Subsea manifolds are very attractive due to the reduction on the capital expenditure (CAPEX) obtained by reducing the number of flowlines and umbilicals, weight cut on the floating production platform due to reduction in the number of risers and reduction in the time required to connect the subsea wells to the platform, allowing for first oil anticipation. These advantages are more evident when a FPSO is used as a production platform.

When in shallow waters, not only the risers, but also the structures and equipment are submitted to different conditions from the ones related to deepwater applications. OGX has developed offshore applications in shallow waters in Campos Basin, Brazil, using a FPSO with Lazy S riser configuration, based on the Midwater Arch systems (MWA). MWA systems are feasible due to OGX application scenario, but they present some disadvantages, such as: high compliance of the buoyant section to the FPSO, large static offset (common issue in shallow waters applications), which makes the MWA carry the risers that are clamped at the top; high manufacturing and installation costs, associated to the high weight of the structure, which includes large and heavy buoys; limitation regarding transportation, sometimes requiring heavy duty trucks, and consequently, more expensive ones. These disadvantages could be avoided by using another type of support structure, but it depends on the application conditions. Aiming to optimize the Lazy S configuration for new applications in shallow waters, a viability study of a most simplified concept of support, fixed and less compliant, was carried out considering as a standard scenario the Waimea field (under development), located in Campos Basin, Brazil. As a result of this study, OGX and Wood Group Kenny developed the conceptual project of an innovative design of Riser Support Structure (RSS). Therefore, this paper addresses the technical challenges that were faced during the design of this new concept of Riser Support Structure for shallow waters in offshore applications, including issues regarding the required structural safe response and aspects comprising installation and some decommissioning considerations. Regarding the design, this paper discusses the structural analyses performed to validate the RSS, which include VIV and Finite Element Analyses, presenting its main results, and the critical issues encountered during these analyses. They include issues such as: Overstress due to combined loads; stress concentration in important structural components; and stress concentration due to impact load (issue recognized during dynamic analysis to simulate the pile driving operation).

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In the petroleum production area, multiphase meters are used to measure the produced fluids - natural gas, oil and water - at in-line flow conditions and without any need of separating the incoming phases. Thus, the Multiphase Flow Meters (MPFMs) offer the possibility of real-time, complete and continuous flow rate measurements. The oil industry has been supportive to the development of this technology and has mainly focusing its application on the offshore production, particularly at the sub-sea area. Several types of tests (e.g., performance, endurance and reliability) have been conducted worldwide and the usually acquired positive results have paved the way to several field applications. Thus, the in-line Multiphase Flow Metering Technology has had a continuous improvement and nowadays several petroleum companies are confidently incorporating this technology into their new designs. The demands associated to the sub-sea multiphase meter operation and its associated levels of reliability are particularly challenging. But, at deep sub-sea production the savings and operational benefits offered by this new technology could be quite significant. Thus, PETROBRAS among others, when considering the benefits of such application has focused its efforts on this technology and aimed its initial application to the sub-sea production. In the summer of 1997, Petrobras installed a multiphase meter in a sub-sea production manifold, at 450 meter of water depth (WD) and 5 km away from the host FPSO (Floating Production, Storage and Offloading) in the Albacora field. That was followed by a second sub-sea multiphase flow meter installed in the Marlim field at 950 meter of water depth (WD) and since then several others subsea manifolds with multiphase flow meters are under installation. This paper reports the long-term field operational experiences, and also gives an evaluation of the measurement performance, compared to the conventional test separator. The high level of development, already achieved by the multiphase flow metering technology, contributed to the PETROBRAS confidence in order to introduce a new generation of manifolds. Sub-sea manifolds can be a very attractive alternative to sub-sea layouts at deepwater fields. A drawback of the sub-sea wells production gathering is the individual well production management. The conventional production well tests when applied to sub-sea production manifolds require additional test flow lines and equipment, besides being time demanding and usually offering some operational problems, naturally, these drawbacks can be surpassed by the application of reliable multiphase flow metering. PETROBRAS is now installing the fourth generation of diverless sub-sea manifolds at Marimba East field. The main innovations are related to the metering system, where the well tests are based on multiphase and single-phase meters. In these manifolds the gas lift test line and production test line were eliminated, allowing significant cost savings. In addition, a multiphase meter will monitor continuously the well flow rates, while single-phase meters will similarly monitor the injection of lift gas. Introduction The main challenge for the next Campos Basin exploitation projects is to provide profitable and competitive solutions for ultra deepwater sub-sea oil fields.

This paper presents a methodology to analyze the risers interference connected to an FPSO, which is using turret moored system in shallow water. It is not feasible in shallow water to use riser free hanging catenary configurations, since there is not enough length in order to dissipate FPSO dynamic response due to wave action, which can cause riser damage at TDP. Furthermore, FPSO static offset is very large, around 30% of water depth, when it is compared with deep water, around 11–12% of water depth. In order to become feasible a large number of risers connected to a FPSO using a turret moored system in shallow water are needed to use compliant configurations, such as: lazy wave, pliant wave and Lazy S. As mentioned above risers compliant configurations are capable to avoid riser damage at TDP, but they present a large lateral motion. Thus, riser interference becomes a critical issue to be overcome. As the applicable standards and rules are not entirely prescriptive about this issue, the riser analyst usually have to adopt independent criteria, such as load cases, internal fluid density, hydrodynamic coefficient considering or not wake effect and clashing criteria (allowable, partially allowable or not). Therefore, the proposed methodology is very robust and was used at FEED studies for FPSO OSX-2/3, both belong to OGX, which are planning to install them at the ending of 2013 in Campos Basin, offshore Brazil.