Seeing the Forest Through the Trees: Improving Microbial Corrosion Screening and Prevention in Unconventional Oilfield Operations

Abstract Objectives/Scope Microbiologically influenced corrosion (MIC) is a complex issue both difficult to diagnose and challenging to treat. Driven by a variety of microbial species combinations under different process conditions and mechanisms, MIC can appear unexpectedly and be over- or under-diagnosed when using insufficient testing or screening methods. This study's objective was to develop an improved MIC threat screening process to aid the development of new early-warning methods for corrosion prevention. Methods, Procedures, Process For MIC screening, traditional and advanced bacteria test methods were used to survey more than two hundred locations including unconventional onshore wells and facilities in the Permian basin. Initial screening tests included standard adenosine triphosphate (ATP), sulfate-reducing bacteria (SRB) and acid-producing bacteria (APB) culture media bottles. After initial screening, a subset of 10 sites was selected for DNA sequencing to identify high interest microbial families/species. Six short-listed sites were then tested for volatile fatty acids (VFA) and for active MIC threat using anaerobic carbon steel enrichment cultures. Results, Observations, Conclusions The screening process identified two final sites of high microbial activity by various metrics including: favorable water chemistry, key field indicators (ATP, SRB, APB), problematic species of MIC interest (H2S or organic acid producers, fermenters, methanogens, etc.), and cultures confirming iron sulfide generation and carbon steel corrosion potential. The process also identified that using standard bacteria tests alone would have over-estimated the MIC threat potential in other field locations, and that deeper investigation with thorough screening methods was needed. The final two locations of high MIC threat were selected for additional investigation and expanded sample collection, which will underpin the development of new genetic tests to streamline future MIC prevention efforts across complex production operations. Novel/Additive Information Highlighting the bigger picture, this study lays out the critical information necessary to accurately assess microbial corrosion threats, guiding engineers away from over- or under-diagnosis of what can be a major asset integrity and production reliability issue. This process helps identify areas to prioritize chemical treatments or material upgrades, and serves as the foundation to use MIC positive areas for new early-warning method development to better protect oilfield production reliability and reduce OPEX.