Petrobras may have record water-depth find

Where Petrobas found more deewater campos oil [52167 bytes]

Petroleos Brasileiro SA (Petrobras) claims it may have set a world record for water depth with a potentially commercial oil discovery.

The strike is one of two ultradeepwater oil discoveries that Brazil's state oil company recently drilled in the offshore Campos basin.

Both wells, Rio de Janeiro Submarino 436 and Rio de Janeiro Submarino 511, are about 130 km east of Sao Tome Cape, off Rio de Janeiro state.

Petrobras 1-RJS-436 found oil in pay at 3,229 m in 1,853 m (6,078 ft) of water about 20 km northeast of giant Albacora field.

That makes it the deepest-water potentially commercial strike in Brazil and perhaps anywhere else, say Petrobras officials.

With potential reserves pegged at 400-600 million bbl of oil, it also would be the third biggest find in the Campos basin.

First and second, respectively, are Marlim, with proved reserves of 1.7 billion bbl and Albacora with 473 million bbl. Both are producing.

Barracuda is the third deepwater giant in the basin.

In addition, Petrobras 1-RJS-511, 15 km north of Albacora field, found oil at 2,673 m in 980 m (3,214 ft) of water. The company estimated potential reserves at 30-40 million bbl.

Brazil has proved reserves of oil, gas, and condensate totaling 11 billion bbl of oil equivalent (BOE). The Campos basin accounts for 84% of that total, or about 8.3 billion BOE. At present, the Campos basin is producing 64% of Brazil's total output of 850,000 b/d.

Meantime, units of Oslo's Kvaerner AS are intensifying operations in Brazil's deepwater arena.

Possible record?

Shell Oil Co. this year set a world record for water depth with its BAHA wildcat, drilled in 7,625 ft of water in the Alaminos Canyon area of the Gulf of Mexico (OGJ, Mar. 18, p. 34). Results of that well have not been disclosed.

Shell also drilled an apparent oil discovery in 1987-88 with the previous water-depth record well on Block 657 in 7,520 ft of water in the gulf's Mississippi Canyon area. Shell abandoned that well but still holds the lease on inactive status.

U.S. Minerals Management Service also lists gulf discoveries by Shell in 7,195 ft of water on Mississippi Canyon Block 522 in 1989 and by Amoco Production Co. on Mississippi Canyon Block 217 in 6,500 ft of water in 1994.

No results or tentative development plans have been disclosed for these finds.

If the Petrobras well is a record, it isn't likely to stand for long. There is under way a headlong rush by companies into the ultradeepwater frontier of the Gulf of Mexico, with many leases acquired in recent lease sales in water depths approaching 10,000 ft, the outer limit of industry's capability (see related story, p. 34).

Discovery status

Lincoln Rumenos Guardado, Petrobras exploration manager, told OGJ the two wildcats are undergoing flow tests, and both discoveries will be appraised with step-out wells.

Drillship NS-14 Seven Seas drilled the apparent record water-depth find after spudding a mere 38 days prior to finding pay.

The drillship, rated to 2,000 m water depth, will drill four appraisal wells in the area.

Appraisal of the field's potential will continue into 1997, ahead of any plans for preliminary design work for possible development schemes.

Production prospects

A pioneer in deepwater drilling and production, Petrobras is grappling with the challenge of how to produce profitably and safely at 2,000 m and beyond.

A successful combination of subsea completions with wet christmas trees and floating production facilities has been used by Petrobras since the early stages of development of Campos basin oil fields.

From the first production in that basin in 1977 to completion of the 4 Marlim well in April 1995-which set a water depth world record for subsea completion at 1,027 m-Petrobras has made significant accomplishments demonstrating that floating production systems and subsea completions are a viable option for ultradeepwater development.

This became the company's preferred option, given its deepwater experience, the simplicity and reliability these systems offered, the option of equipment redeployment, low overall cost per barrel, and the potential for phased development.

The last element became a cornerstone of Petrobras deepwater strategy by offering benefits of minimizing risks and capital exposure while generating cash flow to support subsequent phases.

Before the most recent discovery at 1,853 m, Petrobras reported an oil and gas strike in 1,709 m of water in Marlim Sul, the southern extension of Marlim field that is still being evaluated.

Rodolfo Landim Machado, Petrobras E&P manager for the Campos basin, says that technology is no problem even for such great water depths.

He pointed out that Petrobras is already producing from a water depth of 1,027 m and is in the advanced stage of an R&D program aimed at providing technical capability for oil and gas production in water depths as great as 2,000 m (6,560 ft).

