U.S. patent application number 14/803023 was filed with the patent office on 2016-10-13 for constant force centralizer.
This patent application is currently assigned to Probe Technology Services, Inc.. The applicant listed for this patent is Probe Technology Services, Inc.. Invention is credited to Nathan Church.
Application Number | 20160298396 14/803023 |
Document ID | / |
Family ID | 57073004 |
Filed Date | 2016-10-13 |
United States Patent
Application |
20160298396 |
Kind Code |
A1 |
Church; Nathan |
October 13, 2016 |
CONSTANT FORCE CENTRALIZER
Abstract
A constant force device has at least a first non-constant axial
force driving the first set of arms and a second non-constant axial
force driving the second set of arms, where the two sets of arms
are offset from one another by 90.degree.. Each of the non-constant
axial forces is converted to a radially extending force by the
interaction of a force guide and actuator. The force guide is
attached to the inner mandrel of the constant force device and is
shaped to produce an essentially constant radially extending force
through the entire range of motion of the arms. Typically each arm
of the pair of arms has a pivoting arm and a telescoping arm where
the joint between the pivoting arm and telescoping arm has one or
more wheels to reduce friction as the constant force device moves
through the tubular. Generally the first pair of arms is opposed to
and overlaps by some distance the second pair of arms where the
second pair of arms is 90.degree. offset from the first pair of
arms. Additional features may include friction reducing members at
the joint between the telescoping arm and the pivoting arm, an
extension lock, extension limiters, and rotating force guides.
Inventors: |
Church; Nathan; (Mansfield,
TX) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Probe Technology Services, Inc. |
Fort Worth |
TX |
US |
|
|
Assignee: |
Probe Technology Services,
Inc.
Fort Worth
TX
|
Family ID: |
57073004 |
Appl. No.: |
14/803023 |
Filed: |
July 17, 2015 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
62144657 |
Apr 8, 2015 |
|
|
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
E21B 17/1021 20130101;
E21B 17/1078 20130101 |
International
Class: |
E21B 17/10 20060101
E21B017/10 |
Claims
1. A constant force tool comprising, a pivoting force arm, an axial
biasing device, wherein the axial biasing device exerts an axially
directed force upon the pivoting force arm, a force guide mounted
on a mandrel, wherein the force guide interacts with the pivoting
force arm to convert the axially directed force to a radially
directed force.
2. The constant force tool of claim 1 further comprising a
telescoping arm wherein a first end of the telescoping arm is
pivotally attached to the pivoting force arm.
3. The constant force tool of claim 2 further comprising at least
one wheel mounted at the pivotal attachment between the pivoting
force arm and the telescoping arm.
4. The constant force tool of claim 1 wherein, the axial biasing
device is a spring.
5. The constant force tool of claim 1 wherein, the radially
directed force is substantially constant.
6. The constant force tool of claim 1 wherein, the radially
directed force is constant within about 10% of the maximum radially
directed force.
7. A constant force tool comprising, a pivoting force arm, an axial
biasing device, wherein the axial biasing device exerts an axially
directed force upon the pivoting force arm, a force guide rotatably
mounted on a mandrel, wherein the force guide interacts with the
pivoting force arm to convert the axially directed force to
radially a directed force.
8. The constant force tool of claim 7 further comprising a
telescoping arm wherein a first end of the telescoping arm is
pivotally attached to the pivoting force arm.
9. The constant force tool of claim 8 further comprising a wheel
mounted at the pivotal attachment between the pivoting force arm
and the telescoping arm.
10. The constant force tool of claim 7 wherein, the axial biasing
device is a spring.
11. The constant force tool of claim 7 wherein, the radially
directed force is substantially constant.
12. The constant force tool of claim 7 wherein, the radially
directed force is constant within about 10% of the maximum radially
directed force.
13. A constant force tool comprising, a pivoting force arm, an
axial biasing device, wherein the axial biasing device exerts an
axially directed force upon the pivoting force arm, further wherein
the axially directed force is converted to a radially a directed
force, and an extension limiter.
14. The constant force tool of claim 13 wherein, the extension
limiter prevents the pivoting force arms from extending past a
predetermined maximum.
15. The constant force tool of claim 13 further comprising a
telescoping arm wherein a first end of the telescoping arm is
pivotally attached to the pivoting force arm.
