{"title":"中国西北准噶尔盆地古油藏甲烷生成的证据及其意义","authors":"Wenjie Zhang, Wenxuan Hu, Xiaolin Wang, Jian Cao, Suping Yao, Ning Zhu","doi":"10.1016/j.jseaes.2024.106171","DOIUrl":null,"url":null,"abstract":"<div><p>Methanogenesis is considered to be the dominant type of biodegradation in subsurface oil reservoirs; however, this process is difficult to identify under geological environments. In this study, bitumen, microfossils, and secondary minerals were analysed to reveal the characteristics and conditions of methanogenesis in subsurface oil reservoirs in the Junggar Basin, western China. Bitumen with biodegradation characteristics and nanoscale microfossils were observed in the pores and fractures of reservoirs; these confirmed the existence of microbial activity in the palaeo-oil reservoirs. Secondary calcite that formed simultaneously with bitumen had a high positive δ<sup>13</sup>C (up to +20 ‰), which further suggested that methanogenesis was the main biodegradation type. Based on comprehensive analyses of δ<sup>13</sup>C, <sup>87</sup>Sr/<sup>86</sup>Sr, trace element, and fluid inclusions, the methanogenesis is proposed to occur in Mn-rich and hydrocarbon-bearing fluids at 45℃–85 ℃ (∼1000 m to ∼2200 m subsurface) approximately 230 Mya, which is consistent with the earliest hydrocarbon accumulation in the reservoirs. The results effectively reveal the process of methanogenesis and how it was masked by the charging of late oil, thus demonstrating the advantages of inorganic geochemical analyses when solving problems of oil biodegradation. The established geological model was used to discover the other subsurface methanogenesis cases in the basin and also provides a reference for analysing microbially mediated subsurface carbon cycling.</p></div>","PeriodicalId":50253,"journal":{"name":"Journal of Asian Earth Sciences","volume":null,"pages":null},"PeriodicalIF":2.7000,"publicationDate":"2024-05-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":"{\"title\":\"Evidence and significance of methanogenesis in paleo-oil reservoirs in Junggar Basin, NW China\",\"authors\":\"Wenjie Zhang, Wenxuan Hu, Xiaolin Wang, Jian Cao, Suping Yao, Ning Zhu\",\"doi\":\"10.1016/j.jseaes.2024.106171\",\"DOIUrl\":null,\"url\":null,\"abstract\":\"<div><p>Methanogenesis is considered to be the dominant type of biodegradation in subsurface oil reservoirs; however, this process is difficult to identify under geological environments. In this study, bitumen, microfossils, and secondary minerals were analysed to reveal the characteristics and conditions of methanogenesis in subsurface oil reservoirs in the Junggar Basin, western China. Bitumen with biodegradation characteristics and nanoscale microfossils were observed in the pores and fractures of reservoirs; these confirmed the existence of microbial activity in the palaeo-oil reservoirs. Secondary calcite that formed simultaneously with bitumen had a high positive δ<sup>13</sup>C (up to +20 ‰), which further suggested that methanogenesis was the main biodegradation type. Based on comprehensive analyses of δ<sup>13</sup>C, <sup>87</sup>Sr/<sup>86</sup>Sr, trace element, and fluid inclusions, the methanogenesis is proposed to occur in Mn-rich and hydrocarbon-bearing fluids at 45℃–85 ℃ (∼1000 m to ∼2200 m subsurface) approximately 230 Mya, which is consistent with the earliest hydrocarbon accumulation in the reservoirs. The results effectively reveal the process of methanogenesis and how it was masked by the charging of late oil, thus demonstrating the advantages of inorganic geochemical analyses when solving problems of oil biodegradation. The established geological model was used to discover the other subsurface methanogenesis cases in the basin and also provides a reference for analysing microbially mediated subsurface carbon cycling.