Note: Descriptions are shown in the official language in which they were submitted.
CA 02884798 2016-08-10
DRILL STRING COMPONENTS HAVING MULTIPLE-THREAD JOINTS
CROSS-REFERENCE TO RELATED APPLICATION
[00N] This application claims priority to Provisional Patent Application No
61/700,401,
filed September 13, 2012, entitled "DRILL STRING COMPONENTS HAVING MULTIPLE
THREAD JOINTS".
BACKGROUND OF THE INVENTION
Field of the Invention
[00021 Implementations of the present invention relate generally to
components and
systems for drilling. In particular, implementations of the present invention
relate to drill
components comprising increased strength and resistance to jamming, cross-
threading and
wedging.
Relevant Technolou
[0003] Threaded connections have been well known for ages, and threads
provide a
significant advantage in that a helical structure of the thread can convert a
rotational
movement and force into a linear movement and force, Threads exist on many
types of
elements, and can be used in limitless applications and industries. For
instance, threads are
essential to screws, bolts, and other types of mechanical fasteners that may
engage a surface
(e.g., in the case of a screw) or be used in connection with a nut (e.g., in
the case of a bolt) to
hold multiple elements together, apply a force to an element, or for any other
suitable
purpose. Threading is also common in virtually any industry in which elements
are
mechanically fastened together. For instance, in plumbing applications, pipes
are used to
deliver liquids or gasses under pressure. Pipes may have threaded ends that
mate with
corresponding threads of an adjoining pipe, plug, adaptor, connector, or other
structure. The
threads can be used in creating a fluid-tight seal to guard against fluid
leakage at the
connection site.
[0004] Oilfield, exploration, and other drilling technologies also make
extensive use of
threading. For instance, when a well is dug, casing elements may be placed
inside the well,
The casings generally have a fixed length and multiple casings are secured to
each other in
order to produce a easing of the desired height. The casings can be connected
together using
threading on opposing ends thereof, Similarly, as drilling elements are used
to create a well
CA 02884798 2015-03-11
or to place objects inside a well, a drill rod or other similar device may be
used. Where the
depth of the well is sufficiently large, multiple drill rods may be connected
together, which
can be facilitated using mating threads on opposing ends of the drill rod.
Often, the drill rods
and casings are very large and machinery applies large forces in order to
thread the rods or
casings together.
[0005] Significant efforts have been made to standardize equipment in
oilfield,
exploration and other drilling industries. In the case of drill rods, both
outer and inner
diameter standards have been developed and, in the case of threading, multiple
threading
standards have been developed to allow different manufacturers to produce
interchangeable
parts. For instance exemplary standardization schemes comprise Unified Thread
Standard
(UTS), British Standard Whitworth (BSW), British Standard Pipe Taper (BSPT),
National
Pipe Thread Tapered Thread (NPT), International Organization for
Standardization (ISO)
metric screw threads, American Petroleum Institute (API) threads, and numerous
other thread
standardization schemes.
[0006] While standardization has allowed greater predictability and
interchangeability
when components of different manufactures are matched together,
standardization has also
diminished the amount of innovation in drill component design. In one example,
both outer
and inner diameters of drill rods have been fixed by industry requirements.
Accordingly, the
portion of the wall thickness allocated to mating threads operable to transfer
drilling loads
and to withstand wear due to repeated making and breaking of the drill
components must be
balanced with the remaining material over the threaded portions of components
so that the
components can withstand drilling loads and wear due to abrasion against the
drilled hole
wall and resulting cuttings.
[0007] In another example, threads may be created using existing cross-
sectional
shapes __ or thread form¨and different combinations of thread lead, pitch, and
ntunber of
starts. In particular, lead refers to the linear distance along an axis that
is covered in a
complete rotation. Pitch refers to the distance from the crest of one thread
to the next, and
start refers to the number of starts, or ridges, wrapped around the cylinder
of the threaded
fastener. A single-start connector is the most common, and comprises a single
ridge wrapped
around the fastener body. A double-start connector comprises two ridges
wrapped around the
fastener body. Threads-per-inch is also a thread specification element, but is
directly related
to the thread lead, pitch, and start.
2
CA 02884798 2015-03-11
[0008] While existing threads and thread forms are suitable for a number of
applications,
continued improvement is needed in other areas such as in high torque, high
power, and/or
high speed applications. In one instance, existing thread designs are
inherently prone to
jamming. In another instance, existing thread designs do not use available
material
effectively. In another embodiment, existing thread designs detract from load
capacity of
mated components. In yet another instance, existing thread designs exhibit
excessive wear.
[0009] Jamming is the abnormal interaction between the start of a thread
and a mating
thread, such that in the course of a single turn, one thread partially passes
under another,
thereby becoming wedged therewith. Jamming can be particularly common where
threaded
connectors are tapered. In another instance, existing drill component designs
can have
limited drilling load capacity and fatigue load capacity as a result of the
material afforded to
the male thread or to the underlying material on the male end of a drill
component.
[0010] In certain applications, such as in connection with drill rigs,
multiple drill rods,
casings, and the like can be made up. As more rods or casings are added,
interference due to
wedging or cross-threading can become greater. Indeed, with sufficient power
(e.g., when
made up using hydraulic power of a drill rig) a rod joint can be destroyed.
Coring rods in
drilling applications also often have threads that are coarse with wide, flat
threaded crests
parallel to mating crests due to a mating interference fit or slight clearance
fit dictated by
many drill rod joint designs. The combination of thread tails and flat,
parallel thread crests
on coarse tapered threads creates an even larger potential for cross-threading
interaction,
which may not otherwise be present in other applications.
[0011] In tapered threads, the opposing ends of mate and female components
may be
different sizes. For instance, a male threaded component may taper and
gradually increase in
size as distance from the end increases. To accommodate for the increase in
size, the female
thread may be larger at the end. The difference in size of tapered threads
also makes tapered
threads particularly prone to jamming, which is also referred to as cross-
threading. Cross-
threading in tapered or other threads can result in significant damage to the
threads and/or the
components that include the threads. Damage to the threads may require
replacement of the
threaded component, result in a weakened connection, reduce the fluid-tight
characteristics of
a seal between components, or have other effects, or any combination of the
foregoing.
[0012] For example, tail-type thread starts have crests with a joint taper.
If the male and
female components are moved together without rotation, the tail crests can
wedge together.
If rotated, the tail crests can also wedge when fed based on relative
alignment of the tails. In
3
CA 02884798 2015-03-11
particular, as a thread tail is typically about one-half the circumference in
length, and since
the thread has a joint taper, there is less than half of the circumference of
the respective male
and female components providing rotational positioning for threading without
wedging.
Such positional requirements may be particularly difficult to obtain in
applications where
large feed and rotational forces are used to mate corresponding components.
For instance, in
the automated making of coring rod connections in the drilling industry, the
equipment may
operate with sufficient forces such that jamming, wedging, or cross-threading
is an all too
common occurrence.
[0013] Furthermore, when joining male and female components that are in an
off-center
alignment, tail-type connections may also be prone to cross-threading,
jamming, and
wedging. Accordingly, when the male and female components are fed without
rotation, the
tail can wedge into a mating thread. Under rotation, the tail may also wedge
into a mating
thread. Wedging may be reduced, but after a threading opportunity (e.g.,
mating the tip of
the tail in opening adjacent a mating tail), wedging may still occur due to
the missed
threading opportunity and misalignment. Off-center threads may be configured
such that a
mid-tail crest on the mail component has equal or corresponding geometry
relative to the
female thread crest.
[0014] As discussed above, threaded connectors having tail-type thread
starts can be
particularly prone to thread jamming, cross-threading, wedging, joint seizure,
and the like.
Such difficulties may be particularly prevalent in certain industries, such as
in connection
with the designs of coring drill rods. The thread start provides a leading
end, or first end, of a
male or female thread and mates with that of a mating thread to make a rod or
other
connection. If the tail-type thread starts jam, wedge, cross-thread, and the
like, the rods may
need to be removed from a drill site, and can require correction that requires
a stop in drilling
production.
[0015] Additionally, drill rods and casings commonly make use of tapered
threads and
tapered joints such that the diameters at the thread starts are smaller than
the diameters at the
thread ends. Tapered threads and joints reduce the amount of cross-sectional
material
available to transfer loads. Tapered threads and joints are also prone to
cross-threading
difficulties. Since a coring rod may have a tapered thread, the tail at the
start of the male
thread may be smaller in diameter than that of the start of the female thread.
As a result,
there may be transitional geometry at the start of each thread to transition
from a flush to a
full thread profile. Because the thread start and transitional geometry may
have sizes
4
CA 02884798 2015-03-11
differing from that of the female thread, the transitional geometry and thread
start may mate
abnormally and wedge into each other.
[00161 If there is a sufficient taper on the tail, the start of the male
thread may have some
clearance to the start of the female thread, such as where the mid-tail
geometry corresponds
to the geometry of the female thread. However, the transitional geometry of
the start of the
thread may nonetheless interact abnormally with turns of the thread beyond the
thread start,
typically at subsequent turns of mating thread crests, thereby also resulting
in jamming,
cross-threading, wedging, and the like. Thus, the presence of a tail generally
acts as a wedge
with a mating tail, thereby increasing the opportunity and probability of
thread jamming.
[00171 The limitations of tail-type thread designs are typically brought
about by
limitations of existing machining lathes. In particular, threads are typically
cut by rotational
machining lathes which can only gradually apply changes in thread height or
depth with
rotation of the part. Accordingly, threads are generally formed to include
tails having
geometry and tails identical or similar to other portions of the thread start.
For instance,
among other things, traditional lathes are not capable of applying an abrupt
vertical or near
vertical transition from a flush to full thread profile to rotation of the
part during machining.
The gradual change is also required to remove sharp, partial feature edges of
material created
where the slight lead, or helix angle, of the thread meets the material being
cut.
[00181 Existing thread designs do not necessarily make effective use of
available
material. As explained previously, use of overall root and thread taper
results in loss of
cross-sectional area of a component, and the loss of cross-sectional material
results in
reduced load capacity and fatigue strength for a given component. In another
instance, use of
a single thread provides for ease of manufacture and ease of make and break.
