U.S. patent application number 12/136948 was filed with the patent office on 2009-12-17 for modular low-clearance centralizer and method of making modular low-clearance centralizer.
This patent application is currently assigned to FRANK'S INTERNATIONAL, INC.. Invention is credited to Jean Buytaert.
Application Number | 20090308615 12/136948 |
Document ID | / |
Family ID | 41077801 |
Filed Date | 2009-12-17 |
United States Patent
Application |
20090308615 |
Kind Code |
A1 |
Buytaert; Jean |
December 17, 2009 |
Modular Low-Clearance Centralizer and Method of Making Modular
Low-Clearance Centralizer
Abstract
A low-clearance bow spring centralizer (10) can be made by
providing a plurality of bow spring modules (54), each having an
elongate rib (52) with a first integrally-formed collar segment
(54) at a first end and a second integrally-formed collar segment
(56) at a second end wherein the first collar segment (54) and the
second collar segment (56) are joined to adjacent first and second
collar segments, respectively. The bow spring modules may be
interlinked by welding a seam (55) formed between abutting sides of
adjacent pairs of first collar segments and/or second collar
segments. The sides (54a) of the first collar segment and the sides
(56a) of the second collar segment may each be perpendicular to the
axis of the centralizer bore, and seams (55) therebetween may be
welded to form a first centralizer collar and a second centralizer
collar, coupled one to the other by the ribs (52).
Inventors: |
Buytaert; Jean; (Mineral
Wells, TX) |
Correspondence
Address: |
Streets & Steele-Frank's International.
13831 Northwest Freeway, Suite 355
Houston
TX
77040
US
|
Assignee: |
FRANK'S INTERNATIONAL, INC.
Houston
TX
|
Family ID: |
41077801 |
Appl. No.: |
12/136948 |
Filed: |
June 11, 2008 |
Current U.S.
Class: |
166/378 ;
166/241.7 |
Current CPC
Class: |
E21B 17/1028
20130101 |
Class at
Publication: |
166/378 ;
166/241.7 |
International
Class: |
E21B 19/24 20060101
E21B019/24 |
Claims
1. A method of making a bow spring centralizer to center a tubular
string within a borehole comprising the steps of: providing a
plurality of bow spring modules having an integrally-formed and
curved first collar segment at a first end of an elongate rib, and
an integrally-formed and curved second collar segment at the
second, opposite end of the rib; and coupling the plurality of
first collar segments together to form a first centralizer collar;
and coupling the plurality of second collar segments together to
form a second centralizer collar.
2. The method of claim 1 further comprising the steps of: bending
the first collar segment of a bow spring module to conform to a
curvature of a primary forming block; and bending the second collar
segment of a bow spring module to conform to the curvature of the
primary forming block.
3. The method of claim 2 further comprising the steps of: bending
the first collar segment of a bow spring module to conform to a
curvature of a secondary forming block; and bending the second
collar segment of a bow spring module to conform to the curvature
of the secondary forming block.
4. The method of claim 1 further comprising the steps of: coupling
a spacer to an uncoupled first collar segment of a module; and
coupling a spacer to an uncoupled second collar segment of a
module.
5. The method of claim 1 further comprising the step of: heat
treating the weld seams of the first centralizer collar or the
second centralizer collar.
6. A method of making a bow spring centralizer comprising the steps
of: displacing a male die through a metal plate and into a female
die cavity to form a bow spring module having an elongate rib, an
integrally-formed and curved first collar segment at a first end of
the rib and an integrally-formed and curved second collar segment
at a second end of the rib; repeating the first step to produce a
plurality of bow spring modules; welding the first collar segment
to a collar segment of an adjacent bow spring module to form a
first centralizer collar; and welding the second collar segment to
a collar segment of the adjacent bow spring module to form a second
centralizer collar that is spaced-apart from the first centralizer
collar by the plurality of ribs.
7. A bow spring module to use in making a bow spring centralizer
comprising: an elongate rib having an integrally-formed first
collar segment at a first end and an integrally-formed second
collar segment at a second end; and wherein the first collar
segment comprises two spaced-apart sides and the second collar
segment comprises two spaced-apart sides.
8. The bow spring module of claim 7 wherein at least one of the
two-spaced apart sides of the first collar segment or at least one
of the two-spaced apart sides of the second collar segment are
generally parallel to the axis of a bow spring centralizer that may
be made by interlinking the bow spring modules.
9. The bow spring module of claim 8 wherein one of the two-spaced
apart sides of the first collar segment or one of the two-spaced
apart sides of the second collar segment are beveled.
10. A method of making a bow spring centralizer comprising the
steps of: providing a plurality of bow spring modules comprising an
elongate rib with an integrally-formed first collar segment at a
first end and an integrally-formed second collar segment at a
second end, the first and second integrally-formed collar segments
comprising two spaced-apart sides; and interlinking the plurality
of bow spring modules.