16. The constant force tool of claim 15 further comprising at least
one wheel mounted at the pivotal attachment between the pivoting
force arm and the telescoping arm.
17. The constant force tool of claim 13 wherein, the axial biasing
device is a spring.
18. The constant force tool of claim 13 wherein, the radially
directed force is substantially constant.
19. The constant force tool of claim 13 wherein, the radially
directed force is constant within about 10% of the maximum radially
directed force.
20. A constant force tool comprising, a pivoting force arm, an
axial biasing device, wherein the axial biasing device exerts an
axially directed force upon the pivoting force arm, further wherein
the axially directed force is converted to a radially a directed
force, and a pivoting force arm lock.
21. The pivoting force tool of claim 20 wherein, the pivoting force
arm lock prevents the pivoting force arms from extending prior to a
predetermined event.
22. The pivoting force arm tool of claim 21 wherein, the
predetermined event is exceeding a predetermined pressure
differential.
23. The constant force tool of claim 21 further comprising a
telescoping arm wherein a first end of the telescoping arm is
pivotally attached to the pivoting force arm.
24. The constant force tool of claim 23 further comprising a wheel
mounted at the pivotal attachment between the pivoting force arm
and the telescoping arm.
25. The constant force tool of claim 21 wherein, the axial biasing
device is a spring.
26. The constant force tool of claim 21 wherein, the radially
directed force is substantially constant.
27. The constant force tool of claim 1 wherein, the radially
directed force is constant within about 10% of the maximum radially
directed force.
28. A constant force tool comprising, a first pivoting force arm, a
second pivoting force arm, wherein a first end of the first
pivoting force arm and a first end of the second pivoting force arm
extend toward each other from a first end of a mandrel and from an
opposing second end of the mandrel, further wherein the first
pivoting force arm is circumferentially offset from the second
pivoting force arm, a first axial biasing device that exerts a
first axially directed force upon the first pivoting force arm, a
second axial biasing device that exerts a second axially directed
force upon the second pivoting force arm, a first force guide
mounted on the mandrel, wherein the first force guide interacts
with the first pivoting force arm to convert the first axially
directed force to a substantially constant first radially directed
force, and a second force guide mounted on the mandrel, wherein the
second force guide interacts with the second pivoting force arm to
convert the second axially directed force to a substantially
constant second radially directed force.
29. The constant force tool of claim 28 further comprising a
telescoping arm wherein a first end of the telescoping arm is
pivotally attached to the first pivoting force arm.
30. The constant force tool of claim 29 further comprising a wheel
mounted at the pivotal attachment between the first pivoting force
arm and the telescoping arm.
31. The constant force tool of claim 28 wherein, the axial biasing
device is a spring.
32. The constant force tool of claim 28 wherein, the substantially
constant first radially directed force is constant within about 10%
of the maximum first radially directed force.
33. The constant force tool of claim 28 wherein, the substantially
constant second radially directed force is constant within about
10% of the maximum second radially directed force.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims priority to U.S. Provisional Patent
Application No. 62/144,657 that was filed on Apr. 8, 2015.
FIELD OF INVENTION
[0002] The present invention relates to a device that may apply a
vectored force radially outward from a central axis. Such vectored
force may be applied in multiple directions at once where the
application of the vectored force is to maintain the central axis
of the device relatively aligned with the central axis of the
tubular through which the device passes.
BACKGROUND
[0003] Once a hydrocarbon bearing well has been drilled it is
usually necessary to perform several tests upon the well, for
instance to determine the integrity of the casing after it has been
installed, to determine for instance the quality of the cementing
job, or to determine the presence and locations of any hydrocarbons
adjacent to the well. Such testing is usually done with a set of
instruments referred to as a logging tool. In most instances the
logging tool is lowered into the well on a cable, where the cable
may include a power and/or data line. Logging tools may be
transported through any tubular structure including pipelines and
refineries.
[0004] Certain types of logging tools work best when they are
centrally positioned within the tubular structure being tested. In
order to centrally position the logging tool within the tubular, a
centralizer may be used. Centralizers typically use a set of
springs, such as bow springs, to apply force radially outward from
a central axis. Provided that the force is applied equally in all
directions and that there is sufficient force to overcome any bias
due to the weight of the logging tool, the logging tool will remain
more or less centralized within the wellbore, whether open hole or
cased hole. Unfortunately the diameter of the wellbore varies as
the tool progresses through the wellbore. Variations in diameter
may be due to other tools or equipment located in the wellbore or
to different sizes of casing installed as the well progresses from
the surface to the well's final depth. Other variations in the well
diameter may be due to changes in the well's direction causing the
casing to become ovalized as the tubular bends through turns.
