Information
-
Patent Grant
-
6796377
-
Patent Number
6,796,377
-
Date Filed
Tuesday, July 23, 200222 years ago
-
Date Issued
Tuesday, September 28, 200419 years ago
-
Inventors
-
Original Assignees
-
Examiners
- Bagnell; David
- Bomar; Shane
Agents
- Roddy; Craig W.
- Rahhal; Anthony L.
-
CPC
-
US Classifications
Field of Search
US
- 166 155
- 166 156
- 166 153
- 166 291
- 166 2421
- 166 2411
-
International Classifications
-
Abstract
An apparatus for preventing or limiting the rotation of cementing plugs in a casing string during drillout. The apparatus includes an outer housing with a sleeve disposed therein. The sleeve has an inner surface configured to engage cementing plugs received therein to cause an interference fit. The sleeve will hold the cementing plugs when rotational forces, such as drilling forces, are applied so that during drillout, rotation of the cementing plug is prevented or is at least limited.
Description
The present invention relates generally to drilling and completion techniques for downhole wells, and more particularly to methods and apparatus for limiting the rotation of cementing plugs being drilled out of the plugs.
In the construction of oil and gas wells, a wellbore is drilled into one or more subterranean formations or zones containing oil and/or gas to be produced. During a wellbore drilling operation, drilling fluid (also called drilling mud) is circulated through the wellbore by pumping it down the drill string, through a drill bit connected thereto and upwardly back to the surface to the annulus between the walls of the wellbore and the drill string. The circulation of the drilling fluid functions to lubricate the drill bit, remove cuttings from the wellbore as they are produced and to exert hydrostatic pressure on pressurized fluid contained formations penetrated by the wellbore whereby blowouts are prevented.
In most instances, after the wellbore is drilled, the drill string is removed and a casing string is run into the wellbore while maintaining sufficient drilling fluid in the wellbore to prevent blowouts. The term “casing string” is used herein to mean any string of pipe which is lowered into and cemented in a wellbore including but not limited to surface casing, liners and the like.
Typically, at the beginning of a cementing job, the casing and hole are filled with drilling mud. Very often, a bottom cementing plug is pumped ahead of the cement slurry to reduce contamination at the interface between the mud and cement. The bottom plug is typically constructed to have elastomeric wipers to wipe the casing of drilling mud and thereby separate the drilling mud ahead of the bottom plug from the cement slurry behind the bottom plug. The casing string will have a landing platform for the bottom plug. The landing platform may be a float collar, a float shoe or a shoulder in the casing string. When the bottom plug seats upon the landing platform, the fluid pressure differential created across the bottom plug ruptures a diaphragm at the top of the bottom plug and allows the cement slurry to proceed down the casing through the plug, through the float equipment at the lower end of the casing and up the annular space between the casing and the wellbore.
Once the required amount of cement has been displaced into the well, a top cementing plug, which will likewise have wipers thereon, may be displaced into the casing. The top cementing plug will follow the cement slurry into the casing, and is designed to reduce the possibility of any contamination or channeling of the cement slurry with drilling fluid or other fluid that is used to displace the cement column down into the casing and into the annular space between the casing and the wellbore. The top cementing plug does not have a fluid passage therethrough such that when it reaches the bottom cementing plug, the top cementing plug will cause a shut off of fluids being pumped through the casing.
Once the cement has set up and any other desired operations have been performed, the cementing plugs, along with float equipment therebelow, may be drilled out. In order to do so, the drill string with the drill bit thereon is lowered into the hole until the drill engages the top plug and is rotated. In many instances, however, when the drill bit is rotated, the top plug also begins to rotate on top of the bottom plug, or the bottom plug may rotate on the landing platform, whether the platform is float equipment or a shoulder or other restriction in the casing. Plug rotation costs valuable time and therefore has an economic impact on the cost of the well. Thus, there is a need to eliminate or at least limit the rotation of the cementing plugs during drillout after the cementing job. Several attempts have been made at limiting the rotation of the cementing plugs. One such attempt is described in International Application No. PCT/US00/40545, International Publication No. WO 01/09481 A1, entitled Anti-Rotation Device for Use with Well Tools. Another device for limiting the rotation of plugs is described in U.S. Pat. No. 5,095,980, which discloses a combination non-rotating plug set. Other devices and/or methods are shown in U.S. Pat. No. 5,390,736, U.S. Pat. No. 5,165,474 and U.S. Pat. No. 4,190,111. Although the apparatus and methods described therein may in some cases work well to limit rotation of cementing plugs during drillout, there is a continuing need for an anti-rotation apparatus and method which will consistently limit the rotation of the cementing plugs during drillout and which is easy to use, efficient and inexpensive.
