Abstract
Monitoring of microbial populations in oil and gas operations is routinely conducted in order to evaluate the need for and performance of biocides. Operators utilize a variety of methods designed to determine if bacteria and archaea capable of causing corrosion, fouling, or souring are present in the systems before, during, and after control methods are applied. Each monitoring method has strengths and limitations, and an understanding of the strengths and limitations is crucial to deciding the best method for any given system. The most obvious considerations are the accuracy of the test, cost, ease of use, and time required to obtain the results. How comparable results are from a given location or time to another time, and the value of the data for making higher-level decisions also should be considered. In this study, we will share the results obtained from analyzing samples collected from various phases of natural gas and oil production operations. These locations include microbial populations collected from a range of operating temperatures, pressures and salinities as well as those treated with different types of biocides. Four methods, culture based enumeration using bug bottles with indicator media for sulfate-reducing bacteria (SRB) and acid-producing bacteria (APB), rapid bacterial cell enumeration based on an adenosine triphosphate (ATP) quantification assay, epifluorescence microscopy, and molecular analysis of the microbial populations by DNA isolation and sequencing of 16S amplicons were directly compared. The results are discussed in terms of agreement between the methods, difficulty of the approaches, and the relative value of each data set for future use.
