U.S. patent application number 11/891255 was filed with the patent office on 2009-02-12 for downhole tool with slip elements having a friction surface.
This patent application is currently assigned to Halliburton Energy Services, Inc.. Invention is credited to James L. Barlow.
Application Number | 20090038790 11/891255 |
Document ID | / |
Family ID | 40341817 |
Filed Date | 2009-02-12 |
United States Patent
Application |
20090038790 |
Kind Code |
A1 |
Barlow; James L. |
February 12, 2009 |
Downhole tool with slip elements having a friction surface
Abstract
Slip segments with a friction medium are used to anchor a
downhole tool in a well. Each slip segment has a slip segment body
made of a drillable material. A friction medium is applied to the
outer surface of the slip segment body so that the outer surface of
the slip segment has an increased holding capability in the
well.
Inventors: |
Barlow; James L.; (Duncan,
OK) |
Correspondence
Address: |
JOHN W. WUSTENBERG
P.O. BOX 1431
DUNCAN
OK
73536
US
|
Assignee: |
Halliburton Energy Services,
Inc.
|
Family ID: |
40341817 |
Appl. No.: |
11/891255 |
Filed: |
August 9, 2007 |
Current U.S.
Class: |
166/89.2 |
Current CPC
Class: |
E21B 33/129 20130101;
E21B 33/1204 20130101 |
Class at
Publication: |
166/89.2 |
International
Class: |
E21B 19/10 20060101
E21B019/10 |
Claims
1. Apparatus for anchoring a downhole tool in a well comprising: a
plurality of slip segments disposed about a mandrel of the downhole
tool and movable to a set position wherein the slip segments engage
the well, at least one of the slip segments made of a drillable
material with a friction medium applied to the outer surface
thereof for increasing the gripping capability of the slip segment
to the well.
2. The apparatus of claim 1, wherein the slip segment has a
sandpaper-like outer surface.
3. The apparatus of claim 1, the at least one slip segment
comprising a phenolic slip segment body, the friction medium being
applied to the outer surface of the slip segment body.
4. The apparatus of claim 3, wherein the friction medium is molded
to the phenolic slip segment body.
5. The apparatus of claim 3, wherein the friction medium comprises
aluminum oxide.
6. The apparatus of claim 1, wherein the slip segments have at
least one button secured thereto and extending outwardly from the
outer surface thereof for gripping the casing.
7. The apparatus of claim 1, wherein the plurality of slip segments
are comprised of a non-metallic material.
8. The apparatus of claim 7, wherein the plurality of slip segments
are comprised of a phenolic.
9. The apparatus of claim 8, the friction medium comprising
aluminum oxide applied to the outer surface of the phenolic.
10. The apparatus of claim 8, wherein all of the slip segments
include the friction medium at the outer surface thereof.
11. A downhole tool for use in a well comprising: a mandrel; a slip
ring movable from a set to an unset position, wherein in the set
position the slip ring grippingly engages the well, the slip ring
comprising a drillable material with a friction medium applied on
the outer surface thereof for increasing the gripping capability of
the slip ring to the well.
12. The downhole tool of claim 11 wherein the slip ring comprises a
plurality of slip segments, at least a portion of the slip segments
having the friction medium on an outer surface thereof.
13. The downhole tool of claim 12, wherein the friction medium
comprises aluminum oxide.
14. The downhole tool of claim 12, wherein the slip segments are
comprised of a phenolic.
15. The downhole tool of claim 11 comprising an expandable packer
element disposed about the mandrel and first and second slip rings,
one of the slip rings positioned above the packer element and the
other positioned below the packer element.
16. The downhole tool of claim 15, wherein the first and second
slip rings comprise a plurality of slip segments grippingly
engageable with the well.
17. The downhole tool of claim 16, wherein at least a portion of
the slip segments comprises inserts extending outwardly from an
outer surface thereof.
18. The downhole tool of claim 17 wherein the slip segments
comprise a phenolic slip segment body with aluminum oxide applied
to an outer surface thereof.
