Large diameter subsea pipelines operating mainly in stratified flow are being used
across the world for wet gas transportation over significant distances from offshore fields to
onshore facilities. Understanding corrosion mechanism occurring at the top of the line under
dewing conditions is a key component of operations corrosion management strategy to ensure
long-term pipeline integrity. The challenge in predicting corrosion in sour systems is due to the
varied nature of iron sulfide scales formed over the expected subsea pipeline temperature
ranges and condensation rates that result in different corrosion mechanisms. Current industry
practice is to use sweet corrosion prediction methodologies to establish the risk of top of line
corrosion in sour systems. This paper will demonstrate through field validated laboratory
results that this approach may be inadequate and propose operational practices to manage the
risk of top of line corrosion in large diameter subsea wet gas pipelines.
KEYWORDS: sour corrosion, wet gas pipelines, top of the line corrosion