SUMMARY OF THE INVENTION
The present invention provides an apparatus for preventing, or at least limiting the rotation of a cementing plug during drillout of the cementing plug. The apparatus includes an outer case, which preferably is a joint of casing. The outer case may be referred to as an outer housing or outer sleeve. An inner sleeve is disposed in the outer case. The inner sleeve has an open upper end and an open lower end and is adapted to receive cementing plugs displaced through a casing string during a cementing job. The inner surface of the sleeve is configured and dimensioned so as to cause an interference fit, and thus frictionally engage cementing plugs that are received therein. Engagement between the cementing plugs and the inner sleeve will prevent or at least limit rotation of the cementing plugs during drillout of the cementing plugs after a cementing job. The inner sleeves are preferably comprised of a durable, drillable material.
In one embodiment, the inner sleeve has a tapered inner surface. The tapered inner surface preferably tapers radially inwardly from the upper end of the inner sleeve to the lower end of the inner sleeve. The tapered inner surface may have a circular cross-section so that the inner surface has a generally frustoconical shape, or may define a polygonal cross-section, so that the inner surface defines a polyhedral shape. The apparatus of the present invention limits rotation of cementing plugs by engaging the plugs that are received therein so that when rotational drilling forces are applied, rotation of the plug is prevented or is at least limited.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1
shows a side cross-sectional view of a prior art plug set displaced into a casing.
FIG. 2
shows a side cross-sectional view of an anti-rotation apparatus of the present invention.
FIGS. 3 and 4
show sectional views taken from lines
3
—
3
and
4
—
4
of
FIG. 2
, respectively, and are directed to different embodiments of the anti-rotation apparatus of the present invention.
FIG. 5
shows a side cross-sectional view of the anti-rotation apparatus of the present invention with cementing plugs received therein.
FIG. 6
shows a side cross-sectional view of an additional embodiment of an anti-rotation apparatus of the present invention.
FIG. 7
shows a section view taken from line
7
—
7
of FIG.
6
.
FIG. 8
is a perspective of a sleeve segment of the embodiment of FIG.
6
.
FIG. 9
is a cross-sectional view of an additional embodiment of the anti-rotation apparatus of the present invention.
FIG. 10
is a view from line
10
—
10
of FIG.
9
.
FIG. 11
is a cross-sectional view like that shown in FIG.
9
and shows a frangible portion of the embodiment of
FIG. 9
broken as a result of cementing plugs being received therein.
FIG. 12
shows a side cross-sectional view of an additional embodiment of an anti-rotation apparatus of the present invention.
FIG. 13
shows a side cross-sectional view of an additional embodiment of an anti-rotation apparatus of the present invention.
FIG. 14
is a view from line
14
—
14
of FIG.
13
.
DESCRIPTION OF PREFERRED EMBODIMENTS
Referring now to the drawings and more particularly to
FIG. 1
, a prior art cementing plug set
10
is shown. Plug set
10
includes a top cementing plug
15
and a bottom cementing plug
20
. The plug set
10
is shown in a casing
25
being cemented into a wellbore
30
. Plug set
10
is shown after bottom cementing plug
20
has landed on a landing platform
32
which may comprise a float collar, float shoe or other float equipment, or any other restriction which will allow bottom cementing plug
20
to land, but which will also allow fluid flow therethrough. Bottom cementing plug
20
comprises a body
36
defining a flow passage
38
therethrough. Typically, a rupturable member will be disposed across the top of flow passage
38
such that when bottom cementing plug
20
lands, increasing fluid pressure will cause the rupturable member to burst so that fluid, such as the cement slurry, can flow through flow passage
38
. In
FIG. 1
, the rupturable member has already been ruptured to allow flow through flow passage
38
. Bottom cementing plug
20
also includes an elastomeric cover
40
disposed about body
36
. Elastomeric cover
40
includes a plurality of wipers
42
. As explained above, bottom cementing plug
20
will normally be placed in the casing ahead of the cement slurry to wipe off the inner surface of the casing and separate the drilling fluid from the cement slurry. Top cementing plug
15
has a body
44
with an elastomeric cover
46
disposed thereabout. Elastomeric cover
46
includes elastomeric wipers
48
. Body
44
defines a central cavity
50
.
