Oil souring has important implications with respect
to energy resources. Understanding the physiology of the
microorganisms that play a role and the biological mechanisms
are both important for the maintenance of infrastructure
and mitigation of corrosion processes. The objective of this
study was to identify crude-oil components and microorganisms
in oil-field water that contribute to crude-oil souring. To
identify the crude-oil components and microorganisms that
are responsible for anaerobic souring in oil reservoirs, biological
conversion of crude-oil components under anaerobic conditions
was investigated. Microorganisms in oil field water in
Akita, Japan degraded alkanes and aromatics to volatile fatty
acids (VFAs) under anaerobic conditions, and fermenting
bacteria such as Fusibacter sp. were involved in VFA production.
Aromatics such as toluene and ethylbenzene were
degraded by sulfate-reducing bacteria (Desulfotignum sp.) via
the fumarate-addition pathway and not only degradation of
VFA but also degradation of aromatics by sulfate-reducing
bacteria was the cause of souring. Naphthenic acid and 2,4-
xylenol were not converted.