Parameter sensitivity analysis of gas-lift well unloading processes

Abstract

Gas-lift is one of the most widely used artificial lift methods in oil fields to increase oil recovery. Gas-lift unloading processes are susceptible to hydrodynamic instability, as a small change of parameters may result in instability of the gas-lift well unloading. It is therefore necessary to study the parameter sensitivity of the gas-lift unloading process. Considering the characteristics of the unloading transient process, this paper firstly introduces gas-lift instability. A transient dynamic model of the gas-lift well unloading is then built, with four gas lift valves. This is done using a commercially available OLGA dynamic multiphase flow simulator to simulate the transient dynamic gas-lift unloading process. Finally, this paper analyzes the paramter sensitivity of gas-lift unloading, based on OLGA, and determines how the stability of unloading will be affected when given parameters change within a certain range. Based on the simulation results and analysis, this paper shows that the results provided can be used in gas-lift design, operation and optimization.