Abstract
In 1987, a corrosion review of oilfield flowline and pipeline networks in the United Arab Emirates concluded that pitting corrosion had occurred and that Microbiologically Influenced Corrosion (MIC) was a possible contributor to the corrosion observed. In response to this finding, a comprehensive MIC mitigation and monitoring strategy was put in place. The strategy covered both the production pipelines and also the seawater injection flowlines. For almost 20 years, the high rates of corrosion initially determined have been controlled to acceptable levels and the pipelines and flowlines continue to meet operational performance specifications. In particular, the control of MIC groove corrosion in subsea water injection flowlines is highlighted, given the frequency of reports of failures due to grooves in other seawater injection flowlines around the world. Chemical biocides have been applied to control bacterial growth and activity and regular cleaning pigs introduced to minimise deposits.
An Asset Integrity Management System (AIMS) provides traceability of the development and optimization of the bacterial control (biocide and pigging) and bacterial monitoring (planktonic and sessile) programs, and strives to assure industry best practice for MIC mitigation.
This paper presents a case history for MIC mitigation in aging subsea seawater injection flowlines and discusses the key process controls in these lines over the past 20 years.
