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| Titel |
Methanogenic Oil Degradation in the Dagang Oil Field |
| VerfasserIn |
Nuria Jimenez, Minmin Cai, Nontje Straaten, Jun Yao, Hans Hermann Richnow, Martin Krüger |
| Konferenz |
EGU General Assembly 2014
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250095429
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| Publikation (Nr.) |
 EGU/EGU2014-10880.pdf |
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| Zusammenfassung |
| Anaerobic biodegradation is one of the main in situ oil transformation processes in
subsurface oil reservoirs. Recent studies have provided evidence of biodegradation of residual
oil constituents under methanogenic conditions. Methane, like other biogenic gases, may
contribute to reduce the viscosity of oil and enhance its flow characteristics (making it more
available) but it can also be used as a energy source. So the aim of the present study was to
provide reliable information on in situ biotransformation of oil under methanogenic
conditions, and to assess the feasibility of implementing a MEOR strategy at this
site. For this reason, chemical and isotopic analyses of injection and production
fluids of the Dagang oil field (Hebei province, China) were performed. Microbial
abundances were assessed by qPCR, and clone libraries were performed to study the
diversity. In addition, microcosms with either oil or 13C-labelled hydrocarbons were
inoculated with injection or production waters to characterize microbial processes in
vitro.
Geochemical and isotopic data were consistent with in situ biogenic methane production
linked to aliphatic and aromatic hydrocarbon degradation: GC-MS profiles of petroleum
samples were nearly devoid of n-alkanes, linear alkylbenzenes, and alkyltoluenes, and light
PAH, confirming that Dagang oil is mostly highly weathered. In addition, carbon and
hydrogen isotopic signatures of methane (δ13CCH4 and δDCH4, respectively), and the
bulk isotopic discrimination (Δδ13C) between methane and CO2 (between 32 and
65 ) were in accordance with previously reported values for methane formation
during hydrocarbon degradation. Furthermore, methane-producing Archaea and
hydrocarbon-degrading Bacteria were abundant in produced oil-water samples. On the
other hand, our laboratory degradation experiments revealed that autochthonous
microbiota are capable of significantly degrade oil within several months, with
biodegradation patterns resembling those observed in situ, and of producing heavy methane
from 13C-labelled n-hexadecane or 2-methylnaphthalene (δ13C > 550 and 300,
respectively). These results suggest that in situ methanogenesis may occur from the
aliphatic and polyaromatic fractions of Dagang reservoir fluids. In summary, the
studied areas of the Dagang oilfield may have a significant potential for the in situ
conversion of oil into methane as a possible way to increase total hydrocarbon recovery. |
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