Unfortunately the force applied to different sizes of tubulars by a
standard centralizer varies such that a centralizer may have
sufficient force to keep a logging tool centralized in one size of
tubular, but when the logging tool is in a smaller diameter tubular
such force is excessive, causing damage to the centralizer or even
preventing the centralizer from progressing through the well. On
the other hand while the force applied may be sufficient to keep a
logging tool centralized in one size of tubular, in a larger
diameter tubular such force is inadequate allowing the logging tool
to substantially deviate from the center of the tubular.
[0005] In order to address such concerns many variations of
constant force centralizers have been developed. There are several
constant force centralizers available in the market, but there is
very little information showing quantitative force values vs.
casing size. Ideally, each constant force centralizer would have a
force chart similar to the force chart shown in FIG. 1.
[0006] Though customers seem to have a clear need for a constant
force centralizer, such requests do not appear to include a
definition of "constant." The understanding is that clients just
need a device that keeps their tools centralized in a wide range of
environments.
SUMMARY
[0007] A constant force centralizer is envisioned where a first
non-constant axial force drives the first set of arm assemblies and
at least a second non-constant axial force drives the second set
arm assemblies where the two sets of arm assemblies are offset from
one another by 90.degree.. Typically the non-constant axial forces
are provided by some type of biasing device usually a spring or
compressed gas but other types of biasing devices may be used. A
force guide may be permanently affixed, rotatably attached, or
otherwise mounted on the central mandrel of the constant force
centralizer. Each of the non-constant axial forces is converted to
a radially extending force by an interaction of a three guide and
actuator. The force guide is shaped to produce an essentially
constant radially extending force through the entire range of
motion of the arm assemblies. Preferably the radially extending
force is maintained throughout each arm assembly's travel within
about ten percent of the maximum radially extending force.
Typically, each arm assembly is comprised of a pivoting arm and
telescopic section. Typically a wheel is positioned at the joint of
the pivoting arm and the telescopic section to reduce friction as
the constant force centralizer moves through the tubular. In the
collapsed condition where the pivoting arm and wheel are relatively
close to the mandrel of the constant force centralizer the
telescoping arm is in its substantially shortest state whereas in
the extended condition where the pivoting arm and wheel are at
their maximum distance from the mandrel the telescoping arm is in
its longest state. The telescoping arm is generally necessary in
order to allow the constant force centralizer to reverse direction
when moving from a larger diameter tubular to a smaller diameter
tubular. A portion of the telescoping arm will interact with the
tubular to force the pivoting arm and wheel to retract to at least
a semi-collapsed condition. By utilizing a telescoping arm in place
of a solid arm, the overall length of the constant force
centralizer is shorter than would otherwise be possible, and this
is considered beneficial for many logging tool embodiments.
[0008] It is envisioned that two pairs of arm assemblies will
usually be used in a constant force centralizer. The pairs of arm
assemblies are typically arranged such that a first end of the
first pair and a first end of the second pair of arm assemblies
extend toward each other from a first end of a mandrel and from an
opposing second end of the mandrel. Generally the first pair of arm
assemblies is allowed to collapse into a nested position with the
second pair of arm assemblies. When fully collapsed, opposing pairs
of pivoting arms overlap by some distance. The overlap and
telescoping arms generally allows the tool to be shorter than a
standard tool not having overlapping arms.
[0009] Ovalized casing is encountered occasionally, and
centralization in such conditions can be difficult. Constant force
centralizers offered to date have linked arms providing lateral arm
movement that is symmetric in all directions. In round casing and
in vertical wells, this arrangement is adequate. However, in
deviated wells where the casing is ovalized, these centralizers may
not perform well. In a current embodiment typically the arms that
are offset from one another at some angle, typically 90.degree.,
allow for the offset arms to provide non-symmetric arm movement in
at least two directions providing centralization even in
non-symmetric or ovalized wellbores or tubulars. In certain
situations it has been found that non-symmetric constant force is
necessary such that the tool is held in an eccentric condition
within the well.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] So that the manner in which the above recited features of
the present invention can be understood in detail, a more
particular description of the invention, briefly summarized above,
may be had by reference to embodiments, some of which are
illustrated in the appended drawings. It is to be noted, however,
that the appended drawings illustrate only typical embodiments of
this invention and are therefore not to be considered limiting of
its scope, for the invention may admit to other equally effective
embodiments.
