Note: Descriptions are shown in the official language in which they were submitted.
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CENTRALIZER
This invention relates to a centralizer for
centralizing a tubular in a wellbore.
Centralizers are used to center one tubular member
inside a wellbore or inside another tubular member, e.g. to
center a first casing inside a second casing. Typically
centralizers are placed on the exterior of the inner
tubular member and project outwardly therefrom. In many
typical situations the annular space between the outer
circumference of the inner tubular member and the inner
circumference of the outer tubular member is relatively
constant and it is a straightforward matter to provide a
centralizer with spring bows having the desired radial
projection. However, it is sometimes desirable to be able
to pass an inner tubular member through a relative small
tubular member into an outer tubular member of
significantly greater diameter in which the inner tubular
member is to be centralized.
In accordance with one embodiment of the present
invention there is provided a centralizer comprising a
tubular body having an outer surface; a first groove in the
outer surface of the tubular body, the first groove having
outer and inner side walls; a first collar slidably mounted
on the tubular body within the first groove wherein
longitudinal movement of the first collar in opposite
directions along the tubular body is limited by the inner
and outer side walls; and a plurality of spring bows each
of which has a first end attached to the first collar and a
second end coupled to the tubular body; wherein lengths of
the spring bows and a permitted degree of movement of the
first collar are such that, upon movement of the first
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collar in a direction away from the inner side wall, the
spring bows move inwardly to lie substantially flat against
the outer surface of the tubular body in their innermost
positions.
In accordance with another embodiment of the present
invention there is provided a centralizer apparatus
comprising a tubular body with an exterior surface; a first
collar movably emplaced around the tubular body and movable
longitudinally thereon; a first groove in the exterior
surface of the tubular body, the groove defined by a top
side wall, a bottom side wall, and a middle wall
therebetween; the first collar movably disposed in the
groove, and the first groove top side wall and bottom side
wall limiting first collar movement; a plurality of spring
bows, each spring bow having a first end spaced apart from
a second end, each spring bow biased outwardly from the
tubular body, the first ends connected to the first collar,
so that upon movement of the first collar in a direction
away from the second ends of the spring bows the first ends
move with the first collar and the spring bows move
inwardly toward the tubular body.
Yet another embodiment of the present invention
provides a centralizer apparatus comprising a hollow
tubular body with an exterior surface and a longitudinal
bore therethrough; a first collar movably emplaced around
the tubular body and movable longitudinally thereon; a
plurality of spring bows, each spring bow having a first
end spaced apart from a second end, each spring bow biased
outwardly from the tubular body; a first groove in the
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exterior surface of the tubular body, the groove defined by
a top side wall and a bottom side wall, and a middle wall
therebetween; the first collar movably disposed in the
groove; the first groove top side wall and bottom side wall
limiting first collar movement; the first ends of the
spring bows connected to the first collar, so that upon
movement of the first collar in a direction away from the
second ends of the spring bows the spring bows move
inwardly toward the tubular body; a second collar movably
emplaced around the tubular body and movable longitudinally
thereon; the second ends of the spring bows connected to
the second collar, so that upon movement of the second
collar away from the first collar, the spring bows move
inwardly toward the tubular body; a second groove in the
exterior surface of the tubular body, the second groove
defined by a top side wall and a bottom side wall, and a
middle wall therebetween; the second collar movably
disposed in the groove; and the second groove top side wall
and bottom side wall limiting second collar movement.
Centralizers according to this invention and/or any or
all parts thereof may be made of any suitable material,
including, but not limited to, metal, plastic, fiberglass,
composites, cermets, aluminum, aluminum alloys, brass,
copper, zinc or zinc alloys.
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For a better understanding of the present invention
and to show how the same may be carried into effect
reference will now be made, by way of example, to the
accompanying drawings, in which:-
Fig. la is a side view, partially in cross-section,
of a first embodiment of a centralizer according to the
present invention in an expanded position;
Fig. lb is a cross-sectional view along line lb-lb
of Fig. la;
Fig. 1c is an enlargement of the detail in circle c
in Fig. lb;
Fig. ld Is an enlargement of the detail in circle d
in Fig. la;
Fig. le is a side view, partially in cross-section,
of the centralizer of Fig. la in a compressed position;
Fig. 2 is a cross-sectional view of a tubular body
which forms part of the centralizer of Fig. la;
Fig. 3a is an end view of an alternative spring bow
which may form part of the centralizer of Fig. la;
Fig. 3b is a side view of the sWring bow of Fig.
