Marlim Sul, Campos Basin, Brazil

South Marlim was discovered in November 1987 by the wildcat well 4-RJS-382. The field is located 110km (68 miles) off the northern shore of the Rio de Janeiro state. Water depth varies from 720m in the north, to 2,600m in the south of the field. About 80 per cent of the field area is in a water depth greater than 1,200m.

The deepest well is the South Marlim 3B (MLS 3B) which set a new world water depth record of 1,709m (5,607ft), breaking the 1,615m record, set on Shell's Mensa field a month earlier. Mensa is a natural gas-only well, whereas MLS 3B is both oil and associated gas.

This well was drilled from the dynamically positioned drillship Noble Leo Segerius (formerly Neddrill 1) to a total depth of 3,167m (10,390ft). It discovered 93.5m (307ft) net pay of gas and oil. The well came onstream at an initial rate of 4,500b/d, without gas lift. This will gradually be increased to 7,500b/d of oil.

DEVELOPMENT STRATEGY

Petrobras' initial development plans called for the installation of two semisubmersible producing units, with a processing capacity of 150,000b/d. Following the MLS 3B drill stem tests however, which suggested that the reservoir could contain 1.2 billion bbl of oil in-place alone, Petrobras eventually opted for a two-phase development plan.

Phase one is based upon the Marlim Sul pre-pilot early production system, consisting of the MLS 3B subsea completion (as well as the possibility of including a second satellite well). This well produces into a floating producing, storage, and offloading vessel (FPSO) moored in 1,420m (4,659ft) of water, lying a distance of 3,600m from the wellhead. The FPSO receives the oil and gas, processes it, provides gas lift facilities and stores the oil for offloading operations to a shuttle tanker.

Phase two will exploit the remaining field area and will depend on additional well information, seismic and geological interpretation, as well as technological developments in drilling, completion and equipment.

FPSO

Petrobras selected the converted trading tanker FPSO II for use in the South Marlim. FPSO II originally started life as the 127,000dwt tanker Mariblanca. This was converted, in 1982, for service in the Cadlao field in the Philippines. It was subsequently refurbished and modified for the Linapacan field, also in the Philippines. Following the Marlim Sul contract, the FPSO II was taken to the Sembawang shipyard in Singapore in November 1996 where work commenced on the upgrading.

MOORING

FPSO II is moored on the field by a 19m-diameter single buoy storage (SBS) system, which is permanently connected at the stern, by a rigid yoke. The anchoring arrangement consists of six equally spaced composite catenary anchor legs consisting of wire rope, studlink chain, polyester rope and studlink connected to chain stoppers on the fixed buoy section of the SBS.

The FPSO weathervane capacity is achieved by a three race roller-bearing arrangement, connected to the rotating SBS.

SUBSEA TREE

In the first run, the wet christmas tree was run with flowlines connected to it, using the layaway method. The running of the tree was performed by the DP drillship Noble Roger Eason, after its upgrade to enable it to operate at a depth of 1,800m.

The lines linking the subsea tree with the FPSO, including the 4in annulus flowline, 6in production flowline and 12-function 4,800m-long (15,748ft) umbilical, with a nominal diameter of 120mm (4.76in). These were laid by the Sunrise 2000.

EXPORT

Crude oil transfer is from the flexible risers, through the SBS manifold, the toroidal swivels, the hard piping on the SBS yoke and the pipe swivels across the yoke to tanker articulation; and hard piping to the process deck.