As explained above, top cementing plug
15
is displaced into the casing above the cement slurry to separate the cement slurry from the drilling or other fluids thereabove utilized to urge the cement slurry downwardly through the casing and into the annulus between casing
25
and wellbore
30
.
FIG. 1
shows top cementing plug
15
prior to the time it engages and seats upon bottom cementing plug
20
.
Referring now to
FIG. 2
, an apparatus
60
for limiting rotation of a cementing plug when rotational forces, such as forces applied by a drill bit during drillout, are applied. Apparatus
60
includes an outer case or outer housing
62
. Outer case
62
preferably comprises a casing joint. Apparatus
60
can be threadedly connected in and will make up a part of a casing string lowered into a wellbore. Outer case
62
may also be referred to as a sleeve or outer sleeve
62
. Outer case
62
has lower end
64
and upper end
66
and defines a passageway
68
. Outer case
62
defines an inner diameter
69
, which will preferably be substantially identical to the inner diameter of the casing string in which apparatus
60
is connected. Apparatus
60
has an inner sleeve
70
disposed in outer case
62
. Inner sleeve
70
is preferably comprised of a drillable material.
Inner sleeve
70
has a longitudinal central axis
71
, an upper end
72
and a lower end
74
. Upper and lower ends
72
and
74
are open upper and lower ends and upper end
72
is adapted to receive cementing plugs, such as top and bottom cementing plugs
15
and
20
.
Inner sleeve
70
may comprise an insert that is adhesively or otherwise bonded to outer case
62
or may be molded to outer case
62
. Inner sleeve
70
defines an inner surface, or inner profile
76
. Inner surface
76
is preferably a tapered inner surface
76
, and defines a passageway
78
. A slot
79
may be defined through inner sleeve
70
, and may extend from the upper to the lower end thereof. The slot will allow sleeves made as inserts to expand and compress to varying outer diameters so that the sleeves can be shaped to fit in a range of outer case inner diameters. In the embodiment shown, inner surface
76
tapers radially inwardly from the open upper end
72
to the open lower end
74
of inner sleeve
70
. Inner surface
76
preferably has a constant taper defined thereon. In one embodiment, as shown in
FIG. 3
, inner surface
76
is circular in a cross-section taken perpendicular to longitudinal central axis
71
. Thus, in the embodiment shown in
FIG. 3
, inner surface
76
is frustoconically shaped. In a second embodiment shown in
FIG. 4
, inner surface
76
a
may have a polygonal shape in a cross-section perpendicular to longitudinal central axis
71
a
. Preferably, in the embodiment shown in
FIG. 4
, inner surface
76
a
defines an equilateral polygon. In the embodiment shown in
FIG. 4
, the numeric designations include the subscript a so as to distinguish from the embodiment shown in FIG.
3
. The embodiment in
FIG. 3
has a frustoconically shaped inner surface, and the embodiment shown in
FIG. 4
in cross-section, defines a polygon such that inner surface
76
a
may essentially define a polyhedron or a polyhedral shape.