11. The method of claim 10 wherein interlinking each first collar
segment along each of the sides to an adjacent first collar segment
to form a first centralizer collar includes the step of welding,
and wherein joining each second collar segment along each of the
sides to an adjacent second collar segment to form a second
centralizer collar includes the step of welding.
12. The method of claim 11 further comprising the step of dressing
the welded joints.
13. The method of claim 10 wherein the sides are generally
linear.
14. The method of claim 13 wherein the sides of the first and the
second collar segments are beveled so as to form a channel when
placed in an abutting position along the side of an adjacent first
or second collar segment.
15. A method of making a bow spring centralizer comprising the
steps of: providing a plurality of bow spring modules, joining each
first collar segment along each of the sides to an adjacent first
collar segment to form a first centralizer collar; and joining each
second collar segment along each of the sides to an adjacent second
collar segment to form a second centralizer collar.
16. The method of claim 1 further comprising the step of coupling a
spacer to one of the first collar segment or the second collar
segment to alter the size thereof.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] This invention is directed to a low-clearance centralizer to
center a tubular within a borehole, and to a low-cost method of
making a modular low-clearance centralizer that can radially
collapse to pass through a restriction, and that can deploy to
generally center a tubular within a drilled borehole.
[0003] 2. Description of the Related Art
[0004] Centralizers can be secured at spaced intervals along a
tubular string to provide radial stand-off between the tubular and
the wall of a drilled borehole in which the tubular is installed.
Bow spring centralizers generally comprise a pair of aligned
collars defining a bore therethrough to receive the tubular, and a
plurality of angularly-spaced bow springs biased to provide
stand-off. Bow spring centralizers may collapse to pass, e.g.,
along with the tubular, through restrictions, and to deploy to
provide a generally uniform annulus between the exterior of the
tubular and the wall of the borehole. A centered tubular string
promotes uniform and continuous distribution of cement slurry
around the tubular string for cementing the tubular within a
targeted interval of the borehole. The resulting cement liner can
reinforce the tubular string, isolates the tubular from corrosive
formation fluids and prevents fluid flow between penetrated
geologic formations.
[0005] Bow spring centralizers typically include a pair of
axially-spaced and aligned collars coupled one to the other by a
plurality of angularly distributed bow springs. Some bow springs
centralizers are longitudinally secured along the axis of the
tubular using stop collars to block the centralizers from sliding.
Stop collars can add substantially to the positive outer diameter
(O.D.) of the tubular and can limit passage through a given
restriction.
[0006] The collar's radial thickness added to the exterior of a
tubular is also an important consideration. Low-clearance
centralizers have radially thin collars and bow springs that may
collapse and lie flat along the length of a tubular between the
collars. Fasteners (e.g., rivet, bolt, etc.) to couple the bow
spring to the collars can also add substantially to the positive
O.D. A low-clearance centralizer may be cut from a unitary piece of
tubular pipe to minimize the contribution to the positive O.D. This
method avoids the need for fasteners to couple the bow springs to
the collars and may minimize the positive O.D. of the centralizer.
One method of forming low-clearance centralizers from a unitary
piece of tubular pipe comprises the steps of cutting elongate
coupons from the interior of a tubular to form a cylindrical cage,
and bending the ribs of the cage radially outward to form a
plurality of angularly-spaced bow springs, for example, but not
limited to, a centralizer as described in U.S. patent application
Ser. No. 11/749,544 filed on May 16, 2007 and assigned to the owner
of the present application. For example, the elongate coupons may
be cut from the pipe using a water-jet or laser. The method may
comprise an additional step of heating and quenching the bow spring
centralizer to impart resiliency to the bow springs to enable the
bow springs to collapse and re-deploy to provide stand-off.
[0007] The cost of manufacturing a centralizer is another important
consideration. Dozens or even hundreds of centralizers may be
installed in a single borehole. Low-clearance bow spring
centralizers cut from a unitary piece of tubular may be expensive
to make. Special tools may be needed to cut the coupons from the
tubular, the tubular to form a cylindrical cage, and special tools
may be needed to simultaneously bend the ribs to form bow springs.
These special tools can add substantially to the manufacturing cost
of the centralizer.
[0008] An alternative method of forming a low-clearance centralizer
comprises the steps of forming two cylindrical sleeves and cutting
a plurality of notches in each sleeve, each notch to receive the
end of a pre-formed bow spring. The end of a bow spring may then be
welded to the sleeve along the three-sided perimeter of each notch.
A grinder may be used to dress the resulting weld path defining
each bow spring/collar connection to reduce the diameter, and the
resulting centralizer may be heated and quenched to impart
resiliency to the welded connections. The alternative method
described is time consuming and may require post-fabrication heat
treating and/or quenching to alleviate the heat-affected zones.
[0009] The intended application of the centralizer is an important
factor to be considered in designing the centralizer. Depending on
the application, an operator may need a bow spring with either few
or many bow springs. For example, a thick-walled and/or large
diameter tubular to be disposed in a substantially horizontal
portion of a borehole may need a greater angular concentration of
bow springs to provide the support for adequate stand-off.
