What are ‘Bug Bottles’?
As highlighted in a previous blog, microbes can cause a range of microbiological problems in oil and gas extraction processes. By controlling microbial growth, operators can prevent issues such as:
- reservoir souring and
- costly microbially influenced corrosion.
Various methods are available for monitoring levels of problematic groups of bacteria, like acid-producers and sulfate-reducers. One method that has a well-established history, is the serial dilution most probable number (MPN) culture test, often referred to as “Bug Bottles.” This is a visual method, where the sample is serially diluted in a number of bottles containing growth media, allowed to incubate, and then the MPN is estimated based on the number of bottles that change colour.
The MPN culture test method is simple and easy to interpret, but there are a few limitations:
- incubation times can be significant, requiring up to 28 days depending on the microbe that’s being targeted.
- approximately <1% of microorganisms are culturable, so culture-based results can significantly underestimate the total concentration or overestimate biocide efficacy.
What is qPCR?
A great alternative that has recently gained in popularity is quantitative Polymerase Chain Reaction (qPCR). This is a DNA-based method that can be used to rapidly detect and quantify microorganisms in environmental or industrial samples. Like with serial dilution culture tests, different qPCR assays can be used to identify concentrations of key groups, such as total prokaryotes, sulfate-reducing prokaryotes, or iron-reducing bacteria.
Unlike culture-based methods, qPCR has the advantage of being:
- fast, sensitive, and highly specific.
- results can be obtained within 2.5 hours of sample collection and it does not rely on microbial growth, so it is not limited to only detecting culturable microorganisms.
- it can also be used to process a variety of sample types, such as liquids, solids, and coupons.
Historically, qPCR testing could be relatively complex compared to culture-based tests, but LuminUltra’s GeneCount® qPCR provides a complete off-the-shelf solution with assay kits that were designed and optimized for identifying key target organisms in contaminated samples from industrial, oil & gas, and wastewater facilities. The GeneCount® qPCR test also provides an excellent complement to 2nd Generation ATP® testing, as ATP can be used for routine, day-to-day monitoring, while GeneCount® qPCR can be used for weekly or monthly monitoring, with additional testing for diagnosing any identified issues.