U.S. patent application number 09/871163 was filed with the patent office on 2002-02-21 for friction reduction means.
Invention is credited to Male, Alan Leslie, Nicoll, Garry T..
Application Number | 20020020526 09/871163 |
Document ID | / |
Family ID | 9892642 |
Filed Date | 2002-02-21 |
United States Patent
Application |
20020020526 |
Kind Code |
A1 |
Male, Alan Leslie ; et
al. |
February 21, 2002 |
Friction reduction means
Abstract
A component which is adapted for use in a down hole environment
such as in a well bore (WB), the component being provided with
friction reduction means (20) comprising a rotatable member (28)
mounted in a ball bearing race (27), the ball contacting the wall
of the well bore (WB) such that the rotatable member (28) rotates
upon the ball bearings to allow the component to be repositioned as
necessary in any direction.
Inventors: |
Male, Alan Leslie;
(Aberdeenshire, GB) ; Nicoll, Garry T.;
(Aberdeenshire, GB) |
Correspondence
Address: |
ONEBANE, BERNARD, TORIAN, DIAZ, MCNAMARA & ABELL
P. O. BOX 3507
LAFAYETTE
LA
70502
US
|
Family ID: |
9892642 |
Appl. No.: |
09/871163 |
Filed: |
May 31, 2001 |
Current U.S.
Class: |
166/241.6 ;
175/325.1; 175/325.3 |
Current CPC
Class: |
F16C 2352/00 20130101;
E21B 17/1057 20130101; F16C 29/046 20130101 |
Class at
Publication: |
166/241.6 ;
175/325.1; 175/325.3 |
International
Class: |
E21B 017/10 |
Foreign Application Data
Date |
Code |
Application Number |
May 31, 2000 |
GB |
0013134.2 |
Claims
1. A component which is adapted for use in a down hole environment
such as in a well bore, the component being provided with friction
reduction means comprising a rotatable member mounted in a ball
bearing race, the ball contacting the wall of the well bore such
that the rotatable member rotates upon the ball bearings to allow
the component to be repositioned as necessary in any direction.
2. A component according to claim 1, wherein the ball bearing race
comprises a plurality of micro balls upon which the ball
rotates.
3. A component according to claim 1 or 2, wherein the friction
reduction means further comprises a seat into which the ball
bearing race is mounted.
4. A component according to claim 3, wherein the seat is formed of
solid steel or case hardened steel.
5. A component according to any one of claims 3 to 5, wherein the
component comprises a cover member which cooperates with the seal
to retain the rotatable member in contact with the ball bearing
race.
6. A component according to claim 5, wherein the cover member is
provided with a central aperture through which the rotatable member
projects.
7. A component according to any one of the preceding claims wherein
the diameter of the rotatable member is significantly larger than
the diameter of the ball bearings.
8. A component according to claim 7, wherein the rotatable member
is about 15 mm in diameter and the ball bearings are about 2 mm in
diameter.
9. A component substantially as herein before described with
reference to and as shown in the FIGS. 2 and 2a of the Figures.
10. A casing centraliser comprising a body having an inner surface
and an outer surface, at least one blade provided on the outer
surface of the centraliser for stabilizing the centraliser within a
well bore and providing a path for the flow of drilling fluids,
said centraliser including a component according to any one of the
preceding claims.
11. A casing centraliser according to claim 10, wherein a plurality
of friction reducing means are provided on the blade.
12. A casing centraliser according to claim 10 or 11, wherein the
centraliser is provided with a plurality of blades extending from
one end of the centraliser body to the other.
13. A centraliser substantially as hereinbefore described with
reference to and as shown in FIGS. 3 to 5 of the Figures.
Description
[0001] This invention relates to a friction reduction means and,
more specifically to a friction reduction means which finds
particular application in the field of downhole components that are
used in the completion of oil and gas wells. The invention is most
particularly relevant to downhole equipment such as centralisers
wherein one or more strings of casing are "cemented" within the
well bore and the strings have to be centralised and stabilized
within the bore.