However, the
use of a single thread limits the pressure flank bearing surface area, thus,
the load efficiency
of the component. This practice also limits the material at the thread flank-
to-thread root
interface, the location of maximum stress and for fatigue failure crack
initiation, and the
fatigue strength of the component.
[00191 Furthermore, existing thread designs using a single thread result in
components
that are inherently unbalanced when mating components are brought into
contact. Without
wishing to be bound by theory and/or simulation, when drill string components
having a
single-start thread are brought into mating contact, the pin thread is placed
in tension and the
box thread is placed in compression. It follows that, since the load in a
threaded joint moves
to the first point of mated contact, there is a higher portion of load taken
by the portion of
CA 02884798 2015-03-11
mated thread nearest the first point of contact on one side of the joint. This
unsymmetrical
load response can create a bending load in mated drill string components and
can detract
from load capacity.
[0020] Wear is the erosion or displacement of thread material from its
original position
on the thread surface due to the relative mechanical actions of mating
threads. Existing
thread designs can also be configured to create an interference fit on, for
example, the major
diameter of the mating components. For instance, the male thread crest can be
configured to
create a radial interference with the female thread root. As the threads are
made up, the
interference fit may be a significant source of thread wear as it can add
greatly to the contact
pressure between the threads as they slide relative to one another.
Ultimately, interference
fits on thread features increase thread wear. Thread wear degrades the thread
geometry thus
the load capacity or load efficiency of the drill string component.
[0021] Thus, drawback with traditional threads can be exacerbated with
drilling
components. In particular, the joints of the drill string components can
require a joint with a
high tension load capacity due to the length and weight of many drill strings.
Furthermore,
the joint will often need to withstand numerous makes and breaks since the
same drill string
components may be installed and removed from a drill string multiple times
during drilling of
a borehole. Similarly, the drill string components may be reused multiple
times during their
life span. Compounding these issues is the fact that many drilling industries,
such as
exploration drilling, require the use of thin-walled drill string components.
The thin-wall
construction of such drill string components can restrict the geometry of the
threads.
[0022] Accordingly, a need exists for improved thread designs and drilling
components
that reduce wear, jamming and cross threading as well as use available
material effectively to
increase drilling load capacity and joint reliability.
SUMMARY
[0023] It is to be understood that this summary is not an extensive
overview of the
disclosure. This summary is exemplary and not restrictive, and it is intended
to neither
identify key or critical elements of the disclosure nor delineate the scope
thereof. The sole
purpose of this summary is to explain and exemplify certain concepts of the
disclosure as an
introduction to the following complete and extensive detailed description.
[0024] One or more implementations of the present invention overcome one or
more of
the foregoing or other problems in the art with drilling components, tools,
and systems that
6
CA 02884798 2015-03-11
provide for effective and efficient making of threaded joints. In one aspect,
one or more
implementations of the present invention comprise drill string components
comprising
increased strength and resistance to jamming and cross-threading. Such drill
string
components can reduce or eliminate damage to threads due to jamming and cross-
threading.
In particular, one or more implementations comprise drill string components
having threads
with a leading end or thread start oriented at an acute angle relative to the
central axis of the
drill string component. Additionally or alternatively, the leading end of the
threads can
provide an abrupt transition to full thread depth and/or width. Additionally
or alternatively,
the threads can have at least one of a variable thread pitch and a variable
thread width.
Additionally or alternatively, the threads can have a cylindrical thread root
and a thread crest
that circumscribes a frusta-cone over at least a portion of the axial length
of the threads.
[0025] In one aspect, one or more implementation of a threaded drill string
component
having increased strength and resistance to jamming and cross-threading
comprises a hollow
body having a first end, an opposing second end, and a central axis extending
through the
hollow body. The drill string component also comprises at least one thread
positioned on the
first end of the hollow body. The at least one thread comprises a plurality of
helical turns
extending along the first end of the hollow body. The at least one thread has
a thread depth, a
thread width and a thread pitch. The at least one thread comprises a leading
end proximate
the first end of the hollow body. The leading end of the at least one thread
is orientated at an
acute angle relative to the central axis of the hollow body. The leading end
of the at least one
thread faces toward an adjacent turn of the thread. The thread pitch of the at
least one thread
increases from a first value proximate the leading end over at least a portion
of the axial
length of the plurality of helical turns thereof to a final value at a desired
point on the at least
one thread.
[0026] In one aspect, one or more implementation of a drill string
component having
increased strength and resistance to jamming and cross-threading comprises at
least one
thread having a thread crest and a thread root. The thread root of the at
least one thread
circumscribes a cylindrical surface over the axial length of the plurality of
helical turns
thereof. The thread crest of the at least one thread circumscribes a frusta-
conical surface
extending over at least a portion of the axial length of the plurality of
helical turns thereof.
[0027] In one aspect, one or more implementations of a drill string
component having
increased strength and resistance to jamming and cross-threading comprises a
drill string
component having a plurality of threads.
7
CA 02884798 2015-03-11
[0028] In one aspect, one or more implementations of a drill string
component having
increased strength and resistance to jamming and cross-threading comprises a
drill string
component that eliminates interference fits on thread features. In a further
aspect,
interference fits are provided at non-thread component features such as such
as shoulder
surfaces.
[0029] In another aspect, one or more implementations of a threaded drill
string
component having increased strength and resistance to jamming and cross-
threading
comprises a body, a box end, an opposing pin end, and a central axis extending
through the
body. The drill string component also comprises a female thread positioned on
the box end
of the body. The female thread has a depth and a width. Additionally, the
drill string
component also comprises a male thread positioned on the pin end of the body.
The male
thread has a depth and a width. Each of the female thread and the male thread
comprises a
leading end. The leading end of each of the female thread and the male thread
comprises a
planar surface extending normal to the body. The planar surface of the leading
end of the
female thread extends along the entire width and the entire depth of the
female thread.
Similarly, the planar surface of the leading end of the male thread extends
along the entire
width and the entire depth of the male thread.
[0030] In addition to the foregoing, an implementation of a method of
making a joint in a
drill string with increased strength and without jamming or cross-threading
involves inserting
a pin end of a first drill string component into a box end of a second drill
string component.
The method also involves rotating the first drill sting component relative to
the second drill
string component; thereby abutting a planar leading end of a male thread on
the pin end of the
first drill string component against a planar leading end of a female thread
on the box end of
the second drill string component. The planar leading end of the male thread
is oriented at an
acute angle relative to a central axis of the first drill string component.
Similarly, the planar
leading end of the female thread is oriented at an acute angle relative to a
central axis of the
second drill string component. Additionally, the method involves sliding the
planar leading
end of the male thread against and along the planar leading end of the female
thread to guide
the male thread into a gap between turns of the female thread.
[0031] Additional features and advantages of exemplary implementations of
the
invention will be set forth in the description which follows, and in part will
be obvious from
the description, or may be learned by the practice of such exemplary
implementations. The
features and advantages of such implementations may be realized and obtained
by means of
8
CA 02884798 2015-03-11
the instruments and combinations particularly pointed out in the appended
claims. These and
other features will become more fully apparent from the following description
and appended
claims, or may be learned by the practice of such exemplary implementations as
set forth
hereinafter.
DESCRIPTION OF THE DRAWINGS
[0032] The accompanying drawings, which are incorporated in and constitute
a part of
this specification, illustrate embodiments and together with the description,
serve to explain
the principles of the methods and systems.
[0033] Figure 1 illustrates fragmentary longitudinal sectional view through
a plurality of
connected drill rods in a drill string with a longitudinal intermediate
portion of the drill rods
being broken away;
[0034] Figure 2 is an enlarged fragmentary longitudinal sectional view of
one of the drill
rod joints of Figure 1, the dotted lines indicating the location of the crests
and roots of threads
diametrically opposite those shown in solid lines and the joint being shown in
a hand tight
condition;
[0035] Figure 3 is a fragmentary longitudinal view of a pin end of a drill
rod oriented
axially with the box end of an adjacent drill rod with the box and one half of
the pin being
shown in cross-section;
[0036] Figure 4 illustrates a side view of a male end of a drill string
component and a
cross-sectional view of a female end of another drill string component each
having a thread
with a leading end in accordance with one or more implementations of the
present invention;
[0037] Figure 5 illustrates a side view of an exploded drill string having
drill string
components having leading ends in accordance with one or more implementations
of the
present invention; and
[0038] Figure 6 illustrates a schematic diagram of a drilling system
including drill string
components having leading ends in accordance with one or more implementations
of the
present invention.
DETAILED DESCRIPTION
[0039] Before the present methods and systems are disclosed and described,
it is to be
understood that the methods and systems are not limited to specific synthetic
methods,
specific components, or to particular compositions. It is also to be
understood that the
9
CA 02884798 2015-03-11
terminology used herein is for the purpose of describing particular
embodiments only and is
not intended to be limiting.
[0040] As used in the specification and the appended claims, the singular
forms "a," "an"
and "the" include plural referents unless the context clearly dictates
otherwise. Ranges may
be expressed herein as from "about" one particular value, and/or to "about"
another particular
value. When such a range is expressed, another embodiment includes from the
one particular
value and/or to the other particular value. Similarly, when values are
expressed as
approximations, by use of the antecedent "about," it will be understood that
the particular
value forms another embodiment. It will be further understood that the
endpoints of each of
the ranges are significant both in relation to the other endpoint, and
independently of the
other endpoint.
[0041] "Optional" or "optionally" means that the subsequently described
event or
circumstance may or may not occur, and that the description includes instances
where said
event or circumstance occurs and instances where it does not.
[0042] Throughout the description and claims of this specification, the
word "comprise"
and variations of the word, such as "comprising" and "comprises," means
"including but not
limited to," and is not intended to exclude, for example, other additives,
components, integers
or steps. "Exemplary" means "an example of' and is not intended to convey an
indication of
a preferred or ideal embodiment. "Such as" is not used in a restrictive sense,
but for
explanatory purposes.
[0043] Disclosed are components that can be used to perform the disclosed
methods and
systems. These and other components are disclosed herein, and it is understood
that when
combinations, subsets, interactions, groups, etc. of these components are
disclosed that while
specific reference of each various individual and collective combinations and
permutation of
these may not be explicitly disclosed, each is specifically contemplated and
described herein,
for all methods and systems. This applies to all aspects of this application
including, but not
limited to, steps in disclosed methods. Thus, if there are a variety of
additional steps that can
be performed it is understood that each of these additional steps can be
performed with any
specific embodiment or combination of embodiments of the disclosed methods.
