What is dp drilling rig

Taking into account that drilling equipment must sometimes span thousands of feet of water before even reaching the ocean floor, slight movements above the water's surface can have drastic effects on the drilling operations. Additionally, some offshore developments require floating facilities.

FPSOs and semisubmersible production facilities are positioned above the subsea development, housing production equipment and other machinery. Multiple risers connect the development below the water to the facilities above it. If the wind and waves knock the facilities off-track, the development would have to stop production and undergo extensive repairs.

Keeping floating equipment in position, whether performing drilling or production operations, is an important logistical aspect of the overall procedures. While drilling and production risers are somewhat flexible to provide for limited movements caused by the ocean currents, too much movement can break them and cause drilling or production to cease, as well as costly require repairs.

Like boats, floating facilities can be anchored to the ocean floor. According to the environment and the shape of the vessel, there are myriad ways to moor a vessel, which involves strategically anchoring the vessel by a number of lines to the ocean floor. Most recently, dynamic positioning has offered a more stable way to ensure that the vessel stays in position. Redundancy is achieved either by physical segregation or duplication of equipment.

DP control systems are normally double or triple redundant by design. Additional classification notations have been developed by the major societies, which broadly follow the "consequence class" definitions in the IMO guidance. The highest level of safety and redundancy is named Class 3, which is defined as fully redundant active and passive components. Dynamic positioning or thruster-assisted control systems were used on many of the high-specification semi-submersible units built prior to the offshore drilling slump in the mid 80s.

North-west European experience of DP drilling is relatively new when compared with the large-scale use of DP in other offshore construction and petroleum transport markets. In the 90s, as oil and gas drilling campaigns migrated into increasingly deeper water, it became clear that new tonnage and technologies would be required. Deepwater drilling requires specialised vessels, enabling economic exploration and further exploitation of deepwater prospects. As a result, the 90s saw a resurgence in drillships and high spec semi-submersibles with increased variable deck-load capacities.

A large number of newbuilding contracts were signed in the five year period between and The majority of these units have been built to Class 3, the highest redundancy standard. Systems may also be required to be watertight depending on the vessel and damage to one system must not affect the backup. Systems also must be physically separated for DP3.

Side note here: DP1 vessels are not very common, with DP2 and DP3 becoming more common due to the additional level of safety they provide. OSV testing its azimuth thrusters. Image from MarineLog. DP1 is the most basic standard, with the ability for a ship to automatically hold station. DP2 has redundancy, but DP3 has segregated redundancy that would allow for a more serious failure.

If human lives are on the line, DP2 or DP3 is required. Divers, construction workers, wind installers, and drillers need to stay safe and on location. What types of ships are fitted with DP systems? As technology improves, many new vessels are equipped with dynamic positioning systems. Just a few of the most common types of ships are offshore support vessels, offshore construction vessels, oil rigs, pipe and cable laying vessels, diving support vessels, and cruise ships.

Check out our article on 22 types of dynamically positioned vessels for the full list.