Oil & Gas / Oil services / Offshore platforms 0 comments

(P.S: Sorry for any disturbances the advertisements above may have caused you)
It is seldom that Singapore becomes a world leader in an engineering-related sector; indeed the dominant position in offshore rigs that Keppel and SembMarine have established is said to be quite a piece of luck; major shipbuilders had been in mainstream shipbuilding (container ships, bulk vessels, tankers etc) while Singapore shipbuilders took on specialty construction quietly until it recently exploded into life.

Our two GLCs now command ~80% of the market for new offshore platforms, and have built such a reputation for the Singapore rig-building industry that another company, Labroy, has recently secured a >S$400M rig-building contract with no prior experience. It's time to learn more about the various types of offshore platforms.

Types of offshore platforms

Fixed platform - Built on concrete and/or steel legs anchored directly onto the seabed, supporting a deck with space for drilling rigs, production facilities and crew quarters. Such platforms are, by virtue of their immobility, designed for very long term use. They are economically feasible for installation in water depths up to about 500m.

Compliant tower - Consist of narrow, flexible towers and a piled foundation supporting a conventional deck for drilling and production operations. Compliant towers are designed to sustain significant lateral deflections and forces, and are typically used in water depths ranging from 450-900m.

Semi-submersible platform - One of the most expensive types around. It has legs of sufficient buoyancy to cause the structure to float, but of weight sufficient to keep the structure upright (the complexity makes it easy to understand why they can be expensive to build). Semi-submersible rigs can be moved from place to place; and can be lowered into or raised by altering the amount of flooding in buoyancy tanks; they are generally anchored by cable anchors during drilling operations, though they can also be kept in place by the use of steerable thrusters. Semi-submersible can be used in depths from 200-2000m.

Jackup platforms - Platforms that can be jacked up above the sea, by dint of legs than can be lowered like jacks. These platforms, used in relatively low depths, are designed to move from place to place, and then anchor themselves by deploying the jack-like legs. More mobile than fixed platforms.

Drillship - A maritime vessel that has been fitted with drilling apparatus (had been discussed in Offshore vessels). It is most often used for exploratory drilling of new oil or gas wells in deep water but can also be used for scientific drilling.

Floating production systems - Basically large ships equipped with processing facilities and moored to a location for a long period. The main types of floating production systems are FPSO (floating production, storage, and offloading system), FSO (floating storage and offloading system), and FSU (floating storage unit). FPSO is the most common, representing 60-70% of all floating production systems.

Tension-leg platforms - Floating rigs tethered to the seabed in a manner that eliminates most vertical movement of the structure. TLPS are used in water depths up to about 2000m.

Spar platforms - Moored to the seabed like the TLP, but whereas the TLP has vertical tension tethers the Spar has more conventional mooring lines. The Spar may be more economical to build for small and medium sized rigs than the TLP, and has more inherent stability than a TLP since it has a large counterweight at the bottom and does not depend on the mooring to hold it upright. It also has the ability, by use of chain-jacks attached to the risers, to move horizontally over the oil field.

Singapore shipyard specialties
From the orders that the Big Two have been receiving, it would appear that Keppel's specialties are semi-submersibles and jackups, while Sembcorp Marine tends to concentrate on jackups. Both shipyards also receive many FPSO/FSO construction orders.

References:
(1) Wikipedia article: Oil platforms