Land drilling rigs can be classified according to the drilling depth into different sizes
Light duty rigs: drill holes from about (3000-5000 ft) deep or (1000-1500 meters
Medium duty rigs: drill to depth ranging from (4000-10000 ft) or (1200-3000 meters
Heavy duty rigs: drill holes from about (12000-16000 ft) deep or (3500-5000 meters
Ultraheavy duty rigs: drill holes from about (18000-25000 ft) deep or (5500-7500 meters
ROTARY DRILLING RIG COMPONENTS
The main function of a rotary rig is to drill a hole, or as it is known in the industry, to make hole
Making hole with a rotary rig requires not only qualified personnel, but a lot of equipment as well
In order to learn about the components that it takes to make hole, it is convenient to divide them
into a number of main systems: power, hoisting, rotating, circulating, well control, and well
monitoring system. Various components comprise the systems, but all require power to make
them work
RIG POWER SYSTEM
Most rig power is consumed by hoisting and fluid circulating systems. The other rig systems have
much smaller power requirements. Fortunately, the hoisting and circulating systems generally are
not used simultaneously, so that the same engines perform both functions
Total power requirements for most rigs are from 1000 to 3000 hp provided by one or more
engines depending on well depth and rig design. Power requirements vary for different drilling
jobs, shallow or moderate depth drilling rigs need 500 - 1,000 HP, heavy-duty rigs for 20,000 foot
(6000 meters) holes usually need 3,000 hp, Auxiliary power requirements for lighting, etc., may
be 100 - 500 hp
The early drilling rigs were powered primarily by steam. However, because of high fuel
consumption and lack of portability of the large boiler plants required, steam-powered rigs have
become impractical. Modern rigs are powered by internal-combustion diesel (or gas) engines
.engines and sub-classified depending on the method used to transmit power to the various rig
systems
Diesel electric type
Direct drive type
Diesel electric rigs are those in which the main rig engines are used to generate electricity
Electric power is transmitted easily to the various rig systems(the diesel engines generate and
deliver electric power by cables to electrical then to electric motors attached to the involved
equipments) switch gear then to , where the required work is accomplished through use of electric
motors. Direct-current motors can be wired to give a wide range of speed-torque characteristics
That are extremely well-suited for the hoisting and circulating operations. The rig components
can be packaged as portable units that can be connected with plug-in electric cable connectors
There is considerable flexibility of equipment placement, allowing better space utilization and
weight distribution. In addition, electric power allows the use of relatively simple and flexible
control system. The driller can apply power smoothly to various rig components, thus minimizing
Direct drive rigs accomplish power transmission from the internal-combustion engines using
system of pulleys, gears, chains, belts, and clutches rather than generators and motors. The initial
cost of a direct-drive power system generally is considerably less than that of a comparable
diesel-electric power system. The development of hydraulic drive has improved greatly the
performance of this type of power system. Hydraulic drives reduce shock and vibrational
problems of the direct drive power system. Torque convertors, which are hydraulic drives
designed so that the output torque increases rapidly with output load, are now used to extend the
speed-torque characteristics of the internal-combustion engine over greater ranges that are better
suited to drilling applications. The use of torque convertors also allows selection of engines
based on running conditions rather than starting conditions. Power-system performance
characteristics generally are stated in terms of output horsepower, torque and fuel consumption
for various engine speeds
3000hp =2237099.615 watt equal to the power operates 22371 house lamps.
The power on modern rigs is most commonly generated by diesel-electric power units. The power
produced is AC current which is then converted to DC current by the use of SCR (Silicon
Controlled Rectifier
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