The Importance of Integrated Testing in Seawater Injection Systems: A Microbiological Audit Reveals Microbial Community Shifts and Biocide Efficacy

Abstract Oil and gas seawater injection facilities present complex microbiological environments where harmful microorganisms can proliferate, leading to issues such as biofouling, corrosion, and reservoir souring. This study presents a comprehensive microbiological audit of the largest seawater treatment facility in the Middle East for oil reservoir injection with a capacity of 14 million barrels per day (BPD}. The seawater is treated from the Arabian Gulf and transport across the giant Ghawar and Khurais fields for water injection facilities. During the study, an integrated approach was employed using ATP measurements, bug bottles, qPCR, and NGS to characterize the microbial communities throughout the system. The results demonstrate the value of combining multiple methodologies to obtain a detailed understanding of microbial diversity and activity. ATP provided rapid assessments of overall biomass, bug bottles enabled the isolation and identification of culturable species. qPCR targeted specific functional genes associated with detrimental microbial groups, such as sulfate-reducing bacteria and Archaea. NGS sequencing provided the most comprehensive view of microbial community composition, including unculturable organisms. Importantly, we observed significant shifts in the microflora before and after biocide addition. This integrated approach revealed changes in microbial populations along the seawater injection system and highlighted the biocide's efficacy in targeting specific organisms.