Slug flow control in an S-shape pipeline-riser system using an ultrasonic sensor

Slugging flow poses significant challenges to the offshore multiphase flowline and riser systems. Slug flow is characterized by an uneven flow regime whereby pipeline pressures, temperatures, or flow volume rates fluctuate. One of the most common causes of severe slugging is low pressures which causes buildup of fluid over time, consequentially causes flow and pressure oscillations. This mostly occurs in vertical risers or wells. The negative effects of severe slugging have prompted numerous studies, investments, and efforts to reduce or eliminate the slugging flow. Several active slugging control techniques have been investigated in the oil and gas industries for decades. However, many of these techniques still run the risk of limiting hydrocarbon production due to inappropriate over choking. Other challenges for active slug control include the fact that some systems rely mainly on subsea measurements such as riser base pressure, and most of these subsea measurements are costly, difficult to maintain, not always available, and can be unreliable. As a result, to achieve an efficient slugging control performance, reliable, robust, and efficient measurements that are more sensitive to slugging flow for control are required, which is the motivation for this work. The control of riser slug flow using non-radioactive, non-invasive, and non-intrusive Continuous-wave Doppler ultrasound has been investigated in this work, and provides good control performance. It achieved a larger valve opening than an open-loop unstable system. This outperforms manual choking, which maintains stability at a much lower valve opening.