What is a semi-submersible drilling rig?

A Semi-Submersible Rig or a “Semi-Sub” or a “Semi” or a “Floater” is a drilling rig that is used to drill wells in water depths inaccessible to jack-up rigs (water depths greater than 400 ft). Semi-submersible rigs are buoyant and, unlike jack-up rigs which rest on the seabed, float during drilling operations.

How does a semi-submersible work?

Semi-submersibles are the choice for drilling from a floating position, due to the deep water depths. Semi-submersible (“semi”) rigs float like a ship while being towed into position, where their pontoons can then be flooded, partially submerging the rig. Figure 5-4 illustrates a typical semi-submersible.

What type of MODU was used for the Deepwater Horizon?

Deepwater Horizon was a fifth-generation, RBS-8D design (i.e. model type), deepwater, dynamically positioned, column-stabilized, semi-submersible mobile offshore drilling unit, designed to drill subsea wells for oil exploration and production using an 18.75 in (476 mm), 15,000 psi (100,000 kPa) blowout preventer, and a …

Why is it called a semi-submersible rig?

Unlike a submersible, a semi-submersible vessel is not supported by resting on the seabed. Semi-submersible vessels are able to transform from a deep to a shallow draft by deballasting (removing ballast water from the hull), thereby becoming surface vessels.

What is the meaning of semi-submersible?

Definition of semisubmersible : being a floating deepwater drilling platform that is towed to a desired location and then partially flooded for stabilization and usually anchored.

What is semi-submersible vessel?

Semi-submersible may refer to a self-propelled vessel, such as: Heavy-lift ship, which partially submerge to allow their cargo (another ship) to float into place for transport. Narco-submarine, some of which remained partially on the surface. Semi-submarine, which cannot fully submerge.

Was Deepwater Horizon a semi-submersible?

Deepwater Horizon was a semi-submersible mobile offshore drilling unit, designed to drill wells in new oil fields in ultradeep water. Drilling rigs of this type are operated by service companies which are contracted by oil companies to carry out drilling operations.

How do drillships work?

A drillship is a mobile offshore drilling rig where a mono-hull ship, catamaran, triple-hull ship, or barge is adapted or built for use as a platform. After reaching the well position, the drillship first gets into position with the mooring system or dynamic positioning system, and then begins to drill a well.

How much does a new oil rig cost?

With an average price tag of $650 million, offshore drilling is an expensive proposition. Well, as good places to drill on land dry up or are already being tapped, people turn to the ocean. There is a lot of oil beneath the ocean floor, so the higher startup cost offsets the long term return.

Why was pipe not cut on Deepwater Horizon?

However, because the drill pipe was buckled and off-center inside the blowout preventer, it was trapped and only partially cut. The video explains how this failure directly led to the massive oil spill and contributed to the severity of the incident on the drilling rig.

How do they drill so deep for oil?

Using sonic equipment, oil companies determine the drilling sites most likely to produce oil. Then they use a mobile offshore drilling unit (MODU) to dig the initial well. Some units are converted into production rigs, meaning they switch from drilling for oil to capturing oil once it’s found.

How much does a semi submersible oil rig cost?

Semisubmersible newbuilds range from $460 to $771 million for water depth capacity ranging from 1,640 to 10,000 ft and VDLs between 5,000 and 22,000 tons. Operating displacement varies between 42,000 and 62,000 tons.

What is a deepwater semi-submersible platform?

Deepsea Delta semi-submersible drilling rig in the North Sea. Comparison of deepwater semi-submersible and drillship. A semi-submersible platform is a specialised marine vessel used in offshore roles including as offshore drilling rigs, safety vessels, oil production platforms, and heavy lift cranes.

What is a DP3 semi-submersible?

One of the largest ultra-deepwater 6th generation semi-submersible rigs capable of working in harsh-environment conditions, the Moss Maritime CS50 MK II design ultra-deepwater dynamic positioning (DP3) semi-submersible unit is designed for versatility and flexibility.

What type of drilling rig is Deepwater Horizon?

Deepwater Horizon semi-submersible drilling rig. / 28.736667; -88.386944 / 28.736667; -88.386944 Deepwater Horizon was an ultra-deepwater, dynamically positioned, semi-submersible offshore drilling rig owned by Transocean.

What is offshore drilling?

Offshore drilling in water depth greater than around 520 meters requires that operations be carried out from a floating vessel, since fixed structures are not practical.