SS: Marlim 3 Phase Subsea Separation System: Controls Design Incorporating Dynamic Simulation Work

Abstract

This paper describes the control system design for the Marlim three phase subsea separation system (SSAO) and how the standard subsea control system has been adapted for the new requirements for automated control. This is the most advanced subsea process system to date with several "first ever" applications of separation equipment subsea: harp, pipeseparator, desanders and hydrocyclones. The SSAO has a total of 7 control loops and a number of complex automatic sequences. Further, the paper addresses how dynamic simulation analysis has been used to validate the process control strategy and improve the operational procedures designed during the basic engineering phase. Control and operation of the SSAO has proved to be very challenging for several reasons:• There are strong interactions between different process components • The system dynamics are stiff due to small liquid hold-ups and low GOR in the system • The pressure drops of inline cyclonic equipment need to be balanced to ensure optimal performance • Constraints in valve opening/closing speed and the importance of limiting the number of valve movements put restrictions on controller performance • Instrumentation is limited compared to topside facilities The content described above contain several new aspects compared to a traditional subsea control system and this paper will describe system considerations with regards to implemented process control and also the importance of using dynamic simulations as a design tool.

Controller Design and Control Structure Analysis for a Novel Oil–Water Multi-Pipe Separator

“…Although the pipe separator used in this study is different from those used in [7][8][9][10][11], it is the authors' belief that the results are transferable and that the results presented here can serve as a basis for future control design of pipe separators.…”

“…In [7], a control design study was performed for a complete subsea separation system including a pipe separator. The liquid level in the pipe separator was chosen as the CV, and Proportional-Integral-Derivative (PID) controllers were used in all control loops.…”

A First-Principles Approach for Control-Oriented Modeling of De-oiling Hydrocyclones

“…The Brazilian Marlim field at 870 m water depth has subsea oil−water separation with a hydrocyclone for produced water treatment. 3,4 This is the only one currently in use subsea.…”

Use of subsea technologies for produced water management in offshore fields using integrated asset modeling

“…including other benefits of subsea technologies besides reducing water production. According to several authors (Hannisdal et al, 2012;Pereira et al, 2012;and Hendricks et al, 2016), the application of these subsea installations improves the oil recovery factor (ORF), relieves the platform capacities to receive and produce more oil, avoids shutting wells with high water cut (WCUT), improves oil reserves and decreases back pressures in pipelines. It is also an environmentally attractive solution because water discharge to the sea is minimized.…”

“…For these reasons, Petrobras proposed revitalization of the Marlim, Voador, and Brava fields using subsea technologies. First project was implemented in the Marlim field and called as Marlim SSAO 3-Phase Subsea Separation System (Pereira et al, 2012). The contract for process technology qualification and system prototype supply was established from 2012 to 2013.…”