To produce the deepwater Malampaya gas field, Shell Philippines Exploration BV selected a subsea production system consisting of a cluster well development, initially with five horizontal trees, connected to a central production manifold.
The Malampaya field, in Block SC38 of the South China Sea, is in 750-1,150-m water, with the subsea production system being installed in about 820-m water.
From the manifold, two 30-km flowlines will carry gas to a concrete gravity-based processing platform. Dry compressed gas will than travel through a 500-km pipeline to an onshore gas plant at Botangas and onwards to power-generation facilities near Luzon to generate about 2,700 Mw of power (Fig. 1).
The concrete gravity production structure's base will store condensate that will be exported by shuttle tankers through a catenary anchored-leg mooring (CALM) offloading system 3 km from the platform.
Cooper Cameron Corp., Houston, provided the subsea completion system that includes its MOSAIC product line, including its SpoolTrees. The 10,000-psi working pressure (WP) trees are to be installed guidelineless on drill pipe.
Shell plans to install the subsea system between the fourth quarter 2000 and second quarter 2001, with the manifold load out toward yearend 2000 and the other subsea equipment loaded out in early 2001. Facility commissioning is scheduled for June 2001.
Manifold
Cameron describes the production manifold (Fig. 2) as being retrievable and having the capacity to connect up to ten producing wells, three control umbilicals, and three flowlines. The system integrates two production headers and a pigging loop.
The retrievable production manifold is supported with a three-pile foundation and includes a fixed support structure.
Cameron has configured the manifold with two 14-in. ID headers and a pigging loop. Each header includes a remotely operated vehicle (ROV) operated 16-in., 2,500-lb, welded-body ball valve in an Inconel material trim. The hydraulically actuated valves isolate the pigging loop from the two headers.
Ten modular valve blocks with integral jumper connection hubs are positioned five on each side of the manifold. Each block incorporates hydraulically actuated 5-in., 5,000 psi WP FLS gate valves and McPac clamp-connection hubs. The McPac-hub faces on the well jumpers provide connection points for the 5-in. production bore and two additional 1-in. bores. These 1-in. bores are for methanol injection and annulus access.
Cameron says the manifold and jumper systems provide a fully welded, super-duplex-tubing distribution system from the umbilical to the trees for methanol and annulus fluids. It has inlaid or used solid corrosion-resistant materials on all production-exposed surfaces within the subsea system.
Wellheads, trees
Malampaya wells have single-trip metal sealing wellheads rated for 10,000 psi WP. The 183/4-in. housing hub incorporates a profile designed to accommodate the tree connector. Cameron says this connector is specially designed to meet the bending loads encountered in deepwater applications.
The subsea trees are 5-in. by 2-in. 10,000 psi WP guidelineless horizontal trees. Cameron says the tree spool body is central to the tree assembly and acts as a tubing spool during completion, and as a tree block manifold when the tubing hanger is landed.
The spool body incorporates 5-in., 10,000 psi WP master, wing, and choke isolation valves and 2-in., 5000 psi WP master, workover, and crossover annulus valves. Both production and annulus valves are FLS gate valves with compact modular actuators that include ROV override capabilities. A 0.75-in., 10,000 psi WP gate valve provides methanol injection control.
Each horizontal tree also integrates a 4 1/16-in., 10,000 psi WP Willis CC40 subsea retrievable insert choke to regulate production flow.
