Design and Control of Gas Lift System due to Well Depletion with Levelized Cost Analysis

Gas lift is required to lift the gas on wells that depleted. In the field of X wells located in the offshore area, the necessary gas lift pressure is 1700 psig to maintain the total gas production by up to 11 MMSCFD, whereas the current well pressure is 650 psig. To raise the necessary gas lift pressure, compressor systems are applied. The objective of this research was to select one of two types of compressors (centrifugal and reciprocating) based on their economics. Proportional-Integral (PI) and Proportional-Integral-Derivative (PID) controller is applied and tuned by open loop Ziegler-Nichols (ZN) and closed loop Tyreus-Luyben (TL) method. Integral of Squared Error (ISE) controller performance criteria is applied for controller’s performance evaluation. This thesis will also analyze the dynamic design process with levelized cost method. The result is open loop ZN tuning has a smaller ISE up to 99.33% on a centrifugal compressor configuration and 98.65% for reciprocating compressor configuration than TL method. Reciprocating compressor configuration with a PID controller and ZN tuning able to reduce 22.96% of energy, compared with the centrifugal compressor configuration and tuning PI controller TL tuning.