19. A downhole tool for use in a well comprising:: a mandrel; an
expandable element disposed about the mandrel; a first slip ring
disposed about the mandrel movable from an unset to a set position
wherein the first slip ring grippingly engages the well in the set
position; a second slip ring disposed about the mandrel movable
from an unset to a set position wherein the second slip ring
grippingly engages the well in the set position, wherein at least
one of the first and second slip rings has a friction medium on the
outer surface thereof so that the gripping ability of the slip ring
is greater than the gripping ability of a bare slip ring.
20. The downhole tool of claim 19, the first and second slip rings
comprising a plurality of slip segments retained on the mandrel and
movable to the set position wherein an outer surface of at least a
portion of the slip segments engages the well in the set
position.
21. The downhole tool of claim 20, wherein at least a portion of
the slip segments comprises a phenolic slip segment body with the
friction medium applied thereto.
22. The downhole tool of claim 21, the friction medium comprising
aluminum oxide.
23. The downhole tool of claim 19, the slip rings comprising a
phenolic having the friction medium applied to the outer surface
thereof.
24. The downhole tool of claim 19, the friction medium comprising
aluminum oxide.
Description
BACKGROUND
[0001] Downhole tools for use in oil and gas wellbores often have
drillable components made from metallic or non-metallic materials,
such as soft steel, cast iron, engineering grade plastics, and
composite materials.
[0002] In the drilling or reworking of oil wells, a great variety
of downhole tools are used. For example, but not by way of
limitation, it is often desirable to seal tubing or other pipe in
the casing of the well, such as when it is desired to pump cement
or other slurry down the tubing and force the slurry out into a
formation. It thus becomes necessary to seal the tubing with
respect to the well casing and to prevent the fluid pressure of the
slurry from lifting the tubing out of the well. Downhole tools
referred to as packers and bridge plugs are designed for these
general purposes and are well known in the art of producing oil and
gas.
[0003] Bridge plugs isolate the portion of the well below the
bridge plug from the portion thereabove. Bridge plugs therefore may
experience a high differential pressure and must be capable of
withstanding the pressure so that the bridge plug seals the well
and does not move in the well after it has been set.
[0004] Bridge plugs make use of metallic or non-metallic slip
segments, or slips, that are initially retained in close proximity
to a mandrel but are forced outwardly away from the mandrel of the
tool upon the tool being set to engage a casing previously
installed within an open wellbore. Upon the tool being positioned
at the desired depth, or position, the slips are forced outwardly
against the inside of the casing to secure the packer, or bridge
plug as the case may be, so that the tool will not move relative to
the casing when, for example, operations are being conducted for
tests, to stimulate production of the well, or to plug all or a
portion of the well.
[0005] Cylindrically shaped inserts, or buttons, may be placed in
such slip segments, especially when the slip segments are made of a
non-metallic material such as plastic composite material, to
enhance the ability of the slip segments to engage the well casing.
The buttons must be of sufficient hardness to be able to partially
penetrate, or bite into, the surface of the well casing which is
typically steel. However, especially in the case of downhole tools
being constructed of materials that lend themselves to being easily
drilled from the wellbore once a given operation involving the tool
has been performed, the buttons must not be so hard or so tough to
resist drilling or fouling of the cutting surfaces of the drilling
bit or milling bit. The buttons will at times tear, rupture, or
otherwise alter the slip segments, and thereby become loosened from
the slip segments. When the buttons become loose, the slip segments
may lose some gripping capability, and are therefore susceptible to
movement in the well due to the high pressures experienced in the
well.
[0006] While current slip elements work well in many circumstances,
there is a continuing need to increase the holding capability of
the slips.
SUMMARY
[0007] A downhole tool has a mandrel and an expandable packer
element disposed thereabout for sealingly engaging a well. Slip
assemblies are positioned on the mandrel above and below the packer
element to anchor the downhole tool in the well. Each slip assembly
comprises a slip ring movable from an unset position to a set
position in which the slip ring engages the well. The slip ring
comprises a plurality of slip segments. Each slip segment is
retained about the mandrel and is movable radially outwardly so
that it will engage the well and anchor the well tool in the well.