[0044] The present methods and systems may be understood more readily by
reference to
the following detailed description of preferred embodiments and the Examples
included
therein and to the Figures and their previous and following description.
CA 02884798 2015-03-11
[0045] Implementations of the present invention are directed toward
drilling components,
tools, and systems that provide for effective drill thread components and
efficient making of
threaded joints. For example, one or more implementations of the present
invention comprise
drill string components with increased load efficiency and load capacity, and
that can also be
resistant to wear, jamming and cross-threading. Such drill string components
can reduce or
eliminate damage to threads due to wear, jamming and cross-threading while
also increasing
the load efficiency and load capacity over conventional drilling components.
In particular,
one or more implementations comprise drill string components having multiple
threads with
leading ends or thread starts oriented at an acute angle relative to the
central axis of the drill
string component. Additionally or alternatively, the leading end of the thread
can provide an
abrupt transition to full thread depth and/or width. Furthermore, one or more
implementations of drill string components operable to provide a progressive
fit and that
conserve cross-sectional material comprise at least one of varying thread
width to provide a
progressive fit in an axial direction over at least a portion of the thread
and tapering at least
one of the mating thread crests over at least a portion of the thread while
maintaining a
constant root diameter over the entire thread.
[0046] Reference will now be made to the drawings to describe various
aspects of one or
more implementations of the invention. It is to be understood that the
drawings are
diagrammatic and schematic representations of one or more implementations, and
are not
limiting of the present disclosure. Moreover, while various drawings are
provided at a scale
that is considered functional for one or more implementations, the drawings
are not
necessarily drawn to scale for all contemplated implementations. The drawings
thus
represent an exemplary scale, but no inference should be drawn from the
drawings as to any
required scale.
[0047] In the following description, numerous specific details are set
forth in order to
provide a thorough understanding of the present invention. It will be obvious,
however, to
one skilled in the art that the present disclosure may be practiced without
these specific
details. In other instances, well-known aspects of thread specifications,
thread
manufacturing, in-field equipment for connecting threaded components, and the
like have not
been described in particular detail in order to avoid unnecessarily obscuring
aspects of the
disclosed implementations.
[0048] Turning now to Figure 1, an implementation of an exemplary threaded
drill string
component is illustrated. The threaded drill string components having
increased load
11
CA 02884798 2015-03-11
capacity and load efficiency that can also be joined while avoiding or
reducing the risk of
wear, cross-threading and jamming are described in particular detail below. As
shown in
Figures 1-4, a first drill string component 102 can comprise a body 103 and a
male connector
or pin end 104. A second drill string component 106 can comprise a body 107
and a female
connector or box end 108. The pin end 104 of the first drill string component
106 can be
configured to connect to the box end 108 of the second drill string component
106.
In one or more implementations, each drill string component 102, 106 can
comprise a hollow
body having a central axis 126 extending there through as shown in Figures 1-
4. In
alternative implementations, one or more of the drill string components 102,
106 can
comprise a solid body (such as a percussive drill rod or drill bit) or a
partially hollow body.
More particularly, in the case of a hollow body, the hollow body can comprise
an inner
diameter, an outer diameter and a wall thickness. On one exemplary aspect, the
drill string
component can have the following typical dimensions:
i!i4pletenev
OD (in) 2.20 2.75 3.50 4.50
ID (in) 1.91 2.38 3,06 4.0
Wall Thickness (in) 0.15 0.19 0.22 0.25
Major Diameter (in) 2.09
I 2'61 3.34 4.35
[0049] The pin end 104 can comprise at least one male thread 110 (Le., a
thread that
projects radially outward from outer surface of the pin end 104). The box end
108, on the
other hand, can comprise at least one female thread 112 (i.e., a thread that
projects radially
inward from an inner surface of the box end 108). The at least one male thread
110 and the at
least one female thread 112 can have generally corresponding characteristics
(e.g., width,
height or depth, threaded length, taper, lead, pitch, threads per inch, number
of thread starts,
pitch diameter, mating thread turns, etc.) or they can vary in one or more of
the enumerated
characteristics.
[0050] In another aspect of the present invention, the following ranges and
ratios are
contemplated when determining the characteristics of drill string components
of the present
disclosure:
=
= .
12
CA 02884798 2015-03-11
Wail thickness to outer diameter
(%) 7% 6% 6% 7%
Thread depth to wall thickness
(%) 19% 16% 21% 16%
Range of joint taper (deg) 0.8 1.0 1.0 0.5
Range of flank angle (deg) -10 15 2 -20
Threaded length to diameter (%) 55% 39% 44% 43%
Range of thread pitch (tpl) 3.50 3.00 2.50 1.75
Major diameter less inner
diameter, to wall thickness 62% 62% 70% 63%
Shoulder thickness to wall
thickness (%) 38% 38% 30% 37%
[00511 In one or more implementations, the at least one male thread 110 and
at least one
female thread 112 can comprise straight thread crests and roots. In a further
implementation,
at least one of the crests of the at least one male thread and at least one
female thread 110,
112 are tapered while the thread roots of the threads 110, 112 remain
constant. In another
aspect, it is not necessary that threads 110, 112 be uniform along their
entire length. Indeed,
the at least one male thread 110 may have characteristics corresponding to
those of the at
least one female thread 112 despite the characteristics changing along the
respective lengths
of pin end 104 or box end 108. In one or more implementations, the at least
one male and at
least one female threads 110, 112 can have a variable thread pitch over at
least a portion of
the threads 110, 112. In other additional or alternate implementations, the at
least one male
and the at least one female threads 110, 112 can have a constant pitch as
measured between
thread at least one thread feature and a variable thread width over at least a
portion of the
threads 110, 112. In further or alternate implementations, at least one of the
crests of the at
least one male thread and at least one female thread 110, 112 are tapered over
a desired
portion of the length of the threads 110, 112 while the thread roots of the
threads 110, 112
remain constant.
[00521 In one or more implementations, the male and female threads 110, 112
can
comprise characteristics the same as or similar to those described in U.S.
Patent No.
13
CA 02884798 2016-08-10
5,788,401. For example, in one or more implementations, the male and female
threads
110, 112 have a crest, a root, a pressure flank and a clearance flank.
According to one
aspect, threads 110, 112 can have a pressure flank angle (or thread load flank
angle) that
can be from about -30 to about 15 degrees; more particularly, from about -20
to about -
degrees; and, most particularly, about -20 to about -15 degrees, all measured
relative
to a plane perpendicular to the drill string central axis. As one skilled in
the art will
appreciate in light of the present disclosure, such negative pressure flank
angles can aid
in maintaining the joint in a coupled condition, even under overload and also
reduce
overall stress as compared to positive flank angles.
[0053] In another aspect, the box end and pin end of the drill sting
component can
have shoulders tapered at about 0 to about 15 degrees. In another aspect, the
shoulders
can have an outer diameter thickness of about 0.055 to about 0.080 inches; and
more
particularly, about 0.055 inches, about 0.083 inches, about 0.070 inches or
about 0.075
inches.
[0054] In other aspects, the critical pin section thickness, or the target
material thickness
under the pin thread, can be used as an indicator of ultimate tensile strength
and the stress
amplification resulting from cutting the thread. In one aspect, the critical
pin section
thickness can be from about 40% to about 50% of wall thickness; and more
particularly
about 44%, about 45%, about 46% or about 47% of the wall thickness.
[0055] In other aspects, the critical box shoulder stiffness, or the
section modulus or
'modulus of intertia' of the box shoulder, can contribute torsion strength and
can be
exponentially sensitive to shoulder thickness. In one aspect, the critical box
shoulder
stiffness can be from about 34% to about 48% of the tubing stiffness; more
preferably, about
40%, about 41%, or about 43% of the tubing stiffness.
[0056] One will appreciate in light of the disclosure herein the foregoing
description is
just one configuration for the male and female threads 110, 112. In
alternative
implementations, the configuration of the male and female threads 110, 112 can
differ from
the forgoing description. In certain alternative implementations, the threads
110, 112 can
also have negative pressure flank angles of about 5 to 30 degrees relative to
a plane
perpendicular to the drill string central axis and clearance flanks of an
angle of at least 45
degrees to aid in maintaining the joint in a coupled condition, even under
overload, and
facilitate joint make up. Also, the box end and pin end can have shoulders
tapered at about
5 to 20 degrees.
14
CA 02884798 2015-03-11
[0057] In another aspect, the flank angle can be characterized by a flank
angle radial load
expansion which describes the radial load created by the load flank angle that
must he
absorbed in the joint. As one skilled in the art will appreciate in light of
the present
disclosure, values of flank angle radial load expansion can be bounded by
flank angles that
cause excessive thread stress. Radial loads can be defined as the percentage
of axial load
applied to the thread flank or to the joint determined by the flank angle.
Specifically, the
radial load created is equal to the axial load multiplied by the tangent of
the flank angle. As
one skilled in the art will also appreciate in light of the present
disclosure, positive values of
radial load can cause unwanted expansion while negative values can provide
beneficial
contraction. Contraction is beneficial because it can reduce overall or Von
Mises total stress
levels, and it can increase the contract pressure between mating threads which
increases
friction and the torsion load transferred to the joint. However, the
beneficial contraction due
to negative values of radial load can become undesirable past a certain
threshold. Here, the
flank angle radial load expansion can be from about -18% to about -36%; more
particularly,
from about -18% to about -36%; and even more particularly, about -27%.
[0058] The male thread 110 can begin proximate a leading edge 140 of the
pin end 104.
