Of all the different flow regimes, the one typically of most interest in multiphase subsea production systems is slug flow. Slug flow involves the intermittant production of liquid slugs and gas bubbles, some of which can be hundreds of metres long, and can lead to severe fluctuations in pressures and flowrates throughout the production system if not properly predicted and managed. Such dramatic fluctuations can cause: equipment damage, due to vibration, impact loads and/or enhanced corrosion; large disturbances in the separation facilities, resulting in poor separation of phases; large and rapidly varying compressor loads, resulting in inefficient compressor operations and unwanted flaring; frequent shutdowns and/or adoption of restrictive operating practices, both of which can result in a significant loss of revenue.
Source: API RP 17A, Design and Operation of Subsea Production Systems—General Requirements and Recommendations, Fourth Edition, Reaffirmed 2011. Global Standards