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.
The paper uses a case study approach to present the challenges to develop a large and thick oil carbonate reservoir, full of opportunities but also of uncertainties. Additionally, Libra block development is under a Production Sharing Contract that was awarded to a Consortium where Petrobras is the operator in partnership with Shell, Total, CNOOC Limited and CNPC. This paper will present the main subsea technological achievements made during the execution of the Libra Extended Well Test (EWT) Project so far and also future technologies that will contribute to overcome the full field development challenges.
This paper presents the selected concept, the main challenges of the adopted scenario and in consequence the requirements for a development of an extensive Technological Qualification Program performed on the components and on the whole sub-sea water separation and re-injection pilot system for Marlim field -known as SSAO Marlim Project. Due to being a pioneer project, even considering the previous Troll and Tordis sub-sea separation and re-injection systems, it was necessary to perform a very extensive and broad Technological Qualification Program (TQP). Two main characteristics of the SSAO project are responsible for the mentioned pioneer character of the project. Initially, in opposition to the mentioned existing systems, separated water has to be re-injected in the production reservoir formation, due to non available disposal reservoir in production field area. Thus, required water quality, relating to oil and sediment content after separation, was very strict in order to avoid loss of injectivity. Furthermore, due to the deep water depth of the installation site (870 m) and due to the fact that the SSAO is a pilot for future deep water installations, conventional gravity separators -as used in the mentioned projects -would not be feasible and new technologies, not yet used elsewhere, have to be adopted.
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