Design of a gain matrix for a sliding mode observer for an artificial gas lift system

An Artificial gas lift system is an existing technology in the oil sector; which utilizes the fact that a pressure differential exists in the reservoir´s tubing leading to enhanced oil recovery from the reservoir. Studies were conducted to control this process as it improves the stability and performance of gas lift. The current industrial practice depends on flow measurement as a process variable, yet, it does not depend on the measurements which would be obtained several kilometers below the ground that are technically difficult to approach due to several limitations such as huge pressures. Proper knowledge of the states would leads to a better controller design for this system. In this paper, a methodology towards the design of a sliding mode observer is investigated. The purpose of the observer is to acquire the states of a nonlinear system representing the physical system of a gas lift process in oil wells. The proposed design of an observer is based only on measurements taken above the surface.