U.S. patent application number 16/257231 was filed with the patent office on 2019-08-01 for pressure control devices for sealing around tubular members.
This patent application is currently assigned to National Oilwell Varco, L.P.. The applicant listed for this patent is National Oilwell Varco, L.P.. Invention is credited to Ali A. Al-Quraishi, Christopher Dale Johnson, Ajay V. Kulkarni.
Application Number | 20190234176 16/257231 |
Document ID | / |
Family ID | 65352197 |
Filed Date | 2019-08-01 |
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United States Patent
Application |
20190234176 |
Kind Code |
A1 |
Johnson; Christopher Dale ;
et al. |
August 1, 2019 |
Pressure Control Devices for Sealing Around Tubular Members
Abstract
A pressure control device for sealing about a tubular string
comprises: a flange disposed about a central axis, an annular
extension extending from the flange and an annular seal element
coupled to the annular extension. The seal member includes a
through-passage for receiving the tubular string and an annular
recess in which the annular extension is disposed. The annular
extension includes a radially-inward facing surface that includes a
tapered region that is nonlinear in an axial cross-section for
reducing mechanical stresses in the seal member.
Inventors: |
Johnson; Christopher Dale;
(Houston, TX) ; Kulkarni; Ajay V.; (Sugar Land,
TX) ; Al-Quraishi; Ali A.; (Katy, TX) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
National Oilwell Varco, L.P. |
Houston |
TX |
US |
|
|
Assignee: |
National Oilwell Varco,
L.P.
Houston
TX
|
Family ID: |
65352197 |
Appl. No.: |
16/257231 |
Filed: |
January 25, 2019 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
62622428 |
Jan 26, 2018 |
|
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|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
E21B 33/127 20130101;
E21B 33/06 20130101; E21B 2200/01 20200501; E21B 19/16 20130101;
E21B 33/085 20130101; E21B 33/122 20130101; E21B 33/1243
20130101 |
International
Class: |
E21B 33/124 20060101
E21B033/124; E21B 19/16 20060101 E21B019/16; E21B 33/127 20060101
E21B033/127; E21B 33/122 20060101 E21B033/122 |
Claims
1. A pressure control device for sealing about a tubular string,
comprising: a flange disposed about a central axis, the central
axis disposed on an axial plane; an annular extension extending
from the flange and having a radially-inward facing surface; and an
annular seal element coupled to the annular extension, the seal
member having a through-passage for receiving the tubular string
and an annular recess in which the annular extension is disposed;
wherein the radially-inward facing surface comprises a tapered
region that is nonlinear in an axial cross-section formed on the
axial plane.
2. The pressure control device of claim 1 wherein the
radially-inward facing surface flares outwardly, away from the
through-passage as the radially-inward facing surface extends
axially from flange.
3. The pressure control device of claim 1 wherein the
radially-inward facing surface includes a first end extending from
the flange and a second end spaced from the first end, and wherein
the second end is further from the central axis than the first
end.
4. The pressure control device of claim 3 wherein the
radially-inward facing surface comprises a first region extending
from the first end and a second region extending from the first
region, and wherein the second region is continuously curved in an
axial cross-section formed on the axial plane.
5. The pressure control device of claim 4 wherein the second region
has a constant radius in an axial cross-section formed on the axial
plane.
6. The pressure control device of claim 3 radially-inward facing
surface comprises a first region extending from the first end and a
second region extending from the first region, and wherein the
second region, in the axial cross-section, has a radius that has a
value selected from the range 0 to 30 inches.
7. The pressure control device of claim 1 wherein the annular seal
element comprises: a seal first end adjacent the flange; a seal
second end axially spaced apart from the flange; and a radially
outermost surface having first and second regions; wherein the
first region extends from the seal first end; and wherein the
second region extends from the seal second end toward the seal
first end and is frustoconical.
8. The pressure control device of claim 8 wherein on the radially
outermost surface, the second region intersects the first
region.
9. The pressure control device of claim 1 wherein the
radially-inward facing surface lacks a radially inward annular
protrusion.
10. A pressure control device for sealing about a tubular string,
comprising: a central axis; an annular insert; and an annular seal
element coupled to the annular insert, the annular seal element
comprising: a seal first end disposed adjacent the annular insert;
a seal second end axially spaced apart from the annular insert; a
through-passage extending through the seal first and second ends
for receiving the tubular string; and a radially outermost surface
including a first region extending from the seal first end and a
second region extending from the seal second end toward the first
region; wherein the second region tapers as it extends in a
direction away from the annular insert.
11. The pressure control device of claim 10 wherein second region
on the annular seal element intersects the first region.
12. The pressure control device of claim 10 wherein the second
region on the annular seal element is frustoconical.
13. The pressure control device of claim 10 wherein the annular
insert comprises: an annular flange disposed about the central
axis; an annular extension extending from the flange; and a
radially-inward facing surface extending along the annular
extension; wherein the annular seal element includes an annular
recess in which the annular extension is disposed, annular recess
extending from the seal first end; and wherein radially-inward
facing surface of the annular insert includes a tapered region that
expands radially outwardly as it extends axially away from the
flange.
14. The pressure control device of claim 13 wherein the
radially-inward facing surface further comprises a cylindrical
region extending from the flange to the tapered region.
