Summary
Culture-based methods of traditional microbiology applied to the
microbiological processes involved in souring of oil fields and
microbiologically influenced corrosion (MIC) pose a risk of yielding inadequate
and contradictory results. Any cultivation step will almost certainly alter the
population characteristics and, thus, alter the results on which any evaluation
will be based. The need for cultivation-independent methods has, over the past
10 years, facilitated the development of several analytical methods for the
determination of microbial identity, quantity, and, to some extent, function,
applied directly to samples of the native population. This development so far
has been fairly limited regarding practical application, and it has only
recently been transferred to the offshore industry.
In this paper, we demonstrate the features of these novel techniques and the
benefits of applying them to two situations often encountered in offshore oil
production in the North Sea--nitrate injection and MIC.
The microbiological tools are based on the detection of the genetic material
in microorganisms. The methods include direct counting of specific groups of
microorganisms with microscopy by use of fluorescent in-situ hybridization
(FISH) and other methods that are based on direct extraction of cell genetic
material (i.e., DNA/RNA), such as quantitative polymerase chain reaction (qPCR)
and denaturing-gradient gel electrophoresis (DGGE). The paper will describe
these relatively novel molecular techniques briefly.
The paper documents the microbial-population shifts related to water
breakthrough in a nitrate-treated reservoir and shows that key microbial
populations can be identified and, thereby, this can lead to the creation of
new and strengthened surveillance strategies on microorganisms that cause
souring in these systems.
Additionally, we have shown that when applying these novel techniques to
aggressive corrosion attacks, especially under deposit corrosion, molecular
techniques are powerful tools in identifying the most probable corrosion
process in which microorganisms are implicated.
These examples are described and related to offshore operations. Special
focus is given to the use of the new and improved microbiological data in
relation to designing and testing remedial actions toward oilfield souring and
MIC.
© 2009. Society of Petroleum Engineers
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History
- Original manuscript received:
23 May 2007
- Meeting paper published:
4 September 2007
- Revised manuscript received:
23 April 2008
- Manuscript approved:
7 May 2008
- Published online:
2 March 2009
- Version of record:
26 February 2009
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