Design of gain scheduling control strategy for artificial gas lift in oil production through modified relay feedback test

Artificial gas lift technology is widely used in oil production to sustain oil flow from the well to the surface when reservoir pressure drops. Dynamic model that describes artificial gas lift system is highly nonlinear, which makes the controller design for this system not an easy task. A dynamic model of this system is further detailed with respect to the models available in the literature to account for the depth of the well. Two approaches to controller design are implemented: the first one is based on the local linearization in a number of operating (equilibrium) points that are characterized by different gas flow set points; the other approach is based on the use of the modified relay feedback test (MRFT) applied incrementally in different operating points. In both approaches, the controller is designed as a gain-scheduled PI controller.