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.

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.

This paper presents an overview of the reservoir requirements regarding thedevelopment of the Marlim 3-Phase Subsea Separation System - SSAO (for theterms in Portuguese). Produced water re-injection (PWRI) in the reservoir insuch scenario is a challenging task, regarding the well injectivity maintenance(SSAO-treated produced water suspended solids and oil content, sub-sea andsub-surface facilities materials compatible with the produced watercorrosiveness), geomechanical effects, and biogenic reservoir souringcontrol. Lessons learned from previous PWRI tests and the implications of somealternatives to the subsea separation and re-injection systems are reported. This work comprehends also the definition of chemicals applyed to preventundesirable effects: a bio-dispersant (to avoid biocorrosion and biofouling inthe re-injection system) and a nitrate salt (to oppose biogenic reservoirsouring potential). Relevant operational aspects are mentioned as well, fromchemical injection to the monitoring of both solid particles and oil dropletscontents in the re-injection water stream. Introduction Marlim field area is 149.4 km2 and the water depth range is 650 - 1050 m. Themain reservoirs of Marlim field are turbidites of Oligocene/Miocene age. All ofthe sandstone facies are poorly-consolidated. Reservoir-rock porosity andpermeability are relatively homogeneous, typically ranging 27 - 30 %, and 1,000- 6,500 mD (4,000 mD average), respectively. The oil API varies from 17° to 24° in the main field area and oil saturationpressure is 265 kgf/cm2, which is 22 kgf/cm2 below the reservoir originalpressure. The Marlim reservoir mechanism is solution gas drive. Water injectionhas been selected as the most feasible reservoir pressure maintenance method, thanks to its simplicity, besides factors like deepwater location, reservoircontinuity, relative scarcity of gas, and favorable characteristics of therelative permeability curves. Initial oil production from the Marlim field was in March 1991 and the peak ofproduction was approximately 630,000 bpd of oil in April, 2002. Seawaterinjection started in 1994. Injection pumps were designed to matrix injectionconditions, but considerable injectivity decline was observed in some of theearlier injection wells. Marlim field was developed with subsea wells, so anyworkover operation to restore the injectivity requires a floating rig to beperformed, which makes them very expensive. Therefore, injectivity preservationis essential to assure that the sustainment of the required seawater injectionvolumes. A comprehensive program was established to control the injected waterquality, imposing strict limits to its suspended solids concentration andparticle size, oil and grease content, as well as corrosion-related parameters(oxygen, CO2 and sulfide content, bacteria counts). Injection rate, injectivityindex, frequency of tubing or flowline substitution, corrosion rates andfilterability are also permanently monitored (Pinto et al., 2001). Some of the Marlim field water treatment facilities are nearly reaching theircapacity. An alternative to reduce the topsides water load is to remove water,as much as possible, on the seafloor. So far, it is not considered feasible, onthe subsea system, to achieve the required water quality to discharge it on thesea. The only alternative is to dispose the separated water in subsurface. InMarlim field, it was decided to re-inject the separated water in the reservoiritself, because there are no proper adjacent geological formations to takeit.

The objective of this paper is to describe the adopted procedures and operations that were used to process commissioning and start-up the Marlim Subsea Oil and Water Separation and Water Re-injection System. This system is much more complex than the conventional subsea manifolds and, similarly to the previous phases of this project, the commissioning and start-up phases also faced many challenges that had to be overcome. Several subsea equipment are part of the system; among them we should mention an unconventional "harp" gas-liquid separator, an oil-water "pipeseparator", cyclonic desanders (both for multiphase inlet stream and for produced water stream), two stages of hydrocyclones to remove oil from produced water and a water injection pump. Besides these equipments, instruments and multi-functional control modules are also part of the system. The problems faced during commissioning and start-up activities and the adopted solutions to solve them are also discussed. This paper will cover the start-up activities describing the following sequence:re-start-up of the production well through the subsea system by-pass line to topside,alignment of well multiphase production stream through the subsea separation system to check separation performance and suitability of produced water quality for re-injection andfinally start up of re-injection of produced water into the injection well. The requirements for logistic support that are very much different from the ones required for topside installations are also discussed. New " paradigms" of operating facilities imposed by subsea environment constraints, are also suggested and discussed. Introduction The Marlim Subsea Oil and Water Separation and Water Re-injection System (SSAO) is an innovative pilot project installed as a Pilot System for the well MRL-141, connected to the host production unit (FPSO), P-37, in Marlim Field, Campos Basin. The objectives of the project are: platform debottlenecking of the water treating facilities; increasing production by reduction of back pressure on the wellhead. Besides these objectives, another important aim of the project is to prove the concept and qualify the adopted technologies for future other applications. As a pilot project, the SSAO was designed to work for a minimum of 5 years, without retrieving of any components, removing, treating and re-injecting free water from the production of MRL-141, as shown in Table 1.