(67c) Real Time Monitoring Technique for Detection of Microbial Corrosion in Oil and Gas System

As natural gas production in the United States continues to increase, the abundance of transmission pipelines will increase similarly to accommodate the productivity. These pipelines are susceptible to internal MIC, which is exceedingly difficult to detect. First, MIC is by nature a localized process, and localizing damage is nearly impossible with “bulk” pipeline interrogation techniques. Second, highly specialized techniques are required to reliably diagnose MIC. Third, detection of internal MIC requires removal of samples from the pipeline for analysis and therefore, downtime. Fourth, evidence of MIC may not be evident until the system is “infected” beyond recovery. We have developed an electrochemical approach that involves zero-resistance ammetry (ZRA) measurements along a pipeline to detect MIC. The ZRA approach could be deployed along entire pipelines and would sensitively detect a broad range of in situ microbiological processes.

To develop ZRA as an MIC monitoring tool, we have carried out a series of split chamber ZRA (SC-ZRA) incubations that entail deployment of two steel working electrodes (WE1 and WE2) in chambers separated by a semipermeable membrane. Subsequently, one chamber is inoculated with an individual or consortia of microorganisms, and ZRA and potential measurements made in conjunction with evaluations of microbiological activities. Current direction and magnitude can be indicative of the mechanisms and extents of MIC. The SC-ZRA setup mimics the heterogenous biofilm coverage of metal surfaces that leads to MIC, and we use it to establish the electrochemical signatures of MIC.

In this work, we use consortia and pure cultures of microorganisms isolated from samples taken in natural gas transmission and crude oil pipelines to inoculate SC-ZRA and incubate them under conditions representative of pipeline fluids. We specifically evaluated the impact of differential aeration, fluid flow, and type of microbial metabolism (fermentation, sulfate reduction, methanogenesis, and acetogenesis) on current magnitude, direction, and extent of corrosion. The identification of microbiological processes with electrochemical signatures can then be used to inform the implementation of ZRA measurements as a robust, sensitive and broadly applicable MIC monitoring approach.