[0011] FIG. 1 depicts a calculated and measured force curve of an
embodiment of the invention.
[0012] FIG. 2 depicts a calculated force curve of an alternate
embodiment of the invention.
[0013] FIG. 3 depicts a side view of an embodiment of the invention
in its extended condition.
[0014] FIG. 4 depicts an end view of an embodiment of the
invention.
[0015] FIG. 5 depicts a side view of an embodiment of the invention
in its retracted condition.
[0016] FIG. 6 depicts an end view of an embodiment of the invention
in a partially extended condition in an oval tubular.
[0017] FIG. 7 depicts an extended joint of an embodiment of the
invention.
[0018] FIG. 8 depicts a side view of an alternate embodiment of the
invention in its extended condition.
[0019] FIG. 9 depicts a side view of an alternate embodiment of the
invention having a rotatable force guide in an extended condition
of a constant force centralizer.
[0020] FIG. 10 depicts an orthogonal view of a rotatable force
guide.
[0021] FIG. 11 depicts a side view of an alternate embodiment of
the invention having an extension limiter in a limited extension
condition.
[0022] FIG. 12 depicts a side view of an alternate embodiment of
the invention having an extension lock in a retracted and locked
condition.
[0023] FIG. 13 depicts a close-up of the area A from FIG. 12.
DESCRIPTION
[0024] FIG. 1 depicts a graph of the measured force curve 10 versus
the predicted force curve 14 of an embodiment of the present
invention. The measured force curve 10 is a poly fit of the
measured points 12 while the predicted force curve is a based upon
a computer simulation. A perfectly flat, linear response was the
original design goal, but in order to keep the mechanisms
relatively simple, a slight "curve", as depicted by the predicted
force curve 14 and the measured force curve 10 was thought to be
acceptable.
[0025] FIG. 2 depicts a graph of the predicted force curve 20 of an
alternate embodiment of the present invention. While other force
ranges may be used, the predicted force curve 20 utilizes a force
range of from about 40 pounds of force at the minimum diameter of
just over three inches increasing to about 43 pounds of force at
the mid-range diameter of 8 inches then decreasing again to about
40 pounds of force at the maximum diameter of about thirteen
inches. Such a force range has less than a 10% variation across the
range of applied force from the minimum diameter to the maximum
diameter.
[0026] FIG. 3 is a side depiction of an embodiment of a constant
force centralizer 50 providing a substantially constant radially
outward force throughout a predetermined range of tubular
diameters. The constant force centralizer 50 has an inner mandrel
52, beginning with the right side of the constant force centralizer
50, and at least one axial biasing device such as axial biasing
device 54. A collar 58 is fitted to the mandrel 52 in such a manner
that its position is fixed relative to the mandrel 52. The collar
58 may be threaded, pinned, welded, or formed as an integral part
of inner mandrel 52, or connected by any other means known to the
inner mandrel 52. The axial biasing device 54 typically surrounds
inner mandrel 52 and abuts collar 58. The axial biasing device 54
also abuts a movable sleeve 62. Typically the movable sleeve 62 is
circumferential about an exterior surface of inner mandrel 52. The
movable sleeve 62 is generally only axially movable. A first end 70
and 72 of pivotal force arms 64 and 68 is attached to movable
sleeve 62. Each pivotal force arm 64 and 68 has a recess 74 and 76.
Within each recess 74 and 76 is an actuator 80 and 82, such as a
roller. Each recess 74 and 76 is sized such that when pivotal force
arms 64 and 68 are in the retracted position, lying flat against
inner mandrel 52, most of the force guides 84 and 88 that extend
beyond the exterior surface of inner mandrel 52 are contained
within each recess 74 and 76. The force guides 84 and 88 are fixed
to the inner mandrel 52 and maybe threaded on, pinned on, or formed
as an integral part of the inner mandrel 52. It is generally the
interaction between the force guides 88 and 84 with the
corresponding actuators 80 and 82 that describes the constancy of
the force curves such as the curves in FIGS. 1 and 2. Each force
guide 88 and 84 will have a surface such as surfaces 90 and 92.
