Optimisation of a Gas-Lifted System with Nonlinear Model Predictive Control

Ojonugwa Adukwu (), Darci Odloak and Fuad Kassab
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Ojonugwa Adukwu: Department of Telecommunications and Control, University of Sao Paulo, Sao Paulo 05508-010, Brazil
Darci Odloak: Department of Chemical Engineering, University of Sao Paulo, Sao Paulo 05508-010, Brazil
Fuad Kassab: Department of Telecommunications and Control, University of Sao Paulo, Sao Paulo 05508-010, Brazil

Energies, 2023, vol. 16, issue 7, 1-24

Abstract: A gas-lifted system in a mature oil well can experience casing-heading instability, which reduces the mean oil production and it is not healthy for the downstream equipment. This instability was removed by implementing a terminal equality-constrained nonlinear model predictive control (NMPC) having input targets with control zones in the system. The input-dependent stability behaviour of the gas-lifted system was visualised through the bifurcation diagram and the step responses of the linearised model at various operating points. The controller was then presented. Then, the close-loop feasibility, as well as the convergence, were discussed. The controller stabilised the undisturbed gas-lifted system, improving production by 5.63% compared to the open-loop operation when the system was in casing-heading instability. For the two input case, the steady-state production, aided by the high-input target, reached 12.25 kg/s, which was far more than 9.57 kg/s for the one input case. This controller showed a 3.76% improvement over the PI controller for the same purpose.

Keywords: model predictive control; extended Kalman filter; gas lift; casing-heading instability; optimisation (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2023
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