Practical Use of New Microbiology Tools in Oil Production

Abstract

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.