Brazil's offshore sector has long been a test bed for some of the most innovative subsea technologies. Its latest generation of projects using seabed processing solutions is setting the benchmark in terms of production performance. Advances in the capabilities and reliability of these solutions is dramatically improving recovery rates and lowering development costs.

Petrobras has been striving for years through R&D programs and technology partnerships with key contractors to reach a point where – when the economics and conditions are right – it can move production facilities to the seafloor.

By doing so, the company gains a number of potential advantages, including a reduction in field development costs, increased production rates from subsea wells, reduction in the need for chemical injection, minimized risks to workers, and increases in production by accessing output from previously marginal fields.

Petrobras has been encouraged by similar efforts from likeminded operators elsewhere in the world. These include Shell, with its producing Ormen Lange gas field in the Norwegian Sea 120 km (75 miles) offshore, BG's Scarab/Saffron producing fields in the Mediterranean sea 90 km (75 miles) offshore Egypt; Total's planned Laggan-Tormore West of Shetland development 140 km (87 miles) offshore; Noble Energy's Tamar project in the Mediterranean Sea 90 km (56 miles) offshore Israel that is tied back to a shallow-water platform; and Husky Oil's Liwan development in the South China Sea, which is tied in to a shallow-water platform 75 km (47 miles) away.

A schematic shows how subsea production is used with a number of floating production units. (Images courtesy of FMC Technologies Inc.)

Marlim

Petrobras is driving development of subsea processing, separation, boosting, and gas compression as a means of opening up development opportunities where it can overcome greenfield challenges such as heavy oil, low-reservoir pressures, and hydrate formation. These technologies are equally beneficial for brownfield projects, like Marlim, where its capabilities for enabling increased oil recovery can help battle declining oil and gas production, increasing water production, and constrained topside facilities.

Marlim, in the northeast Campos basin, produced first oil in March 1991. At one time, the field was the world's largest subsea development. Today, it is being targeted for another world "first" – a deepwater subsea oil/gas/water and sand separation system, which will not only have to deal with heavy oil and increasing water production but also be able to reinject water into the reservoir to boost production in 914 m (3,000 ft) water depth. With oil in place estimated at 9 Bbbl, a small percentage gain in ultimate reserves at Marlim represents a sig- nificant increase in production. The main purpose of the subsea system is to debottleneck the existing floating production facility and increase production by removing unwanted water from the production stream at the seabed. This system also will be the first to use water reinjection to increase reservoir pressure and boost production.

One of the main contractors helping Petrobras to achieve its goals on Marlim is FMC Technologies Inc.

The subsea separation, pumping, and water reinjection system will be installed in 899 m (2,950 ft) water depth to meet the challenge of increased water production. When the system receives a mixture of oil, gas, water, and sand, it will separate the gas from the liquids. Then the heavy oil will be separated from the water using a novel pipe-separation design licensed and developed in cooperation with Statoil.

The system also integrates FMC's proprietary water-treatment and sand-handling technologies. Separated gas will be added back to the oil stream to aid in lifting the oil to the floating production unit, while the separated water will be pumped back into the reservoir to increase production.

"I think the belief is, within Petrobras, that this is technology that helps them deal with the severe water cut issues they have on many of their subsea wells," FMC CEO Gremp said in a recent company briefing. Once Petrobras gets comfortable with the technologies, he said, the company will likely apply them to its older wells with high water cuts.

Equipment for Marlim was scheduled for delivery in 3Q 2011 and should be installed by the end of the quarter. Systems integration testing is under way and should be complete by year-end.

FMC has developed subsea compression station modules that eliminate the need for surface production facilities and support production from reservoirs otherwise not seen as economically attractive.

Petrobras has awarded FMC an additional subsea separation and boosting system contract for the brownfield Congro and Corvina development, also in the Campos basin. This project is the contractor's fourth implementation of subsea processing technologies in Brazil, following Phases I and II of Shell's BC-10 development and the Marlim separation project. The project also is one of the best demonstrations of how subsea systems can reduce surface facility needs. The installation of two subsea separation systems will allow the demobilization of one existing production platform , something of a milestone moment for subsea processing technologies.

In addition to a subsea gas/liquid separation and boosting system for each of the fields, the scope of supply includes two subsea manifolds that will each perform production and gas lift injection for 10 wells, two subsea boosting module stations, pipeline tie-in equipment, and subsea control systems. The control system incorporates an innovative subsea robotics technology (designed by Schilling Robotics) to operate the manifold and separation station valves and eliminate multiple actuators and associated controls, providing Petrobras with a cost-effective solution.

According to Gremp, Brazil's deepwater sector will see additional subsea processing projects, with up to 12 similar systems expected to be ordered by Petrobras once it has fully evaluated the performance of the Marlim pilot project.

The Brazilian operator is already contemplating incremental orders for Marlim, he said, "and the potential for this technology is significant for many fields that Petrobras has."

Petrobras recently wound up its successful Procap 3000 research program, which was a driver for many of the operator's deepwater advances. "This was an important milestone when we realized that water column depth no longer presented a barrier," said Carlos Tadeu Fraga, executive manager of Cenpes, Petrobras' R&D Center. "In the Future Vision Procap program, we are laying emphasis on the pursuit of solutions that could significantly alter current standards for developing deepwater fields.

"Among the innovations we are working on at present are the intensive use of nanotechnology and subsea systems for production processing. This marks a new stage in this fantastic voyage."