Averaging Level Control of a Separator using Gain Scheduling

Abstract

In mature production wells slugging is, or can be, a major challenge when it comes totuning of the first separator control loops. The objectives of the tuning are to minimizethe variation of the outflow, whilst at the same time keeping the level within the upperand lower alarm limits. This control regime is often referred to as Averaging Level Control.Most of the level controllers on production platforms can handle both Proportionalplus Integral action (PI) controller and gain scheduling. PI control is the most commonlevel controller on site due to shortage of tuning tools for gain schedulers. If the gainscheduler is in use, it is often tuned in an ad hock manner.This thesis presents the development of a tuning tool for averaging level control ofa separator using gain scheduling. The thesis is carried out in collaboration with ABBEnhanced Operation & Production. From the results of the tuning two different conceptsare presented, one being pure level controller and the other being a gain scheduler thatcombines the properties of a level and flow controller based on the flow controller on site.To the knowledge of the author and thesis supervisor, this way of tuning a separatorfor averaging level control using gain scheduling does currently not exist, and is thusinnovative and represents a new point of view in gain scheduled control of separators.