Simulator and controller tuning/testing rig for artificial gas lift

Artificial Gas Lift (AGL) technology is used in mature oil wells to increase the oil production rate. Improper control of this system can produce casing heading instability resulting in slug flow and problems in downstream equipment. The AGL system has very complex nonlinear dynamics, which makes the tuning of the controller parameters difficult on a real system. In this paper, an AGL simulator is developed to test and tune the controllers before installation in the field. The simulator uses the concept of Hardware-In-the-Loop (HIL) which emulates the real behavior of gas lift system and connects to a Programmable Logic Controller (PLC) or Distributed Control System (DCS) to design and optimize control algorithms. The AGL simulator uses accurate model and high performance processing. It is equipped with a Human Machine Interface (HMI), which displays the status of AGL system using animation and trending so that slugging can be easily identified. The HIL can be operated in two modes: real time and accelerated time. An example of control tuning method using Modified Relay Feedback Test (MRFT) is used to demonstrate controller gain tuning in accelerated mode, based on its performance on the AGL simulator. The proposed HIL simulator can prove to be a convenient practical tool used for testing automation solutions before connecting them to real gas lift process in the field.