Conversely, a relatively low-weight tubular to be installed in a
substantially vertical section of a borehole may require fewer bow
springs to adequately center the tubular.
[0010] What is needed is a method of making a low-clearance bow
spring centralizer that reduces the cost of manufacture while
retaining the benefits of a close-tolerance bow springs
centralizer. What is needed is a method to make a low-clearance bow
spring centralizer that does not require special manufacturing
tools that may be expensive to purchase and/or operate. What is
needed is a bow spring centralizer that is easily customizable for
the intended application. What is needed is a low-clearance bow
spring centralizer that performs as well as a centralizer cut from
a unitary piece of tubular, but is less expensive and easier to
make. What is need is a method of making a low-clearance
centralizer that maximizes production capacity for a given heating
and/or quenching facility.
SUMMARY OF THE PRESENT INVENTION
[0011] An embodiment of the present invention satisfies one or more
of the above-stated needs. An embodiment of the invention provides
an efficient and inexpensive method to make a low-clearance modular
bow spring centralizer to center a tubular within a drilled
borehole. A centralizer may be made at a lower cost according to an
embodiment of the present invention, and may perform as well as a
more expensive centralizer that is made from a unitary piece of
tubular material. An embodiment of the invention provides a bow
spring module that may be used to make a low-clearance
centralizer.
[0012] In one embodiment, the method may include the steps of
providing a plurality of bow spring modules and interlinking the
plurality of bow spring modules together to form a bow spring
centralizer with low-clearance centralizer collars. Each of the bow
spring modules may comprise an elongate rib having an
integrally-formed first collar segment at a first end and an
integrally-formed second collar segment at a second end. Each bow
spring module may be made by cutting and forming the bow spring
module from a plate of suitable material such as, for example,
low-carbon steel. More specifically, each bow spring module may be
cut and formed using a displaceable male die and a corresponding
stationary female die cavity into which the male die may be
forcibly inserted using, for example, a hydraulic press. A plate of
material, such as, for example, low-carbon steel, may be disposed
intermediate the male die and the female die cavity prior to
displacement of the male die into the female die cavity to cut and
form a bow spring module. The process may be repeated using
additional plates.
[0013] It should be appreciated by those skilled in the art that
the process of forming bow spring modules in this manner may be
automated. It should be understood by those skilled in the art that
the bow spring module produced in this manner may be shaped
according to the corresponding shape of the male die and the female
die cavity, and that a large number of generally identical bow
spring modules may be inexpensively and/or rapidly produced.
[0014] It should be further understood that bow spring modules
produced in this manner may be efficiently stacked and/or handled,
and that the residual material stresses resulting from the cold
working of a metal, e.g., low-carbon steel, plate material may be
removed by heating the bow spring module for a period of time, and
then by quenching the bow spring module, e.g., by immersion in
water, to impart desired metallurgical resiliency to the metal,
e.g., low-carbon steel material.
[0015] In one embodiment, the method of making a low-clearance
centralizer may comprise the steps of providing a plurality of bow
spring modules, each of the bow springs modules having an elongate
rib integrally formed with an arcuate first collar segment at a
first end of the rib and an arcuate second collar segment at a
second end of the rib, interlinking the plurality of first collar
segments to form a first centralizer collar, and interlinking the
plurality of second collar segments to form a second centralizer
collar. The resulting bow spring centralizer may comprise the first
centralizer collar spaced apart from and coupled to the second
centralizer collar by and through the generally angularly
distributed plurality of ribs.
