The World's Biggest Conversion

Abstract The use of floating production systems converted from semisubmersible drilling units has been deemed a practical solution compared to the costly and time-consuming construction of custom-built floating systems. Although conversions are usually limited in the available deckload and production throughput and water injection capacities, the Petrobras 19 project has challenged all limitations designing a converted production platform with capacity of 16,000 m3/ d of oil, 3,000,000 Nm3/d of gas and 30,000 m3/d of water injection. This paper describes the development of Petrobras 19 production platform (P-19) in the Marlim field, some of the unique features of the platform and the key project decisions that affected platform design, construction and installation. The Marlim Field Development The Marlim field is located in the northeast sector of the Campos Basin, offshore Brazil, lying about 150 km northeast of Macae. Water depth over the field site ranging from 650 to 1050 meters. The reservoir is oligocene aged sandstone deposit located at a depth of approximately 2,640 meters below the sea bottom. A summary of the fluid and reservoir parameters for the Marlim field is shown in Table 1. The Marlim development studies favored a four phased development. The first two phases aimed at both a better understanding of the reservoir and deep water technology development. These phases were carried out by two platforms Petrobras 13 (P-13) and Petrobras 20 (P-20). The third phase will be accomplished with Petrobras 18 (P-18, installed in may/94), Petrobras 19 (P-19, will be installed in jun/97) and P-20 (installed in the previous phase). Major components of the system currently envisioned for this phase are shown in Fig. 1. P-19 will be moored in the north portion of the field, in 770 meters of water depth. The oil production will be exported via two 12 inches pipelines to a pipeline end manifold (PLEM), located approximately 22 km away, in 200 meters of water. From the PLEM there are two selected export routes, both with shuttle tankers. The first and the preferential route is through a tanker maintained on location using a single point mooring system with catenary anchor leg mooring buoy (CALM buoy). The second route (also with pigging purpose) is through a permanently moored converted tanker FSO P-32, using turret type mooring. Gas production will be exported via 10 inches flexible pipeline to P-18, located 4.5 km south. The expected oil production as well as water injection demand are shown in Fig. 2. P-19 design requirements to accomplish this expected production are shown in Table 2. Selected Platform for Conversion The platform acquired for conversion was a third generation semi-submersible drilling unit "Threasure Stawinner". The unit was design and built (in 1983) as a column stabilized and thruster assistant semi-submersible drilling unit. The unit has two lower hulls (pontoons) which support six columns and a box type superstructure, and bracings, horizontal diagonals and vertical diagonals are provided to enable the unit to have sufficient strength.