FIG. 5
shows a plug set, such as plug set
10
in a casing string of which apparatus
60
is a part. As shown in
FIG. 5
, bottom cementing plug
20
has been displaced into the casing string and has engaged a landing platform
80
which as set forth above may comprise a float collar, a float shoe or other float equipment, or may comprise a shoulder or other restriction in the casing which provides a barrier to stop bottom cementing plug
20
. Top cementing plug
15
is shown just prior to the time that it engages bottom cementing plug
20
. Top and bottom cementing plugs
15
and
20
are received in the open upper end
72
of inner sleeve
70
. Top and bottom cementing plugs
15
and
20
have an unrestrained outer diameter defined by the wipers thereon that is greater than inner diameter
69
, and thus greater than the inner diameter of the casing
25
, so that the plugs will effectively wipe the inner surface of the casing
25
as it passes therethrough. Top and bottom cementing plugs
15
and
20
will therefore be engaged by the inner surface of inner sleeve
70
, or
70
a
, in the embodiment of
FIG. 4
, upon entering through the open upper end thereof. The thickness of inner sleeves
70
and
70
a
in the embodiments herein is shown exaggerated relative to the thickness of the wall of the outer case for purposes of clarity. As top and bottom cementing plugs
15
and
20
are displaced downwardly in passageway
78
, the engagement, or interference with tapered inner surface
76
will increase. Inner sleeve
70
is preferably made from a durable, yet drillable material. Once the cementing job is complete, and bottom cementing plug
20
has reached landing platform
80
and top cementing plug
15
has landed on bottom cementing plug
20
, it is necessary to drill out top and bottom cementing plugs
15
and
20
and any float equipment therebelow. The interference fit between inner sleeve
70
and top and bottom cementing plugs
15
and
20
will prevent, or at least limit, the rotation of the cementing plugs during drillout. In other words, when rotational forces are applied to drill out top and bottom cementing plugs
15
and
20
, inner sleeve
70
will engage and hold top and bottom cementing plugs
15
and
20
in place. The discussion herein with respect to the embodiment in
FIG. 3
, applies equally to the embodiment of FIG.
4
.
An additional embodiment of an apparatus for preventing or at least limiting rotation of a cementing plug when rotational forces, such as drilling forces, are applied thereto is shown in
FIGS. 6-8
and is designated by the numeral
90
. Apparatus
90
comprises an outer case or outer housing
92
having an inner diameter
93
. Outer housing
92
is preferably a casing joint. An inner sleeve
94
is disposed in an outer case
92
. Inner sleeve
94
may be an extruded or molded sleeve and is preferably adhesively or otherwise bonded to outer case
92
. Inner sleeve
94
has open upper end
96
and open lower end
98
. Inner sleeve
94
defines a generally cylindrical inner surface
100
having a plurality of protrusions
102
extending radially inwardly therefrom. Protrusions
102
preferably comprise ribs or teeth
102
extending from the upper end
96
to the lower end
98
of inner sleeve
94
. Ribs
102
may be of any desired cross-sectional shape, and in the embodiment shown are generally triangular in cross-section.
Inner sleeve
94
is preferably comprised of a plurality of inner sleeve segments
104
. Each sleeve segment has an upper end
106
, a lower end
108
and first and second edges
110
and
112
. First edge
110
has a boss
114
connected to and extending therefrom. A groove
116
is defined in inner sleeve segment
104
at second edge
112
thereof. Boss
114
is adapted to mate with and be received in groove
116
so the plurality of inner sleeve segments
104
, and in the embodiment shown eight inner sleeve segments
104
, can be secured together to form inner sleeve
94
.
As is apparent, cementing plugs used in cementing jobs, like top and bottom cementing plugs
15
and
20
will be received in upper end
96
of inner sleeve
94
and will be displaced downwardly until they engage landing platform
118
. Ribs
102
on inner sleeve
94
will engage the cementing plugs and will hold the plugs so that when rotational forces, such as drilling forces, are applied thereto, the rotation of the cementing plugs will be prevented, or will be limited during drillout.
An additional embodiment of an apparatus for limiting rotation of a cementing plug in a casing string while rotational forces such as drilling forces, are applied thereto, is shown in
FIGS. 9-11
and is generally designated by the numeral
120
. Apparatus
120
comprises an outer case or outer housing
122
which is preferably a casing joint. An inner sleeve
124
is disposed in outer housing
122
. Inner sleeve
124
preferably is comprised of a durable, drillable material. Inner sleeve
124
has upper end
126
, lower end
128
, outer surface
130
and inner surface
132
defining passageway
134
. Inner sleeve
124
is a frangible inner sleeve, and may be made of a frangible plastic or composite, such as phenolic plastic. Inner sleeve
124
has a plurality of grooves
136
defined in the outer surface
130
thereof. Each groove
136
defines a frangible section
138
. The plurality of frangible sections
138
may be collectively referred to herein as frangible portion
140
.