[0016] In an alternate embodiment, the method comprises the steps
of providing a plurality of bow spring modules, each bow spring
module having an elongate rib with an integrally formed first
collar segment at a first end of the rib and an integrally formed
second collar segment at a second end of the rib, imparting a
desired arcuate shape to the first collar segment using, for
example, a forming block, imparting the desired arcuate shape to
the second collar segment, interlinking the plurality of first
collar segments to form a first centralizer collar having a bore of
a diameter corresponding to the arcuate shape imparted to the
collar segments, and interlinking the plurality of second collar
segments to form a second centralizer collar of the same bore. It
should be understood that this method may be used to modify bow
spring modules that have a first collar segment and a second collar
segment, each having an original radius of curvature, so that the
first and second collar segments will have a larger or a smaller
radius of curvature, and interlinking the modified bow spring
modules may result in a low-clearance bow spring centralizer for
being received on a larger or smaller diameter tubular. It should
be understood that the use of, for example, a forming block to
modify the curvature of the first collar segment and second collar
segment of a set of bow spring modules may change the number of bow
spring modules that are interlinked to form a bow spring
centralizer in accordance with the disclosed method. For example,
but not by way of limitation, a bow spring module may, in one
embodiment, comprise a first collar segment and a second collar
segment coupled one to the other by an elongate rib, and the first
and second collar segments may each comprise a radius of curvature
of 9 inches, and each may comprise an angular span of 60 degrees so
that a set of six of these bow spring modules may be interlinked in
accordance with the disclosed method to form a bow spring
centralizer with a first collar having a diameter of 18 inches and
a second collar having a corresponding diameter, the second collar
coupled to the first collar through the six elongate ribs. If a bow
spring centralizer having a diameter of 24 inches is needed, the
bow spring modules may be modified using, for example, a forming
block to change the shape and the radius of curvature of the first
collar segment and the second collar segment of each bow spring
module prior to interlinking the bow spring modules to form the bow
spring centralizer. For example, but not by way of limitation, if a
bow spring module with a first collar segment and a second collar
segment, each having a radius of curvature of 9 inches and an
angular span of 60 degrees, is modified using a forming block so
that the radius of curvature of the first and second collar
segments is expanded to 115/8 inches, the angular span of the
modified first collar segment and second collar segment might be
decreased to only about 36 degrees, and the number of the modified
bow spring modules that will be interlinked to form a bow spring
centralizer would be increased to 10. It should be understood that,
where the "take-out" or the arc-length of the first and the second
collar segments of a set of bow spring modules that have been
modified using, for example, a forming block, does not provide the
a desired diameter when interlinked with an integral number of
similar or identical modified bow spring modules, one or more
spacers may be coupled between two or more adjacent bow spring
modules to provide
[0017] In an alternate embodiment, an apparatus may comprises a bow
spring module comprising an elongate rib, a first collar segment at
a first end of the rib and a second collar segment at a second end
of the rib, each of the first and second collar segments having
sides disposed generally laterally to the center of the collar
segment aligned with the rib. In one embodiment, the apparatus may
comprise beveled edges along the sides of the first collar segment
and the second collar segment. The beveled edges may facilitate
welding of a plurality of the first collar segments together to
form a first centralizer collar and welding a plurality of second
collar segments to form a second centralizer collar, each having a
generally circular cross-section. In one embodiment, the beveled
edges on the sides of the first and second collar segments may be
formed during the steps of forming the first and second collar
segments.
[0018] In one embodiment, a male die and the female die cavity may
be machined and formed to simultaneously cut a bow spring module
comprising an elongate rib, an integrally-formed first collar
segment at a first end of the rib and an integrally-formed second
collar segment at a second end of the rib, from the metal plate,
and also to impart a desired curvature and/or contour to each of
the first integrally-formed collar segment, the second
integrally-formed collar segment and the rib of the bow spring
module, all as the male die enters and then seats within the female
die cavity. Forming of these components of the bow spring module
may include imparting a desired curve or contour to the rib between
the first collar segment and the second collar segment, and/or
imparting a curvature of a uniform radius, in a direction generally
transverse to the plane of the arc of the rib, to both the first
collar segment and the second collar segment. A generally
corresponding curvature may be imparted to each of the first collar
segment and the second collar segment, and the imparted curvature
may correspond to a desired diameter for the first and second
centralizer collars to be formed by coupling the bow spring
modules. For example, but not by way of limitation, the male die
and the corresponding female die cavity may be formed so that the
bow spring modules are formed, upon being cut from a metal plate,
to comprise an elongate rib with a first end and a second end, a
first integrally-formed collar segment with a radius of curvature
of 9 inches at the first end, and a second integrally-formed collar
segment with the same radius of curvature at the second end. The
first collar segment and the second collar segment may each
comprise an arc having an angular span of 60 degrees so that, when
six substantially identical bow spring modules are joined together
by coupling the sides of the first collar segments to form a first
centralizer collar, and by coupling the sides of the second collar
segments to form a second centralizer collar, the first and the
second centralizer collars will each have a diameter of 18 inches,
and the first and the second centralizer collars will be coupled
one to the other by the six ribs (for bow spring modules having a
single rib). It should be noted that a bow spring centralizer
formed using one embodiment of this method may further comprise six
generally longitudinal straight welds in the first centralizer
collar, and an additional six generally longitudinal straight welds
in the second centralizer collar, and the welds will be
strategically disposed within portions of the first and second
centralizer collars that will bear relatively little stress during
installation of the tubular within a well. More specifically, the
welds will not be at or adjacent to the critical connections
between the first or second ends of the ribs and the first or
second collar segments, respectively, which are integrally-formed
and remain unaffected by welding. It should also be noted that the
rib portion of the bow spring module may comprise a simple curve
that may have a generally constant or a variable radius of
curvature along the span of the rib. Alternately, the rib portion
of the bow spring module may comprise a more complex contour that
may have two or more sub-portions, and each sub-portion may
comprise a curve that may have a generally constant or a variable
radius of curvature along the span of the rib. A bow spring module
rib having either of these rib structures, or yet another rib
structure, may be included within a bow spring module.