For example, Figure 1-3 illustrate that the male thread 110 can be offset a
distance (shown
has a linear distance 116) from the leading edge 140 of the pin end 104. The
offset distance
can allow for an un-mated shoulder portion of a threaded member to be
elastically
compressed under torque applied during joint make-up. As one skilled in the
art will
appreciate, a resulting joint can maintain a pre-loaded condition given an
applied make-up
torque wherein a sufficient amount of offset distance can be required to allow
thread travel
and can allow a "pre-load" to build as the shoulder undergoes elastic
compression. This "pre-
load" can be required to maintain the joint in a closed condition while under
large drilling
tension loads or deviation bending loads that could otherwise cause the
shoulder interface to
open, thus increasing the bending load on the pin and creating the potential
for the pin end to
undergo fatigue failure. Accordingly, in various aspects, the offset distance
116 may vary as
desired, and can particularly be different based on the size of the drill
string component 102,
configuration of the thread 110, or based on other factors. In at least one
implementation, the
offset distance 116 is between about one-half and about twice the width 118 of
the male
thread 110. Alternatively, the offset distance 116 may be greater or lesser.
For example, in
one or more implementations the offset distance 116 is zero such that the male
thread 110
begins at the leading edge 140 of the pin end 104.
is
CA 02884798 2015-03-11
[0059] Similarly, female thread 112 can begin proximate a leading edge 120
of the box
end 108. For example, Figures 1-4 illustrate that the female thread 112 can be
offset a
distance (shown has a linear distance 122) from the leading edge 120 of the
box end 108.
The offset distance 122 may vary as desired, and can particularly be different
based on the
size of the drill string component 106, configuration of the female thread
112, or based on
other factors. In at least one implementation, the offset distance 122 is
between about one-
half and about twice the width 124 of the female thread 112. Alternatively,
the offset
distance 122 may be greater or lesser. For example, in one or more
implementations the
offset distance 122 is zero such that the female thread 112 begins at the
leading edge 120 of
the box end 108.
[0060] Furthermore, the offset distance 116 can be equal to the offset
distance 122 as
shown in Figures 1-4. In alternative implementations, the offset distance 122
may be greater
or smaller than the offset distance 116. In any event, as the leading edge 140
of the pin end
104 is inserted into the box end 108 and rotated, the male thread 110 may
engage the female
thread 112, and the pin end 104 may advance linearly along a central axis 126
of the box end
108.
[00611 More particularly, the male and female threads 110, 112 can be
helically disposed
relative to the respective pin and box ends 104, 108. In other words, each of
the male thread
110 and the female thread 112 can comprise a plurality of helical turns
extending along the
respective drill string component 102, 106. As the male and female threads
110, 112 mate,
the threads may therefore rotate relative to each other and fit within gaps
between
corresponding threads. In Figures 1-4, the male thread 110 generally winds
around pin end
104 at an angle 128, which can also be measured relative to the leading edge
140 of the pin
end 104.
Multiple Thread Starts
[0062] One or more implementations of the present invention comprise drill
string
components having a plurality of threads. For example, in one or more
implementations, the
drill string component comprises at least two threads having respective thread
starts that are,
optionally, evenly spaced about the leading end of the drill string component.
[0063] In one aspect, use of multiple threads can increase the thread load
flank bearing
surface area and can result in a greater overall load efficiency when pin and
box components
are joined together. In one example, use of two threads doubles the thread
bearing area as
compared to a single thread when all other thread characteristics are held
constant.
16
CA 02884798 2015-03-11
[0064] In another aspect, use of multiple threads can also increase the
thread flank-to-
thread root interface material and, correspondingly, the fatigue strength of
the drill
component. Without wishing to be bound by theory and/or simulation, the thread
flank-to-
thread root interface is the location of maximum stress and for fatigue
failure crack initiation
in drill string component joints. It follows that, all other things held
constant, use of multiple
threads can increase the fatigue strength of the drill component since the
available material
fatigue strength is reduced by the mean load as illustrated by a standard
Modified Goodman
Fatigue Diagram.
[0065] In a further aspect, use of multiple threads spaced equally about
the respective
leading ends of drill string components can increase the load capacity of
drill string
components placed in mating contact by creating a symmetrical load response
about the
central axis of the component.
[0066] On the other hand, the thread lead angle can increase as the thread
pitch decreases
and the number of threads is increased. Increasing the thread lead angle past
an optimal
angle can decrease the break-out torque requirement such that mating drill
string components
could disassemble in use. In another aspect, individual thread width and,
correspondingly,
load shear area can decrease as the number of threads on a given drill
component increase,
ultimately leading to thread shear overload failure.
[0067] In one embodiment, a number of threads that increases the load
efficiency, load
capacity and fatigue strength of the drill string component while maintaining
acceptable
thread lead angles and shear area for a drill string component of given
dimensions can be
determined to be the maximum number of threads possible where the thread width
is not less
than the thread height. In another embodiment, this disclosure provides for
drill string
components having at least two threads, and, preferably from about two to
about four threads,
operable to increase the load efficiency, load capacity and fatigue strength
of the drill string
components while maintaining acceptable thread lead angles and shear area over
conventional single-thread drill string components.
[0068] In one example, at least two male threads 110 can begin proximate to
a leading
edge 140 of pin end 104. In a further aspect, the at least two male threads
can be spaced
equally about a leading edge 140 of pin end 104. For example, it is
contemplated that a pin
end has two male threads having thread starts spaced about 180 degrees apart
and proximate
to a leading edge 140 of pin end 104. In another example, it is contemplated
that a pin end
17
CA 02884798 2015-03-11
has three male threads, having thread starts that can be spaced about 120
degrees apart and
proximate to a leading edge 140 of pin end 104.
[0069] Similarly, at least two female threads 112 can begin proximate to a
leading edge
120 of box end 108. In a further aspect, the at least two female threads can
be spaced equally
about a leading edge 120 of box end 108. For example, it is contemplated that
a box end 108
has two female threads 112 having thread starts spaced about 180 degrees apart
and
proximate to a leading edge 120 of box end 108. In another example, it is
contemplated that
a box end 108 has three female threads 112 having thread starts that can be
spaced about 120
degrees apart and proximate to a leading edge 120 of box end 108.
[0070] More particularly, at least two male threads 110 and at least two
female threads
112 can be helically disposed relative to the respective pin and box ends 104,
108. In other
words, each of the male threads 110 and each of the female threads 112 can
comprise a
plurality of helical turns extending along the respective drill string
component 102, 106.
Each of the male threads 110 and each of the female threads 112 can each
comprise leading
ends oriented at an acute angle relative to and equally spaced about the
central axis of the
respective drill string component 102, 106. As the at least two male threads
110 and the at
least two female threads 112 mate, the threads may therefore rotate relative
to each other and
fit within gaps between corresponding threads and eventually form a drill
string joint.
Accordingly, in one or more embodiments, a drill string joint is formed having
increased load
efficiency, load capacity, and fatigue strength while maintaining acceptable
thread lead
angles and shear area for a given diameter drill string component.
Optimal Material Cross-Sections for Maximum Load Capacity
[0071] One or more implementations of the present invention comprise drill
string
components that substantially eliminate overall root and thread taper in favor
of at least one
of varying thread pitch, varying thread width, and tapering at least a portion
of the thread
crest while providing a uniform thread root. Another aspect of the present
invention
comprises drill string components that eliminate overall root and thread taper
in favor of at
least one of varying thread pitch, varying thread width and tapering at least
a portion of the
thread crest while providing a uniform thread root.
[0072] In one aspect, material typically lost to overall joint and thread
taper is conserved
by providing drill string components having at least one thread comprising a
thread pitch that
varies from a first value proximate the leading end over at least a portion of
the axial length
of the plurality of helical turns thereof to a final value at a desired point
on the at least one
18
CA 02884798 2015-03-11
thread thereby selectively enabling an axial progressive fit. In one aspect,
the thread pitch
can increase uniformly from the first value over at least the first turn to a
final value over at
least the final turn of the plurality of helical turns. In an alternative
aspect, the thread pitch
can increase non-uniformly from the first value to a final value over the full
axial length of
the plurality of helical turns. In a further aspect, the thread pitch can
increase from the first
value to a final value across a portion of the axial length of the plurality
of helical turns and
can remain constant thereafter. In yet another aspect, the at least one thread
can have a pitch
that varies from about 2.0 to 5.0 threads/inch, preferably from about 3 to
about 4 threads/inch
and, most preferably, from about 3 to about 3.5 threads/inch. In other
aspects, the thread can
have a varying pitch over at least one turn and, preferably, two turns of the
thread. In
alternative aspect, the thread can have a pitch that varies from the leading
end to the trailing
end of the thread.
[0073] In another aspect, material typically lost to overall joint and
thread taper is
conserved by providing drill string components having at least one thread
comprising a
thread pitch that is constant when measured from at least one given thread
feature but whose
width can vary from a first value proximate the leading end over at least a
portion of the axial
length of the plurality of helical turns thereof to a final value at a desired
point on the at least
one thread thereby selectively enabling an axial progressive fit. In one
aspect, the thread
width can increase uniformly from the first value over at least the first turn
to a final value
over at least the final turn of the plurality of helical turns. In an
alternative aspect, the thread
width can increase non-uniformly from the first value to a final value over
the full axial
length of the plurality of helical turns. In a further aspect, the thread
pitch can increase from
the first value to a final value across a portion of the axial length of the
plurality of helical
turns and can remain constant thereafter. In other aspects, the thread load
flank can be held at
a constant pitch while the lead flank increases. In alternative aspects, the
thread lead flank
can be held at a constant pitch while the pitch of the load flank increases.
In yet other
aspects, the mid-point of the thread can have a constant pitch while both
flanks have a
varying pitch. In even further aspects, the varying pitch of the load flank
can be different
from the varying pitch of the lead flank.
[0074] In yet another aspect, the at least one thread can have a width that
varies from
about 50% of full thread width proximate the leading end and increases to full
thread width
proximate the trailing end of the thread. In a further aspect, the at least
one thread can have a
width that varies from about 75% of full thread width proximate the leading
end and
19
CA 02884798 2015-03-11
=
increases to full thread width proximate the trailing end of the thread. In
other aspects, the
thread can have a varying width over at least one turn and, preferably, two
turns of the thread.
In alternative aspect, the thread can have a width that varies from the
leading end to the
trailing end of the thread. In one exemplary embodiment, a 2 tpi thread having
a full width of
1/4" proximate the trailing end can have a reduced width of about 1/8" at the
leading end. As
one skilled in the art will appreciate, the spacing between the adjacent turns
of the at least one
thread is largest at the leading end and provides additional axial clearance
when starting
threads.
