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.
TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractSubsea water separation is an attractive method for debottlenecking water-processing capacity where it cannot be accomplished topside. This enables additional oil production to an existing host facility which is an alternative for several platforms on the Marlim field in the Campos Basin. Ever since the last decade several operators have started their projects, all focused on light oils. Petrobras has aimed at subsea water separation for heavy oils in very deep waters -a natural consequence of its large portfolio of oils with API lower than 20 degrees, as is the case of Marlim. However these low API and high-viscosity oils pose a huge challenge as their emulsions are much more difficult to break and heating is not considered an option. The subsea separation pilot system has to consider new compact separation technology instead of conventional gravity separators, aiming scaling up to a definitive system, since in this system it will be impossible to use a huge gravity separator (implying thick shells, required to resist external pressure). For that purpose, there are a series of R&D projects targeting different technology gaps foreseen in subsea processing equipment. Experimental tests for emulsion generation prediction, development of additives with chemical compatibility, determining reservoir limitations of oil and solids content in injected water, studies on slug flow impact and mitigation strategies, solids handling, water cut measurement method are some of the projects. In terms of subsea equipment several new technologies are under evaluation to be employed underwater for the first time. Equipments as hydrocyclone, electrocoalescer and oil in water monitor are the main ones, and availability of those ones is a major issue. This article shows an overview of the design premises for a prototype on the Marlim scenario, the results of the subsea processing investigations and their impact on defining the process conception and the design specifications for the subsea system.
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.
In the last 30 years or more PETROBRAS discoveries offshore were predominantly in deepwater. The successful history was supported, among other pillars, on a policy of investing aggressively on R&D projects through its R&D Programs like PROCAP-3000, among others. Specifically, Subsea Technology and Process have done much to unlock the non-conventional deepwater and heavy oil resources offshore Brazil and will continue to do so. High levels of activity in these areas will remain necessary with increased technology content. In particular, the shift to Subsea Processing is becoming more marked as a means to: 1-anticipate production, 2-improve reservoir recovery, 3-debottleneck high water flow rate field platforms and 4-allow marginal fields development. Actually, after successful implementation of several - technology projects, on subsea boosting and processing, the leading operators in these technologies have demonstrated that subsea processing is definitely a field development tool as predicted decades ago. Bearing in mind the above considerations, this paper introduces the updates on PETROBRAS most recently subsea boosting and processing efforts. The work hereafter includes applications and developments on the following technologies: Subsea Raw Water Injection, High Power ESP, Subsea Gas-liquid and Oil-Water Separation, Subsea Multiphase Pumping, Seabed ESP. It examines the main hurdles for applying these technologies Offshore Brazil on long tie-backs and ultra-long tie-backs (for instance: producing subsea to beach or very long tie-backs - 150 km or more). Introduction One can say that boosting technologies will permit to construct the subsea to shore system; nevertheless these are just part of the technological puzzle. There are still several technologies to come out of the box to construct an oil or gas subsea to shore. Some of the hurdles are complexities for instance on the conventional issues like: flow assurance, corrosion protection, chemical injection, emulsion handling, water production and slugs. Additionally it is necessary also to carry out new technology developments on electric power, on deepwater oil-water separation, on multiple emulsion formation. Actually the subsea to shore concept comes to compete mainly as an alternative to offshore platforms where no existing infrastructure is present. The high prices (and the time schedule) for constructing new platforms and the raising prices of operational expenditure scores heavily for the subsea to shore and stimulates efforts, studies and technology developments to achieve it. Nevertheless, new developments that configure a typical scenario for the subsea to shore approach are not easily found these days. Petrobras operated oilfields, on the other hand, present several opportunities to develop some important components either on boosting or on subsea processing, to improve recovery of mature fields, making use of subsea installations to overcome limitations imposed by the existing infrastructure. Small fields where old floating units can be replaced by subsea systems or fields where subsea boosting or processing systems optimize the production are the predominant scenario. These equipment developments, together with additional studies, are intended to provide the necessary tools to be applied on most scenarios. Petrobras applications nowadays are dominated by fields producing oil with associated gas and along the discussion on the main issues involved in subsea boosting and processing systems we will be updating the information about the company efforts on its projects. External Energy for Flow: alternatives When extremely long tie-backs for oil wells are mentioned, one always thinks either in high DeltaP seafloor multiphase pumps or reboosting stations. Long distances does not necessarily mean that the friction losses on the subsea pipeline are the highest. It is not uncommon the cases where the pressure drop due to hydrostatic column may be five to ten times higher than the pressure drop on the horizontal flow. This can be reached for instance with 250 km tie-back, with a 28 degree API on 18" pipeline. So it is not always necessary a reboosting system along the pipelines, on extremely long pipelines.
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