Inner sleeve
124
defines an inner diameter
142
. Inner diameter
142
is smaller in magnitude than the outer diameter of the cementing plugs to be received therein. Thus, cementing plugs, such as top and bottom cementing plugs
15
and
20
will be received in the open upper end
126
of inner sleeve
124
and will engage the inner surface
132
thereof. Inner sleeve
124
has an expandable profile such that cementing plugs received therein will apply forces to inner sleeve
124
as the cementing plugs are displaced downwardly therethrough. The interference between the cementing plugs and inner sleeve
124
will cause frangible portion
140
to break, thus, as shown in
FIG. 11
, exposing a plurality of edges
144
. Thus, inner sleeve
124
has an expandable profile that will break along frangible portion
140
when cementing plugs are received therein. Edges
144
are exposed when frangible portion
140
breaks. Rotational forces applied to the cementing plug during drillout will attempt to rotate the cementing plugs received in inner sleeve
124
. Edges
144
will engage the cementing plugs, and preferably the wipers thereon, to prevent or limit rotation. As shown in
FIG. 11
, material from cementing plugs may be extruded into grooves
136
as drilling forces are applied to the cementing plug, which will aid in preventing, or at least limiting the rotation of cementing plugs during drillout.
An additional embodiment of an apparatus for preventing, or limiting the rotation of cementing plugs during drillout is shown in FIG.
12
and is generally designated by the numeral
150
. Apparatus
150
comprises an outer case or outer housing
152
having inner diameter
153
. Outer housing
152
preferably is a casing joint. Apparatus
150
further includes an inner sleeve
154
preferably comprised of a durable material having an upper end
156
, a lower end
158
, an outer surface
160
and an inner surface
162
, which comprises a plurality of curved inner surfaces. In the embodiment shown, the curved, or arcuately shaped inner surfaces curve radially inwardly from both the upper and lower ends. Inner surface
162
curves radially inwardly from upper end
156
thereof to a first inner diameter
164
and then curves radially outwardly therefrom to second inner diameter
166
which is larger than first inner diameter
164
. Inner surface
162
curves radially inwardly from second inner diameter
166
to a third inner diameter
168
. Apparatus
150
thus has multiple tapered or curved surfaces to provide an engagement surface for cementing plugs received therein. Inner surface
162
may be generally said to define an hourglass shape. Cementing plugs, such as top and bottom cementing plugs
15
and
20
, will be received in the open upper end
156
of inner sleeve
154
. Cementing plugs received in inner sleeve
154
will be engaged by inner surface
162
. Once the cementing job is complete, such that bottom cementing plug
20
has landed, or seated on a landing platform such as landing platform
169
, inner surface
162
will engage cementing plugs to prevent, or at least limit the rotation of the cementing plugs during drillout.
An additional embodiment for an apparatus for preventing, or limiting the rotation of cementing plugs during drillout is shown in
FIGS. 13 and 14
and is generally designated by the numeral
170
. Apparatus
170
comprises an outer case or outer housing
171
which is preferably in a casing joint. Outer case
171
has an inner diameter
172
, and has a durable material
174
affixed thereto defining an inner dimension
175
that will engage and thus cause an interference fit with cementing plugs received therein. Durable material
174
has an open upper end
176
and an open lower end
178
, and defines an inner surface
180
. The method of making apparatus
170
may comprise spraying durable material
174
on the inner diameter
172
of outer casing
171
to a sufficient thickness such that it will cause an interference fit with cementing plugs received therein. The method may further comprise placing aggregate material
182
in durable material
174
. The aggregate material may be sprayed onto outer case
171
with durable material
174
or may be placed in or sprayed into durable material
174
after such material has been sprayed on outer case
171
. Aggregate material
182
may include material such as sand, gravel, walnut hulls, fiberglass and, as set forth above, can be added to the spray on durable material either during or following the spray operation. The aggregate material will give apparatus
170
a rough surface that will provide friction with the cementing plugs and thus limit or prevent rotation of the cementing plugs during drillout. The durable material to be sprayed on inner surface or outer case
171
can be any durable material that would bond to the outer casing and that will withstand fluid flow, such as two-part epoxies, rubber, urethane and other thermoplastics. Rather than spraying, adhesives such as an epoxy-type adhesive can be applied to the outer case
171
by any means known in the art, and aggregate material can be sprayed or otherwise placed in the adhesive. An additional method for making apparatus
170
comprises fabricating a sandpaper-like sheet of durable material with aggregate therein, and gluing, or otherwise affixing the sheet to outer case
171
.
