Sulfide generation by sulfate-reducing prokaryotes (SRP) is the major cause of reservoir
souring and microbiologically influenced corrosion (MIC). The monitoring of SRP in oil fields is typically
carried out by cultivation based methods. It is widely accepted that the cultivation approach grossly
underestimates population sizes by several orders of magnitude due to the majority of SRP in oil field
samples being not readily viable in selective culture media.
In this paper molecular microbiology methods (MMM) are used to unveil the true
distribution of SRP in oil field systems. These techniques are based on characterization of DNA and/or
RNA content in the samples rather than on viable counts of some microorganisms. Case studies on
produced water, injection water, and scale are described, showing how a combination of polymerase
chain reaction (PCR) and quantitative fluorescence in situ hybridization (qFISH) has detected a
diversity of sulfate-reducing as well as other sulfide-producing, troublesome microorganisms (TM) far
exceeding what was previously recognized. Moreover, a quantitative polymerase chain reaction (qPCR)
has been applied as a step towards a further understanding of the role of SRP in oil fields. The new
qPCR approach specifically targets functional genes involved in sulfate reduction. This paper presents
the first proof-of-concept for the qPCR technique applied in enumeration of SRP in the Danish Sector of
the North Sea.
Keywords: oil field souring, microbiologically influenced corrosion (MIC), sulfate-reducing
prokaryotes (SRP), quantitative fluorescence in situ hybridization (qFISH), quantitative polymerase
chain reaction (qPCR), denaturing gradient gel electrophoresis (DGGE)