[0002] In the completion of such wells, a cement slurry is pumped
downwardly within each casing string and upwardly within the
annulus thereabout, and thus between the well bore and the
outermost string or between and inner string and the next outer
string. Desirably, the cement column is of substantially uniform
thickness about the casing, and, in any event, the casing should
not lay up against the side of the well bore or outer casing. It is
important that the casing be cemented in the centre of the well
bore in order to make better producing wells, prevent interzonal
and intrazonal communication, and provide uniform loading which may
prevent collapsed casing in the wells and zones that have a history
of collapsing casing before the end life of the well. Properly
centred casing is important not only in and across the production
zones, but also in other zones to reduce bad cement jobs around
protective casing shoe joints, and thus reduce expensive cement
squeeze jobs for production and for getting good casing shoe
seats.
[0003] It is therefore common practice in the industry to dispose
so called centralisers along the desired length of the casing. The
centralisers are so placed on the casing that after the casing is
run in the well bore, the centralisers will be in a position to
support the casing off the side of the well bore in zones of
interest.
[0004] A well bore is not a true vertical hole in the earth, but
has areas of directional turns, bends and vertical deviation
changes. When casing is run into the well bore it has to contour
with the well bore. The outline of the casing in the well bore may
result in severe or continuous contact with the well bore, with
more severe contour changes resulting in more severe contacts. This
realisation makes a supportive casing centraliser a necessary tool
towards centering the casing in a well bore to attain the desirable
cement coverage around the casing.
[0005] Known centralisers comprise an annular body which surrounds
the casing string, the body having a plurality of blades projecting
from the outer surface thereof. The blades contact the inner
surface of the well bore and stabilize the casing string in the
well bore whilst providing a path for drilling fluids to flow past
the centraliser.
[0006] Although known centralisers are suitable for use during
operations running casing down vertical sections of the well bore,
it will be understood that problems arise when the well bore
deviates from vertical. In these cases, the centraliser is not
aided by gravity to pass along the well bore. By definition the
centralisers contact the inner surface of the well bore and
therefore frictional forces are encountered when running casing in
such circumstances. Additional force must be used in order to feed
the well casing through the well bore in such areas. This can lead
to high production times and reduced life of the centralisers.
[0007] With this in mind, friction reducing means have been
proposed for incorporation into centralisers and are shown in
WO/95/21986. Whilst this document goes some way to overcoming
frictional problems associated with casing centralisers, the
solution which is proposed is not ideal for use in some sections of
well bore for example, where the bore deviates greatly from
vertical. The friction reducing means is in the form of a plurality
of rollers, each mounted to the centraliser through an axle which
must be located in suitable apertures in the centraliser blade.
Whilst this allows for friction reduction in a vertical direction,
the rollers can only move in one direction and therefore no
friction reduction is experienced during rotation of the
centraliser for repositioning. Also, any point loading on the
roller tends to bend the axle and therefore render the friction
reduction element redundant.
[0008] Furthermore, the downhole environment is one which is, by
its very nature, dirty and small particles of oil, dirt, soil etc
can become lodged within the rollers and prevent the rollers from
operating properly.
[0009] It is an object of the present invention to provide a
friction reducing means which, when mounted in a downhole component
such as a centraliser which, like those described above may be
disposed about a casing joint or indeed connected into the casing
string through a threaded coupling, which overcomes or at least
mitigates the above described problems.
[0010] According to one aspect of the present invention there is
provided a component which is adapted for use in a down hole
environment such as in a well bore, the component being provided
with friction reduction means comprising an outer ball mounted in a
ball-bearing race, the outer ball contacting the wall of the well
bore. The outer ball allows the component to move smoothly down the
well bore and allows the component to be repositioned as often as
necessary either rotationally, horizontally or vertically as the
outer ball and ball bearing race allow for universal movement as
opposed to movement in one direction which was possible with the
known roller based friction reduction systems.
[0011] The ball bearing race comprises a plurality of micro balls
upon which the outer ball rotates.
