Microbiologically Influenced Corrosion (MIC) is one of the most damaging forms of corrosion. Microorganisms naturally present in the reservoir or introduced to it by contaminated injection water can travel through the network and find their way to the pipeline. An oil production field was protected from microorganisms by treating its water injection system with nitrate. The nitrate treatment was deactivated in 2017 where the SRB population has increased dramatically over the years. This was evident by an increase in the H2S levels detected in the associated gas and the water injection system as a result of SRB metabolic activities. Pipeline-D, which is considered the backbone of this field, suffered from severe internal corrosion. A comprehensive corrosion risk assessment was conducted to identify causal factors of the severe corrosion and provide remedial measures for Pipeline-D that led to $7.5 MM cost avoidance.