The current world record water depth for oil and gas production was set this year by Shell's Mars tension leg platform (TLP) development in the Gulf of Mexico in 2,930 ft of water. That record is set to be eclipsed next year with installation of two more Shell gulf projects, the Ram-Powell TLP (3,220 ft) and Mensa subsea development (5,400 ft).

Given Petrobras' penchant for putting ultradeepwater finds on line fairly quickly with early production pilots based on floaters and subsea wells (Marlim and Albacora), those records also may not last long.

Deepwater prospects

According to Petrobras E&P officials, the deepwater production system of the future will be heavily based on high-productivity wells.

Horizontal and multilateral well technology will be a key component in this game, provided that 3D seismic data and good reservoir characterization are available.

The utilization of intervention vessels could be an alternative to use of semisubmersibles, which are more expensive and not always available. Another potential bottleneck is the size of the ultradeepwater pipelaying vessel fleet, points out Joao Carlos de Luca, a former Petrobras E&P director and now aide to the president of Braspetro, Petrobras' foreign arm.

Although the capability to lay 12-in. pipelines in 2,440 m of water does exist, this can be accomplished by only a few vessels. In this regard, operators and contractors have to work together to find the most convenient way to make pipelaying operations feasible in ultradeep waters, adds de Luca.

Petrobras is taking several coordinated actions to ensure availability of rigid and flexible pipe, umbilicals, and offshore construction vessels for increasingly deeper waters. Some strategies include: development of products under cooperative agreements, notably involving the use of new materials to trim weight and improve corrosion resistance (fiber reinforced plastics) and thermal insulation characteristics.

FPSOs, subsea systems

De Luca also notes there is a trend in the use of tanker-based floating production, storage and offloading (FPSOs) vessels in offshore development.

FPSOs are favored more and more, owing to their large deck-load capacity to install processing equipment and ability to store and offload oil production through shuttle tankers, thus eliminating, or at least postponing, the need for export lines.

In Petrobras' view, FPSO units can be moored at a maximum water depth of 1,500 m. According to de Luca, the use of tension-leg mooring systems will make it possible to position FPSOs in waters deeper than 1,500 m.

The present subsea hardware technology can be easily extended, with minor modifications, to beyond 1,800 m, claims de Luca.

The industry has also put much effort into simplification of manifolds. The use of multiphase meters on subsea trees will allow the elimination of test lines and headers, thus reducing manifold weight and size.

Considering that the number of trees and manifolds used by Petrobras will double the next 5 years, the company has been carrying out a pioneering, aggressive standardization program whose results so far make it possible, for instance, to interchange trees from different manufacturers.

Petrobras anticipates the deepwater production system of the future will have a few high-productivity subsea horizontal wells connected to subsea manifolds and then to boosting systems.

Subsea boosting

The attractiveness of subsea boosting has been confirmed by studies conducted by Petrobras for possible application in the three giant deepwater fields under development in the Campos basin.

These studies indicated good economic results due to the higher initial production rates and consequent early cash flow, as well as a small increase in ultimate oil recovery. A reduction of 10-30% in the cost per barrel produced was found to be typical.

From the boosting systems, oil and gas production would be sent to high processing capacity FPSOs moored in water depths of 1,000-1,500 m.

The oil produced would be transferred to shuttle tankers connected in tandem, while the associated gas is compressed either for injection or for export to shore via steel pipelines.

The wells, manifolds, and subsea boosters will be served by multipurpose service vessels (MSVs), thus reducing the need for workover rigs.

One important question that remains is whether the industry can supply Petrobras and other operators' demand for subsea equipment, or if this should be regarded as a bottleneck to deepwater development, either in Brazil or worldwide. Petrobras contends that engineering, rather than manufacturing capacity, is the main concern for operators.

Deepwater manifold tenders

Kvaerner FSSL, the British submersible control systems producer, in September commissioned two manifolds in Albacora field.

Meantime, affiliate Kvaerner Oilfield Products do Brasil (KOP) is preparing for two Petrobras tenders for installation of manifolds in Marlim and Marimba fields in the Campos basin.

The electrohydraulic multiplexed control system, installed in the MSP-DL1 and MSP-DL2 manifolds in Albacora, will be operated from the P-25 platform. Projected for guidelineless intervention operations with the help of a remote operation vehicle (ROV), this will be the first such system to operate in Brazilian waters, at a record water depth of 680 m.