U.S. patent application number 15/271944 was filed with the patent office on 2018-03-22 for centralized wiper plug.
This patent application is currently assigned to BAKER HUGHES INCORPORATED. The applicant listed for this patent is BAKER HUGHES INCORPORATED. Invention is credited to Gilberto Cortez, Victor A. Cortez, Christopher K. Elliott.
Application Number | 20180080304 15/271944 |
Document ID | / |
Family ID | 61617486 |
Filed Date | 2018-03-22 |
United States Patent
Application |
20180080304 |
Kind Code |
A1 |
Cortez; Victor A. ; et
al. |
March 22, 2018 |
Centralized Wiper Plug
Abstract
A wiper plug has a elastomeric fin assembly straddled by
centralizers that have the capacity to flex through restrictions
while being strong enough to centralize and scrape a surrounding
tubular wall. The centralizers reduce wear on the rib/fin assembly
particularly on long horizontal runs. The centralizers can be a
continuous spiral or a series of circumferentially offset spiral
segments on a common hub. The spiral segments contain brushes
extending from a base where the base and the mounting slot have a
dovetail relationship for fixation to the wiper plug body. The plug
body consist of three separate segments that are threaded together
in order to trap the brush segments in the dovetail channels.
Inventors: |
Cortez; Victor A.; (Houston,
TX) ; Elliott; Christopher K.; (Houston, TX) ;
Cortez; Gilberto; (Spring, TX) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
BAKER HUGHES INCORPORATED |
Houston |
TX |
US |
|
|
Assignee: |
BAKER HUGHES INCORPORATED
Houston
TX
|
Family ID: |
61617486 |
Appl. No.: |
15/271944 |
Filed: |
September 21, 2016 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
E21B 17/22 20130101;
E21B 17/1014 20130101; E21B 33/16 20130101 |
International
Class: |
E21B 37/02 20060101
E21B037/02; E21B 17/10 20060101 E21B017/10 |
Claims
1. A wiper plug for downhole use, comprising: a mandrel; a wiper
fin between spaced centralizers on said mandrel.
2. The wiper plug of claim 1, wherein: at least one of said
centralizers further comprises a continuous helix extending for at
least 360 degrees.
3. The wiper plug of claim 1, wherein: at least one of said
centralizers further comprises circumferentially spaced helical
segments.
4. The wiper plug of claim 3, wherein: adjacent said segments have
axially overlapping or aligned opposed ends.
5. The wiper plug of claim 3, wherein: an open helical passage is
defined between adjacent segments.
6. The wiper plug of claim 1, wherein: at least one of said
centralizers comprises bristles.
7. The wiper plug of claim 1, wherein: at least one of said
centralizers comprises a continuous flexible material.
8. The wiper plug of claim 1, wherein: at least one of said
centralizers is mounted to said mandrel in a dovetailed groove.
9. A wiper plug for downhole use, comprising: a mandrel; a seal
assembly and at least one centralizer on said mandrel, said
centralizer comprising a continuous helix or spaced helical
segments.
10. The wiper plug of claim 9, wherein: adjacent said segments have
axially overlapping or aligned opposed ends.
11. The wiper plug of claim 9, wherein: said segments are secured
in place on one end by shoulder of center mandrel.
12. The wiper plug of claim 9, wherein: an open helical passage is
defined between adjacent segments.
13. The wiper plug of claim 9, wherein: said centralizer comprises
bristles.
14. The wiper plug of claim 9, wherein: said centralizer comprises
a continuous flexible material.
15. The wiper plug of claim 9, wherein: said centralizer is mounted
to said mandrel in a dovetailed groove.
Description
FIELD OF THE INVENTION
[0001] The field of this invention is wiper plugs and more
particularly those used in cementing horizontal runs where the plug
is centralized as it wipes.
BACKGROUND OF THE INVENTION
[0002] Wiper plugs are used in applications such as cementing to
clear the inner wall of the string of remnants of the cement that
was earlier delivered through the string through a cementing shoe
and into a surrounding annular space to seal around the tubular
string. The wiper plug design typically features flexible members
designed to bend in contact with the inner wall of the string as
pressure behind the plug pushes the plug to a stop, which is
referred to as bumping the plug. The flexible members can be
tapered toward the uphole end to enhance the contact with the
inside wall of the string in response to the pressure applied from
above to advance the plug. Typically the wipers are made of rubber
or some other flexible material compatible with well
conditions.
[0003] One concern particularly on long horizontal runs is that the
rubber ribs will wear on the low side of the wiper plug to an
extent that they will not effectively wipe, leaving remnants of
cement stringers as the ribs wear. Another design parameter for
wiper plugs is that in some applications the plugs need to pass
through a restriction so there must be some flexibility in the
exterior wiping structure that will allow such restrictions to be
cleared without compromising the wiper fins.
[0004] In the past bow spring centralizers in combination with a
wiper device were used to clean drill strings as shown in U.S. Pat.
No. 5,641,018. Wiper darts with a bow spring centralizer between
leading and trailing inclined rubber ribs are shown in U.S. Pat.
No. 7,228,897; U.S. Pat. No. 7,069,992 and U.S. Pat. No. 7,063,152.
Spiral scraping devices mounted to a tubular string for paraffin
and the like are shown in U.S. Pat. No. 2,870,845. String mounted
wiping devices for cement distribution and casing cleaning in the
form of axial blades or spirals are shown in U.S. Pat. No.