[00751 In yet another aspect, material typically lost to overall joint and
thread taper is
conserved by providing drill string components having at least one thread
comprising a root
that circumscribes a cylindrical surface extending over the full axial length
of the plurality of
helical turns of the thread and a crest that circumscribes a frusta-conical
surface extending
over at least a portion of the axial length of the plurality of helical turns
thereof, thereby
selectively enabling a radial progressive fit. The generatrix of the frusta-
conical surface is a
straight line having an angle relative to the central axis of the hollow body.
In one aspect, the
crest circumscribes a frusta-conical surface over the full axial length of the
plurality of helical
turns. In another aspect, the at least one thread can have a frusta-conical
crest over at least a
portion of the axial length of the at least one thread with the generatrix of
the frusta-cone
having an angle of about 0.75 to 1.6 degrees while the at least one thread can
have cylindrical
roots. In another aspect, the crest circumscribes a frusta-conical surface
extending the axial
length of at least one turn of the thread and, preferably at least two turns
of the thread. In
alternative aspects, the axial length can be substantially the full axial
length of the thread.
[00761 In yet another aspect, material typically lost to overall joint and
thread taper is
conserved by providing drill string components having both at least one thread
comprising a
thread pitch that varies from a first value proximate the leading end over at
least a portion of
the axial length of the plurality of helical turns thereof to a final value at
a desired point on
the at least one thread, and further comprising a thread root that
circumscribes a cylindrical
surface extending over the full axial length of the plurality of helical turns
and a thread crest
that circumscribes a frusta-conical surface extending over at least a portion
of the axial length
of the plurality of helical turns thereof thereby selectively enabling both an
axial progressive
fit and a radial progressive fit.
[0077] In one example, at least one male thread 110 can begin proximate to
a leading
edge 140 of pin end 104. The at least one male thread 110 can comprise a
plurality of helical
CA 02884798 2015-03-11
turns extending along the respective length of pin end 104. In a further
aspect, the at least
one male thread can have a pitch that increases from a first value proximate
the leading edge
140 over at least a portion of the axial length of the plurality of helical
turns thereof to a final
value at a desired point on the at least one male thread 110 and be held
constant thereafter. In
another aspect, the at least one male thread can have a pitch that increases
from a first value
proximate the leading edge over the entire portion of the axial length of the
plurality of
helical turns thereof to a final value. In alternative aspects, the pitch can
increase uniformly
or non-uniformly across the axial length of the at least one male thread 110.
For example, it
is contemplated that a pin end has two male threads having a pitch that
increases from the
leading edge of pin end 104 to a final value at a desired point along the
axial length of the
thread, such point being measured from the pin end 104.
[0078] Similarly, at least one female thread 112 can begin proximate to a
leading edge
120 of box end 108. The at least one female thread 112 can comprise a
plurality of helical
turns extending along the respective length of box end 108. In a fluffier
aspect, the at least
one female thread can have a pitch that increases from a first value proximate
the leading
edge 120 over at least a portion of the axial length of the plurality of
helical turns thereof to a
final value at a desired point on the at least one female thread 112 and be
held constant
thereafter. In another aspect, the at least one female thread can have a pitch
that increases
from a first value proximate the leading edge 120 over the entire portion of
the axial length of
the plurality of helical turns thereof to a final value. In alternative
aspects, the pitch can
increase uniformly or non-uniformly across the axial length of the at least
one female thread
112. For example, it is contemplated that a pin end has two female threads
having a pitch
that increases from the leading edge 120 of box end 108 to a final value at a
desired point
along the axial length of the thread, such point being measured from the box
end 108.
[0079] More particularly, at least one male thread 110 and at least one
female thread 112
can be helically disposed relative to the respective pin and box ends 104,
108. In other
words, the at least one male thread 110 and the at least one female thread 112
can comprise a
plurality of helical turns extending along the respective drill string
component 102, 106. The
at least one male thread 110 and the at least one female thread 112 can each
comprise leading
ends oriented at an acute angle relative to and spaced about the central axis
of the respective
drill string component 102, 106. As the at least one male thread 110 and the
at least one
female thread 112 mate, the threads may therefore rotate relative to each
other and fit within
gaps between corresponding threads and eventually form a drill string joint. A
progressive fit
21
CA 02884798 2015-03-11
in the axial direction is selectively created between the respective pin and
box ends 104, 108
as the pitch of at least one of the at least one male thread 110 and the at
least one female
thread 112 increases. Accordingly, in one or more embodiments, a drill string
joint is formed
having optimal material cross sections for maximum load capacity.
[0080] In another example, at least one male thread 110 can begin proximate
to a leading
edge of pin end 104. The at least one male thread 110 can comprise a plurality
of helical
turns extending along the respective length of pin end 104 and can also have
at least one
thread feature with a constant pitch across the axial length of the thread.
Exemplary thread
features whose pitch can be held constant can include the load flank, the
leading flank, the
thread midpoint, and the like. In a further aspect, the at least one male
thread can have a
thread width that increases from a percentage of the full thread width
proximate the leading
edge over at least a portion of the axial length of the plurality of helical
turns thereof to the
full thread width at a desired point on the at least one male thread 110 and
be held constant
thereafter. In another aspect, the at least one male thread can have a thread
width that
increases from a percentage of the full thread width proximate the leading
edge over the
entire portion of the axial length of the plurality of helical turns thereof
to the full thread
width. In alternative aspects, the thread width can increase uniformly or non-
uniformly
across the axial length of the at least one male thread 110. For example, it
is contemplated
that a pin end has two male threads where at least one male thread has at
least one feature
having a constant pitch across the entire axial length of that thread and a
width that increases
from a percentage of full thread width at the leading edge of pin end 104 to
the full thread
width at a desired point along the axial length of the thread.
[0081] Similarly, at least one female thread 112 can begin proximate to a
leading edge
142 of box end 108. The at least one female thread 112 can comprise a
plurality of helical
turns extending along the respective length of box end 108 and can also have
at least one
thread feature with a constant pitch across the axial length of the thread.
Exemplary thread
features whose pitch can be held constant can include the load flank, the
leading flank, the
thread midpoint, and the like. In a further aspect, the at least one female
thread can have a
thread width that increases from a percentage of the full thread width
proximate the leading
edge 142 over at least a portion of the axial length of the plurality of
helical turns thereof to
the full thread width at a desired point on the at least one female thread 112
and be held
constant thereafter. In another aspect, the at least one female thread can
have a thread width
that increases from a percentage of the full thread width proximate the
leading edge 142 over
22
CA 02884798 2015-03-11
the entire portion of the axial length of the plurality of helical turns
thereof to the full thread
width. In alternative aspects, the thread width can increase uniformly or non-
uniformly
across the axial length of the at least one female thread 112. For example, it
is contemplated
that a box end has two female threads where at least one female thread has at
least one feature
having a constant pitch across the entire axial length of that thread and a
width that increases
from a percentage of full thread width at the leading edge 142 of box end 108
to the full
thread width at a desired point along the axial length of the thread.
[00821 More particularly, at least one male thread 110 and at least one
female thread 112
can be helically disposed relative to the respective pin and box ends 104,
108. In other
words, the at least one male thread 110 and the at least one female thread 112
can comprise a
plurality of helical turns extending along the respective drill string
component 102, 106. The
at least one male thread 110 and the at least one female thread 112 can each
comprise leading
ends oriented at an acute angle relative to and spaced about the central axis
of the respective
drill string component 102, 106. As the at least one male thread 110 and the
at least one
female thread 112 mate, the threads may therefore rotate relative to each
other and fit within
gaps between corresponding threads and eventually form a drill string joint. A
progressive fit
in the axial direction is selectively created between the respective pin and
box ends 104, 108
as the width of at least one of the at least one male thread 110 and the at
least one female
thread 112 increases while at least one feature of both the at least one male
thread 110 and the
at least one female thread 112 has a constant pitch across the axial length of
the respective
thread. Accordingly, in one or more embodiments, a drill string joint is
formed having
optimal material cross sections for maximum load capacity.
[0083] In another example, at least one male thread 110 can begin proximate
to a leading
edge of pin end 104. The at least one male thread 110 can comprise a plurality
of helical
turns extending along the respective length of pin end 104. In one aspect, the
at least one
male thread 110 can have a thread root that circumscribes a cylindrical
surface over the entire
axial length of the plurality of helical turns. In a further aspect, the at
least one male thread
110 can have a thread crest that circumscribes a frusta-conical surface from a
first diameter
proximate the leading edge extending over at least a portion of the axial
length of the
plurality of helical turns thereof to a final diameter at a desired point on
the at least one male
thread 110 and be held constant thereafter. The generatrix of the frusta-
conical surface is a
straight line passing through the thread crests that lies at an angle relative
to the central axis
extending through the hollow body. In another aspect, the at least one male
thread 110 can
23
CA 02884798 2015-03-11
have a thread crest that circumscribes a frusta-conical surface from a first
diameter proximate
the leading edge extending over the full axial length of the plurality of
helical turns thereof to
a final diameter. For example, it is contemplated that a pin end has at least
one male thread
having a thread crest that circumscribes a cylinder and a thread crest that
circumscribes a
frusta-conical surface from a first diameter proximate the leading edge
extending over at
desired portion of the axial length of the plurality of helical turns thereof
to a final diameter at
a desired point on the at least one male thread 110 and held constant
thereafter.
[0084] Similarly, at least one female thread 112 can begin proximate to a
leading edge
120 of box end 108. The at least one female thread 112 can comprise a
plurality of helical
turns extending along the respective length of box end 108. In one aspect, the
at least one
female thread 112 can have a thread root that circumscribes a cylindrical
surface over the
entire axial length of the plurality of helical turns. In a further aspect,
the at least one female
thread 112 can have a thread crest that circumscribes a frusta-conical surface
from a first
diameter proximate the leading edge 120 extending over at least a portion of
the axial length
of the plurality of helical turns thereof to a final diameter at a desired
point on the at least one
female thread 112 and be held constant thereafter. The generatrix of the
frusta-conical
surface is a straight line passing through the thread crests that lies at an
angle relative to the
central axis extending through the hollow body. In another aspect, the at
least one female
thread 112 can have a thread crest that circumscribes a frusta-conical surface
from a first
diameter proximate the leading edge 120 extending over the full axial length
of the plurality
of helical turns thereof to a final diameter. For example, it is contemplated
that a box end
108 has at least one female thread 112 having a thread crest that
circumscribes a cylinder and
a thread crest that circumscribes a frusta-conical surface from a first
diameter proximate the
leading edge 120 extending over at desired portion of the axial length of the
plurality of
helical turns thereof to a final diameter at a desired point on the at least
one female thread 112
and held constant thereafter.
