Biogenic Methane Accumulation and Production in the Jurassic Low-Rank Coal, Southwestern Ordos Basin
Geological conditions are the key for coalbed methane (CBM) accumulation and production. However, the geological feature of CBM accumulation and production in the Jurassic of Ordos Basin lacks systematic and detailed evaluation, resulting in poor CBM production in this area. This study has determine...
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MDPI AG
2022-04-01
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| Online Access: | https://www.mdpi.com/1996-1073/15/9/3255 |
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| author | Chao Zheng Dongmin Ma Yue Chen Yucheng Xia Zheng Gao Guofu Li Weibo Li |
| author_facet | Chao Zheng Dongmin Ma Yue Chen Yucheng Xia Zheng Gao Guofu Li Weibo Li |
| author_sort | Chao Zheng |
| collection | DOAJ |
| description | Geological conditions are the key for coalbed methane (CBM) accumulation and production. However, the geological feature of CBM accumulation and production in the Jurassic of Ordos Basin lacks systematic and detailed evaluation, resulting in poor CBM production in this area. This study has determined the genetic types of gas according to geochemistry characteristics of the gas, the geological factors to control CBM accumulation and production performance were revealed, and a comprehensive method was established to evaluate favorable areas based on 32 sets of CBM well production data from Jurassic Yan’an Formation. The results show the coal macerals are rich in inertinite (41.13~91.12%), and the maximum reflectance of vitrinite (<i>R</i><sub>o,max</sub>) in coal is 0.56~0.65%. According to gas compositions and carbon isotopes analysis, the δ<sup>13</sup>C(CH<sub>4</sub>) is less than −55‰, and the content of heavy hydrocarbon is less than 0.05%. The value of C<sub>1</sub>/(C<sub>2</sub> + C<sub>3</sub>) is 6800~98,000, that is, the CBM is a typical biogenic gas of low-rank coal. The CBM accumulation model is the secondary biogenic on the gentle slope of the basin margin, in which gas content is closely related to buried depth and hydrodynamic environment, i.e., the high gas content areas are mainly located in the groundwater weak runoff zone at the burial depth of 450 m~650 m, especially in the syncline. Meanwhile, gas production mainly depends on the location of the structure. The high gas production areas of vertical wells were distributed on the gentle slope with high gas content between anticline and syncline, and the horizontal wells with good performance were located near the core of the syncline. According to the above analysis combined with the random forest model, the study area was divided into different production favorable areas, which will provide a scientific basis for the CBM production wells. |
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| spelling | doaj.art-69b4da92d6bb482298177d85d4c0f9ff2023-11-23T08:08:44ZengMDPI AGEnergies1996-10732022-04-01159325510.3390/en15093255Biogenic Methane Accumulation and Production in the Jurassic Low-Rank Coal, Southwestern Ordos BasinChao Zheng0Dongmin Ma1Yue Chen2Yucheng Xia3Zheng Gao4Guofu Li5Weibo Li6School of Geology and Environment, Xi’an University of Science and Technology, Xi’an 710054, ChinaSchool of Geology and Environment, Xi’an University of Science and Technology, Xi’an 710054, ChinaSchool of Geology and Environment, Xi’an University of Science and Technology, Xi’an 710054, ChinaSchool of Geology and Environment, Xi’an University of Science and Technology, Xi’an 710054, ChinaSchool of Energy and Power Engineering, Xi’an Jiaotong University, Xi’an 710049, ChinaState Key Laboratory of Co-Mining Coal and Coalbed Methane Technology, Jincheng 048000, ChinaShaanxi Geological Science and Technology Center, Xi’an 710054, ChinaGeological conditions are the key for coalbed methane (CBM) accumulation and production. However, the geological feature of CBM accumulation and production in the Jurassic of Ordos Basin lacks systematic and detailed evaluation, resulting in poor CBM production in this area. This study has determined the genetic types of gas according to geochemistry characteristics of the gas, the geological factors to control CBM accumulation and production performance were revealed, and a comprehensive method was established to evaluate favorable areas based on 32 sets of CBM well production data from Jurassic Yan’an Formation. The results show the coal macerals are rich in inertinite (41.13~91.12%), and the maximum reflectance of vitrinite (<i>R</i><sub>o,max</sub>) in coal is 0.56~0.65%. According to gas compositions and carbon isotopes analysis, the δ<sup>13</sup>C(CH<sub>4</sub>) is less than −55‰, and the content of heavy hydrocarbon is less than 0.05%. The value of C<sub>1</sub>/(C<sub>2</sub> + C<sub>3</sub>) is 6800~98,000, that is, the CBM is a typical biogenic gas of low-rank coal. The CBM accumulation model is the secondary biogenic on the gentle slope of the basin margin, in which gas content is closely related to buried depth and hydrodynamic environment, i.e., the high gas content areas are mainly located in the groundwater weak runoff zone at the burial depth of 450 m~650 m, especially in the syncline. Meanwhile, gas production mainly depends on the location of the structure. The high gas production areas of vertical wells were distributed on the gentle slope with high gas content between anticline and syncline, and the horizontal wells with good performance were located near the core of the syncline. According to the above analysis combined with the random forest model, the study area was divided into different production favorable areas, which will provide a scientific basis for the CBM production wells.https://www.mdpi.com/1996-1073/15/9/3255low-rank coalbiogenic methanegeological factoraccumulationproduction |
| spellingShingle | Chao Zheng Dongmin Ma Yue Chen Yucheng Xia Zheng Gao Guofu Li Weibo Li Biogenic Methane Accumulation and Production in the Jurassic Low-Rank Coal, Southwestern Ordos Basin Energies low-rank coal biogenic methane geological factor accumulation production |
| title | Biogenic Methane Accumulation and Production in the Jurassic Low-Rank Coal, Southwestern Ordos Basin |
| title_full | Biogenic Methane Accumulation and Production in the Jurassic Low-Rank Coal, Southwestern Ordos Basin |
| title_fullStr | Biogenic Methane Accumulation and Production in the Jurassic Low-Rank Coal, Southwestern Ordos Basin |
| title_full_unstemmed | Biogenic Methane Accumulation and Production in the Jurassic Low-Rank Coal, Southwestern Ordos Basin |
| title_short | Biogenic Methane Accumulation and Production in the Jurassic Low-Rank Coal, Southwestern Ordos Basin |
| title_sort | biogenic methane accumulation and production in the jurassic low rank coal southwestern ordos basin |
| topic | low-rank coal biogenic methane geological factor accumulation production |
| url | https://www.mdpi.com/1996-1073/15/9/3255 |
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