Nowadays oil and gas development projects encounter many challenges from the design phase to the production phase including operational issues. Many of these challenges are related to the need to explore deeper and further from the coast. In transporting gas systems, situations such as low temperatures can lead to hydrate formation; presence of liquids can produce severe slugging in risers and receiving facilities; and transient events can jeopardize the integrity of the system.
This paper presents a flow assurance study conducted to improve the design and reliability of an off-shore transporting gas system. The gas production system used for this study consisted of an offshore field positioned approximately 120 miles offshore in medium depth waters of approximately 360-480 feet. Four producing platforms convey the gas production to a tie-in platform and then it is transported via a 38-inch pipeline to a gas processing plant on shore. Sea water temperatures as low as 43°F during the winter were considered thus, hydrate formation and liquid management assessments were conducted using a multiphase software simulation tool. A detailed hydrothermal model of the entire system was developed and different operating conditions were evaluated using worst case scenarios for hydrate formation, liquid accumulation, and slugging. Hydrate inhibitor rates were calculated using a temperature depression safety margin, and the amount of inhibitor lost during the gas and liquid phases. This paper presents the methodology used in the assessments
