Malampaya, South China Sea, Philippines

The Malampaya field is located 80km off the coast of Palawan Island, in the Republic of the Philippines. In August 1998, Shell Philippines Exploration BV awarded Brown & Root a US$432 million design, procurement, fabrication, installation and commissioning contract.

The platform consists of a deck, supported by a concrete gravity sub-structure (CGS). The processed gas will be compressed and exported through a 504km pipeline to the Batangas onshore facility at Luzon Island, in the Philippines.

The condensate will be stabilised on the topsides, stored in the CGS and then exported to a shuttle tanker, through a catenary anchored leg mooring (CALM) system, located 3km from the platform. The design capacity of the integrated CGS and deck is 508 million ft³ gas and 32,800bbl of stabilised condensate per day.

The platform is located in water 43m deep and the deepwater subsea wells are at a depth of 850m.

TOPSIDES

The topsides were subcontracted to Sembawang Marine & Offshore Engineering (SMOE). This contract involved the fabrication, onshore commissioning and load-out of a three-level integrated deck, together with a living quarters module that can accommodate up to 44 people.

The topsides measure 40x90m in plan and reach 25m, from the base of the cellar deck to the helideck. The lower (cellar) deck, contains the major pumps, heavy wall vessels and workshops.

The middle deck (or production deck) contains the separation equipment and the electrical-control module. The equipment on the top deck (or weather deck) includes two export gas compressors, three power-generation gas turbines and a crane.

The initial operating weight of the topside is 13,000t. This equates to a loadout weight - excluding the transportation frame - of 10,000t and, as such, this will be the heaviest topside ever constructed by SMOE.

Fabrication of the deck commenced at Sembawang's yard, located in the north of Singapore, in June 1999 and is scheduled for completion and onshore testing by February 2001.

CGS

The topsides will sit on a concrete gravity sub-structure (CGS) - the first to be constructed in the Philippines. Brown and Root subcontracted the work to the Malampaya CGS Alliance, which consists of John Holland, Arup Energy and Van Oord ACZ, for the engineering, procurement, construction and installation of the structure.

The CGS consists of a rectangular-based caisson, measuring 112mx70m on plan and which is 16m high. It has four shafts extending 15m above water level, to provide support to a deck, with an operational weight of 13,000t. In addition to providing deck support, the CGS is used for temporary storage of up to 385,000bbl of condensate, produced from the subsea wells located 30km away.

The CGS subcontract will be the single biggest value subcontract placed by BRES, under its Malampaya platform contract. The CGS will be constructed in a purpose-built dry-dock, located in Subic Bay. In total, the CGS will contain some 66,000t of concrete, 7,100t of reinforcing steel and 600t of pre-stressing steel strands.

This CGS will be placed on a pre-prepared foundation to accommodate the unevenness of the seabed. This will involve placing 17,000t of rock, in 361 mounds, on the seabed. To allow access to the open sea, a channel 150m wide and 12m deep has been dredged.

After installation, 3,000t of rock was placed around the corners of the CGS for scour protection and 75,000t of iron ore was placed in the open cells.

In December 2001, an extended well test of the thin oil rim beneath the field initially yielded about 8,000 barrels of oil per day (bpd). The well test was performed by the Atwood Falcon drilling rig and Stena Natalita floating storage unit. It is also believed to be the deepest horizontal subsea well test undertaken in the world at a depth of about 850m.