derrick
A derrick is a free-standing tower with associated equipment that is used to drill wells for crude oil , natural gas , brine or water (thermal) (mining: to sink ). In some cases, a derrick is also used to overwhelm an existing borehole or to fill a borehole that is no longer economically viable.
In addition to the scaffolding, essential components of a derrick are the substructure, the working platform, the finger platform, the clamp (crane hook) and the lifting gear . Functionally other accessories such as the blowout preventer (BOP), the locking system, the flushing pumps , the flushing system or devices for energy supply (diesel-electric, diesel-mechanical or electric) do not belong directly to the tower .
Depending on the force or torque transmission to the drill string and drill bit to distinguish between turntable drive or power swivel (English: Top Drive ). With the turntable drive, the power is transmitted via a so-called (four-, six- or octagonal) drive rod ( Kelly ) and a rotating device on the work platform. The more modern power turret drive transfers the power directly to the head of the drill rod.
In most cases, drilling rigs and thus their size are classified based on the hook loads (tensile loads) they can carry out. Light drilling rigs are designed for hook loads of up to around 100 tons, medium drilling rigs are able to pull around 200 tons, and heavy systems can have hook loads of up to 700 tons.
Small and medium-sized drilling rigs are usually designed to be easy to dismantle, mostly in the form of a telescopic mast that is mounted on a vehicle and thus swiveled hydraulically at the drilling site and extended to the full height. The total height is limited to about 30 m due to the permissible vehicle lengths. Heavy drilling rigs are usually dismantled into transportable units and driven to the next drilling site with heavy transporters.
After completion of the drilling or the subsequent completion work (installation of the production line), regardless of whether mineral resources such as crude oil or natural gas were searched for or an exploratory well (exploration well) was sunk, the derrick is no longer necessary. Instead of the drilling tower or the closing devices ( blowout preventer ) belonging to the tower, a flange and an eruption cross are usually installed in the event of oil, gas or water discoveries, and an oil pump (e.g. horse head pump ) for low- pressure oil wells . On drilling rigs , the derrick is usually left standing after the drilling work has been completed so that further work can be carried out.