3a;
Fig. 4 is a side view, partially in cross-section,
of a second embodiment of a centralizer according to the.
present invention;
Fig. 5 is a side view, partially in cross-section,
of a third embodiment of a centralizer,according to the
present invention;
Fig. 6 is a side view, partially in cross-section,
of a fourth embodiment of a centralizer according to the
present invention;
Fig. 7 is a side view, partially in cross-section,
of a fifth embodiment of a centralizer according to the
present invention;
Fig. 7b is a partial cross-section view along line =
7b-7b of Fig. 7a;
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Fig. 8 is a side view, partially in cross-sectlon,
of a sixth embodiment of a centralizer according to the
present invention;
Fig. 9a is an end view of a seventh embodiment of a
centralizer according to the present invention taken in
the direction of arrow 9a in Fig. 9b;
Fig. 9b is a partial side view of the centralizer
of Fig. 9a;
Fig. 10a is a partial side view of an eighth embo-
diment of a centralizer according to the present inven-
tion;
Fig. lOb is a partial side view of the centralizer
of Fig. lOa;
Fig. 11 is a side view of a ninth embodiment of a
centralizer according to the present invention; and
Fig. 12 is a side view in cross-section of a tubu-
lar body which can form part of_certain centralizers
according to the present invention.
Referring to Figs. 1 to 3, a centralizer 10 accord-
ing to the present invention comprises a tubular body 12
with a central longitudinal bore 14 running there-
through. The upper and lower ends of the tubular body
12 are threaded so that the centralizer 10 may be read-
ily incorporated in a length of casing or a string of
tubulars.
Formed in or machined into the exterior surface 16
of the tubular body 12 are upper and lower collar
grooves 18 and a spring bow groove 22.
A first collar 24 is slidably disposed in the upper
collar groove 18 and a second collar 26 is slidably
disposed in the lower collar groove 18. A plurality of
spring bows 20 are arranged circumjacent the tubular
body 12 with their respective ends secured to the first
and second collars 24, 26.
As better shown in Fig. ic the end 28 of each
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spring bow 20 is recessed in a groove 32 in a respective
collar so that it does not extend radially beyond the
radial outer surface 34 of the first and second collars
24, 26.
As shown in Fig. le, the first and second collars
24, 26 have moved apart from each other in their respec-
tive collar grooves 18; and the spring bows 20 have
collapsed with a major portion thereof in the spring
bow groove 22.
A bottom ridge 23 (Fig. 2) provides a stop against
which the second collar 26 abuts when it has moved in
response to contact of the spring bow 20 with the wall
of a tubular during insertion therein. Once such abut-
ment occurs, the spring bows 20 are deflected radially
inwardly as the centralizer 10 moves downwardly.
Fig. 3b shows a spring bow 50 with a body 52 and
ends 54, 56. Fig. 3a shows that the end 54 (like the
end 56) has a curved shape to accommodate the curved
exterior surface 16 of the tubular body 12. The curved
shape also permits the ends 54, 56 to "hug" the exterior
surface 16. The spring bows 20 have non-curved ends 28
but may be replaced with spring bows similar to the
spring bow 50.
Fig. 4 illustrates a second embodiment of a centra-
lizer 60 according to the present invention which is
like the centralizer 10 (with like numerals indicating
similar parts). However, the centralizer 60 has only
one collar groove 18 and only one slidable collar 24.
The lower collar 26 is held fast in a groove 27. The
tubular body 13 (like the tubular body 12) has a bore 15
(like the bore 14) therethrough. Upon movement of the
collar 24, the spring bows 20 can move toward and col-
lapse =
against an exterior surface of the tubular body
13.
Fig. 5 illustrates a third embodiment of a centra-
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lizer 70 according to the present invention (in which
parts similar to those of centralizer 10 bear the same
identifying numerals). The essential difference is that
whilst the upper ends of the spring bows 23 are secured
to collar 24, which is slidably mounted on the tubular
body 17 the other ends are welded direct to the tubular
body 17. A single continuous recess 29 is provided to
accommodate the spring bows 23 when they collapse.
Fig. 6 illustrates a fourth embodiment of a centra-
lizer 80 according to the present invention. A plural-
ity of spring bows 81 have a first end 82 secured to a
tubular body 83 of the centralizer 80. A second end 84
of each spring bow 81 is receivable in and movable in a
recess 85 formed in or milled in the tubular body 83. A
bore 86 extends through the body 83. Upon contact of
the spring bows 81 with an interior of another tubu:Lar
or a wellbore, the spring bows move toward the tubular
body 83 with their ends 84 moving in the grooves 85 so
that the spring bows collapse against the tubular body
83.