Generally the surfaces 90 and 92 are linear surfaces at some angle
.alpha. relative to the axis of mandrel 52 where the angle .alpha.
provides a reasonably flat force curve. The angle .alpha. in FIG. 3
is 47.degree..
[0027] Continuing with the left side of the constant force
centralizer 50, the constant force centralizer 50 has at least one
axial biasing device such as axial biasing device 56. A collar 100
is fixed onto a second end 102 of inner mandrel 52. The collar 100
is typically threaded onto inner mandrel 52 but may be pinned,
welded, or formed as an integral part of inner mandrel 52. The
axial biasing device 56 typically surrounds inner mandrel 52 and
abuts collar 100. The axial biasing device 56 also abuts a movable
sleeve 104. Typically the movable sleeve 104 is circumferential
about an exterior surface of inner mandrel 52. The movable sleeve
104 is generally only axially movable. A second end 106 and 108 of
telescopic arms 110 and 112 is attached to movable sleeve 104.
[0028] A first end 114 and 116 of telescopic arms 110 and 112 is
pivotally connected to a second end 120 and 122 of pivotal force
arms 64 and 68. Generally, at the pivotal connection where first
end 114 and second end 122 as well as first end 116 and second end
120 are connected, a wheel, such as wheel 124 and 126, a roller, a
skid, or other friction reducer is attached. Generally it is at
wheels 124 and 126 that the constant force is applied to the casing
or other tubular in a direction perpendicular to the long axis of
the constant force centralizer 50.
[0029] When the constant force centralizer is in a tubular with
sufficiently small diameter, each of the pivotal force arms 64, 68,
and telescopic arms 110, and 112 will be in a collapsed position
such that wheels 124 and 126 are at a minimal radial distance from
inner mandrel 52. With wheels 124 and 126 at their minimal radial
distance from inner mandrel 52, axial biasing device 54 is at
maximum compression thereby applying the maximum normal force
against movable sleeve 62. The force applied by axial biasing
device 54 is transferred to the movable sleeve 62. The force
applied by axial biasing device 54 is not necessarily constant.
Movable sleeve 62 in turn transfers the force to pivotal force arms
64 and 68. Subsequent movement of pivotal force arm 64 is guided by
actuator 80 acting on surface 90 causing end 122 to move in a
direction substantially perpendicular to the axis of the mandrel
52. The dimensions of pivotal force arm 64, actuator 80, force
guide 88, movable sleeve 62, collar 58 and biasing device 54 are
chosen so that the force from the biasing device 54 is transferred
to the wheel 124 in such manner that that force of wheel 124
against the tubular remains reasonably constant as the diameter of
the tubular changes. Movement of pivotal force arm 68 is guided by
actuator 82 acting on surface 92 causing end 120 to move in a
direction substantially perpendicular to the axis of the mandrel
52. The dimensions of pivotal force arm 68, actuator 82, force
guide 84, movable sleeve 62, collar 58 and biasing device 54 are
chosen so that the force from the biasing device 54 is transferred
to the wheel 126 in such manner that that force of wheel 126
against the tubular remains reasonably constant as the diameter of
the tubular changes.
[0030] When the constant force centralizer 50 moves from a large
diameter tubular to a smaller diameter tubular the force vectors
are reversed such that the wheels 124 and 126 are forced inward
exerting force through the pivotal arm 64 and 68 to the actuators
80 and 82 were the forces are redirected by the interaction of the
actuators 80 and 82 with force guides 84 and 88 into movable sleeve
62 and ultimately into axial biasing device 54.
[0031] As indicated in FIG. 2, a current embodiment of the tool
produces 40 lbs of radial force at the wheels 124 and 126 at the
joint between pivoting force arms 64 and 68 and telescoping arms
110 and 112. The force response is adjustable with the nominal
radial force either increased or decreased. Such increases or
decreases may be adjusted where biasing devices 54 and 56 may be
replaced with springs, gas chambers, etc. having proportionally
higher or lower force rates. If needed, shims can add compression
to the biasing devices 54 and 56 and thereby increase the axial
force. A flatter force response curve, see FIGS. 1 and 2, is
achievable if a more complex shape is machined into the force
guides 84 and 88.