3,351,136 and a spiral string centralizer is shown in U.S. Pat. No.
1,959,368. A wiper plug with a leading disc-shaped centralizer is
shown in FIG. 5 of U.S. Pat. No. 5,004,048.
[0005] The wiper plug of the present invention features spaced
centralizers ahead and behind the sealing assembly for the plug.
The centralizers combine features of flexibility and a defined
height to allow passage through restrictions with enough rigidity
to centralize and clean the string as the assembly passes by. The
centralizer can be an array of brush bristles having a spiral
appearance where the bristles are connected to a common base pushed
into a dovetailed groove for mounting. Other arrangements are
contemplated where each spiral leading and trailing ends are closed
off with flat members that flex. These and other aspects of the
present invention will be more readily understood by those skilled
in the art from a review of the description of the preferred
embodiment and the associated drawings while understanding that the
full scope of the invention is to be determined by the appended
claims.
SUMMARY OF THE INVENTION
[0006] A wiper plug has a elastomeric fin assembly straddled by
centralizers that have the capacity to flex through restrictions
while being strong enough to centralize and scrape a surrounding
tubular wall. The centralizers reduce wear on the rib/fin assembly
particularly on long horizontal runs. The centralizers can be a
continuous spiral or a series of circumferentially offset spiral
segments on a common hub. The spiral segments contain brushes
extending from a base where the base and the mounting slot have a
dovetail relationship for fixation to the wiper plug body. The plug
body consist of three separate segments that are threaded together
in order to trap the brush segments in the dovetail channels.
BRIEF DESCRIPTION OF THE DRAWINGS
[0007] FIG. 1 illustrates the spiral segment embodiment of the
centralizers;
[0008] FIG. 2 is a section view of a complete 360 degree spiral
centralizer;
[0009] FIG. 3 is a perspective view of the centralizer in FIG.
2;
[0010] FIG. 4 is a variation of FIG. 2 showing the mandrel
segments;
[0011] FIG. 5 shows a mounting detail for brush type centralizers
into a dovetail groove;
[0012] FIG. 6 is an enlarged view of the circle labeled 6 in FIG. 2
focusing on the mounting of the continuous spiral embodiment.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0013] FIG. 1 shows a segmented spiral version of centralizers for
a wiper plug 10. Plug 10 has an uphole centralizer assembly 12 and
a downhole centralizer assembly 14 that straddle a wiper fin
assembly 16. In this embodiment the centralizer assemblies 12 and
14 comprises circumferentially spaced segments 18 that are spirally
oriented on a hub or mandrel 20 and 52. The circumferential
coverage of each spiral segment 18 varies with its height. The
number of segments is variable and their spacing is preferably even
so that in an axial direction an end 22 abuts or overlaps an end 24
of the adjacent spiral segment for continuous circumferential for
not only centralizing but also for scraping. The segments 18 can be
a collection of brush bristles 26 held in a common base 28 as shown
in FIG. 5. The base 28 has a dovetail shape to be inserted into a
mating shaped slot 30 best shown in FIG. 6. Once fully inserted
into slot 30 the mandrel is threaded to the fin section which
shoulders against the open end of the dovetail channel, trapping
the brush segments in place. Both the tail and nose sections rely
on the wiper fin section shouldering against groove opening to keep
brushes secured.
[0014] Other aspects of the wiper 10 shown in FIG. 1 are grooves 32
and 34 for o-rings that are not shown and a slip assembly 36 all of
which go onto a bore in a tubing string or another plug when the
wiper 10 bumps. These features are known in current plugs. The
wiper fin portion can have one or more ribs 38 that can be
perpendicular to the axis of the hub or mandrel 20. Although three
are shown other numbers can be used. Alternatively the ribs can be
skewed to the axis of hub 20 as in ribs 40 and 42 with or without
use of perpendicular ribs 38.
[0015] Referring back to the centralizers 12 and 14 in FIG. 1 open
gaps 44 and 46 are present at the uphole and downhole ends of the
segments 18. The segments 18 have enough flexibility to bend to get
through restrictions but at the same time enough structural
rigidity to centralize wiper fin assembly 16 particularly in long
horizontal runs to avoid it wearing unevenly to the point where the
plug 10 can no longer wipe efficiently from uphole. The rigidity of
the segments 18 whose ends rub the surrounding tubular wall also
helps to wipe the walls clear. This is helpful particularly from
the downhole centralizer assembly 14 so that the wiper fin assembly
16 will see less wear otherwise caused by being propelled over
cement debris if not dislodged first by the downhole centralizer
assembly 14. The use of an uphole and downhole centralizer aids the
centralizing function with front and rear support.
[0016] FIGS. 2 and 3 show a continuous spirals 70 and 72 for at
least 360 degrees and supported off mandrel 74 and 78. Although a
single helix is shown multiple nested helixes are also envisioned.
Here or with the design using segments 18 the bristle brush design
of FIG. 5 can be used or the shape can be a continuous solid shape
that is made of a flexible material that can withstand the well
conditions long enough to bump the plug. Either way the
centralizers present little resistance to subsequent milling out.
The flexibility of the helical or segmental designs can be varied
not only by the material selection but also the thickness of the
solid material or the bristle density. Some materials that can be
used are plastics, soft metals or composite materials. The above
description is illustrative of the preferred embodiment and many
modifications may be made by those skilled in the art without
departing from the invention whose scope is to be determined from
the literal and equivalent scope of the claims below:
* * * * *