[00851 More particularly, at least one male thread 110 and at least one
female thread 112
can be helically disposed relative to the respective pin and box ends 104,
108. In other
words, the at least one male thread 110 and the at least one female thread 112
can comprise a
plurality of helical turns extending along the respective drill string
component 102, 106. The
at least one male thread 110 and the at least one female thread 112 can each
comprise leading
ends oriented at an acute angle relative to the central axis of the respective
drill string
component 102, 106. In one aspect, both the at least one male thread 110 and
the at least one
24
CA 02884798 2015-03-11
female thread 112 can have a thread root that circumscribes a cylindrical
surface over the
entire axial length of the plurality of helical turns. In a further aspect, at
least one of the at
least one male thread 110 and the at least one female thread 112 can have a
thread crest that
circumscribes a frusta-conical surface from a first diameter proximate the
leading edge
extending over at least a portion of the axial length of the plurality of
helical turns thereof to a
final diameter at a desired point on the at least one female thread 112 and be
held constant
thereafter. As the at least one male thread 110 and the at least one female
thread 112 mate,
the threads may therefore rotate relative to each other and fit within gaps
between
corresponding threads and eventually form a drill string joint. A progressive
fit in the radial
direction is selectively created between the respective pin and box ends 104,
108 as the crest
diameter of at least one of the at least one male thread 110 and the at least
one female thread
112 increases. Accordingly, in one or more embodiments, a drill string joint
is formed
having optimal material cross sections for maximum load capacity.
[0086] In another example, at least one male thread 110 can begin proximate
to a leading
edge of pin end 104. The at least one male thread 110 can comprise a plurality
of helical
turns extending along the respective length of pin end 104. In one aspect, the
at least one
male thread can have at least one of a pitch and a width that increases from a
first value
proximate the leading edge over at least a portion of the axial length of the
plurality of helical
turns thereof to a final value at a desired point on the at least one male
thread 110 and be held
constant thereafter. In a further aspect, the at least one male thread 110 can
have a thread
root that circumscribes a cylindrical surface over the entire axial length of
the plurality of
helical turns. In yet a further aspect, the at least one male thread 110 can
have a thread crest
that circumscribes a frusta-conical surface from a first diameter proximate
the leading edge
extending over at least a portion of the axial length of the plurality of
helical turns thereof to a
final diameter at a desired point on the at least one male thread 110 and be
held constant
thereafter. The generatrix of the frusta-conical surface is a straight line
passing through the
thread crests that lies at an angle relative to the central axis extending
through the hollow
body. In another aspect, the at least one male thread 110 can have a thread
crest that
circumscribes a frusta-conical surface from a first diameter proximate the
leading edge
extending over the full axial length of the plurality of helical turns thereof
to a final diameter.
For example, it is contemplated that a pin end has at least one male thread
having a thread
crest that circumscribes a cylinder and a thread crest that circumscribes a
frusta-conical
surface from a first diameter proximate the leading edge extending over at
desired portion of
the axial length of the plurality of helical turns thereof to a final diameter
at a desired point on
CA 02884798 2015-03-11
the at least one male thread 110 and held constant thereafter. The at least
one male thread
110 also has at least one of a pitch and a width that increases from the
leading edge of pin end
104 to a final value at a desired point along the axial length of the thread,
such point being
measured from the pin end 104.
[00871 Similarly, at least one female thread 112 can begin proximate to a
leading edge
120 of box end 108. The at least one female thread 112 can comprise a
plurality of helical
turns extending along the respective length of box end 108. In one aspect, the
at least one
male thread can have at least one of a pitch and a width that increases from a
first value
proximate the leading edge 120 over at least a portion of the axial length of
the plurality of
helical turns thereof to a final value at a desired point on the at least one
female thread 112
and be held constant thereafter. In a further aspect, the at least one female
thread 112 can
have a thread root that circumscribes a cylindrical surface over the entire
axial length of the
plurality of helical turns. In yet a further aspect, the at least one female
thread 112 can have a
thread crest that circumscribes a frusta-conical surface from a first diameter
proximate the
leading edge 120 extending over at least a portion of the axial length of the
plurality of
helical turns thereof to a final diameter at a desired point on the at least
one female thread 112
and be held constant thereafter. The generatrix of the frusta-conical surface
is a straight line
passing through the thread crests that lies at an angle relative to the
central axis extending
through the hollow body. In another aspect, the at least one female thread 112
can have a
thread crest that circumscribes a frusta-conical surface from a first diameter
proximate the
leading edge 120 extending over the full axial length of the plurality of
helical turns thereof
to a final diameter. For example, it is contemplated that a box end 108 has at
least one
female thread 112 having a thread crest that circumscribes a cylinder and a
thread crest that
circumscribes a frusta-conical surface from a first diameter proximate the
leading edge 120
extending over at desired portion of the axial length of the plurality of
helical turns thereof to
a final diameter at a desired point on the at least one female thread 112 and
held constant
thereafter. The at least one female thread 112 also has at least one of a
pitch and a width that
increases from the leading edge 120 of box end 108 to a final value at a
desired point along
the axial length of the thread, such point being measured from the box end
108.
[0088] More particularly, at least one male thread 110 and at least one
female thread 112
can be helically disposed relative to the respective pin and box ends 104,
108. In other
words, the at least one male thread 110 and the at least one female thread 112
can comprise a
plurality of helical turns extending along the respective drill string
component 102, 106. The
26
CA 02884798 2015-03-11
at least one male thread 110 and the at least one female thread 112 can each
comprise leading
ends oriented at an acute angle relative to the central axis of the respective
drill string
component 102, 106. In one aspect, both the at least one male thread 110 and
the at least one
female thread 112 can have a thread root that circumscribes a cylindrical
surface over the
entire axial length of the plurality of helical turns. In a further aspect, at
least one of the at
least one male thread 110 and the at least one female thread 112 can have a
thread crest that
circumscribes a frusta-conical surface from a first diameter proximate the
respective edge
114, 120 extending over at least a portion of the axial length of the
plurality of helical turns
thereof to a final diameter at a desired point on the respective at least one
thread and be held
constant thereafter. As the at least one male thread 110 and the at least one
female thread 112
mate, the threads may therefore rotate relative to each other and fit within
gaps between
corresponding threads and eventually form a drill string joint. A progressive
fit in the radial
direction is selectively created between the respective pin and box ends 104,
108 as the crest
diameter of at least one of the at least one male thread 110 and the at least
one female thread
112 increases. Also, a progressive fit in the axial direction is selectively
created between the
respective pin and box ends 104, 108. As at least one of the pitch and the
width of at least one
of the at least one male thread 110 and the at least one female thread 112
increases.
Accordingly, in one or more embodiments, a drill string joint is formed having
optimal
material cross sections for maximum load capacity.
Anti-Jamming Thread Starts
[00891 One or more implementations of the present invention comprise drill
string
components having threads whose respective leading ends are oriented at an
acute angle
relative to the central axis of the drill string component and, additionally
or alternatively, the
leading end of the thread can provide an abrupt transition to the full thread
depth and/or
width.
[00901 The male thread 110 can comprise a thread width 118 and the female
thread 112
can comprise a thread width 124 as previously mentioned. As used herein the
term "thread
width" can comprise the linear distance between edges of a thread crest as
measured along a
line normal to the edges of the thread crest. One will appreciate that the
thread widths 118,
124 can vary depending upon the configuration of the threads 110, 112. In one
or more
implementations, the thread width 118 of the male thread 110 is equal to the
thread width 124
of the female thread 112. In alternative implementations, the thread width 118
of the male
thread 110 is larger or smaller than the thread width 124 of the female thread
112.
27
CA 02884798 2015-03-11
[0091] The male thread 110 can comprise a thread depth 130 and the female
thread 112
can comprise a thread depth 132. As used herein the term "thread depth" can
comprise the
linear distance from the surface from which the thread extends (i.e., the
outer surface of the
pin end 104 or inner surface of the box end 108) to most radially distal point
on the thread
crest as measured along a line normal to the surface from which the thread
extends. One will
appreciate that the thread depths 130, 132 can vary depending upon the
configuration of the
threads 110, 112 and/or the size of the drill string components 102, 106. In
one or more
implementations, the thread depth 130 of the male thread 110 is equal to the
thread depth 132
of the female thread 112. In alternative implementations, the thread depth 130
of the male
thread 110 is larger or smaller than the thread depth 132 of the female thread
112.
[0092] In one or more implementations, the thread width 118, 124 of each
thread 110,
112 is greater than the thread depth 130, 132 of each thread 110, 112. For
example, in one or
more implementations, the thread width 118, 124 of each thread 110, 112 is at
least two times
the thread depth 130, 132 of each thread 110, 112. In alternative
implementations, the thread
width 118, 124 of each thread 110, 112 is approximately equal to or less than
the thread depth
130, 132 of each thread 110, 112.
[0093] As alluded to above, both the male and female threads 110, 112 can
comprise a
leading end or thread start. For example, Figures 1-4 illustrate that the male
thread 110 can
comprise a thread start or leading end 114. Similarly, the female thread 112
can comprise a
thread start or leading end 120.
[0094] In one or more implementations, the leading end 114 of the male
thread 110 can
comprise a planar surface that extends from the outer surface of the pin end
104. For
example, the leading end 114 of the male thread 110 can comprise a planar
surface that
extends radially outward from the outer surface of the pin end 104, thereby
forming a face
surface. In one or more implementations the leading end 114 extends in a
direction normal to
the outer surface of the pin end 104. In alternative implementations, the
leading end 114
extends in a direction substantially normal to the outer surface of the pin
end 104 (i.e., in a
direction oriented at an angle less than about 15 degrees to a direction
normal to the outer
surface of the pin end 104). In still further implementations, the leading end
114 can
comprise a surface that curves along one or more of its height or width.
