Global Optimization Techniques in Gas Allocation for Continuous Flow Gas Lift Systems

Abstract

Abstract Continuous flow gas lift is one of the most common artificial lift methods in use. It works by injecting a continuous volume of high pressure gas into the tubing or tubing/casing annulus to lighten the column of oil and thus facilitate extraction. Excessive gas input is costly because of high gas prices and compressing costs. Inefficient gas allocation in a field with limited gas availability also reduces production and profitability. Historically, a sensible allocation was achieved using a technique called the equal slope allocation method. This method uses graphical procedures to optimally allocate gas to a group of wells in order to optimize total oil production. However, there is a disadvantage in this method, as it can not be applied to wells where there is not an instantaneous response to gas injection. The purpose of this paper is to present a methodology for automatically determining the optimum gas injection rate for a group of wells in order to maximize the total oil production rate for a given total amount of gas. The search algorithm proposed is a combination of stochastic domain exploration and a heuristic calculation of a descent direction, in order to avoid stopping the algorithm at a local optimum.