This paper initially discusses the tendency to wider the conceptual envelop of subsea systems in oil production installations. From the conventional boosting systems to more complex gas/oil/water separation equipment and even polishing devices for coarsely separated fluid stream, there is nowadays a tendency to increase the complexity of subsea production systems far beyond manifolds and other maneuver stations. In sequence the pros and cons of subsea processing as an alternative to conventional topside primary processing are also discussed. Restrictions of the subsea environment and the consequent requirement for unconventional solutions and equipments comparing to topside traditional separation equipment are also mentioned. The limitations of the expression "subsea processing" are emphasized and both advantages and technological gaps of new "building blocks" for processing plant for topside and subsea application are discussed. Besides, operational aspects are also addressed so as to emphasize the new challenges subsea systems pose to operation crew: some important paradigm changes should be captured by operators when changing from a topside plant to a subsea system. The problems arising from having a new subsea system connected to an old production unit in a brown field are also discussed. The drive for the qualification of new conceptions and new equipment is approached not only for subsea use but also for the new generation of topside production facilities. The paper tries to bring some conclusions on the means to allow further development -filling up the gaps -and qualification of the new "compact" or "in-line" building blocks for subsea processing plants. However, it must be emphasized that the focus of this work is on processing technology not on equipment or marinization technologies. Thus, subsea engineering (hardware) qualification is beyond the scop of this work.

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.

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.

During the last years, a lot of work have been done focusing on development of low shear valves solutions to be applied on petroleum primary process plants. The main goal of the low shear valve is to generate water-in-oil (WiO) and oil-in-water (OiW) emulsions that can be easier treated by the separation process, when compared with emulsion generated by conventional valves. This paper presents experimental results of a comparison between a commercial low shear valve and a conventional valve. Both valves were installedin parallel on a test loop and the fluids used for all test matrix points were potable water mixed with Petrobras Marlim Crude Oil. The test matrix includes variation of differential pressure on valves, flowrates and concentration of water/oil. Samples were collected downstream of both valves and led to settle into several residence times. The degree of contamination of both phases were analyzed for all residence times. The benefit of the application of low shear valve was quantified for all test conditions and the results were very promissory. The pressure drops across valves were selected considering typical values observed at Petrobras choke valves and control level valves. For almost all test matrix's points the emulsion generated by the low shear valve showed at least a slight benefit, allowing have better water quality after settling. The low shear valve solution showed to be a promissory technology but the magnitude of the benefit is very influenced by valve process operation conditions.