[0095] Furthermore, in one or more implementations the leading end 114 of
the male
thread 110 can ex-tend the full thread width 118 of the male thread 110. In
other words, the
leading end 114 of the male thread 110 can extend from a leading edge to a
trailing edge 138
28
CA 02884798 2015-03-11
of the male thread 110. Thus, the planar surface forming the leading end 114
can span the
entire thread width 118 of the male thread 110.
[0096] Additionally, in one or more implementations the leading end 114 of
the male
thread 110 can extend the full thread depth 130 of the male thread 110. In
other words, a
height of the leading end 114 of the male thread 110 can be equal to the
thread depth 130.
Thus, the planar surface forming the leading end 114 can span the entire
thread depth 130 of
the male thread 110. As such, the leading end 114 or thread start can comprise
an abrupt
transition to the full depth and/or width of the male thread 110. In other
words, in one or
more implementations, the male thread 110 does not comprise a tail end that
tapers gradually
to the full depth of the male thread 110.
[0097] Along similar lines, the leading end 120 of the female thread 112
can comprise a
planar surface that extends from the inner surface of the box end 108. For
example, the
leading end 120 of the female thread 112 can comprise a planar surface that
extends radially
inward from the inner surface of the box end 108, thereby forming a face
surface. In one or
more implementations the leading end 120 extends in a direction normal to the
inner and/or
outer surface of the box end 108. In alternative implementations, the leading
end 120 extends
in a direction substantially normal to the inner or outer surface of the box
end 108 (i.e., in a
direction oriented at an angle less than about 15 degrees to a direction
normal to the inner
and/or outer surface of the box end 108). In still further implementations,
the leading end 120
can comprise a surface that curves along one or more of its height or width.
For example, the
leading end 114 and the leading end 120 can comprise cooperating curved
surfaces.
[0098] Furthermore, in one or more implementations the leading end 120 of
the female
thread 112 can extend the full thread width 124 of the female thread 112. In
other words, the
leading end 120 of the female thread 112 can extend from a leading edge 144 to
a trailing
edge 144 of the female thread 112. Thus, the planar surface forming the
leading end 120 can
span the entire thread width 124 of the female thread 112.
[0099] Additionally, in one or more implementations the leading end 120 of
the female
thread 112 can extend the full thread depth 132 of the female thread 112. In
other words, a
height of the leading end 120 of the female thread 112 can be equal to the
thread depth 132.
Thus, the planar surface forming the leading end 120 can span the entire
thread depth 132 of
the female thread 112. As such, the leading end 120 or thread start can
comprise an abrupt
transition to the full depth and/or width of the female thread 112. In other
words, in one or
more implementations, the female thread 112 does not comprise a tail end that
tapers
29
CA 02884798 2015-03-11
gradually to the full depth of the female thread 112. In the illustrated
implementation, the
leading end or thread start 120 of the female thread 112 is illustrated as
being formed by
material that remains after machining or another process used to form the
threads. Thus, the
leading end or thread start 120 may be, relative to the interior surface of
the box end 108,
embossed rather than recessed.
[001001 In one or more implementations, the leading end 114 of the male thread
110 can
have a size and/or shape equal to the leading end 120 of the female thread
112. In alternative
implementations, the size and/or shape of the leading end 114 of the male
thread 110 can
differ from the size and/or shape of the leading end 120 of the female thread
112. For
example, in one or more implementations the leading end 114 of the male thread
110 can be
larger than the leading end 120 of the female thread 112.
[001011 In one or more implementations, the leading ends 114, 120 of the male
and female
threads 110, 112 can each have an off-axis orientation. In other words, the
planar surfaces of
the leading ends 114, 120 of the male and female threads 110, 112 can each
extend in a
direction offset or non-parallel to a central axis 126 of the drill string
components 102, 106.
For example, as illustrated by Figures 1-4, the planar surface of the leading
end 114 of the
male thread 110 can face an adjacent turn of the male thread 110. Similarly,
planar surface of
the leading end 120 of the female thread 112 can face an adjacent turn of the
female thread
112.
[00102] More particularly, the planar surface of the leading end 114 of the
male thread 110
can extend at an angle relative to the leading edge 140 or the central axis
126 of the pin end
104. For instance, in Figures 1-4, the planar surface of the leading end 114
of the male thread
110 is oriented at an angle 146 relative to the central axis 126 of the drill
string component
102, although the angle may also be measured relative to the leading edge 114.
The
illustrated orientation and existence of a planar surface of the leading end
114 is particularly
noticeable when compared to traditional threads, which taper to a point such
that there is
virtually no distance between the leading and trailing edges of a thread,
thereby providing no
face surface.
[00103] Similar to the leading end 114, the leading end 120 of the female
thread 112 can
extend at an angle relative to the leading edge 120 or the central axis 126 of
the pin end 104.
For instance, in Figures 1-4, the planar surface of the leading end 120 of the
female thread
112 is oriented at an angle 148 relative to the central axis 126 of the drill
string component
106, although the angle may also be measured relative to the leading edge 120.
CA 02884798 2015-03-11
[00104] The angles 146, 148 can be varied in accordance with the present
disclosure and
comprise any number of different angles. The angles 146, 148 may be varied
based on other
characteristics of the threads 110, 112, or based on a value that is
independent of thread
characteristics. In one or more implementations, angle 146 is equal to angle
148. In
alternative implementations, the angle 146 can differ from angle 148.
[00105] In one or more implementations the angles 146, 148 are each acute
angles. For
example, each of the angles 146, 148 can comprise an angle between about 10
degrees and 80
degrees, about 15 degrees and about 75 degrees, about 20 degrees and about 70
degrees,
about 30 degrees and about 60 degrees, about 40 degrees and about 50 degrees.
In further
implementations, the angles 146, 148 can comprise about 45 degrees. One will
appreciate in
light of the disclosure herein that upon impact between two mating leading
ends 114, 120 or
start faces with increasing angles 146, 148, there is decreasing loss of
momentum and
decreasing frictional resistance to drawing the threads 110, 112 into a fully
mating condition.
In any event, a leading end 114 of the male thread 110 can mate with the
leading end 120 of
the female thread 112 to aid in making a joint between the first drill string
component 102
and the second drill string component 106.
[00106] By eliminating the long tail of a thread start and replacing the tail
with a more
abrupt transition to the full height of the thread 110, 112, a leading ends
114, 120 or thread
start face can thus be provided. Moreover, while the leading ends 114, 120 may
be angled or
otherwise oriented with respect to an axis 126, the thread start face may also
be normal to the
major and/or minor diameters of cylindrical surfaces of the corresponding pin
and box ends
104, 108. Such geometry eliminates a tail-type thread start that can act as a
wedge, thereby
eliminating geometry that leads to wedging upon mating of the pin and box ends
104, 108.
[00107] Moreover, as the pin and box ends 104, 108 are drawn together, the
leading ends
114, 120 or thread starts may have corresponding surfaces that, when mated
together, create a
sliding interface in a near thread-coupled condition. For instance, where the
leading ends
114, 120 are each oriented at acute angles, the leading ends 114, 120 or
thread start faces may
engage each other and cooperatively draw threads into a fully thread-coupled
condition. By
way of example during make up of a drill rod assembly, as the pin end 104 is
fed into the box
end 108, the leading ends 114, 120 can engage and direct each other into
corresponding
recesses between threads. Such may occur during rotation and feed of one or
both of the drill
string components 102, 106. Furthermore, since thread start tails are
eliminated, there are
31
CA 02884798 2015-03-11
few¨if any¨limits on rotational positions for mating. Thus, the pin and box
ends 104, 108
can have the full circumference available for mating, with no jamming prone
positions.
[00108] In one or more implementations, a thread 110 may be formed with a tail
using
conventional machining processes. The tail may be least partially removed to
form the
leading end 114. In such implementations, a tail may extend around
approximately half the
circumference of a given pin end 104. Consequently, if the entire tail of the
thread 110 is
removed, the thread 110 may have a leading end 114 aligned with the axis 126.
If, however,
more of the thread 110 beyond just the tail is removed, leading end 114 may be
offset relative
to the axis 126. The tail may be removed by a separate machining process.
Although this
example illustrates the removal of a tail for formation of a thread start, in
other embodiments
a thread start face may be formed in the absence of creation and/or subsequent
removal of a
tail-type thread start. For example, instead of using conventional machining
processes, the
thread is formed using electrical discharge machining. Electrical discharge
machining can
allow for the formation of the leading end 114 since metal can be consumed
during the
process. Alternatively, electrochemical machining or other processes that
consume material
may also be used to form the leading ends 114, 120 of the threads 110, 112.
Optimal Interference Fit
[00109] One or more implementations of the present invention comprise
eliminating
interference fits on thread features and, optionally, relocating the
interference fit to other joint
features such as radially mating shoulder surfaces. In one aspect, male and
female threads
110, 112 can have relative depths such that the male thread crest maintains a
radially spaced
relationship with the mating female root while the female thread crest meets
the male thread
root. In another aspect, the male and female threads 110, 112 can have
relative depths such
that the female thread crest maintains a radially spaced relationship with the
mating male
thread root while the female thread crest meets the male thread root. In
another aspect, male
and female threads 110, 112 can have relative depths such that the male thread
crest
maintains a radially spaced relationship with the mating female root and the
female thread
crest maintains a radially spaced relationship with the mating male thread
root. In one aspect,
the radial spacing between mating thread crests and roots can be from about
.001 to about
.010 inches, more particularly from about .003 to about .007 inches and, most
preferably
about .005 inches. In an alternative aspect, the radial spacing between mating
thread crests
can be from about 1% to about 5%, more particularly from about 1.5% to about
3%, and most
particularly from about 2% to about 2.5% of the wall thickness of a hollow
body.
