Kelly drive
Encyclopedia
A kelly drive refers to a type of well drilling device on an oil drilling rig
that employs a section of pipe with a polygonal (three-, four-, six-, or eight-sided) or splined
outer surface, which passes through the matching polygonal or splined kelly (mating) bushing and rotary table
. This bushing is rotated via the rotary table and thus the pipe and the attached drill string turn while the polygonal pipe is free to slide vertically in the bushing as the bit digs the well deeper. When drilling, the drill bit
is attached at the end of the drill string
and thus the kelly drive provides the means to turn the bit (assuming that a downhole motor is not being used).
The kelly is the polygonal tubing and the kelly bushing is the mechanical device that turns the kelly when rotated by the rotary table
. Together they are referred to as a kelly drive. The upper end of the kelly is screwed into the swivel, using a left-hand thread to preclude loosening from the right-hand torque applied below. The kelly typically is about 10 ft (3 m) longer than the drill pipe segments, thus leaving a portion of newly drilled hole open below the bit after a new length of pipe has been added ("making a connection"), and the drill string has been lowered until the kelly bushing engages again in the rotary table.
The kelly hose
is the flexible, high-pressure hose connected from the standpipe
to a gooseneck pipe on a swivel above the kelly and allows the free vertical movement of the kelly while facilitating the flow of the drilling fluid
down the drill string
.
See List of components of oil drilling rigs to view a diagram.
Drilling rig
A drilling rig is a machine which creates holes or shafts in the ground. Drilling rigs can be massive structures housing equipment used to drill water wells, oil wells, or natural gas extraction wells, or they can be small enough to be moved manually by one person...
that employs a section of pipe with a polygonal (three-, four-, six-, or eight-sided) or splined
Rotating spline
Splines are ridges or teethon a drive shaft that mesh with grooves in a mating piece and transfer torque to it, maintaining the angular correspondence between them....
outer surface, which passes through the matching polygonal or splined kelly (mating) bushing and rotary table
Rotary table (drilling rig)
A rotary table is a mechanical device on a drilling rig that provides clockwise rotational force to the drill string to facilitate the process of drilling a borehole.In the diagram, #20 is the rotary table...
. This bushing is rotated via the rotary table and thus the pipe and the attached drill string turn while the polygonal pipe is free to slide vertically in the bushing as the bit digs the well deeper. When drilling, the drill bit
Drill bit (well)
A ', is a device attached to the end of the drill string that breaks apart, cuts or crushes the rock formations when drilling a wellbore, such as those drilled to extract water, gas, or oil....
is attached at the end of the drill string
Drill string
A drill string on a drilling rig is a column, or string, of drill pipe that transmits drilling fluid and torque to the drill bit. The term is loosely applied as the assembled collection of the drill pipe, drill collars, tools and drill bit...
and thus the kelly drive provides the means to turn the bit (assuming that a downhole motor is not being used).
The kelly is the polygonal tubing and the kelly bushing is the mechanical device that turns the kelly when rotated by the rotary table
Rotary table (drilling rig)
A rotary table is a mechanical device on a drilling rig that provides clockwise rotational force to the drill string to facilitate the process of drilling a borehole.In the diagram, #20 is the rotary table...
. Together they are referred to as a kelly drive. The upper end of the kelly is screwed into the swivel, using a left-hand thread to preclude loosening from the right-hand torque applied below. The kelly typically is about 10 ft (3 m) longer than the drill pipe segments, thus leaving a portion of newly drilled hole open below the bit after a new length of pipe has been added ("making a connection"), and the drill string has been lowered until the kelly bushing engages again in the rotary table.
The kelly hose
Kelly hose
A Kelly hose is a flexible, steel reinforced, high pressure hose that connects the standpipe to the kelly and allows free vertical movement of the kelly while facilitating the flow of drilling fluid through the system and down the drill string....
is the flexible, high-pressure hose connected from the standpipe
Standpipe
In North America, a standpipe is a type of rigid water piping which is built into multi-story buildings in a vertical position, to which fire hoses can be connected, allowing manual application of water to the fire...
to a gooseneck pipe on a swivel above the kelly and allows the free vertical movement of the kelly while facilitating the flow of the drilling fluid
Drilling fluid
In geotechnical engineering, drilling fluid is a fluid used to aid the drilling of boreholes into the earth. Often used while drilling oil and natural gas wells and on exploration drilling rigs, drilling fluids are also used for much simpler boreholes, such as water wells. Liquid drilling fluid...
down the drill string
Drill string
A drill string on a drilling rig is a column, or string, of drill pipe that transmits drilling fluid and torque to the drill bit. The term is loosely applied as the assembled collection of the drill pipe, drill collars, tools and drill bit...
.
See List of components of oil drilling rigs to view a diagram.