Achieve biocide selection optimization and cost effectiveness with Kill Studies
Biocide selection studies, also known as kill studies, are conducted benchtop or in a lab to determine the right microbial control product. Application environments, process components and fluid systems are mirrored to provide representative data and an understanding of the products behaviour in a specific application. Kill studies can range from everyday bottle testing procedures, to very in depth lab projects. The key to using the information to supplement the decision making process is understanding the testing limitations.
Before conducting a kill study, the parameters for successful application need to be determined. These are defined as the key performance indicators (KPI) and are important considerations within the decision making process. (i.e. to establish microbial control at or below 50/pg of ATP per ml of fluid for 1 week in a high iron brine). Once a target is established, the study has a tangible objective.
A basic kill study has 3 components
Incorporating all of these factors in the test, and using the correct fluids and commercial products, provides representative data for evaluation.
- the water/fluid system
- the biocidal products being evaluated
- the process or environmental factors such as temperature, additives, filtration or other water
The final step is to use a microbial enumeration technology that will generate the required data for review. ATP testing technology is best suited for kill studies as it enumerates the total living microbial load and can be executed in minutes. The biocides used in oil and gas applications are non-specific meaning they don’t target APB’s versus SRB’s in planktonic studies, so an effective kill will target the entire community. Additional microbial testing technologies may be applied in the selection process to supplement with speciation, such as DNA testing.
The following are some examples of kill studies conducted for different applications. Each had different KPI’s based on the application type.
Microbial control in the tank farm was required prior to injection. A glute/quat was tested against the 2K7, and looked comparable in the lab studies as shown, but wasn’t having the same effectiveness on site. The client switched to 2K7 Biocide and saw reduced counts in the tankage, as well as reduced numbers at the end of the pipelines injection wells. There was some indirect treatment improvements that helped reduce demulsifier requirements at the facility that the client attributed to this biocide application as well.
Note: Higher microbial counts are seen at short contact times, due to the mechanism of kill by 2K7. The ATP is still intact as the cell dies. This is expected especially at less than 24hrs of contact.
2K7 Biocide and Glute/Quat: Tank 1 Treatment
2K7 Biocide and Glute/Quat: Tank 2 Treatment
Due to pad completions the well would be shut in for up to 4 weeks prior to flow back. Long term control was required. The initial kill study showed reduced microbial counts up to 3 weeks with a number of biocide dosages. Control was established at 100pg of ATP per ml for this client. Upon re-inoculating a select number of tests with 1 ml of the original source waters (at 1183 pg of ATP/ml) you can see the only samples with a residual kill are the 2K7 Biocide dosed waters.
Frac Water Planktonic LifeCheck Assess
The waters were grabbed pre-chem and dosed at the noted active concentrations. 2K7 Biocide achieved control for 48hrs at 25-100ppm whereas the glute required higher concentrations of 125-250ppm active in order to maintain the same control. Long term contact was not tested for this client.
Biocide Selection Guide
Water is a part of oil and gas operations “tap to cap” from drilling new wells, operating pipelines and facilities, to final abandonment of wells and equipment. Effective operations and longevity of asset life rely on proper microbial control programs. Biocide use includes not only understanding the objectives of control, but also what influences the performance of the various biocides.
Frequently Asked Questions
The reason MIC is defined as “influenced” is because the bacteria don’t directly corrode the metal, but they accelerate the process by affecting the chemical reactions that cause corrosion. Biofilms – layers of bacteria in a matrix of slime – grow on metal surfaces changing the physical and chemical micro-environment. For example, anaerobic sulfate reducing bacteria (SRB) convert sulfate into hydrogen sulfide – a strong acid. This effectively creates a mini battery, with the metal pipe providing the negative and positive poles (anode and cathode). The resulting localized chemical reactions dissolve the metal within a small area – increasing the chances of metal failure.
Other types of bacteria have been implicated in MIC, such as acid producing bacteria (APB) and metal reducing or oxidizing bacteria (MRB and MOB); however, more research is needed.
ATP monitoring offers a powerful combination of speed, versatility, portability, and accuracy for microbial testing. All living cells contain ATP regardless of whether they are bacteria, fungi, or any other type of microbe. As such, its measurement is a direct indication of the microbial content in your sample. Our LifeCheck ATP test kit is an easy, fast and accurate microbial enumeration method, valuable in routine monitoring and supporting microbial management programs.