TABLE OF CONTENTS In thermal-hydraulic design of multiphase flow transmission systems, the system designer is faced with several challenges associated with multiphase flow, which can significantly change design requirements. The goal of any pipeline designer is to secure "flow assurance," i.e., the transmission system must operate in a safe, efficient, and reliable manner throughout the design life. Failure to do so has significant economic consequences, particularly for offshore gas production systems. "Flow assurance" covers the whole range of possible flow problems in pipelines, including both multiphase flow and fluid-related effects such as gas hydrate formation, wax and asphaltene deposition on walls, corrosion, erosion, scaling, emulsions, foaming, and severe slugging. However, the major flow assurance issues for raw gas transmission lines are hydrates, corrosion, wax, and severe slugging, which are discussed individually in different sections later. The avoidance or remediation of these problems is the key aspect of flow assurance that enables the design engineer to optimize the production system and to develop safe and cost-effective operating strategies for the range of expected conditions, including start-up, shutdown, and turndown scenarios. However, as production systems go deeper and deeper, flow assurance becomes a major issue for offshore production and transportation systems, where traditional approaches are inappropriate for deepwater development systems due to extreme distances, depths, temperature, or economic constraints (Wilkens, 2002).
A gas hydrate is an ice-like crystalline solid called a clathrate, which occurs when water molecules form a cage-like structure around smaller guest molecules. The most common...
