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Drilling Engineering – PE311 Rotary System. Introduction to Rotary System. The main parts of the rotary system (or the drill string) are: 1. Swivel 2. Kelley 3. Rotary table 4. Drillpipe 5. Drill collars 6. Heavy wall drill pipe Stabilizer Rotary reamers - PowerPoint PPT Presentation
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Drilling Engineering – Fall 2012
Prepared by: Tan Nguyen
Drilling Engineering – PE311
Rotary System
Drilling Engineering – Fall 2012
Prepared by: Tan Nguyen
The main parts of the rotary system (or the drill string) are:
1. Swivel
2. Kelley
3. Rotary table
4. Drillpipe
5. Drill collars
6. Heavy wall drill pipe
7. Stabilizer
8. Rotary reamers
Note: the bottomhole assembly (BHA) is that portion of the drill string between the drill pipe and the drill bit.
Introduction to Rotary System
Drilling Engineering – Fall 2012
Prepared by: Tan Nguyen
The rotary system is the heart of the rotary drilling rig; its function involves
transmitting rotating function to the drillstring and consequently the bit.
As the drill string moves downhole, it is subjected to a variety of stresses, including
tension, compression, vibration, torsion, friction, formation pressure and circulating
fluid pressure. It is also exposed to abrasive solids and corrosive fluids.
The drill string not only must be sturdy enough to withstand this hostile
environment, but it must be lightweight and manageable enough to be efficiently
handled within the limits of the rig's hoisting system. At the same time, it must:
provide weight to the bit; allow control over wellbore deviation; and help ensure
that the hole stays "in gauge".
Introduction to Rotary System
Drilling Engineering – Fall 2012
Prepared by: Tan Nguyen
The rotary swivel connects the circulating
system to the rotary system while providing a
fluid seal that must absorb rotational wear while
holding pressure. The swivel is hung under the
traveling block and directly above the Kelley. It
provides the ability for the Kelly to rotate while
the traveling block to remain in a stationary
rotational position while simultaneously allowing
the introduction of drilling fluid into the drill
string.
Swivel
Drilling Engineering – Fall 2012
Prepared by: Tan Nguyen
The Kelley is of square or hexagonal cross-
section that screws into the drillstring while
providing a flat surface for applying torque to
rotate the pipe. The main function of a kelly is to
transfer energy from the rotary table to the rest
of the drill string.
Kelley
Drilling Engineering – Fall 2012
Prepared by: Tan Nguyen
The longest portion of the drill string consists of
connected lengths of drill pipe. The primary
purposes of drill pipe are to provide length to the
drill string and transmit rotational energy from
the Kelly to the bottomhole assembly and the
drill bit. The drillpipe connects the rig surface
equipment with the bottomhole assembly and
the bit, both to pump drilling fluid to the bit and to
be able to raise, lower and rotate the bottomhole
assembly and bit.
Drillpipe
Drilling Engineering – Fall 2012
Prepared by: Tan Nguyen
Hole size, well depth, casing and cementing requirements, subsurface pressures,
circulating system and drilling mud parameters, hoisting capacity, pipe availability and
contract provisions are among the factors that influence drill pipe selection.
The American Petroleum Institute has established standards for drill pipe
manufacturing practices, dimensions, strengths and performance properties. These
standards appear in the following publications:
• API Spec 5D: This American Petroleum Institute (API) specification covers seamless
steel drill pipe used in the oil and gas industry
• API Bul 5C2, Bulletin on Performance Properties of Casing, Tubing and Drill Pipe;
API-standard drill pipe is available in three length ranges: Range 1(18-22 ft), Range 2
(27-30 ft) and Range 3 (38-45 ft). Range 2 is the length most commonly used, making
the "average" length of a drill pipe joint about 30 feet.
Drillpipe
Drilling Engineering – Fall 2012
Prepared by: Tan Nguyen
Drillpipe
Drilling Engineering – Fall 2012
Prepared by: Tan Nguyen
The drill collars provide weight and
stability to the drill bit, maintain tension
on the drill pipe and help keep the hole
on a straight course. Drill collars are
thick-walled tubular pieces machined
from solid bars of steel. The bars of
steel are drilled from end to end to
provide a passage to pumping drilling
fluids through the collars.
Drill Collar
Drilling Engineering – Fall 2012
Prepared by: Tan Nguyen
To accurately control the amount of force applied to the bit, the driller carefully
monitors the surface weight measured while the bit is just off the bottom of the
wellbore. Next, the drillstring (and the drill bit), is slowly and carefully lowered until
it touches bottom. After that point, as the driller continues to lower the top of the
drillstring, more and more weight is applied to the bit, and correspondingly less
weight is measured as hanging at the surface.
Downhole MWD sensors measure weight-on-bit more accurately and transmit the
data to the surface.
Drill Collar
Drilling Engineering – Fall 2012
Prepared by: Tan Nguyen
To avoid fatigue failures, the drill
pipe and uppermost drill collars need
to be kept in tension at all times.
Tension can be maintained by
running an adequate number of
collars in the bottomhole assembly
to ensure that the neutral point (that
is, the point below which the drill
string is in compression, and above
which it is in tension) will always be
below the drill pipe
Drill Collar
Drilling Engineering – Fall 2012
Prepared by: Tan Nguyen
Serves as an intermediate-weight drill string member between the drill pipe and
the much heavier drill collars, thereby reducing fatigue failures, providing
additional hole stability and aiding in directional control.
The most important drill string application for heavy wall drill pipe is in the so-
called zone of destruction — the area above the topmost drill collars where drill
pipe fatigue failure is most likely to occur. To reduce fatigue failures in this area of
the borehole, 18 to 21 joints of heavy wall drill pipe should be run above the drill
collars. This provides a gradual change in stiffness between drill collars and drill
pipe. Also, the ability of the heavy wall drill pipe to bend (unlike drill collars) serves
to relieve high stresses at the connections.
Heavy Wall Drill Pipe
Drilling Engineering – Fall 2012
Prepared by: Tan Nguyen
Heavy wall drill pipe was first used in directional drilling, which generally requires
flexibility in the drill string. It is now widely used in vertical and horizontal drilling as
well. With less wall contact than would be experienced with drill collars, its usage
reduces torque and wall-sticking tendencies. Its smaller degree of wall contact,
together with its greater stiffness relative to regular drill pipe, results in increased
stability and better directional control. Heavy wall drill pipe is also useful in
reducing hook loads, making it ideal for smaller rigs drilling deeper holes.
Heavy Wall Drill Pipe
Drilling Engineering – Fall 2012
Prepared by: Tan Nguyen
Centralize the drill collars, help maintain the hole at full-
gauge diameter and aid in directional control. Stabilizers,
by centralizing the drill string at selected points in the
borehole, can be used to:
•Ensure that the weight of the drill collars is concentrated
on the bit;
•Reduce torque and bending stresses in the drill string;
•Prevent wall-sticking or key-seating of the drill collars;
•Maintain constant bit direction in straight-hole drilling.
Stabilizer
Drilling Engineering – Fall 2012
Prepared by: Tan Nguyen
The Rotary Reamer is designed for various reams in drilling operation. In very hard formations, the outside cutting structure of a bit gradually wears away if it is not protected. This results in a hole diameter that becomes smaller with increasing depth
When a hole is severely undergauge, it is necessary to ream each new bit back to bottom before drilling can resume. This not only costs rig time and reduces bit life, but it increases the possibility of sticking the drill string.
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Reamer