Thus, the present invention is well adapted to carry out the object and advantages mentioned as well as those which are inherent therein. While numerous changes may be made by those skilled in the art, such changes are encompassed within the spirit of this invention as defined by the appended claims.
Claims
- 1. Apparatus for limiting rotation of a cementing plug during drillout of the cementing plug, the apparatus comprising:an outer housing; and a sleeve disposed in the housing, the sleeve having an open upper end and an open lower end and having a tapered inner surface, wherein a cementing plug may be received in the sleeve through the open upper end, and wherein the tapered inner surface will cause an interference between the cementing plug and the sleeve to limit rotation of the cementing plug during drillout, the sleeve defining a longitudinal slot therethrought extending from the open upper end to the open lower end thereof, the inner surface of the sleeve between the longitudinal edges defined by the slot comprising a smooth inner surface having no protrusions or indentations.
- 2. The apparatus of claim 1 wherein the sleeve has a constant taper on the inner surface from the upper end to the lower end of the sleeve.
- 3. The apparatus of claim 1 wherein the sleeve tapers radially inwardly from the upper end to the lower end thereof.
- 4. The apparatus of claim 1 wherein the inner surface of the sleeve is frustoconically shaped.
- 5. The apparatus of claim 1 wherein the tapered inner surface defines a circle in a cross-section perpendicular to a longitudinal central axis of the sleeve.
- 6. Apparatus for limiting rotation of a cementing plug during drillout of the cementing plug, the apparatus comprising:an outer housing; and a sleeve disposed in the housing, the sleeve having an open upper end and an open lower end and having a tapered inner surface, the tapered inner surface defining a polygon in a cross-section perpendicular to a longitudinal central axis of the sleeve wherein a cementing plug may be received in the sleeve through the open upper end, and wherein the tapered inner surface will cause an interference between the cementing plug and the sleeve to limit rotation of the cementing plug during drillout.
- 7. The apparatus of claim 6, the sleeve having a slot extending from the open upper end to the open lower end thereof.
- 8. The apparatus of claim 6, wherein the polygon is an equilateral polygon.
- 9. The apparatus of claim 8, wherein the inner surface of the sleeve tapers radially inwardly from the upper end to the lower end thereof.
- 10. Apparatus for limiting rotation of a cementing plug during drillout of the cementing plug, the apparatus comprising:an outer housing; and a sleeve disposed in the housing, the sleeve having an open upper end and an open lower end and having a tapered inner surface, wherein a cementing plug may be received in the sleeve through the open upper end, and wherein an inner surface of the sleeve will cause an interference between the cementing plug and the sleeve to limit rotation of the cementing plug during drillout, the inner surface of the sleeve defining a polyhedron.
- 11. The apparatus of claim 10, wherein the inner surface of the sleeve defines an equilateral polygon in a cross-section perpendicular to a longitudinal axis of the sleeve.
- 12. The apparatus of claim 10, wherein the inner surface tapers radially inwardly from the upper end to the lower end thereof.
- 13. The apparatus of claim 10, wherein the sleeve has a constant taper on the inner surface thereof from the open upper end to the open lower end.
- 14. The apparatus of claim 10, the sleeve having a slot therethrough extending from the open upper end to the lower end thereof.
US Referenced Citations (32)
Foreign Referenced Citations (2)
Number |
Date |
Country |
WO 0109480 |
Feb 2001 |
WO |
WO 0109481 |
Feb 2001 |
WO |