The slip segments comprise a slip segment body with a friction
medium applied to the outer surface. A plurality of inserts, or
buttons may be secured to the slip segments, and will extend
outwardly from the outer surface thereof. The friction medium
increases the ability of the slip segment to hold the well tool in
the well and to withstand pressures experienced in the well. The
surface of the slip segment with the friction medium thereon may be
a sandpaper-like surface.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] FIG. 1 is a cross section of a downhole tool disposed in a
well.
[0009] FIG. 2 is an enlarged cross-sectional side view of a slip
segment with a friction medium applied to the outer or engagement
surface thereof.
[0010] FIG. 3 is an exploded end view of two slip segments with
friction medium applied to the outer or engagement surface
thereof.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT
[0011] Referring to the drawings, FIG. 1 shows well 10 comprising a
wellbore 12 with a casing 14 cemented therein. Downhole tool 16
comprises a mandrel 18 with an outer surface 20 and an inner
surface 22. The tool in FIG. 1 may generally be referred to as a
bridge plug since downhole tool 16 has an optional plug 24 pinned
within mandrel 18 by radially oriented pins 26. Plug 24 has a seal
28 located between plug 24 and mandrel 18. The overall tool
structure would be suited for use as and referred to as a packer if
plug 24 was not incorporated and fluid communication was allowed
through the tool. Other components may be connected so that the
packer, without plug 24 may be used, for example, as a frac
plug.
[0012] A spacer ring 30 is mounted to mandrel 18 with a pin 32. A
slip assembly 34 is disposed about mandrel 18 and spacer ring 30
provides an abutment which serves to axially retain slip assembly
34. Downhole tool 16 has two slip assemblies 34, namely a first
slip assembly and second slip assembly which are shown in the
drawings and are designated in the drawings as first and second
slip assemblies 34a and 34b for ease of reference. The slip
assemblies will anchor downhole tool 16 in well 10. The structure
of slip assemblies 34a and 34b is identical, and only the
orientation and position on downhole tool 16 are different. Each
slip assembly 34 includes a slip ring 36 and slip wedge 38 which is
pinned into place with pins 40.
[0013] Slip ring 36 is an expandable slip ring 36 which has a band
42 disposed in grooves 44. Retaining band 42 will retain slip ring
36 in an unset position about mandrel 18 when downhole tool 16 is
lowered into the well. Slip rings 36 may be moved or radially
expanded from the unset to the set position which is seen in FIG. 1
in which the first and second slip rings 36 engage casing 14 to
hold downhole tool 16 in the well.
[0014] Slip rings 36 are comprised of a drillable material, for
example a molded phenolic. A friction medium 37, such as for
example aluminum oxide, is applied to the outer surface of the
phenolic material, so that the outer surface 46 of slip ring 36
comprises the friction medium. Slip rings 36 may be made from other
drillable materials as well such as drillable metals, composites
and engineering grade plastics. The remainder of the slip assembly
and other components of the tool may likewise be made from
drillable materials. A plurality of inserts or buttons 48 are
secured to slip ring 36 by adhesive or by other means and extend
radially outwardly from outer surface 46. The buttons are comprised
of material of sufficient hardness to partially penetrate or bite
into the well casing and may be comprised, for example, of tungsten
carbide or other materials. The buttons may be, for example, like
those described in U.S. Pat. No. 5,984,007. In the set position as
shown in FIG. 1, buttons 48 will engage or grip casing 14 to hold
tool 16 in place.
[0015] Each slip ring 36 is preferably comprised of a plurality of
slip segments 50. Slip segments 50 have inner surface 52, outer
surface 54 and first and second sides 56 and 58, respectively.
Outer surface 54 of each slip segment comprises a portion of outer
surface 46 of slip ring 36. Slip segments 50 are shown in FIGS. 3
and 4. Slip rings 36 may include, for example, six to eight slip
segments 50 that encircle mandrel 18. Slip ring 36 may include more
or less than six or eight segments, and the examples herein are
non-limiting.
