Rig Components

There are five main systems that compose the drilling rig:

  1. Hoisting
  2. Drive
  3. Fluid Handling/Circulating
  4. Well Control
  5. Substructure
  6. Pipe Handling


Responsible for the lifting of the loads that the rig is supposed to bear during its operations. Typically the major load that the equipment is responsible for is the lifting of drill pipe, tubulars and the drilling assemblies.

The equipment will be responsible for lifting the pipe into position as well as bearing the weight of the continuous length of drill pipe and assembly in the hole from the rotary table to the bottom of the wellbore.

Hoisting Components

  • Derrick – The frame work that supports hoisting equipment and transmits the load to the substructure.
  • Crown Block – The uppermost point of the derrick. It consists of a series of sheaves which the drill line is wound on. It is the stationary part of the block and tackle hoisting arrangement that hoists the drill pipe.
  • Travelling Block – this is the moving part of the block and tackle arrangement that lifts the drill pipe and assembly. It consists of a series of sheaves upon which drill line is wound continuously between itself the crown block and the draw works.
  • Drill Line – a continuous length of wire that is wound around the draw works, crown block and travelling block. It is eventually secured to a point on the derrick.
  • Draw Works – this is drum that the drill line is wound on. It is powered by either an engine or electric motor depending on the rig. It provides the power needed to lift the load that the derrick will bear.


These are the prime movers that are needed for the rig to function.

  • Rotary Drive – This is the system that provides/imparts rotational motion to the still string via the rotary table. Typically the motor or engine uses a chain or gear drive to turn the rotary table.
  • Top Drive – The modern way of imparting rotational motion to the drill string. Usually the top drives sits atop the drill string and is a self contained electric motor or hydraulic unit that provides the rotational motion.
    • Kelly/Power Sub – This is the mechanical device that transmits the rotational from the rotary table or top drive to the drill string.
  • Rig Engines – These provide power to do many things. Chief among them is to run the generators to generate electricity. In older rigs they may help in moving the rig (Carrier Borne land rigs) and in providing power to the rotary drive.

Fluid Handling/Circulating

Concerned with the equipment that is used in the formulation and maintenance of the drilling fluid used during rig operations.

  • Mud Pumps – This provides the drilling fluid with the pressure to move throughout the circulating system. These are critical when considering the hydraulic work the BHA and the bit will do when drilling.

They must be able to provide the necessary pressure head to overcome the pressure loss the that fluid will experience from the rig through the standpipe, down the drill string, across the BHA and bit up the annulus and back into the pits.

  • Shale Shakers – A basic means of controlling and removing the solids from the drilling fluid returning from the well bore. Typically they are located above the “Possum Belly”. They work by sifting the return fluid through sieves (which can be changed depending on drilled cutting size) allowing the fluid to return to the circulating system. The solids are then dis-carded.
  • Other Solid Control Equipment (Centrifuges and Desanders) – These pieces of equipment allow for more sophisticated solids removal or for fine solids where shale shakers can’t properly filter. They can be used for special purposes such as barite recovery or for environmental purposes when disposal of mud waste is difficult or regulated.
  • Degasser – Used in cases when the returning mud has gas. It helps to quickly remove the gas physically by agitating the mud.
  • Mud Pits – These are the tanks that allow for the storage and the formulation of the drilling fluids.
  • Slug Pit – Part of the mud pit system that allows for the mixing of special chemicals to be added to the fluid system.
  • Possum Belly – This is an old and affectionate name for the tank that sits below the shale shakers. It is the first tank that returning mud collects in.
  • Standpipe – This is a vertical pipe that runs along the derrick, it carries fluid from the mud pumps to the top of the drill string. It attaches to the kelly hose which accommodates the motion of the system up and down.

Well Control

This is the system of piping, and valves that allows for the controlling of well pressures when the rig in on site. This type of system is not usually sized by engineers in the field. This is often a component of the rig and comes with it as part of the rig design. You can however purchase individual pieces and create your own, however it is best to keep to (rig) manufacturers guidelines.

  • The BOP – this is the device responsible for the opening and closing of the well bore when the rig is onsite. It allows for the isolation of the well bore from the rig in the event of an emergency.
    • Ram Type – This type of BOP uses a rams to close the well or to close the annular space around the pipe.
      • Pipe rams have attachments at the end to fit securely around the pipe thus ensuring a good seal with the pipe remaining in the hole. Only the annulus is sealed a fluid path is maintained through the pipe.
      • Blind rams will only close across if there is no pipe in the hole, they do however allow for isolation of the wellbore and the rig.
      • Shear rams have attachments that can in the worst case scenario severe the pipe entirely, totally isolating the rig and wellbore.
    • Annular Preventers – These use a packing element instead of rams to seal the annular area around the pipe.
  • Diverter – This only allows for the rig to divert the well bore fluid ONLY. It does not allow for the rig to isolate the wellbore. Typically this is only used to drill the upper hole sections between 0’ to 750’.
  • Accumulators – These are essentially pressure bottles that store the compressed air to rapidly actuate the rams in the event of a well control incident.


This is the structure upon which the drilling floor and the rotary table is mounted on/within. This area provides the space for the drilling crews to work on, make and break connections, and conduct operations. The sub-structure on a land rig is placed on the ground atop the wellbore and encloses the well control equipment. It connects to other areas of the rig by means of catwalks, ramps and stairs.

In the case of the off shore rig the substructure is mounted to a hull or pontoon that allows for it to float of has a mechanism for it to imbed itself on the seabed (think the legs of a jack-up).

Pipe Handling

These are the accompanying tools that are used in the execution of drilling operations. Such tools are specific to the drilling floor and are specific to the drilling operations.

Wrenches – These are commonly known as “tongs” and they are used to apply to torque to make and break pipe connections

Elevators – These are specific to the diameter of the pipe and are used to lift the individual sections as well as the drill string. They are engineered to cradle the pipe at the shouldered connection ends. They are attached to travelling block which allow for the hoisting.

Kelly Spinner – Used to slowly rotate the Kelly and drill pipe on making a connection. They do not apply a significant amount to torque.

Hooks – Allows for the attachment of links to the travelling block.

Links – Allows the elevators to be attached to the hooks. In a top drive system

Slips – These allow for the drill pipe to be suspended from the rotary table. It “chucks” the drill string in the rotary table.

Slings – Chain or rope lengths that are used to lift the tubular and tools from the pipe rack to the drill floor. These are usually attached to the sand line or an auxiliary hoist independent of the draw works line.

Pipe Handling/Racking – Specific machines and hoists that are external to the derrick that aid in the lifting of drilling tubular to and from the drilling floor.


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