Subsea Processing and Boosting in Brazil: Future Vision
Authors: Carpenter Chris 
Published: February 2015

This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper OTC 24498, ’Subsea Processing and Boosting in Brazil: Status and Future Vision’ by F.A. Albuquerque, M.G. Morais, M.L. Euphemio, C. Kuchpil, D.G. Duarte, and R.T. Orlowski, Petrobras, prepared for the 2013 Offshore Technology Conference Brasil, Rio de Janeiro, 29-31 October. The paper has not been peer reviewed.

Subsea processing and boosting can be key enablers and optimization alternatives for challenging field developments whose benefits increase with water depth, flow rates, and stepouts. This paper summary focuses upon reporting new research-and-development (R&D) initiatives related to subsea processing and boosting offshore Brazil.

Introduction

In the initial exploitation stages of offshore oil and gas fields, the main concern involves the initial investment to construct the production units, drill the wells, and install all equipment necessary for production. Operators usually adopt a conventional solution at this stage, failing to view new technologies as a first alternative. Such technologies are usually considered only when they are vital for a specific field development.

For most fields in the Campos basin offshore Brazil, the main recovery mechanism from the beginning of production is waterflooding. A typical curve of produced fluids starts with the predominance of oil rising to the production plateau until the water breakthrough occurs. At this point, production presents increasing water content in the liquid stream. Therefore, because a massive water injection is necessary to maintain the pressure of the reservoir, after a few years the water cut increases considerably. Additionally, there is a need to overcome the constraints of existing platforms.

There are currently additional motivations for using subsea technology. Revitalization of mature fields can provide opportunities to develop subsea separation technologies for higher flow rates (including higher water cuts) and to develop subsea multiphase pumps for higher differential pressures, among other options. Other possible scenarios include small fields where old floating units can be replaced by subsea systems or fields where subsea boosting or processing systems optimize the production.

For a discussion of past and current proven technologies, concepts, and approaches that have been used as building blocks for new developments in both green and brown fields, please see the complete paper.

Future Vision of Subsea Processing and Boosting: Ongoing R&D Initiatives

There are several new R&D initiatives related to subsea processing and boosting being considered by the operator for application in potential scenarios involving both mature fields and green fields. These initiatives include the following:

Compact subsea oil/water-separation system

Compact subsea gas/liquid-separation system

Subsea gas-compression system

High-differential-pressure multiphase pump

Compact Subsea Oil/Water-Separation System. One of the main objectives of a subsea oil/water-separation system is to perform the primary processing of fluids on the seabed, providing produced water with a destination other than the topside facilities at the floating production unit. This is an attractive option for most of the fields in their mature phase of production.

Subsea separation is also interesting from the point of view of primary processing, because the sooner the water is removed from the production stream, the easier it is to treat both water and oil streams. All the shearing on the multiphase production stream to the topside installations that takes place when production is routed to a platform is greatly reduced, making treatment at least potentially easier and more effective. This kind of separation system is used mainly for mature fields, and it can be considered for application in a specific area with an existing infrastructure or for revitalization of a mature field in a remote region. To enable production in these mature-field remote regions, in which oil-flow rates are not high enough to justify a dedicated platform, the adoption of a subsea oil/water-separation system can be a solution.

The Troll pilot, installed in 1999, was the first subsea oil/water-separation system installation. In 2007, the Tordis system, designed for higher flow rates, was installed. In 2012, the Marlim threephase subsea oil/water-separation system, which reinjects water into the same producing reservoir, was installed; it is the world’s first system for deepwater separation of heavy oil and water.