[0019] As a further example, the die and the die cavity may be
machined to impart a desired contour to the rib of the bow spring
module. It should be noted that a rib of a bow spring may comprise
a shape other than an arc, and may comprise a contour that includes
a complex shape or a combination of arcs. For example, but not by
way of limitation, the rib of each bow spring module made using the
die and the die cavity may be generally curved along a center
portion that is intermediate the first and second ends of the rib,
generally straight along at least a portion of the rib intermediate
the first end and the center portion, generally straight along at
least a portion of the rib intermediate the second end and the
center portion, and again curved, in a direction opposite the
direction of curvature of the center portion, at a portion of the
rib adjacent to the first end, and also curved, again in a
direction opposite the direction of curvature of the center
portion, at a portion of the rib adjacent to the second end. This
contour may be used to provide smooth transitions along each rib of
a bow spring centralizer in order to eliminate stress
concentrations and to prevent excessive pressure from being applied
to the tubular on which the centralizer is received. It should be
understood that the curved portions of the rib may not conform to a
constant radius of curvature but may instead comprise transition
portions intermediate the center portion and the adjacent portions
that are curved in the opposite direction. Specifically, each rib
may terminate at the first end and also at the second end in a
generally flattened end portion that is adjacent to the connection
between the rib/collar segment. This contour prevents undue fatigue
and stress concentration at the rib/collar segment connections, and
generally distributes the flexure of the rib over the three curved
portions of the rib. It should be understood that the contour of
the rib of a centralizer may be made according to certain
performance parameters such as, but not limited to, the desired
stand-off and restoring force. It should be understood that the
male die cavity and the female die may be machined to impart other
features to each bow spring module. For example, but not by way of
limitation, the bow spring module may, in addition to the curvature
and the contour described above, be formed with a crease, e.g., a
longitudinal crease, in at least a portion of the rib to impart
additional structural rigidity and/or to increase the restoring
force of the bow spring rib.
[0020] 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. However, that the appended
drawings illustrate some embodiments of this invention and are
therefore not to be considered limiting of its scope, for the
invention may admit to other embodiments.
BRIEF DESCRIPTION OF THE DRAWINGS
[0021] FIG. 1A is a perspective view of a female die cavity that
may be used to produce a bow spring module according to one
embodiment of the method.
[0022] FIG. 1B is a perspective view of a male die that may be
used, along with the female die cavity of FIG. 1A, to produce a bow
spring module according to one embodiment of the method.
[0023] FIG. 2 is a perspective view of the male die of FIG. 1B
arranged for the protruding portions to be disposed against and
through a metal plate and into the female die cavity of FIG. 1A to
produce an embodiment of a bow spring module.
[0024] FIG. 3 is an elevation view of one embodiment of a bow
spring module that may be produced using the die, die cavity and
metal plate of FIG. 2.
[0025] FIG. 4 is a perspective view of the bow spring module of
FIG. 3 showing the curved elongate rib, a curved first collar
segment at a first end of the rib, and a curved second collar
segment at a second end of the rib.
[0026] FIG. 5 is an elevation view of one embodiment of a
clamp/mandrel supporting two bow spring modules, each like the one
shown in FIGS. 3 and 4, one adjacent to the other, and in position
to be joined along two seams: a first seam between the two adjacent
first collar segments, and a second, aligned seam between two
adjacent second collar segments.
[0027] FIG. 6 is one embodiment of a modular bow spring centralizer
that may be formed by coupling three additional bow spring modules
to the two bow spring modules shown in FIG. 5. Specifically, the
embodiment of the modular bow spring centralizer of FIG. 6 may be
formed by coupling the first collar segments of a plurality of bow
springs modules to form a first centralizer collar, and by coupling
the second collar segments of the plurality of bow spring modules
to form a second centralizer collar.
[0028] FIG. 7 is a schematic showing the complex weld pathway that
may be used to couple the end of a conventional rib to a
conventionally notched low-clearance centralizer collar.
[0029] FIG. 8 is a schematic showing the simple weld pathway that
may be used to couple two first collar segments of a pair of
adjacent bow spring modules according to one embodiment of the
present invention.
DETAILED DESCRIPTION OF AN EMBODIMENT
[0030] FIG. 1A is a perspective view of a female die cavity 22 that
may be used to produce one embodiment of a bow spring module
according to one embodiment of the invention. The die cavity of
FIG. 1A comprises a first collar segment recess 22a, a second
collar segment recess 22b, and a rib recess 22c connecting the
first collar segment recess 22a to the second collar segment recess
22b. It should be understood that the first collar segment recess
22a and the second collar segment recess 22b may be generally
identical, and each may comprise a uniformly curved bottom having a
generally uniform radius of curvature, and the bottom may be
recessed and/or surrounded by a generally vertical wall.