[0012] According to a further aspect of the present invention there
is provided a casing centraliser comprising a body having an inner
surface and an outer surface, at least one blade provided on the
outer surface of the centraliser for stabilizing the centraliser
within a well bore and providing a path for the flow of drilling
fluids, friction reducing means being provided within the blade,
the friction reducing means comprising an outer ball mounted in a
ball-bearing race, the outer ball contacting the wall of the well
bore.
[0013] Preferably, a plurality of friction reducing means are
provided on the blade.
[0014] Advantageously, the centraliser is provided with a plurality
of blades extending from one end of the centraliser body to the
other.
[0015] One embodiment of the present invention will now be
described with reference to the accompanying drawings in which:
[0016] FIG. 1 is a perspective schematic view of a known
centraliser;
[0017] FIG. 2 is a cross-sectional view of a friction reducing
means of a centraliser according to one aspect of the present
invention;
[0018] FIG. 2a is a cross-sectional view of the friction reducing
means of Figure s, with an alternative fixing means;
[0019] FIG. 3 is a part cross-section view of a centraliser
comprising the friction reducing means of FIG. 2;
[0020] FIG. 4 is a side view of the centraliser of FIG. 2; and
[0021] FIG. 5 is a side view of the centraliser of FIG. 2, with an
alternative form of blade construction.
[0022] Turning now to the Figures, in FIG. 1, a known centraliser
is shown. The well bore WB is substantially vertical, although it
will be understood that it may deviate a rather substantial amount
with respect to the vertical. A casing or liner C is cemented CM
into the well bore. As can be see, the diameter of the well bore is
uneven throughout its length, with restricted areas at random
points along its length. The casing string CS is made up of a
plurality of casing joints CJ, each having a box at one end and a
pin at the other end for connection to adjacent joints making up
the string.
[0023] Each of the centralisers is indicated in its entirety by
reference number 10 and is disposed about a casing joint for
maintaining the joint substantially centred within the well bore so
that a cement column of substantially even thickness may form about
the casing string. It will be understood that the number and
spacing of the centralisers along the length of the casing string
may vary at the will of the operator of the well.
[0024] In any event, such centralisers comprise a tubular body 11
which is constructed to fit closely about the casing joint, and a
plurality of blades 12 which extend longitudinally along the outer
diameter of the body thereto in generally equal spaced apart
relation.
[0025] More particularly, in the illustrated embodiment the body is
of circumferentially continuous construction and of sufficient
thickness for adequate strength. The side edges of adjacent blades
are disposed apart to allow ample fluid passage, and yet provide
bearing surfaces of ample width at the wall of the well bore. In
order to assemble the centraliser on the casing joint CJ, the body
of the centraliser is slipped over the pin end of the joint prior
to make up of the pin with a box end on an adjacent casing
joint.
[0026] FIG. 2 is a cross-section through a friction reducing means
20 adapted to be mounted into the blade 12 of a centraliser 10
according to one aspect of the present invention. A straight blade
centraliser is illustrated although the present invention is
equally suitable for use with spiral blade centralisers. Each blade
12 may be provided with friction reducing means 20 or they may be
provided on selected blades only.
[0027] The friction reducing means 20 comprises a seat 21 formed of
solid steel or alternatively case hardened steel, the seat being
sized to be mounted within the blade 12 of the centraliser. The
seat has an upper surface 22 which is semi-circular in
configuration as shown in FIG. 2. The thickness of the seat is
significant in allowing greater loads to be transmitted through the
element into the seat as will be described later. This also
increases the wear resistance of the seat which is important in the
environment it is adapted to operate in.
[0028] The outer surface 23 of the seat is substantially tubular in
configuration. The lower region 24 of the seat is provided with an
integral flange 25 which extends outwardly from the outer wall of
the seat to form an upper facing shoulder 26.
