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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.

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TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractFor the control of any process it is essential to establish a mathematical model capable to correlate the operational and free variables to the respond variables. Experimental studies conducted at a lab pilot plant with different Brazilian crude oil showed that the performance of the electrostatic desalting process can be simulated by using a semi-empiric mathematical model. After an intermediate validation step, the results obtained from this model were used to determine the proper treatment conditions of several offshore desalting plants installed in Campos Basin -Rio de Janeiro, Brazil. The present work shows how the proposed mathematical model was established and its correlation with the data taken from the pilot plant for different crude oils in the range of 15° API up to 30°API. Finally it is shown the correlation relating the data obtained from the proposed model and others collected from processing plants installed in different refineries and offshore production systems.

This paper was prepared for presentation at the 1999 SPE International Symposium on Oilfield Chemistry held in Houston, Texas, 16-19 February 1999.