A drilling platform (also rig ) as an offshore structure is an artificial footprint in the sea, which serves for sinking of wells, mostly in search of oil or natural gas.
A total of five types can be distinguished:
- The platform is connected to a solid base made of steel or concrete on the seabed. It is towed by tugs to the target area and there lowered, where it remains until scrapping.
- The platform of a jack-up rig (English: Jack -up rig ) stands on scaffolding legs and is vertically movable. It is moved by tugs or transported by special cargo ships over long distances. They can be used up to a water depth of 130 m.
- The semi-submersible rig (English: Semi -submersible rig ) floating on pontoons. Filled ballast tanks allow this rig type, even under adverse weather conditions relative to lie quietly. Some of these rigs are kept in position by far designed anchor above the borehole by computer control and GPS through their own drives. The drive consists of several to 360 ° swiveling thrusters (English: thruster ); as is, for example, in every corner of a thruster. This kind of drilling rigs is used in large water depths up to 3500 m. Since the semi-submersible drilling rig floats, it is one of the most mobile rig types.
- The so-called TLP ( the abbreviation of tension leg platform) is related to the semi-submersible island. However, in this case, the drilling rig with steel cables that are under high voltage and extend vertically, supported above the borehole. A TLP is also often used as a production platform.
- The drillship represents another form dar. These vessels are used in very deep water (over 3000 m are common) and held by the ship's propulsion system to position. The drive is similar to the semi-submersible drilling rig often from swiveling thrusters or propellers gondolas, which are positioned depending on the design of the ship.
The rig is towed or driven to completion of one or more holes to the next job. Then, if necessary, a production platform over the holes is placed, then the extraction, processing and further transport of petroleum or natural gas takes over.
The world's biggest ever production platform is the Norwegian Sea Troll oil company Statoil with a million tons of displacement. It measures from the bottom of the base to the tip of the gas flare mast 472 meters above sea level and stands on the seabed in 303 m water depth. Stood them next to the Eiffel Tower, the Sea Troll this would tower over 148 meters.
From platforms from is not just bored vertically into the depths. The available options were the Abteufung one or more holes of a drilling platform has been around since 1975 with the cantilever and also there was at that time already the kickoff holes, ie it could (mostly the Rotliegend ) are drilled at an angle of oil or gas carrier. This went on for a deposit even at long range with the Richtbohrmethode only been encountered and the intersected in different horizons. But if the date is drilled reservoir formation fractures occur (so-called anticlines, Discordanzen ), so of course is also given the opportunity to reach drilling technology from the same place these. But even here the distance limits, partly because of the hook load of the drill or the rule load of the derrick, used by the drill pipe and the Tensionsfähigkeit and through the mud pumps used with the drilling fluid used and also used. Today comes through the bohrtechnischen progress and improved drilling fluids quite another possible use in the offshore production for use, namely horizontal drilling through the reservoir encountered in their position on several hundred meters. By this directional drilling, it is possible to open up a deposit also from the side along its entire length and thus the oil or gas flow to increase significantly. Thus, from a frequently encountered and also recoverable deposit drilling technology completely sunk a few (expensive) drilling and production platforms and are thus completely developed for subsequent oil or natural gas production.
A special form of drilling rigs are the research platforms used in small numbers at the edge of Antarctica, the holes down to bring both under the sea and " untereisisch ", mostly to operate geological research, for example geological climate research and paleontological geology or by seismographs for earthquake preparedness and attach - exploration.
Platforms often serve as weather stations and assist them with their measured values, over the oceans usually only sparse data for weather calculations.
For example, after the oil fields are exhausted, there is at least the theoretical possibility to sink these drilling and production platform (see eg Brent Spar) and thus create an artificial coral reef. Due to the heavy pollution of such industrial facility this way of disposal is hardly feasible without damaging most of which already polluted environment on. Therefore decided the 15 participating States of the OSPAR 1998 Conference sinking a ban on oil platforms in the North Atlantic.
Drilling platforms provide apart from local pollution as an industrial plant, a potentially major threat to the environment as a whole, since in particular fast very large bodies of water can be contaminated by oil spills by so-called " blowouts ". For example, the oil spill in the Gulf of Mexico was triggered by the explosion of the Deepwater Horizon in 2010, approximately 700,000 cubic meters of oil flowed into the sea by the.
Drilling platforms can also form new habitats for marine animals for the duration of their existence but. On oil rigs in the North Sea has long been settled rapidly growing tropical bivalve species to the permanently warm conveyor pipes and prepare there with stronger growth problems. You die when the delivery stop and leave a crust that is populated again on resumption of production.