Implementation of a Microbial Control Program for an Offshore Production System in Nigeria

A 30-year-old offshore pipeline system in Nigeria was found to have severe internal corrosion, which was attributed to microbiologically influenced corrosion (MIC).  A laboratory investigation was undertaken to develop a microbial and solids control program to overcome the most significant challenges including: the inability to pig the majority of the system, treating isolated sump tanks that likely harbor large quantities of bacteria, and minimizing internal corrosion of a critical pipeline delivering crude oil to the processing facility.  The laboratory findings were presented at NACE International 2010 (TEG 286X).  Based on the laboratory testing, a program was implemented in the field that included a surface-active and non-oxidizing biocide for microbial control, a solid biocide for extended treatment of sump tanks, and a cleaner to assist in removing solids from unpiggable parts of the production system.  Success of the program was measured by several different metrics.  Bacterial loads were compared year-on-year for the incumbent versus the new biocide using serial dilution and ATP quantification.  In addition, bacterial enumeration was correlated to biocide residuals and used to optimize the biocide treatment dosage.  Bacterial control in sump tanks using a solid biocide was evaluated via a 10 tank field trial to establish biocide efficacy and length of control.  Most importantly, the success of the program was measured by comparing results of intelligent pig runs before and after implementation of the new treatment program.