[0031] FIG. 1B is a perspective view of a male die 24 that may be
used with the female die cavity of FIG. 1A to produce an embodiment
of a bow spring module according to one embodiment of the
invention. The male die 24 comprises a first collar segment
protrusion 24a, a second collar segment protrusion 24b and a rib
protrusion 24c connecting the first collar segment protrusion 24a
and the second collar segment protrusion 24b. The first protrusion
24a, second protrusion 24b and the rib protrusion 24c of the male
die 24 may each generally correspond in shape, size and contour to
the first collar segment recess 22a, the second collar segment
recess 22b and rib recess 22c, respectively. It should be
understood that the male die 24 may be receivable into and
removable from the mating female die cavity using a press (not
shown), e.g., a hydraulic press. It should be further understood
that the first collar segment recess 22a, the second collar segment
recess 22b and rib recess 22c may be surrounded by a generally
vertical base portion that generally matches and is receivable
within the vertical wall recess portion of the female die cavity of
FIG. 1A. For example, but not by way of limitation, the width 23 of
the first and second collar segment recesses 22a and 22b of FIG. 1A
may be only slightly greater than the width 25 of the corresponding
first collar segment protrusion 24a and second collar segment
protrusion 24b. It should be understood by those skilled in the art
that these components cooperate to shear a bow spring module blank
from the metal plate 50 shown in FIG. 2 during the process of
disposing the male die 24 into and against the female die cavity 22
upon or prior to final seating of the male die with the female die
cavity.
[0032] The protrusions 24a, 24b and 24c of the male die cavity may
each comprise a curved shape and/or contoured shape that generally
matches the corresponding recesses 22a, 22b and 22c of the female
die cavity, respectively. The contoured shape may, in one
embodiment, impart a generally desired bow or curve to the rib of a
bow spring module produced by disposing the metal plate 50
intermediate the male die and the female die cavity. Similarly, the
curved and/or contoured shapes may impart a generally desired
radius to the first collar segment and the second collar
segment.
[0033] It should be understood that, in an alternate embodiment, a
bow spring module may be produced using an equivalent two-step or a
three-step method. For example, in an alternate embodiment of the
method, the male die may be flat along its protruding faces, and
the female die cavity may also be flat along the corresponding
receiving faces to cut a flat bow spring module blank from a metal
plate disposed intermediate the male die and the female die cavity.
A bow spring module blank produced in this manner may be flat like
the metal plate from which it is cut. The resulting flat bow spring
module blank may then be formed into a bow spring module using, for
example, forming blocks and a press, rollers or other devices used
to impart a desired contour or curve to the rib of the bow spring
module, and a desired radius of curvature to the first and second
collar segments at the first end and the second end of the rib.
[0034] FIG. 2 is a perspective view of the male die 24 (of FIG. 1B)
positioned to be disposed, in the direction of arrow 21 through a
generally flat metal plate and at least partially into the female
die cavity 22 (of FIG. 1A) to produce an embodiment of a bow spring
module. The first collar segment protrusion 24a is aligned with the
corresponding first collar segment recess 22a, the second collar
segment protrusion 24b is aligned with the corresponding second
collar segment recess 22b, and the rib protrusion 24c is aligned
with the corresponding rib recess 22c. The metal plate 50 disposed
intermediate the male die 24 and the female die cavity 22 may, for
example, a flat plate of ASTM D 4310 metal, and may be, for
example, 0.125-0.20 inches thick. It should, however, be understood
that materials other than ASTM D 4310 and thicknesses outside the
range of 0.125-0.20 inches may be used to achieve the benefits
provided by the invention.
[0035] FIG. 3 is an elevation view of an embodiment of a bow spring
module 51 that may be produced using the die 22, die cavity 24 and
the metal plate 50 of FIG. 2. The bow spring module 51 of FIG. 3
comprises a rib 52, a first collar segment 54 coupled to the first
end 52a of the rib 52, and a second collar segment 56 coupled to
the second end 52b of the rib 52. The contour or curve of the rib
52, and curvature of the first collar segment 54 and the second
collar segment 56, are visible in the perspective view of FIG.
4.
[0036] FIG. 4 is a perspective view of the bow spring module 51 of
FIG. 3 comprising the contoured or curved rib 52, the curved first
collar segment 54 at the first end of the rib 52, and the curved
second collar segment 56 at the second end of the rib 52. It should
be understood that the bow spring module shown in FIGS. 3 and 4 may
be produced using either of the embodiments of the method described
above, e.g., using a single-step or a dual-step method, or in other
embodiments known to those skilled in the art without departure
from the spirit and scope of the invention.
[0037] The bow spring module of FIG. 4 comprises a first collar
segment 54 disposed at the first end of the rib 52 and a second
collar segment 56 at the second end of the rib 52. It should be
understood that the first collar segment 54 and the second collar
segment 56 are depicted with a generally uniform and common radius
of curvature as shown by arrows 59. The first collar segment 54 and
the second collar segment 56 shown in FIGS. 3 and 4 each comprise
sides 54a and 56a, respectively, that are generally lateral to the
rib and collar segment connection. The sides 54a and 56a may be, in
one embodiment, generally parallel and perpendicular to the plane
of the ends 54c and 56c lie. Each of the first collar segment 54
and the second collar segment 56 may be generally formed as a
curved plate, and as an angular portion of a cylindrical sleeve.
