This paper presents the experience brought from the oil-water subsea separatorproject developed for the Marlim field, known as SSAO Marlim. Here, it will beaddressed the inherent arising challenges from a project of a subsea separationequipment, from the subsea mechanical design perspective, with special focus tothe additional requirements to the normally presented in conventional subseaequipment for oil and gas production. It will be part of the discussion the architecture selected for the system andthe main challenges imposed by:–Separation process (gas-liquid, liquid-liquid and sand removal system);–Requirements for modularization, installation and retrieval of subseacomponents;–Installation concept. Introduction The oil-water subsea separator is installed in a water depth of approximately870m in the Marlim field, located in the Campos basin, Brazil. The subseaseparation station has an envelope of 29m length, 10.8m width, 8.4m height andan overall assembly weight in-air of 392ton, and it will receive productionfrom selected well, separate produced water from oil and sand and re-inject itinto Marlim production reservoir via a centrifugal pump. The water separationhappens into a Pipe SeparatorTM based on a gravitational concept, while waterpolishment to meet quality requirements, i.e. reduce oil content in water toacceptable levels for the re-injection into reservoir, is performed by cyclonicequipment. The equipment also has a sand management system which the main aimis to minimize the operational impact induced by solids production. Figure 1 illustrates the oil-water subsea separation system of Marlim.

To surpass the main challenges established by deep water, high gas-oil flowratios, flow assurance and constant increases in produced water, Petrobras is developing, within PROCAP Technology Program - Future Vision, several projects in the subsea processing area, such as: Compact Oil-Water and Gas-Liquid Separation Systems, Multiphase Pump with High Differential Pressure and Gas Compression System. The main applications of these projects are in fields with high fraction of gas and water, in fields/discoveries located far away from Production Units and to increase the reservoir recovery factor. Furthermore, the application of these technologies may have great benefits, such as: production anticipation, reduction of process system footprint on the Production Unit, decrease in CAPEX/OPEX and especially an increase of the topside oil processing capacity. This paper aims to present an overview of those technologies being developed in PROCAP - Future Vision. Also, this article shows the main motivations of these developments, the main benefits of using each technology, the technological challenges and gaps, typical application scenarios and results of the evaluations performed so far. Major petroleum companies are searching for new technical solutions that fulfill their needs of reducing both CAPEX and OPEX while increasing oil and gas production. The development of new subsea processing technologies, as stated above, will enable, and in some cases reinforce, the use of these technologies for deepwater and/or subsea to shore scenarios. Introduction Subsea processing is a key enabler for challenging field developments, and their benefits increase with water depth, flowrates and step-out. Regarding subsea separation, these advantages are maximized when employing subsea compact separation technologies. Also, subsea processing brings HSE benefits related to reduction of waste disposal to sea, an environmental contribution of subsea oil-water separation systems, and the possibility of using smaller platforms - or none at all - due to the use of processing equipment on the seabed instead of topside, reducing operational risks. In terms of compact separation technology development, Petrobras has been conducting several R&D initiatives for the last ten years. Firstly, these R&D initiatives were developed for topside and onshore applications, but always keeping on mind the subsea employment. In order to evaluate these technologies several tests have been performed. More recently, the Marlim SSAO 3-Phase Subsea Separation System is a very significative example of compact subsea technology employment, for a single producer well application. Multiphase boosting is always considered as a good alternative to develop oilfields, mainly for remote areas. Petrobras invested a lot on the development of twin screw and helicoaxial concepts for multiphase pumps, targeting applications with required differential pressures up to 60 bar. Recently, analysis has indicated that High Differential Pressure Subsea Boosting (up to 150 bar) is economically and technically attractive to various Petrobras scenarios and, because of that, many R&D efforts are being done to develop such technology.

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 Marlim SSAO 3-Phase Subsea Separation System is the world's first systemfor deepwater separation of heavy oil and water which re-injects water in thesame producer reservoir. The major difficulty for reinjection in the producerreservoir is the strict water quality requirement, limiting maximum solidparticles (sand) and residual oil content. This challenging application posedinnumerous challenges to the project and the solutions developed give aworldwide pioneering characteristic to this system. This paper provides anintroduction to the Marlim SSAO System and is one of a set of papers presentedat OTC-2012. It gives a project overview from the topside facilities to thesubsea production systems. Included also are the project drivers, main premisesand objectives, and the management strategy used in the execution of such asophisticated. Introduction The Marlim SSAO 3-Phase Subsea Separation System (" SSAO" being the acronym inPortuguese for Separação Submarina Água-Óleo - Subsea Oil-Water Separation) isa pilot system for oil-water subsea separation systems. The project has as itsprimary goal to prove and to develop the technology basis for potentialapplication in several other existing mature fields to optimizeproduction. The costs of processing and disposing of water in the topside facility arehigh, such that the possibility of separating water from oil on the seabed, anddirect re-injection, reduces operational costs and simultaneously debottleneckstopside facilities, allowing increase of production. Another key feature is the contribution to optimize the oil process fortransportation and the water process for disposal. On new projects these maylead to smaller platforms for the same process capacity, increasing productionand in some cases, increasing oil recovery factor. Initially the SSAO technology will be applied in fields that are trending tohigh watercuts like Marlim, Marlim Sul, Albacora, and Golfinho and later it isexpected to be used in the Pre-Salt fields. The SSAO is also an environmental friendly technology as it reduces wastedisposal to sea. Considering that environmental legislation is continuouslybeing made ever stricter for disposal of water with oil content, thistechnology contributes to the sustainability of the oil industry in thefuture. In order to establish the design parameters produced water reinjection testswere performed on the Marlim Field. To ensure that the system would achievethese parameters, a Technology Qualification Program was performed for the mainprocess stages and some specific key components were also tested for their newmission. The introduction of subsea processing in a mature field still requires newequipment to be installed topside. Finding room on the P-37 floating productionunit was a very challenging task. Modifications to the unit were required andthis had to be addressed and managed starting in the early phases of theproject, with very detailed planning to enable safe installation andcommissioning while the platform was producing. Due to the size and challenges of this R&D project, there was a high levelof involvement from both PETROBRAS management and technical personnel, with theproject execution being very closely monitored employing live Risk Managementon an almost day by day basis.

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