[0032] As further indicated in FIG. 3, the force guides 84 and 88
are generally fixed to the inner mandrel 52 of the constant force
centralizer 50. In a current embodiment. the force guides 84 and 88
have an angle .alpha. where the angle .alpha. is about 47.degree.
relative to the axis of the inner mandrel 52 achieving a
substantially constant force response as indicated in FIG. 2. The
force guide angle and/or shape controls the shape of the force
response curves such as the force response curves in FIGS. 1 and
2.
[0033] FIG. 4 is an end view of the fully collapsed constant force
centralizer 50. In the embodiment of the constant force centralizer
depicted an outside diameter of 3.5 inches was chosen as the
nominal diameter of the centralizer. A smaller outer diameter can
be achieved in the centralizer design by scaling down the size of
the components.
[0034] In general, for wireline tools, shorter tools are preferred.
As tools become shorter, their overall weight is reduced. In one
embodiment of the 3.5 inch diameter constant force centralizer 100,
the total tool weight is less than 40 pounds. With this in mind, as
indicated below, several unique design features were employed to
minimize the tool length. As shown in FIG. 5, one embodiment of the
constant force centralizer 100 has a length of 26.8 inches. The
relatively short tool length of the design is a result of
offsetting the pivoting force arms 102, 104, and 106. The pivoting
force arm 102 is attached to movable sleeve 108 while pivoting
force arm 104 is attached to movable sleeve 110 by pin 112 and
pivoting force arm 106 and is attached to movable sleeve 110 by pin
114. The pivoting force arm 102 is connected to telescoping arm 122
at the joint 132. Also at joint 132 are wheels 116 and 117.
Telescoping arm 122 has a first portion 124, connected to pivoting
force arm 102 at joint 132, and a second portion 126. Second
portion 126 is attached to movable sleeve 110 via pin 134. In this
embodiment the second portion 126 slides within the first portion
124. The other two pivoting force arms 104 and 106 seen in FIG. 5
are each rotated 90.degree. around the central axis of the constant
force centralizer 100. For ease of reference only pivoting force
arm 104 will be further described. As described previously pivoting
force arm 104 is attached to movable sleeve 110 by pin 112. The
pivoting force arm 104 is connected to telescoping arm 128 at the
joint (not shown) where wheel 118 is attached to the constant force
centralizer 100.
[0035] As can be seen in FIG. 5 the movement of the arms occurs in
two planes (not shown). The two planes are perpendicular to each
other and both planes contain the axis of the constant force
centralizer 100. Additionally each of the wheels 116 and 118 are
offset by some axial distance D. The distance D may vary depending
upon whether the arms are fully extended or fully collapsed or at
some point in between.
[0036] When the arms are fully open the wheels 116 and 118 are
axially offset by 1.35 inches. When the arms are fully closed the
wheels 116 and 118 are axially offset by 2.1 inches. With offset
wheels, the centralizer 100 can traverse radial upsets in the
tubular more easily, and erratic tool movement is minimized.
[0037] Generally by having the telescoping arms 122 and 128
attached to their respective pivoting force arms 102 and 104 the
respective axial biasing devices 140 and 142 operate to apply force
to their associated wheels 116 and 118 independently.
[0038] The wheels 116, 118, 117 and 120, at each of the joints
between the pivoting force arms 102, 104, and 106 and the
telescoping arms 122, 128, and 130 are free to rotate even when the
tool is completely closed to its minimum outside diameter. In the
embodiment of the constant force referred to in FIG. 2 the constant
force centralizer is designed to open from about 3.5 inches to
about 12.7'' which is the inner diameter of typical casing that has
an outer diameter of 133/8 inches. As shown in FIG. 2, about 40
pounds of centralizing force is active across that entire
range.
[0039] In an embodiment of the current invention of the constant
force centralizer 100 from FIG. 5 as further depicted in FIG. 6 the
pivoting force arm 102 is paired with the pivoting force arm 107 on
the opposite side of the constant force centralizer 100. The
opposing pivoting force arms 102 and 107 move symmetrically with
one another. The telescoping arm 128 is paired with the telescoping
arm 130 on the opposite side of the constant force centralizer 100.
The opposing telescoping arms 128 and 130 move symmetrically with
one another.