[0016] Slip segments 50 include a slip segment body 60 which has
friction medium 37 applied to the outer surface 62 thereof so that
the outer surface 54 of each slip segment comprises friction medium
37. When outer surface 54 engages casing 14, friction medium 37
will engage casing 14 to increase the holding capability of slip
segment 50 over the holding capability of a bare slip segment
(i.e., a slip segment with no friction medium applied to the slip
segment body). At least one and preferably all of slip segment
bodies 60 are comprised of a drillable material, for example, a
molded phenolic. The friction medium may be applied to one or more
of the slip segment bodies 60 to increase the coefficient of
friction between the slip segments 50 and casing 14. Friction
medium 37 may be for example crushed ceramics, carbide particles,
steel particles, granite particles and, as set forth above,
aluminum oxide in the described embodiment. The aluminum oxide may
be applied to slip segment body 60 for example by molding aluminum
oxide into the phenolic slip segment body. Slip segments 50 will
preferably have a sandpaper-like outer surface 54.
[0017] A packer element assembly 64 which includes at least one
expandable packer element 66 is positioned between slip wedges 38.
Packer shoes 68 may provide axial support to the ends of packer
element assembly 64.
[0018] In operation, downhole tool 16 is deployed in well 10 using
known deployment means such as for example jointed or coiled
tubing. Downhole tool 16 will be in an unset position wherein tool
16 does not engage well 10. Thus, neither slip ring 36, nor packer
element assembly 64 will engage casing 14 in the unset position. In
the unset position, spacer ring 30, slip ring 36a and slip wedge
38a are all in an initial position about mandrel 18 and are
positioned axially upwardly and radially inwardly from the set
position shown in FIG. 1. When downhole tool 16 reaches a desired
location in the well, each of slip rings 36a and 36b are moved
radially outwardly to the set position shown in FIG. 1, and tool 16
may be left in well 10. Downhole tool 16 separates well 10 into
upper well portion 10a and lower portion 10b. The upper and lower
portions 10a and 10b are isolated from one another by well tool 16
which in the embodiment shown is a bridge plug. Tool 16 will
typically experience high differential pressures in well 10 which
will try to move the well tool 16 in well 10 after tool 16 has been
set. The gripping engagement between slip segments 50 and casing 14
will hold the well tool 16 in place. Friction medium 37 at the
outer surface 54 of slip segments 50 will increase the coefficient
of friction over that which is seen with the material that
comprises the slip segment body, and as such increases the holding
capability over a bare slip segment body.
[0019] When well tool 16 is set in well 10, buttons 48 will bite,
or cut into casing 14 as slip segments 50 move radially outwardly
from the unset position. Outer surface 54 of at least a portion of
slip segments 50 will engage casing 14 in the set position.
[0020] It is known that buttons 48 may tear or rupture the slip
segment body 60 or otherwise become loosened from slip segment body
60. When this occurs, slip segment surface 54 may contact casing 14
so that all or most of surface 54 is in contact with casing 14, and
friction becomes a greater component of the holding ability of slip
rings 36 in well 10. The likelihood of slippage may increase in
such cases. While slip segment bodies with no friction medium
applied thereto provide some gripping capability, they do not
provide the holding force that is provided with the slip segments
described herein.
[0021] The increased coefficient of friction between friction
medium 37 at outer surface 54 and casing 14 is such that an
increased holding capability is supplied by slip segment 50. Slip
rings 36 comprised of slip segments 50 will hold well tool 16 in
place at pressures higher than is possible with bare slip segments.
For example, a tool utilizing phenolic slip segments with no
friction medium applied thereto can typically withstand
differential pressures less than 10,000 psi without slippage. Tests
have shown that a well tool with phenolic slip segments utilizing
aluminum oxide as a friction medium as described herein can
withstand differential pressures of greater than 10,000 psi with no
slippage.
[0022] Thus, it is seen that the apparatus and methods of the
present invention readily achieve the ends and advantages mentioned
as well as those inherent therein. While certain preferred
embodiments of the invention have been illustrated and described
for purposes of the present disclosure, numerous changes in the
arrangement and construction of parts and steps may be made by
those skilled in the art, which changes are encompassed within the
scope and spirit of the present invention as defined by the
appended claims.
* * * * *