Offshore oil rigs are of the following types:
Floating Production Rig:
When oil firms spread out into more and more deeper waters, they have to
start applying methods other than conventional methods of receiving oil up to
the surface.
This type of deep water rigs are floating and semisubmersible, i.e., floating partially over the water level while pumping oil out of deep wells. Some rig use wire rope to connect with a stabilizing anchor, while others applies "dynamically positioned," system using computer-synchronized thrusters to maintain them in position.
Some rig use wire rope to connect with a stabilizing anchor, while others applies "dynamically positioned," system using computer-synchronized thrusters to maintain them in position.
These floating production systems are used in water depths from 600 to 6,000 feet.
Because these rig’s wellheads are positioned on the sea bed rather than a surface platform, as on fixed-platform rigs, additional measures should be taken to prevent leakages.
An instrument on deepwater wellheads called "blowout preventer" is used to prevent oil from dripping. Usually, these types of rigs are amongst the most common types of offshore rigs employed in the Gulf of Mexico.
Seastar or Tension-leg platform: Seastar or Tension-leg platform type of rigs are deployed to drill more than a mile, which are assembled by a floating surface construction embraced in position by rigid, vertical ligaments attached to the sea bottom.
For drilling smaller reservoirs in constricted regions, oil companies may as alternative use small types of rigs well-known as "Seastar," which permits for comparatively low-priced production of small deepwater oil reserves that would or else be too expensive to drill.
Tension-leg platform or Seastar rigs can drill to depths from 600 to 3,500 feet.
Jack-up Rig: Jack-up rigs were typically
used in shallow water since it was impractical to lower their legs in deeper
offshore, but latest oil rigs such as the Tarzan-class rigs are now crossing
those bounds.
Shallow water offshore oil reservoirs which are of small size which do not require a permanent platform or for drilling exploratory wells, oil firms uses Jack-up drill rig.
These rig’s barge are towed into location by tug boats usually two or three tug boats, and then lower its hold up legs down to the sea bottom, lifting up the rig above the water level. The rig is then set up to the required heights along its big holdup legs.
Jack-up Rigs are also considered as safer than various other types of mobile rigs, such as drilling ships or drilling barges, because their deck amenities are elevated from the water and hence less vulnerable to sea waves and rough weather.
Fixed platform: They can drill about 1,500 feet below the sea level, but they are expensive to construct, so they generally need a bigger oil finding to authorize their formation.
Compliant tower: The compliant towers operate at larger depths than platform rigs, possibly up to 3,000 feet below the sea surface.
Spar platform: These platform are named after the giant, perpendicular "spar" (also called mast) of a ship, spar-platform rigs are assembled by one, wide-diameter cylinder to support a surface platform from the sea bed.
A typical spar platform in the Gulf of Mexico is constructed by a 130-foot-wide cylinder, and about 90 percent of its whole structure is submerged.
Spar cylinders platform are utilised at depths up to 3,000 feet, but present machinery can deepen this to about 10,000 feet, assembling them one of the deepest-drilling types of offshore rigs.
Subsea system: Subsea systems are deployed in water depths up to 7,000 feet.