[0040] The telescoping arms 128 and 130 arms are generally
orthogonal to the pivoting force arms 102 and 107. The pivoting
force arms 102 and 107 are typically coupled to each other such
that the axial biasing device 140 drives both of the pivoting force
arms 102 and 107. While the telescoping force arms 128 and 130 may
be linked to the same movable sleeve 108 as the pivoting force arms
102 and 107 the telescoping mechanism does not allow force to be
applied by movable sleeve 108 to the telescoping force arms 128 and
130. In oval holes, conventional wisdom suggests that one pair of
arms, either the pivoting force arms 102 and 107 or the telescoping
arms 128 and 130, will naturally align with the "long axis" of the
hole. In FIG. 6 the long axis of the tubular 136 is depicted as
being 12.4 inches as shown by reference numeral 133 while the short
axis of the tubular 136 is depicted as being 11.3 inches as shown
by reference numeral 135. The position of the constant force
centralizer as depicted in FIG. 6 is preferable and is likely to
maintain good tool centralization in oval holes.
[0041] Several features of the constant force centralizer are
intended to minimize rolling friction. The wheels 150 and 152, as
depicted in FIG. 7, in an embodiment of the constant force
centralizer are preferably as large in diameter as possible, here
1.3 inches in diameter as shown by reference numeral 154, without
exceeding the desired 3.5 inch constant force centralizer outside
diameter. Maximizing the wheel diameter allows each wheel 150 and
152 to last longer and roll more smoothly across irregularities in
the tubular. Typically, each joint between the telescoping arm 158
and the pivoting arm 156 arm has two wheels 150 and 152 at the
joint. Each wheel rolls independently on ball bearings 160.
[0042] As shown in FIG. 8, when an embodiment of the constant force
centralizer 200 is fully open, the pivoting force arms 202 and 204
are at an angle .beta. relative to the axis of the constant force
centralizer 200. In this instance angle .beta. is 30.degree.. The
telescoping arms 206 and 208 are at an angle .OMEGA. relative to
the axis of the constant force centralizer 200. In this instance
angle .OMEGA. is 35.degree.. Generally, it is desired to have the
angles .beta. and .OMEGA. as shallow as possible in order to help
the constant force centralizer 200 slide through any restrictions
that may exist within the tubular.
[0043] FIG. 9 is a depiction an alternative embodiment of the
constant force centralizer 300. In some instances it has been found
desirable to allow the inner mandrel 302 to remain fixed to the
wireline or other transporting device while allowing the components
of the centralizer assembly including the rotatable force guide
304, pivoting force arms 306, telescoping arms 308, first axial
biasing device 312, first movable sleeve 316, second axial biasing
device 314, second movable sleeve 318, and other associated
portions of the centralizer assembly to rotate around the inner
mandrel 302. By allowing the centralizer assembly to rotate around
the inner mandrel 302 the wireline (not shown) avoids becoming
twisted thereby avoiding any torque build up on account of constant
force centralizer 300.
[0044] FIG. 10 is a depiction of the rotatable force guide 304 from
FIG. 9. The rotatable force guide 304 typically consists of a
first-half 356 and a second half 358. Each half 356 and 358 has a
semicircular section such as 366 and semicircular section 364 each
half 356 and 358 also has at least a portion of the force guide 304
attached to the semicircular sections 366 and 364. The upper force
guide includes a relatively linear surface 370 set at an angle
.alpha. to the central axis of the inner mandrel 302 of the
constant force centralizer 300. The upper force guide also includes
a means to pivotally attach a limiting arm (not shown) such as
providing a slot 372 for a wrist pin (not shown). The lower force
guide includes a relatively linear surface 368 set at an angle
.alpha. to the central axis of the inner mandrel 302 of the
constant force centralizer 300. The lower force guide also includes
a means to pivotally attach a limiting arm (not shown) such as
providing a slot 374 for a wrist pin (not shown).
[0045] In the embodiment shown the rotatable force guide 304 is
applied to the inner mandrel 302 by placing each half 356 and 358
such that the semicircular portions 364 and 366 surround the inner
mandrel 302. Then using bolts such as bolts 362 and 360 to fix each
half 356 and 358 in place around inner mandrel 302. It is
envisioned that any known means of manufacturing a rotatable force
guide could be used for instance in some instances the force guide
304 could be machined out of a solid piece of material and then
slid onto the mandrel 302 from one end.
