Application of fuzzy observer and controller in gas-lifted oil wells

System dynamics stability has been used to construct stability maps for gas-lifted oil wells. A fuzzy TS model is constructed based on proposed stability maps and fuzzy Kalman filter concept is used to estimate immeasurable state variables in noisy environment of well operation. Then, fuzzy linear quadratic Gaussian regulator is constructed by combination of fuzzy estimator and fuzzy TS controller to stabilize the highly oscillatory well operations. The quadratic stability of the overall closed-loop system is evaluated in terms of Lyapunov with a less conservative criterion. Simulations are performed using a standard multi-phase flow simulator and variable input command signals are introduced to the system. Satisfactory results are obtained in terms of estimation and stabilization.