Artificial gas lift in oil wells: Control oriented modelling and simulation.

摘要

Artificial gas lift has become very popular in today's oil production industry. That is because of the dramatic reduction of oil reserves around the world. Optimizing the production of an oil well using this technique of assisted lift is becoming more important. To successfully accomplish that, an accurate model of the system is required.;In this master thesis, a nonlinear model for artificial gas lift is derived and controlled based on previous literature studies. In control theory the most common control methods are based on linear systems, hence for nonlinear models, linearizing the model is a typical course of action used initially when designing a controller. Several set points are taken to linearize the model, and design a PID controller. To further study the nonlinear model, a nonlinear controller was designed. The Modified Relay Feedback Test (MRFT) was used for nonparametric tuning of the PID controllers. Results of both the linear and nonlinear model are compared for model verification.;In field applications though, not all parameters of a system are known, and so a sensitivity analysis is done for the approximated unknown parameters. Using the sensitivity analysis, a model-assisted tuning of the PID controllers is developed for the system.