When the correct plurality of the bow spring modules are coupled,
such as by welding, along the sides 54a of a first collar segment
54 of a first bow spring module 51 to abutting sides 54a of first
collar segments 54 of two adjacent bow spring modules 51, the
coupled first collar segments 54 together will form a first
centralizer collar having a bore therethrough to encircle a tubular
received therethrough, as is shown in FIG. 6. It should be
understood that the sides 56a of the second collar segment 56 may
be, in one embodiment, generally aligned with the sides 54a of the
first collar segment 54, and that positioning two adjacent bow
spring modules 51, one adjacent the other, to abut a side 54a of
one with a side 54a of the other to form a longer, but
circumferentially continuous arc, would also therefore position a
side 56a of the second collar segment 56a of the one bow spring
module 51 to simultaneously abut with a side 56a of the other bow
spring module 51. It should be further understood that joining the
abutting sides, such as by welding, would fix the two adjacent bow
spring modules 51 in position one relative to the other, and
additional bow spring modules 51 may then be joined in a similar
fashion until a complete bow spring centralizer, for example, is
made.
[0038] FIG. 5 is an elevation view of an embodiment of a
clamp/mandrel 60 that may be used to secure adjacent bow spring
modules 51, one adjacent to the other, and positioned to be
interlinked along the two aligned and separated seams, the first
seam intermediate adjacent first collar segments 54 and the other
seam intermediate adjacent second collar segments 56. The
clamp/mandrel 60 of FIG. 5 comprises a generally upright base 60B
having an interior bore to receive therein a generally concentric
portion 68 of a cap 60A. The base 60B may further comprise a
plurality of radially protruding circumferential ridges 65
separated by a plurality of gaps 66 intermediate the ridges 65. The
clamp/mandrel 60 may further comprise a plurality of upper clamp
brackets 61a, each supporting a clamp 63, and the clamp/mandrel 60
may further comprise a plurality of lower clamp brackets 61b, each
supporting a clamp 63.
[0039] In the embodiment of the clamp/mandrel 60 shown in FIG. 5, a
bow spring module 51 may be positioned against the clamp/mandrel 60
so that it is supported by one of the ridges 65, and so that each
upper clamp bracket 61a and related clamp 63 may be used to secure
a first collar segment 54 of a bow spring module 51 to the
clamp/mandrel 60, and each clamp bracket 61b and related clamp 63
may be used to secure a second collar segment 56 of a bow spring
module 51 to the clamp/mandrel 60 to secure two adjacent bow spring
modules 51 in position for the seam 47a formed by sides 54a of
abutting first collar segments 54 and the seam 47b formed by sides
56a of abutting first collar segments 56 may be welded or otherwise
joined to connect the bow spring modules 51.
[0040] It should be understood that other devices may be used to
secure one or more bow spring modules 51 in position to be joined
along the sides 54a of the first collar segments 54 and along the
sides 56a of the second collar segments 56, and that the
clamp/mandrel 60 of FIG. 5 should not be considered to be limiting
of the scope of the claims below. Each claimed method may be used,
and each claimed apparatus may be made, without the specific
embodiment of the clamp/module 60 of FIG. 5.
[0041] In one embodiment, the sides 54a and 56a of the first collar
segments 54 and the second collar segments 56, respectively, are
beveled so that the first seam 47a and/or the second seam 47b each
comprise a channel that may be welded by filling the channel with
material to fuse the work pieces and to form a welded seam, as
shown as element 55 in FIG. 6.
[0042] FIG. 6 is one embodiment of a bow spring centralizer 10 that
may be formed by interlinking three additional bow spring modules
to the two joined bow spring modules shown in FIG. 5. Specifically,
the embodiment of the modular bow spring centralizer of FIG. 6 may
be formed by coupling the first collar segments 54 of a plurality
of bow springs modules to form a first centralizer collar 20, and
by coupling the second collar segments of the plurality of bow
spring modules to form a second centralizer collar 30, so that the
first collar and the second collar our coupled one to the other
through a plurality of bow springs 52. The bow spring centralizer
10 formed according to this method may be formed by positioning two
bow spring modules 51, one adjacent the other, as shown in FIG. 5,
and by then making two generally straight-line welds 55, one at the
first collar segment 54 and another at the second collar segment
56, to couple each bow spring module 51 to an adjacent bow spring
module 51. The last joined bow spring module 51 in the illustrated
embodiment will require a total of four straight-line welds, two
aligned welds to the penultimate bow spring module 51 and two
aligned welds to one of the original pair of bow spring modules 51
joined one to the other as shown in FIG. 5. It should be understood
that a clamp/mandrel 60 like the one shown in FIG. 5 could be used
to secure and position all of the bow spring modules 51 utilized to
form a bow spring centralizer 10, and then to weld all of the bow
spring modules together to form the centralizer, and that it is not
necessary to begin with only a pair of bow spring modules.
