Changes

==Rotating system==

==Rotating system==

The rotating system consists of the rotary table and the ''drill stem'' (kelly, drill string, and bit). The ''rotary table'' is a square hole in the derrick floor with a rotary bushing that is used to turn the ''kelly bushing'' and kelly. The ''kelly'' is a square or hexagonal length of pipe that is screwed on the drill pipe and used to convey the rotary movement to the drill string and bit. The ''drill string'' refers to the combination of drill pipe, collars, and other bottom hole assembly components. (For more information on bottom hole assemblies, see chapter on “[[Wellbore trajectory]]” in Part 3.) Attached to the end of the drill collars is the ''bit''. The bit does the actual grinding or cutting of the rock. The style of bit used is dependent on the rock type and drilling conditions. Common bit types include drag, tri-cone, insert, PDC, and diamond.

The rotating system consists of the rotary table and the ''drill stem'' (kelly, drill string, and bit). The ''rotary table'' is a square hole in the derrick floor with a rotary bushing that is used to turn the ''kelly bushing'' and kelly. The ''kelly'' is a square or hexagonal length of pipe that is screwed on the drill pipe and used to convey the rotary movement to the drill string and bit. The ''drill string'' refers to the combination of drill pipe, collars, and other bottom hole assembly components. (For more information on bottom hole assemblies, see [[Wellbore trajectory]].) Attached to the end of the drill collars is the ''bit''. The bit does the actual grinding or cutting of the rock. The style of bit used is dependent on the rock type and drilling conditions. Common bit types include drag, tri-cone, insert, PDC, and diamond.

The hole is drilled by adding joints or lengths of drill pipe to the end of the kelly. When pipe is added, the hoisting system is used to pick up the kelly so that it hangs from the derrick above the rotary table. ''Tongs'' (large pipe wrenches) or chains are used to unscrew the kelly from the previous joint of pipe. The kelly is then screwed into a new joint of pipe that has been temporarily stored in the ''mouse hole'', a cased opening in the rig floor. The kelly and the new joint of pipe are then screwed on the previous pipe and lowered into the hole so that drilling can resume. When all of the pipe is pulled out of the hole, it is referred to as a ''trip''. Pulling out part of the drill string, then returning to drilling, is called a ''short'' or ''wiper trip''. Such trips are performed to verify that the drill string can move through a recently drilled potentially troublesome section of the borehole.

The hole is drilled by adding joints or lengths of drill pipe to the end of the kelly. When pipe is added, the hoisting system is used to pick up the kelly so that it hangs from the derrick above the rotary table. ''Tongs'' (large pipe wrenches) or chains are used to unscrew the kelly from the previous joint of pipe. The kelly is then screwed into a new joint of pipe that has been temporarily stored in the ''mouse hole'', a cased opening in the rig floor. The kelly and the new joint of pipe are then screwed on the previous pipe and lowered into the hole so that drilling can resume. When all of the pipe is pulled out of the hole, it is referred to as a ''trip''. Pulling out part of the drill string, then returning to drilling, is called a ''short'' or ''wiper trip''. Such trips are performed to verify that the drill string can move through a recently drilled potentially troublesome section of the borehole.

==Circulating system==

==Circulating system==

Circulation of ''[[drilling fluid]]'' (mud) serves several functions on a rig, including cooling the bit, providing hole stability, and aiding in formation evaluation. (For more information on drilling fluid, see the chapter on “[[Drilling fluid]]” in Part 3, and for more on how the circulating system aids in formation evaluation, see the chapter on “[[Mudlogging: Drill cuttings analysis]]” also in Part 3.)

Circulation of [[drilling fluid]] (mud) serves several functions on a rig, including cooling the bit, providing hole stability, and aiding in formation evaluation. (For more information on drilling fluid, see [[Drilling fluid]], and for more on how the circulating system aids in formation evaluation, see [[Mudlogging: drill cuttings analysis]].)

[[Drilling fluid]] is circulated by the mud pumps. The volume of mud being pumped is measured by the stroke counters, and the rate of movement is recorded by the stand pipe pressure. The stand pipe connects the mud pumps to the kelly hose. The kelly hose is connected to the swivel on top of the kelly. Mud is pumped down the drill string through the bit and up the ''annulus'' or “back side” (the space between the drill pipe and the borehole). Returning mud flows down the flowline into a ''surge tank'' (possum belly) and across the shale shakers. ''Shale shakers'' are vibrating screening devices that are designed to shake so as to separate out the drill cuttings from the mud. The shale shakers are the first place that drill cuttings can be examined and where the gas is extracted from the mud (Figure 2). After going through the shake shakers the mud passes through a series of tanks or pits where the finer solids are removed via desanders, desilters and centrifuges, and the mud properties are adjusted. Pits are named for their function (e.g., shale pit, settling pit, volume pit, mixing pit, and suction pit). The mud pumps are charged from the suction pit. Excess mud can also be diverted from the metal mud pits into a large, plastic lined reserve pit located to the side of the rig.

[[Drilling fluid]] is circulated by the mud pumps. The volume of mud being pumped is measured by the stroke counters, and the rate of movement is recorded by the stand pipe pressure. The stand pipe connects the mud pumps to the kelly hose. The kelly hose is connected to the swivel on top of the kelly. Mud is pumped down the drill string through the bit and up the ''annulus'' or “back side” (the space between the drill pipe and the borehole). Returning mud flows down the flowline into a ''surge tank'' (possum belly) and across the shale shakers. ''Shale shakers'' are vibrating screening devices that are designed to shake so as to separate out the drill cuttings from the mud. The shale shakers are the first place that drill cuttings can be examined and where the gas is extracted from the mud (Figure 2). After going through the shake shakers the mud passes through a series of tanks or pits where the finer solids are removed via desanders, desilters and centrifuges, and the mud properties are adjusted. Pits are named for their function (e.g., shale pit, settling pit, volume pit, mixing pit, and suction pit). The mud pumps are charged from the suction pit. Excess mud can also be diverted from the metal mud pits into a large, plastic lined reserve pit located to the side of the rig.