</p></div>\",\"PeriodicalId\":50253,\"journal\":{\"name\":\"Journal of Asian Earth Sciences\",\"volume\":null,\"pages\":null},\"PeriodicalIF\":2.7000,\"publicationDate\":\"2024-05-08\",\"publicationTypes\":\"Journal Article\",\"fieldsOfStudy\":null,\"isOpenAccess\":false,\"openAccessPdf\":\"\",\"citationCount\":\"0\",\"resultStr\":null,\"platform\":\"Semanticscholar\",\"paperid\":null,\"PeriodicalName\":\"Journal of Asian Earth Sciences\",\"FirstCategoryId\":\"89\",\"ListUrlMain\":\"https://www.sciencedirect.com/science/article/pii/S1367912024001664\",\"RegionNum\":3,\"RegionCategory\":\"地球科学\",\"ArticlePicture\":[],\"TitleCN\":null,\"AbstractTextCN\":null,\"PMCID\":null,\"EPubDate\":\"\",\"PubModel\":\"\",\"JCR\":\"Q2\",\"JCRName\":\"GEOSCIENCES, MULTIDISCIPLINARY\",\"Score\":null,\"Total\":0}","platform":"Semanticscholar","paperid":null,"PeriodicalName":"Journal of Asian Earth Sciences","FirstCategoryId":"89","ListUrlMain":"https://www.sciencedirect.com/science/article/pii/S1367912024001664","RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q2","JCRName":"GEOSCIENCES, MULTIDISCIPLINARY","Score":null,"Total":0}
Evidence and significance of methanogenesis in paleo-oil reservoirs in Junggar Basin, NW China
Methanogenesis is considered to be the dominant type of biodegradation in subsurface oil reservoirs; however, this process is difficult to identify under geological environments. In this study, bitumen, microfossils, and secondary minerals were analysed to reveal the characteristics and conditions of methanogenesis in subsurface oil reservoirs in the Junggar Basin, western China. Bitumen with biodegradation characteristics and nanoscale microfossils were observed in the pores and fractures of reservoirs; these confirmed the existence of microbial activity in the palaeo-oil reservoirs. Secondary calcite that formed simultaneously with bitumen had a high positive δ13C (up to +20 ‰), which further suggested that methanogenesis was the main biodegradation type. Based on comprehensive analyses of δ13C, 87Sr/86Sr, trace element, and fluid inclusions, the methanogenesis is proposed to occur in Mn-rich and hydrocarbon-bearing fluids at 45℃–85 ℃ (∼1000 m to ∼2200 m subsurface) approximately 230 Mya, which is consistent with the earliest hydrocarbon accumulation in the reservoirs. The results effectively reveal the process of methanogenesis and how it was masked by the charging of late oil, thus demonstrating the advantages of inorganic geochemical analyses when solving problems of oil biodegradation. The established geological model was used to discover the other subsurface methanogenesis cases in the basin and also provides a reference for analysing microbially mediated subsurface carbon cycling.
期刊介绍:
Journal of Asian Earth Sciences has an open access mirror journal Journal of Asian Earth Sciences: X, sharing the same aims and scope, editorial team, submission system and rigorous peer review.
The Journal of Asian Earth Sciences is an international interdisciplinary journal devoted to all aspects of research related to the solid Earth Sciences of Asia. The Journal publishes high quality, peer-reviewed scientific papers on the regional geology, tectonics, geochemistry and geophysics of Asia. It will be devoted primarily to research papers but short communications relating to new developments of broad interest, reviews and book reviews will also be included. Papers must have international appeal and should present work of more than local significance.
The scope includes deep processes of the Asian continent and its adjacent oceans; seismology and earthquakes; orogeny, magmatism, metamorphism and volcanism; growth, deformation and destruction of the Asian crust; crust-mantle interaction; evolution of life (early life, biostratigraphy, biogeography and mass-extinction); fluids, fluxes and reservoirs of mineral and energy resources; surface processes (weathering, erosion, transport and deposition of sediments) and resulting geomorphology; and the response of the Earth to global climate change as viewed within the Asian continent and surrounding oceans.