Figs. 7a and 7b illustrate a fifth embodiment of a
centralizer 90 according to the present invention which
has a tubular body 91 with a bore 92 therethrough. A
plurality of spring bows 93 each has an end 94 secui-ed
to the tubular body 91 and an end 95 freely movable iri a
slot 96 extending through a portion of the tubular body
91. If desired a recess may be provided beneath each
spring bow 93 to receive some, a major portion of, or
all of it upon collapse of the spring bows against the
tubular body 91.
Fig. 8 shows a centralizer 40 like the centralizer
90; (and like aspects bear like identifying numerals);
but the spring bows 93 have a tab end 41 which is mov-
able in an enlarged portion 42 of a slot 43. It is
within the scope of this invention to provide a tab 41
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and a slot 43 for the opposing spring bow ends. Such a
tab end and enlarged groove portion may be used with the
ends 84 of the spring bows 81 in the centralizer 80 of ~
Fig. 6. In one aspect the tab end may be a piece which
is initially separate from the spring bow, but which is
secured to a spring bow end (e.g. by welding, screws, or
bolts) once the spring bow end is inserted into and
through a slot.
It is within the scope of this invention to provide
structures which project beyond the exterior surface of
a centralizer body and confine a spring bow end with the
spring bow end movable in the structure so that the
spring bow can collapse. Alternatively such a structure
may be provided on a collar that is fixed (movably or
immovably) around a centralizer body or around a groove
in a centralizer body.
Figs. 9a and 9b show a seventh embodiment of a
centralizer 100 according to the present invention with
a tubular hollow body 101, a single spring bow end
retainer 102 and a spring bow 103. Any number of spring
bow retainers 102 and spring bows 103 may be used spaced
apart around the outer circumference of the tubular
hollow body 101. The tubular retainer 102 has two
upright arms 104, each with a shoulder 105, and with a
gap 106 between them. A portion 107 of the spring bow
103 is movably confined beneath the shoulders 105 and an
outwardly extending portion 108 moves in the gap 106.
An end 109 of the spring bow is larger than a space 110
between two stop members 111, thus preventing the spring
bow from separating from the tubular body 101.
Figs. l0a and lOb show a centralizer 120 with a
tubular body 121 and one (or more) spring bows 122. An
end 123 of the spring bow 122 is movably disposed under
a bar 124 which holds the end of the spring bow and
prevents it separating from the tubular body 121. An
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arch 125 in the end of the spring bow 122 moves over a
stop member 126, e.g. when the spring bow 122 moves
inwardly to collapse against the tubular body 121. In
preferred embodiment the various parts, grooves, reces-
ses, etc. are sized, disposed and configured to permit
full collapse of the spring bow(s) against and/or into
the tubular body. The end of the spring bow moves in a
recess 129. The end of the spring bows 122 may have tab
ends similar to those shown in Fig. 8.
Fig. 11 shows a centralizer 130 with a hollow
tubular body 131. A top end groove 132 and a bottom end
groove 133 are formed in the outer surface 134 of the
hollow tubular body 131. The end grooves are sized and
configured to permit ends 135 and 136 of a spring bow
140 to move therein so that a body 141 of the spring bow
140 may move into a longitudinal groove 137 in the outer
surface 134 when the spring bow 140 is collapsed toward
the hollow tubular body 131. Retainers 145 (like 'the
retainers 102, Fig. 9a) hold tab ends 146 of the spring
bow 140 as they move within the retainers 145.
Fig. 12 illustrates a tubular body 29 (like the
tubular body 12, Fig. 2); but which has only one large
groove 55 therearound for accommodating two movable
collars (like, e.g., collars 24, 26, Fig. la) and the
spring bows. In any embodiment of this invention the
tubular body may be solid or it may have a fluid flow
bore or bores therethrough.
In certain embodiments of the present invention it
is preferred that the parts, grooves, and recesses are
sized, configured, and disposed so that the collars and
spring bows, upon collapse of the spring bows against
the apparatuses tubular body, do not project beyond the
tubular body's exterior surface more than 9.5mm (three-
eighths of an inch). In other embodiments this pre-
ferred length is no more than 6.4mm (one-fourth inch);
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3.2mm (one-eighth inch); 1.6mm (one-sixteenth inch); or
zero. In other embodiments the collars and spring bows
are within grooves or recesses and are below the level of the exterior surface
of the tubular body.
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