32
CA 02884798 2015-03-11
[001101 As previously mentioned, in one or more implementations the drill
string
components 102, 106 can comprise hollow bodies. More specifically, in one or
more
implementations the drill string components can be thin-walled. In particular,
as shown by
Figures 1-4, the drill string component 106 can comprise an outer diameter
150, an inner
diameter 152, and a wall thickness 154. The wall thickness 154 can equal one
half of the
outer diameter 150 minus the inner diameter 152. In one or more
implementations, the drill
string component 106 has a wall thickness 154 between about approximately 5
percent and
15 percent of the outer diameter 150. In further implementations, the drill
string component
106 has a wall thickness 154 between about approximately 6 percent and 8
percent of the
outer diameter 150. One will appreciate that such thin-walled drill string
components can
limit the geometry of the threads 112. However, a thin-walled drill string
component can
nonetheless comprise any combination of features discussed hereinabove despite
such
limitations.
[00111] Referring now to Figure 5, the drill string components 102, 106 can
comprise any
number of different types of tools. In other words, virtually any threaded
member used on a
drill string can comprise one or more of a box end 108 and a pin end 104
having leading ends
or thread starts as described in relation to Figures 1-4. For example, Figure
5 illustrates that
drill string components can comprise a locking coupling 201, an adaptor
coupling 202, a drill
rod 204, and a reamer 206 can each comprise both a pin end 104 and a box end
108 with
leading ends 114, 120 having increased load efficiency and load capacity, and
that can also
be resistant to wear, jamming and cross-threading as described above in
relation to Figures 1-
4. Figure 5 further illustrates that drill string components can comprise a
stabilizer 203, a
landing ring 205 and a drill bit 207 including a box end 108 with a leading
end 120 having
increased load efficiency and load capacity, and that can also be resistant to
wear, jamming
and cross-threading as described above in relation to Figures 1-4. In yet
further
implementations, the drill string components 102, 106 can comprise casings,
reamers, core
lifters, or other drill string components.
[00112] Referring now to Figure 6, a drilling system 300 may be used to
drill into a
formation 304. The drilling system 300 may comprise a drill string 302 formed
from a
plurality of drill rods 204 or other drill string components 201-207. The
drill rods 204 may
be rigid and/or metallic, or alternatively may be constructed from other
suitable materials.
The drill string 302 may comprise a series of connected drill rods that may be
assembled
section-by-section as the drill string 302 advances into the formation 304. A
drill bit 207 (for
33
CA 02884798 2015-03-11
example, an open-faced drill bit or other type of drill bit) may be secured to
the distal end of
the drill string 302. As used herein the terms "down," "lower," "leading," and
"distal end"
refer to the end of the drill string 302 including the drill bit 207. While
the terms "up,"
"upper," "trailing," or "proximal" refer to the end of the drill string 302
opposite the drill bit
207.
[00113] The drilling system 300 may comprise a drill rig 301 that may rotate
and/or push
the drill bit 207, the drill rods 204 and/or other portions of the drill
string 302 into the
formation 304. The drill rig 301 may comprise a driving mechanism, for
example, a rotary
drill head 306, a sled assembly 308, and a mast 310. The drill head 306 may be
coupled to
the drill string 302, and can rotate the drill bit 207, the drill rods 204
and/or other portions of
the drill string 302. If desired, the rotary drill head 306 may be configured
to vary the speed
and/or direction that it rotates these components. The sled assembly 308 can
move relative to
the mast 310. As the sled assembly 308 moves relative to the mast 310, the
sled assembly
308 may provide a force against the rotary drill head 306, which may push the
drill bit 207,
the drill rods 204 and/or other portions of the drill string 302 further into
the formation 304,
for example, while they are being rotated.
[00114] It will be appreciated, however, that the drill rig 301 does not
require a rotary drill
head, a sled assembly, a slide frame or a drive assembly and that the drill
rig 301 may
comprise other suitable components. It will also be appreciated that the
drilling system 300
does not require a drill rig and that the drilling system 300 may comprise
other suitable
components that may rotate and/or push the drill bit 207, the drill rods 204
and/or other
portions of the drill string 302 into the formation 304. For example, sonic,
percussive, or
down hole motors may be used.
[00115] As shown by Figure 6, the drilling system 300 can further comprise a
drill rod
drill rod clamping device 312. In 'Anther detail, the driving mechanism may
advance the drill
string 302 and particularly a first drill rod 204 until a trailing portion of
the first drill rod 204
is proximate an opening of a borehole fonned by the drill string 302. Once the
first drill rod
204 is at a desired depth, the drill rod clamping device 312 may grasp the
first drill rod 204,
which may help prevent inadvertent loss of the first drill rod 204 and the
drill string 302
down the borehole. With the drill rod clamping device 312 grasping the first
drill rod 204,
the driving mechanism may be disconnected from the first drill rod 204.
[00116] An additional or second drill rod 204 may then be connected to the
driving
mechanism manually or automatically using a drill rod handling device, such as
that
34
CA 02884798 2016-08-10
described in U.S. Patent No. 8,186,925, issued on May 29, 2012. Next driving
mechanism
can automatically advance the pin end 104 of the second drill rod 204 into the
box end 108
of the first drill rod 204. A joint between the first drill rod 204 and the
second drill rod 204
may be made by threading the second drill rod 204 into the first drill rod
204. One will
appreciate in light of the disclosure herein that the leading ends 114, 120 of
the male and
female threads 110, 112 of the drill rods 204 can prevent or reduce jamming
and cross-
threading even when the joint between the drill rods 204 is made automatically
by the drill
rig 301.
1001171 After the second drill rod 204 is connected to the driving mechanism
and the first
drill rod 204, the drill rod clamping device 312 may release the drill 302.
The driving
mechanism may advance the drill string 302 further into the formation to a
greater desired
depth. This process of grasping the drill string 302, disconnecting the
driving mechanism,
connecting an additional drill rod 204, releasing the grasp, and advancing the
drill string 302
to a greater depth may be repeatedly performed to drill deeper and deeper into
the formation.
1001181 Accordingly, Figures 1-Y, the corresponding text, provide a number of
different
components and mechanisms for making joints between drill string components
with
increased load efficiency and load capacity, and that can also be resistant to
wear, jamming
and cross-threading. In addition to the foregoing, implementations of the
present invention
can also be described in terms acts and steps in a method for accomplishing a
particular
result. For example, a method of a method of making a joint in a drill string
with increased
load efficiency and load capacity and with resistance to wear, jamming and
cross-threading is
described below with reference to the components and diagrams of Figures 1
through Y.
1001191 The method can involve inserting a pin end 104 of a first drill string
component
102 into a box end 108 of a second drill string component 106. The method can
also involve
rotating the first drill sting component 102 relative to the second drill
string component 108.
The method can further involve abutting a planar leading end 114 of a male
thread 110 on the
pin end 104 of the first drill string component 102 against a planar leading
end 120 of a
female thread 112 on the box end 108 of the second drill string component 106.
1001201 The planar leading end 114 of the male thread 110 can be oriented at
an acute
angle 146 relative to a central axis 26 of the first drill string component
102. Similarly, the
planar leading end 120 of the female thread 112 can be oriented at an acute
angle 148 relative
to a central axis 26 of the second drill string component 106.
CA 02884798 2015-03-11
[00121] The method can further involve sliding the planar leading end 114 of
the male
thread 110 against and along the planar leading end 120 of the female thread
112 to guide the
male thread 110 into a gap between turns of the female thread 112. Sliding the
planar leading
end 114 of the male thread 110 against and along the planar leading end 120 of
the female
thread 112 can cause the first drill string component 102 to rotate relative
to the second drill
string component 106 due to the acute angles 146, 148 of the planar leading
ends 114, 120 of
the male and female threads 110, 112. The method can involve automatically
rotating and
advancing the first drill sting component 102 relative to the second drill
string component
106 using a drill rig 301 without manually handling the drill string
components 106, 108.
[00122] The planar leading end 120 of the female thread 112 can extend along
an entire
depth 132 of the female thread 110. The planar leading end 114 of the male
thread 110 can
extend along an entire depth 130 of the male thread 110. When rotating the
first drill sting
component 102 relative to the second drill string component 108, the depths of
the planar
leading ends 114, 120 of the female thread 112 and the male thread 110 can
prevent jamming
or wedging of the male and female threads 110, 112.
[00123] Thus, implementations of the foregoing provide various desirable
features. For
instance, by including leading ends or start faces which are optionally the
full width of the
thread, the tail-type thread start can be eliminated, thereby allowing: (a)
substantially full
circumference rotational positioning for threading; and (b) a guiding surface
for placing
mating threads into a threading position. For instance, the angled start face
can engage a
corresponding thread or thread start face and direct the corresponding thread
into a threading
position between helical threads. Moreover, at any position of the
corresponding threads, the
tail has been eliminated to virtually eliminate wedging prone geometry.
[00124] Similar benefits may be obtained regardless of whether threading is
concentric or
off-center in nature. For instance, in an off-center arrangement, a line
intersecting a thread
crest and a thread start face may comprise a joint taper. Under feed, the
thread start face can
mate with the mating thread crest in a manner that reduces or eliminates
wedging as the
intersection and subsequent thread resist wedging, jamming, and cross-
threading. In such an
embodiment, a joint taper may be sufficient to reduce the major diameter at a
smaller end of a
male thread to be less than a minor diameter at a large end of a female
thread. Thus, off
center threading may be used for tapered threads.
[00125] Threads of the present disclosure may be formed in any number of
suitable
manners. For instance, as described previously, turning devices such as lathes
may have
36
CA 02884798 2016-08-10
difficultly creating an abrupt thread start face such as those disclosed
herein. Accordingly, in
some embodiments, a thread may be formed to comprise a tail. A subsequent
grinding,
milling, or other process may then be employed to remove a portion of the tail
and create a
thread start such as those described herein, or may be learned from a review
of the disclosure
herein. In other embodiments, other equipment may be utilized, including a
combination of
turning and other machining equipment. For instance, a lathe may produce a
portion of the
thread while other machinery can further process a male or female component to
add a thread
start face. In still other embodiments, molding, casting, single point
cutting, taps and dies,
die heads, milling, grinding, rolling, lapping, or other processes, or any
combination of the
foregoing, may be used to create a thread in accordance with the disclosure
herein.
1001261 The present invention can thus be embodied in other specific forms.
The described
embodiments are to be considered in all respects only as illustrative and not
restrictive. The
scope of the invention is, therefore, indicated by the appended claims rather
than by the
foregoing description. All changes that come within the meaning and range of
equivalency of
the claims are to be embraced within their scope.
37