[0043] FIG. 7 is a schematic showing the complex weld path to
couple the generally box end 58 of a conventionally-formed bow
spring within a corresponding notch within a conventionally-formed
low-clearance collar. The complex weld pathway shown in FIG. 7
comprises a first leg 53a, a second leg 53b, and a third leg 53c,
and the three of these legs 53a, 53b and 53c are not aligned one
with the others, and each is at an angle with at least one of the
other two. It should be understood that the rib/collar connection
53 formed in this manner will comprise a substantial heat-affected
zone and require a greater amount of time and skill to weld as
compared to the welded seam 55 shown in FIGS. 6 and 8. It should be
further understood that stresses imparted to the rib/collar
connection 53 shown in FIG. 7 as the centralizer is collapsed to
pass through restrictions as the tubular on which the centralizer
is received is installed in a well are more likely to compromise
the connection 53 as a result of the complex geometry and the
arrangement of the first leg 53a, the second leg 53b, and the third
leg 53c, one relative to the others.
[0044] FIG. 8 is a schematic showing the linear weld path 55 used
to couple two first collar segments 54 of a pair of adjacent bow
spring modules 51 according to one embodiment of the method. Each
rib 52 shown in FIG. 8 is connected to the integral first collar
segment 54 at an integral connection 52a, and the resulting
connection 52a is superior in strength and resilience, and is
unaffected by the heat-affected zone, as compared to the complex
connection shown in FIG. 7. It should be understood that the first
centralizer collar 20 formed in this manner and shown in FIGS. 6
and 8 can be generally identical to the corresponding connection at
the second centralizer collar (not shown in FIG. 8--see FIG. 6),
and that the position of the weld seam 55 is in a relatively
low-stress portion of the collars 20 and 30. The weld seam 55 can
be in a low-stress portion of the collars 20 and 30 because the
great majority of the forces imparted to the collars 20 and 30
result from friction and interference between the bow spring
centralizer 10, which is generally coupled to the pipe string to
move down the bore hole with the pipe string, and the wall of the
borehole as the pipe string and centralizer are installed into the
borehole. These forces imparted to the bow spring centralizer 10
are generally isolated to the bow spring ribs 52 that provide
stand-off between the pipe string and the wall of the borehole. The
ribs 52 may flex and collapse according to the forces imparted by
wall of the borehole, and these forces are transferred, to some
extent, to the rib/collar connections. The weld seams 55, however,
are subjected to relatively little stress because, under normal
circumstances during pipe running operations, there is no expansion
of the pipe string within the collars, and the portions of the
collars 20 and 30 subjected to forces transferred from the ribs 52
are remote from the weld seams 55.
[0045] It should be understood that a bow spring centralizer made
according to the method may comprise a plurality of ribs equal in
number to the plurality of bow spring modules joined to make the
centralizer. It should be understood that one embodiment of a bow
spring centralizer may comprise a plurality of ribs on a bow spring
module. It should be further understood that, while the appended
drawings illustrate a bow spring centralizer comprising bow spring
modules with a bow spring/collar connection generally aligned with
the center of each first collar segment and also generally aligned
with the center of each second collar segment thereon, a bow spring
module could comprise a first collar segment and a second collar
segment, each having a bow spring/collar segment connection that is
not centered in this manner. It should be understood that the first
collar segment and/or the second collar segment could be offset or
eccentrically connected to the first end or the second end of the
rib, respectively.
[0046] It should be understood that a spacer, such as, but not
limited to, an extender, link, tab or tongue, may be coupled to a
first collar segment or to a second collar segment, or both, of a
bow spring module to modify or alter the size, reach, span or
breadth of the bow spring module without deviating from the general
purpose of the bow spring module or from the scope of this
invention. Various modifications to the bow spring module to
accommodate or to facilitate the coupling of bow spring modules or
spacing of bow spring modules within the bow spring centralizer may
be employed.
[0047] The term "interlinking," as used in the claims and the
specification herein, does not mean that each bow spring module is
linked or coupled directly to each of the other bow spring modules
used in a plurality to make a bow spring centralizer, but instead
means that each bow spring module is linked, directly or indirectly
through other bow spring modules, to the plurality of the bow
spring modules used in a plurality to make a bow spring
centralizer.
[0048] The terms "comprising," "including," and "having," as used
in the claims and specification herein, shall be considered as
indicating an open group that may include other elements not
specified. The terms "a," "an," and the singular forms of words
shall be taken to include the plural form of the same words, such
that the terms mean that one or more of something is provided. The
term "one" or "single" may be used to indicate that one and only
one of something is intended. Similarly, other specific integer
values, such as "two," may be used when a specific number of things
is intended. The terms "preferably," "preferred," "prefer,"
"optionally," "may," and similar terms are used to indicate that an
item, condition or step being referred to is an optional (not
required) feature of the invention.
[0049] While the invention has been described with respect to a
limited number of embodiments, those skilled in the art, having
benefit of this disclosure, will appreciate that other embodiments
can be devised which do not depart from the scope of the invention
as disclosed herein. Accordingly, the scope of the invention should
be limited only by the attached claims.
* * * * *