Abstract
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.
