ABSTRACT
Top of Line Corrosion (TLC) occurs in a multiphase flow when water vapor condenses at the top and the sides of the pipeline, leading to a severe corrosion attack. This study investigated the probabilistic risk of TLC for wet sour gas subsea pipeline using flow modeling and corrosion predications. The flow assurance hydraulic study showed that most of water drops out over the first few kilometers as the gas is cooled and becomes much less through the rest of the offshore part until they reach onshore area where the gas temperature drops further due to Joule-Thomson effect. It was anticipated that corrosion activities will be higher at the high condensation locations. The corrosion prediction modeling revealed high corrosion severity driven by Top of Line Corrosion (TLC). In order to maintain the system integrity the internal coating supplemented by V-jet batch inhibitor injection has been selected to protect against TLC. This study has realized the challenge to apply the batch treatment as it requires process interruption to meet scraper speed limitations. Therefore, the industry path forward should consider the development of novel TLC treatments to be applied with no impact on operations.
INTRODUCTION
The hydrocarbon exploration in the ocean and deep sea started as early as 1850s, when the first drilling was carried out in California. Other early oil exploration activities were later recorded in Pakistan (1886), Peru (1869), India (1890) and Dutch East Indies (1893).1 In 1930s, the development of the Gulf of Mexico as an offshore area started with oil first being produced in 1938. The production from the North Sea brought more technical challenges in to the offshore industry. The North Sea was first explored as a potential offshore area in the early 1960s.2 Since then the pace of oil exploration and production in shallow water has gradually increased to deep water with the exploration phase starting in 1975 while production began twenty years later.2