Optimization of Gas Injection Allocation in a Dual Gas Lift Well System

Abstract

1. Abstract Optimization problem for oil production in a multi gas lift wells system is discussed. The main problem is to identify allocation of gas injection for each well to obtain maximum total oil production. The gas injection rate is constrained by a maximum limit. Oil production rate is a nonlinear function of gas injection rate, which is unknown explicitly. In existing approaches, the nonlinear function is estimated from empirical or numerical simulation data, by curve fltting using regression method, or estimated by piecewise linear function. We developed here, a mathematical model for gas lift well system, where the ∞uid ∞ow in reservoir and pipes consists of liquid and gas, so the conditions represent two phase ∞ow phenomena. Relationship between gas injection and oil production is given implicitly from the model. We have also developed a computation scheme to solve the optimization problem. Considering complexity of the problem, computation scheme is developed based on genetic algorithms. Our results show quite good estimation for optimum solution. The approach also gives better quality prediction over existing approach, since all computation results come from the model, not from regression or interpolation. 2. Keywords: Gas Lift, Gas Lift Performance Curve, Constrained Optimization, Genetic Algorithm.