Large fluctuations in gas and/or liquid production can lead to major disruptions on the topside facilities. These fluctuations are caused by the fluid composition, geometrical layout and operating conditions of the production system. With the current trends of:
Producing marginal gas/condensate and oil fields to existing facilities with subsea tie-backs,
Developing more deepwater fields,
Producing from existing production facilities towards the end of field life cycle, irregular production or slugging pipeline systems are observed more frequently. Therefore, slug mitigation techniques may achieve significant value impact on the business. The most recent technology in Shell for slug control is the Smart Choke. This technology consists of a single control valve that is installed between the riser top and the first stage separator. It is an active slug control device acting on gas and liquid surges without the requirement of phase separation upstream of the control valve. The basic control mechanism maintains a constant total volumetric flow at the system outlet. Furthermore, a detection algorithm is incorporated, which detects 'liquid only' or 'gas only' production. Based on this, the controller will switch between the different control modes for slug control. Additional to this flow controller, a slow valve position controller and a differential pressure override controller is used to ensure that the output of the volumetric flow controller remains in the range of the normal (or desired) operating valve position.