The number of FPSO's installed on marginal Fields k increasing while the life of these Fields is often unpredictable. The possibility that a tanker-based FPSO may easily be relocated after depletion of a marginal field may become a key factor to the decision making process in respect of small field development.
This paper will describe the circumstances under which the tanker-based "FPSO II" was disconnected from the Cadlao Field in the Philippines (after 10 years and 3 months uninterrupted operation), towed to Singapore, for refurbishment and modification, towed back to the Philippines and installed on the new West Linapacan Field in a water depth of 1150 ft. The Scope of Work included the replacement of over 800 tonnes structural steel in the tanker, extensive work on the process equipment and instrumentation plus a comprehensive refurbishment programme for the SBS mooring system and the vessel machinery.
The whole project was executed under very tight time constraints and less than 6 months elapsed between last oil at Cadlao and first oil at West Linapacan.
The 127,000 dwt converted tanker FPSO II owned and operated by SBM Inc. went into operation on the Cadlao Field, offshore Philippines in August 1981. This Field in 300 ft water depth was produced through 611flowlines from 2 wells. Each well was also connected to 611service lines thus requiring a 4 path 611 swivel mounted on the SBS mooring buoy. The SBS mooring buoy was attached to piles driven in the sea bed by six 611 ? 5½11diam. chains. The production facilities mounted on the tanker deck were designed to handle 30,000 BPD oil and a ground flare was installed to flare up to 6.5 MMCFD excess gas.
The 3-phase production and test separators also removed the produced water which was passed through a skimmer/degasser to 2 series operated slops tanks where it was de-oiled and pumped overboard. The design and operation of the FPSO II on the Cadlao Field has been extensive y reported in various publications.1–6Fig. 1 shows the FPSO II operational configuration in the Cadlao Field.
In 1986, the Cadlao Field concession was ceded to Alcorn who had also obtained the Matinloc Field concession situated nearby. A new bare-boat charter was negotiated for the FPSO 11 and the Matinloc Field then connected to it. This required modifications to the production manifolding and the installation of a metering/prover loop system on the FPSO 11 to fiscalize the Matinloc crude.
This mode of operation continued until November 1991 when the production had fallen to an uneconomic level and it was decided to relocate the FPSO 11 to West Linapacan Field.
During its 10 year operation in this area the FPSO 11 had a remarkable record of having virtually no down time.
Fig.2 shows the location of the West Linapacan Field situated in 1150 ft water depth 55 km from the Palawan Island coast.