[0046] FIG. 11 is a depiction an alternative embodiment of the
constant force centralizer 400. In some instances it has been found
desirable to limit the outward translation of the pivoting force
arm 402 in turn limiting the outward translation of the telescoping
force arm 404 and wheel 406. Such a limitation may be useful in,
for instance, circumstances where the constant force centralizer
400 may pass through very large openings such as when it passes
through a blowout preventer which might cause damage to the
constant force centralizer 400.
[0047] One such extension limiter may use a link 410 attached to
the inner mandrel 412 or as is shown in FIG. 11 a first end of link
410 is attached to the rotatable force guide 414 by wrist pin 416
within slot 472. A second end of link 410 is attached to pivoting
force arm 402 by wrist pin 418 within slot 420. Wrist pin 418 is
configured such that it may slide within slot 420 depending upon
the extension position of wheel 406 as wheel 406 moves towards
inner mandrel 412 wrist pin 418 will move towards wheel 406 within
slot 420. However as wheel 406 moves away from inner mandrel 412
wrist pin 418 moves within slot 420 towards movable sleeve 422.
Eventually wrist pin 418 reaches the end of slot 420 closest to
movable sleeve 422 whereupon wheel 406 is prevented from moving any
further radially outward from inner mandrel 412.
[0048] FIG. 12 is a depiction of an alternative embodiment of a
portion of a constant force centralizer 500. In most instances it
has been found to be preferable to restrict any expansion of the
force pivoting arms 502, 504, and 506 as well as the associated
telescoping arms 508, 510, and 512 until at least the constant
force centralizer 500 has been deployed into the tubular or
wellbore. Preferably a lock will maintain the pivoting force arms
and telescoping arms in the retracted position until some
predetermined parameter is reached. For instance a pressure
actuated retaining pin 520 may be used where the pressure actuated
retaining pin 520 is designed to protrude from the force guide 522
when the constant force centralizer 500 is below some preset
pressures such as atmospheric pressure. The portion of the pressure
actuated retaining pin 520 that protrudes from the force guide 522
engages pivoting force arm 502 and prevents it from opening. When
the constant force centralizer 500 enters the tubular the external
pressure may be increased such that at some predictable point the
pressure will be sufficient to force the pressure actuated
retaining pin 520 inward into its recess within the force guide
522. With the pressure actuated retaining pin 520 moved inward the
pivoting force arm 502 is released so that the wheel 524 may move
radially outward to engage the tubular at the predetermined force
level.
[0049] FIG. 13 is section A from FIG. 12. FIG. 13 depicts force
guide 522 having the pressure actuated retaining pin 520 within
recess 524. In the embodiment shown in FIG. 13 a pressure actuated
retaining pin is utilized. In other instances the retaining pin
could be actuated by temperature, elapsed time, a sacrificial wear
pin, by a chemical reaction, or by an electrical signal. A portion
526 of the pressure actuated retaining pin 520 extends from force
guide 522 into a port 528 within pivoting force arm 502. The
pressure actuated retaining pin 520 and recess 524 form a chamber
530 sufficient to allow the pressure actuated retaining pin 522 to
move into the recess 524 within force guide 522 upon the
application of sufficient force to port 528 and acting upon the
portion of the pressure actuated retaining pin 522 that extends
into port 528. The pressure actuated retaining pin 522 may be held
outwardly extended by the force exerted upon the pressure actuated
retaining pin 522 by the pivoting force arm 502 and/or may have any
other means known in the industry for securing the pressure
actuated retaining pin 522.
[0050] While the embodiments are described with reference to
various implementations and exploitations, it will be understood
that these embodiments are illustrative and that the scope of the
inventive subject matter is not limited to them. Many variations,
modifications, additions and improvements are possible. Variations
are likely to be beneficial when employed in tools such as
calipers, anchoring devices, eccentering devices, and downhole
tractors.
[0051] While the embodiments shown are described with the intention
of maintaining a substantially constant radial force across the
full operating range of the device, it is understood that, if
desired, the mechanism can be modified to achieve different radial
forces within different size tubulars.
[0052] Plural instances may be provided for components, operations
or structures described herein as a single instance. In general,
structures and functionality presented as separate components in
the exemplary configurations may be implemented as a combined
structure or component. Similarly, structures and functionality
presented as a single component may be implemented as separate
components. These and other variations, modifications, additions,
and improvements may fall within the scope of the inventive subject
matter.
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