Malaysia International Shipping Corp. (MISC), a subsidiary of Petronas Carigali Malaysia, produced first oil in April, from the Penara and North Lukut fields 20-km apart in the South China Sea, around 300-km off the coast of West Malaysia. This marked the successful completion of the development project.
The field development features rigid pipelines connecting wellhead platforms on each of the fields to two pipeline end manifolds (PLEM)s on opposite sides of the turret-moored FPSO Bunga Kertas, which is stationed in 62-m water depth between the two fields. The FPSO, a 223-m, 88,000-dwt tanker conversion, supports full separation and fluid treatment systems, gas compression and treatment for gas lift/injection, utility systems, living quarters, control, and emergency systems.
Stabilized crude flows to export tankers moored in tandem with the FPSO, while compressed gas for re-injection and gas lift returns through the pipelines to the two fields.
The Bunga Kertas is designed for a 10-yr service life without dry-docking and can handle maximum production of 30,000 b/d of oil and 60 MMcf/d of natural gas with a produced water content of 20,000 b/d.
MISC awarded NKT Flexibles and its Malaysian agent Kingsar Sdn. Bhd. the contract for the entire flexible pipe system connecting the two subsea PLEMs with the FPSO's submerged turret, supplied by single buoy moorings. Petronas provided the PLEMs directly through MISC. Intec Engineering acted as the system interface coordinator on behalf of MISC. By bringing all the involved parties together at the conversion yard on several occasions during the course of the project, MISC ensured a close dialogue on critical aspects of the project.
NKT Flexibles' scope of work comprised the design, engineering, and manufacture of four dynamic flexible risers, two complete mid-water arch systems, and other accessories such as bend restrictors and bend stiffeners. Two flexible risers, one 12-in. inside diameter (ID) production riser and one 6-in. ID gas lift/injection riser and flowline approaching the turret from opposite directions, connect the subsea flowlines from the Penara and North Lukut fields, to the FPSO.
Engineering of the riser configuration was the main challenge due to the shallow water depth, the relatively large horizontal FPSO offsets, and exposure to the harsh environmental conditions of the South China Sea. The solution for both riser systems is a lazy-S riser configuration featuring two mid-water arches, each with a buoyancy structure anchored to a seabed gravity base. This presents a very stable and reliable riser configuration with minimum maintenance, and allows oil production to be maintained under all specified weather conditions. Even if damage arises to the buoyancy structure, the riser configuration should remain intact.
Mid-water arch details
Each of the mid-water arch systems features a buoyancy structure tethered to a seabed gravity base.
The buoyancy structure consists of a steel structure with two cylindrical tanks, each divided into four internal compartments. Total net buoyancy of the structure is 90 tonnes.
The seabed base is a gravity base structure manufactured in steel and concrete. For ease of installation, the seabed base is designed with two separate ballast blocks, thereby reducing the required lifting capacity. Total weight of the seabed base, including ballast blocks is around 280 tonnes. The tethers for the buoyancy structure contribute an additional 8 tonnes.
NKT Flexibles' facilities in Kalundborg, Denmark, manufactured the flexible risers and shipped them to Malaysia on two 9.2-m offshore reels, ready for offshore installation. Fabrication of the two mid-water arch systems was sub-contracted to Malaysia Shipyard and Engineering (MSE) in Pasir Gudang, Malaysia. DNV carried out third-party design review and inspection services throughout the project. Project hand-over of the flexible riser system took place in October 2003 at MSE in Pasir Gudang.
For NKT Flexibles, this was its second project in recent years offshore Malaysia and its third consecutive project with Petronas involvement – the other two being the Ruby FPSO project in Vietnam and the Talisman PM-3 project in Malaysia.
Flexible riser details
- Two 12-in. ID dynamic riser for oil production
2,175 psi / 53° C Length 181 m
- One 6-in. ID dynamic riser for gas injection 2,204 psi / 53° C Length 179 m
- One 6-in. ID dynamic riser for gas lift
2,204 psi / 53° C Length 179 m
- Internal carcass formed in stainless steel 316L
- Polymer inner liner; high density polyethylene (HDPE) and nylon (PA11)
- Two layers of C-shaped pressure armor wire; cold rolled wire
- Two layers of rectangular tensile armor wire; cold rolled wire
- Polymer outer sheath; U/V stabilized nylon (PA11)
- 12-in. ID riser, NKT standard E/F c/w 13.5/8-in. 10,000 psi API RTJ flange, Inconel 625
- 6-in. ID riser, NKT standard E/F c/w 9-in. 10,000 psi API RTJ flange, Inconel 625 mid-water arch