PETROBRAS PUSHING EDGE OF DEEPWATER FRONTIER

Brazil's Petroleos Brasileiro SA continues to extend the frontier of subsea technology, especially in the deepwater Campos basin.

The basin has huge hydrocarbon potential. Brazil's supergiant Albacora and Marlim field complexes in the Campos basin are expected to account for most of the projected near doubling of Brazil's oil production this century (OGJ, Mar. 11, p. 38).

Among recent technological advances Petrobras has:

Started an extensive deepwater production technology capability program covering more than 100 research projects in collaboration with dozens of domestic and international entities.
Installed the first guidelineless deepwater wet christmas trees in the Campos basin, part of Marlim's early production system.
Developed a special purpose deepwater template manifold.
Developed a multiplexed subsea control and monitoring system for working in more than 1,000 m of water.
Let contract to a joint venture of Fluor Ocean Services International and Sweden's GVA to develop basic design for a tension leg platform capable of working in 1,000 m of water and producing 100,000 b/d of oil and about 70 MMcfd of gas.
Developed a hyperbaric pressure simulation chamber capable of simulating pressure equal to that in 1,000 m of water.
Implemented more advances in tools and basic equipment for remote operated vehicles (ROVs).

THE KEY: OFFSHORE

Although significant hydroCarbon potential is turning up in Brazil's Amazon region (OGJ, Feb. 12, 1990, p. 19), it is likely that Brazil's offshore holds the key to its production future.

A comparison of production figures spanning the past 2 decades underscores the Brazilian offshore's significance. At the end of the 1960s, when Brazil began to mount its offshore push, the country's oil production averaged 160,000 b/d-less than 35% of domestic oil demand-and reserves totaled only 800 million bbl.

Production currently is approaching 700,000 b/d, and proved and probable reserves are estimated at 7 billion bbl. Petrobras has disclosed an ambitious $16 billion program to hike production to 1 million b/d by 1995, with most of those outlays targeted for offshore, notably in deep water.

Petrobras by 1985 had tested more than 60 wells in water depths of more than 500 m, including recovering commercial volumes in a gas discovery in 953 m and an oil discovery in 1,565 m.

DEEPWATER POTENTIAL

The only Brazilian deepwater oil field outside the Campos basin is an oil discovery in the Sergipe-Alagoas basin to the north.

Petrobras classifies deepwater as water depths exceeding 400 m.

The Campos basin, off Rio de Janeiro state, covers about 100,000 sq km and features water depths of as much as 3,400 m. Almost all producing fields are in a corridor about 30 km wide and 120 km long in waters less than 400 m.

Although proved reserves off Brazil are still fairly modest at about 2 billion bbl, original oil in place (OOIP) volumes in the Campos and Sergipe-Alagoas basins are estimated at 22.7 billion bbl.

Campos oil fields in more than 400 m of water include Marimba, Albacora, Marlim, 1-RJS-359, 1-RJS-366, 4-RJS-377, 4 RJS-381, 4-RJS-382, 3-RJS-397, 4-RJS-403, and 1-RJS-409. In the Sergipe-Alagoas basin, only 1-SES-92 oil field lies in more than 400 m of water.

Turning those OOIP volumes into proved reserves will depend on how well Petrobras develops and assimilates increasingly sophisticated technology to work in ultradeep water.

The state company is following up on discoveries and developing new prospects targeting Oligocene turbidites off the northeastern state of Ceara in 1,285 m and 1,890 m of Water and off Para state in 1,200 m and 1,920 m of water.

Petrobras is using Campos basin geological models for the frontier areas and expects potential reserves levels to be comparable.

In addition, there are still deeper pay prospects to be tested in the Campos basin, notably the Coquinas member of Aptian Lagoa Feia formation.

DEEPWATER SUCCESSES

The Petrobras focus on deepwater technology has been buoyed by a string of successful completions and deepwater production records in recent years.

Petrobras officials are leaning more and more toward floating drilling-production systems with subsea completions as attractive development options, even in more than 1,000 m of water.

In more than 63,360 man-hr of deepwater drilling operations and 13,100 man-hr of production tests, in water depths averaging 904 m, Petrobras recorded no serious accidents.

The results of deepwater exploration in the Campos and Sergipe-Alagoas basins encouraged Petrobras to press still more work. By yearend 1989, it had installed more than 15 subsea manifolds and 140 wet Christmas trees.

CHRISTMAS TREES, TEMPLATE

Petrobras installed the first of 10 deepwater guidelineless wet Christmas trees in about 400 m of water in Marimba field last year (OGJ, Feb. 12, 1990, p. 20).

The trees are being supplied under a $15 million contract with CBV Industria Mecanica SA and FMC Subsea Systems.

To be used mainly in Marlim and Albacora fields, the trees each weigh 50 tons and stand 30 ft tall. In all, Petrobras plans to drill 221 wells in Albacora and 145 wells in Marlim with dynamically positioned drillships or semisubmersibles.

Petrobras claimed the world water depth record for production, 2,365 ft (721 m), at yearend 1990 with installation of the second such tree as part of Marlim's prepilot early production system (OGJ, Sept. 10, 1990, p. 21). Plans call for a third tree to be installed as part of the Marlim prepilot.

The trees are lowered from a dynamically positioned vessel by means of a riser and seated on the wellhead. All hydraulic functions are operated by remote control, eliminating the need for divers for installation. Installation is monitored by a television camera mounted on an ROV.

The Petrobras designed Octos 1000 is a special purpose template manifold for deepwater use.

It is a seven well unit that allows guideline or guidelineless operations, simplifies leveling and foundation work, minimizes cuttings falling from the unit during drilling, and expedites ROV operations.

MUXCOM

Tests of a new underwater control system in Bonito field in the Campos basin were to begin late in 1990.

Development of the multiplexed control and monitoring system (Muxcom) began in 1988 by Brasnor, Braspetro's subsidiary in Norway. The idea is to develop a low cost alternative to complex electrohydraulic control and monitoring systems that require higher installation and maintenance costs.

Muxcom entails installing a seafloor pod that receives and sends electronic signals to an interactive computer system onboard a platform. Technicians on the platform operate and monitor valves and gather well data.

The Muxcom, tested in a Norwegian laboratory to operate in 1,000 m of water, was to be installed in 190 m of water in Bonito field for 1 year of tests.

It is designed to monitor and control well production with only one umbilical line at a cost of half or one third that of a $3-4 million conventional system typical in the North Sea or off Brazil. Muxcom systems are fabricated by Ferranti of the U.K.