[0029] A layer of grease (not shown) is provided over the upper
surface 22 of the seat and a plurality of micro ball bearings 27
are provided within the seat 21 to cover the upper surface 22
thereof. There may be around 100 micro balls provided to cover the
surface of the seat. A rotatable member such as an outer ball 28 is
then rotatably mounted within the seat, upon the micro ball
bearings 27. The outer ball rotates smoothly upon the micro ball
bearings and, in the example illustrated, is significantly larger
in diameter than the micro ball bearings. In this example the outer
ball is around 15 mm in diameter as compared to the micro ball
bearings which are around 2 mm in diameter each.
[0030] A cover member 29 is mounted over the outer ball 28, the
cover member is a substantially hollow tubular member. The lower
end 30 of the outer wall 31 of the cover member is chamfered
inwards 32 so that when the cover member is mounted on the seat,
the chamfered edge lies at or adjacent to the shoulder 26 of the
seat.
[0031] The lower portion 33 of the inner surface 34 of the cover
member lies against the tubular section of the seat 21 and is
provided with an internal facing chamfer 35 which fits over the
upper surface of the seat at the outer edges thereof. An arcuate
recess 36 extends from the internal facing shoulder over the micro
ball bearings 27 mounted in the seat and functions to allow the
ball bearings to rotate around the seat in use.
[0032] The upper portion 37 of the inner surface 34 of the cover
member is adapted to provide an arcuate surface 38 which supports
and retains the outer ball 28 of the friction reducing means,
without restricting the rotation of the outer ball. The upper
portion of the cover has a chamfered surface 39 which improves
radial clearances on the blades. During assembly, the cover member
29 may be press fit over the seat portion 21 of the friction
reducing means.
[0033] As described above, the friction reducing element is adapted
to be mounted within the blade 12 of a centraliser 10. As shown in
FIG. 3 a blind bore 30 is provided in each of the blades and a
friction reducing element is mounted into each bore 30. The
friction reducing means may be secured in a push-fit manner within
the bore.
[0034] Alternatively, the external surface of the cover may be
threaded 40 (FIG. 2a) with corresponding threads provided within
the bore to allow the element to be threaded into position.
[0035] In FIG. 5 an alternative form of blade construction is
illustrated. In this example, the blades have a tapered nose
section 41 which improves the penetration of the centraliser into
the casing and also cigars a path for the friction reduction
unit.
[0036] In use, the ball outer 28 of the friction reducing means
projects significantly beyond the cover member 29. This allows the
surface of the ball to contact the internal wall of the well bore
casing without blocking the path for well fluids which is provided
between the various blades 12 of the centraliser 10.
[0037] The micro ball bearings 27 upon which the outer ball is
mounted ensures that the friction reducing element efficiently
reduces frictional forces which act upon the surface of the blades
of the centraliser which come into contact with the inner surface
of the well bore casing. This enables the casing string to be
quickly and efficiently run in the well bore.
[0038] The above described centraliser is subject to lower
frictional forces when being run in the well bore which is
particularly important when running casing or liner in extended
reach and long horizontal sections of the well as centraliser is
subject to reduced drag and torque forces and the wear on the
centraliser is minimised in comparison to known centralisers.
[0039] The vertical load acting on the large diameter ball is
transmitted through the micro balls (ball bearings) to the seat and
does not transmit to the cover member.
[0040] Tests have indicated that an element as described in a
centraliser can withstand compression loads up to at least 18,000
KG which is substantially greater than that of any known friction
reduction unit.
[0041] A further advantage of such centralisers is that the use of
water based drilling muds is permitted during drilling operations
and this is both economically and environmentally superior to the
use of oil based muds.
[0042] The production costs for this element is less than for the
corresponding roller arrangement as there is a general reduction in
the number of components used, the design is simplified and this
leads to a reduction in the time taken to fit the friction
reduction elements into the component.
[0043] The above description has been directed towards a casing
centraliser which is mounted around a casing string but could also
be directed towards any component which is adapted to be used in a
similar environment, such as for example an in-line centraliser
which is connected into the pipe line via suitable threaded
couplings, pipe collar, float equipment and stabilisers.
* * * * *