Proposta de controle automático e monitoramento operacional do bombeio centrifugo submerso em sistemas de produção offshore

Abstract

The automation of artificial lift methods has great potential to increase operational efficiency of petroleum wells. In this context, this work presents a proposal for automatic control and operational monitoring applied to Electrical Submersible Pumps in a Pumping Module, which is part of an offshore production system. The proposal involves the implementation of PID controllers in a switching structure composed of control loops of the pressure differential supplied by the pump and of the intake pressure, and a monitoring layer of the control system performance. The controllers are designed to a) control the ESP operating point and b) prevent the occurrence of operational instabilities caused by high gas void fractions (GVF) on its intake. Three major steps were performed on this work: 1) design and implementation of PID controllers on a transient flow simulator (OLGA) using a model of offshore well; 2) data simulation associated with process failures in closed loop which were related to changes on subsea equipment conditions and in properties of fluids, reservoir and plant; and 3) treatment and analysis of data in Matlab applying fault detection and diagnosis techniques based on principal component analysis (PCA) and Hotteling’s T2 and Q statistics. The results indicate that the application of classical control theory contributes to the ESP automation ensuring the control of the pump operating point on events of acceleration/deceleration and the uninterrupted operation of the artificial lift system in conditions that would lead to high GVF on pump. In addition, the monitoring layer is crucial to detect and diagnose failures in the process, indicating to operator the situations that require controller tuning and adjustment of setpoints in order to keep the performance which it was designed for.