Continuous Biocide Application Improves Life of Facility, Reducing Average Corrosion Rates by 35 to 77% Without Rotation of Biocides

Abstract Controlling microbiologically influenced corrosion (MIC) is of critical importance to midstream and upstream operators. MIC can proceed at aggressive localized rates causing unpredictable and premature failures. MIC control through biocide application can help minimize the environmental impact, providing safe and effective transport of crude oil essential to ensuring supply during the energy transition. Many operators feel they must rotate biocides and use batch treatments to avoid creating a biocide resistant microbial population. While this is a long-standing, industry-wide chemical treating opinion, very few, if any, biocide resistant examples exist in the oil and gas literature. This study presents a comprehensive, data-driven analysis using extensive field data to evaluate the efficacy of continuous biocide treatment for controlling MIC without inducing microbial resistance. An operator encountering MIC-induced pin hole leaks at the 6 o’clock position within a crude oil transport line used a continuous treatment application with the same biocide for approximately 1 year, where treatment rates remained constant. Extensive molecular monitoring using the AccuCountTM adenosine triphosphate (ATP) and adenosine monophosphate (AMP) methods focused on maintaining effective kill at the facility inlet. More than 900 bacteria samples and over 120 weight loss coupons were collected over the course of the trial year. A 35 to 77% reduction in corrosion rate (mpy) across the system was recorded at the inlet, tanks, and outlet manifold. An effective inlet kill was maintained over 97% until the system received an influx of solids, when the kill rate dropped to 83% which coupled with an increase in AMP dormancy indicators. Once the incoming solids subsided, the effective inlet kill returned to approximately 98% with no changes in the chemical program. Without effective monitoring, one might think the change in effective kill was the result of biocide resistance, rather it was a change in the system that effected the kill efficiency. This novel data set shows that maintaining a high effective kill over time may be paramount in biocide treating applications to reduce MIC risk. The data demonstrates that continuous biocide with a high kill efficiency can provide treatment without creating a biocide-resistant population. This work suggests that changes in the system need to be evaluated before assuming a less effective kill is related to biocide resistance.