–8.43% and 3×10−4–2.23×10−1 mD, respectively. FE-SEM observation and correlation analysis show shale porosity is dominated by organic matter (OM) pores, followed by interparticle (interP) pores related to brittle minerals. CH4, derived from oil cracking, is the main component of shale gas, but its proportion is lower than that in Fuling and Weiyuan areas, probably due to the weak preservation condition. Desorption gas and lost gas determined by in situ desorption test are 0.42–1.54 cm3/g and 1.9–7.14 cm3/g, respectively, and Langmuir volume (VL) from isothermal adsorption experiment is 1.63–4.78 cm3/g. Shale gas content is positively correlated with micropore volume, mesopore volume and TOC content but negatively correlated with macropore volume and clay mineral content, indicating that methane is preferentially stored in micropores (<2 nm) and mesopores (2–50 nm) related to OMs. By comparing actual total gas content with theoretical gas content, shale gas is considered to exist primarily in sorbed state, and the free gas proportion can increase with increased TOC content, due to that OM pores with larger sizes are also main space for free gas. Combined with the two methods, it can result in accurate calculations of shale gas reserves and free/sorbed gas ratio. Based on this understanding, a model of shale gas occurrence was proposed, which can provide a reference for shale gas exploitation in normal pressure areas.http://dx.doi.org/10.1155/2022/2036451 |
| spellingShingle | Taotao Cao Hu Liu Anyang Pan Mo Deng Qinggu Cao Ye Yu Yanran Huang Zhenghui Xiao Marine Shale Gas Occurrence and Its Influencing Factors: A Case Study from the Wufeng-Longmaxi Formation, Northwestern Guizhou, China Geofluids |
| title | Marine Shale Gas Occurrence and Its Influencing Factors: A Case Study from the Wufeng-Longmaxi Formation, Northwestern Guizhou, China |
| title_full | Marine Shale Gas Occurrence and Its Influencing Factors: A Case Study from the Wufeng-Longmaxi Formation, Northwestern Guizhou, China |
| title_fullStr | Marine Shale Gas Occurrence and Its Influencing Factors: A Case Study from the Wufeng-Longmaxi Formation, Northwestern Guizhou, China |
| title_full_unstemmed | Marine Shale Gas Occurrence and Its Influencing Factors: A Case Study from the Wufeng-Longmaxi Formation, Northwestern Guizhou, China |
| title_short | Marine Shale Gas Occurrence and Its Influencing Factors: A Case Study from the Wufeng-Longmaxi Formation, Northwestern Guizhou, China |
| title_sort | marine shale gas occurrence and its influencing factors a case study from the wufeng longmaxi formation northwestern guizhou china |
| url | http://dx.doi.org/10.1155/2022/2036451 |
| work_keys_str_mv | AT taotaocao marineshalegasoccurrenceanditsinfluencingfactorsacasestudyfromthewufenglongmaxiformationnorthwesternguizhouchina AT huliu marineshalegasoccurrenceanditsinfluencingfactorsacasestudyfromthewufenglongmaxiformationnorthwesternguizhouchina AT anyangpan marineshalegasoccurrenceanditsinfluencingfactorsacasestudyfromthewufenglongmaxiformationnorthwesternguizhouchina AT modeng marineshalegasoccurrenceanditsinfluencingfactorsacasestudyfromthewufenglongmaxiformationnorthwesternguizhouchina AT qinggucao marineshalegasoccurrenceanditsinfluencingfactorsacasestudyfromthewufenglongmaxiformationnorthwesternguizhouchina AT yeyu marineshalegasoccurrenceanditsinfluencingfactorsacasestudyfromthewufenglongmaxiformationnorthwesternguizhouchina AT yanranhuang marineshalegasoccurrenceanditsinfluencingfactorsacasestudyfromthewufenglongmaxiformationnorthwesternguizhouchina AT zhenghuixiao marineshalegasoccurrenceanditsinfluencingfactorsacasestudyfromthewufenglongmaxiformationnorthwesternguizhouchina |