15. A pressure control device for sealing about a tubular string,
comprising: a central axis disposed on an axial plane; an annular
insert comprising: a flange disposed about the central axis; an
annular extension concentric with the flange and extending from the
flange; and a radially-inward facing surface extending along the
annular extension; and an annular seal element coupled to the
annular extension, the annular seal element comprising: a seal
first end disposed adjacent the flange; a seal second end axially
spaced apart from the flange; a through-passage extending through
the seal first and second ends for receiving the tubular string; an
annular recess in which the annular extension is disposed, the
annular recess extending from the seal first end; and a radially
outermost surface including a first region extending from the seal
first end and a second region extending from the seal second end
toward the first region; wherein the radially-inward facing surface
of the annular insert includes a tapered region that expands
radially outwardly as it extends axially away from the flange.
16. The pressure control device of claim 15 wherein the second
region on the annular seal element intersects the first region.
17. The pressure control device of claim 15 wherein the tapered
region is continuously curved on the axial plane.
18. The pressure control device of claim 17 wherein the tapered
region of the annular insert has a constant radius on the axial
plane.
19. The pressure control device of claim 15 wherein the
radially-inward facing surface of the annular insert comprises: a
first end coupled to the flange, a second end spaced from the first
end; and a cylindrical region extending from the first end; wherein
the tapered region extends from the cylindrical region toward the
second end.
20. The pressure control device of claim 19 wherein the tapered
region of the radially-inward facing surface intersects the second
end at a fillet; and wherein on the axial plane, the tapered region
intersects the fillet at a tangent line that is disposed at angle
between 5 and 45 degrees, inclusive, with respect to the central
axis.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims benefit of U.S. provisional
application Ser. No. 62/622,428 filed Jan. 26, 2018, and entitled
"Pressure Control Devices for Sealing Around Tubular Members,"
which is hereby incorporated herein by reference in its entirety
for all purposes.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
[0002] Not applicable.
BACKGROUND
Field of the Disclosure
[0003] The present disclosure relates generally to drilling systems
and to rotating control devices (RCD) for such systems. More
particularly, the disclosure relates to systems and methods for
providing annular seals between concentric fluid conduits as they
rotate relative to each other and as one of the fluid conduits
moves axially through the RCD.
Background to the Disclosure
[0004] In applications requiring the transmission of fluid under
relatively high pressure, it is sometimes necessary to interconnect
a rotatable conduit with a stationary conduit, and to provide seals
therebetween to prevent leakage of the pressurized fluid. One such
application is in drilling operations where a drill pipe or another
tubular member passes through a rotating control device (RCD),
where the outer housing of the RCD remains stationary while an
internal sleeve and packing elements, which are seals, surround and
rotate along with the drill pipe. In this arrangement the sleeve
and the drill pipe are rotatable conduits. Each packing element
includes a rigid annular insert having a mounting flange and a
resilient annular seal element that surrounds and contacts the
pipe. The packing elements allow the drill pipe to move axially
into or out from a wellbore without fluid leakage.
[0005] During operation, axial movement of the drill pipe through
the RCD causes the resilient the seal elements to deform, expanding
and contracting in response to varying outside diameter of the
drill pipe and its joints. Such deformation induces life-reducing
and thus undesirable mechanical stress in the seal elements.
[0006] FIG. 1 shows a finite element analysis (FEA) plot of stress
induced within a resilient, annular seal element PA2 of a
conventional packing element. The plot shows stress results for
regions along a cross-section; even so, the results are
representative of volumetric portions of the seal element. Seal
element PA2 extends from a first end PA4 to a second end PA6 and
includes a through-passage PA8, an annular recess PA10 extending
inward from first end PA4, and a radially outermost surface PA12.
Although not shown, the FEA included boundary conditions that
assume a rigid flanged, annular insert of the packing element is
located along the radially outer portion of first end PA4 and
within annular recess PA10. Annular recess PA10 is generally
cylindrical, having axially extending walls. In the plot, a box end
20 of a drill pipe 22 is located within a seal element PA2 with
neck 24 of box end 20 axially aligned with the innermost end of
recess PA10, adjacent the indentation PA11. More specifically, the
plot represents a situation in which drill pipe 22 is being pulled
upward through seal element PA2. In the plot, stress levels are
normalized to values from 0 to 1 in multiple increments, as show on
legend 30. For the sake of discussion, three stress levels SL1,
SL2, SL3 will be considered, with each stress level representing
one or more increments in legend 30. In this scenario, a region of
low stress SL1 in seal element PA2 occurs throughout a majority of
seal element PA2, extending axially inward from ends PA4, PA6 and
along the outermost surface PA12 and the lower and upper portions
of through-passage 266. A region of elevated stress SL2 occurs
adjacent neck 24, adjacent recess PA10, and below recess PA10. A
region of highest stress SL3 extends radially between neck 24 and
the innermost end of recess PA10, spanning the entire radial
distance therebetween.
[0007] When it is believed that a seal failure may have occurred,
drilling operations are typically halted so that the seals can be
inspected and possibly replaced. However, drilling costs are very
high, such that downtime must be avoided or minimized as much as
possible. Consequently, systems and apparatus that extend the life
of the packing elements would be welcomed by the industry.
BRIEF SUMMARY OF THE DISCLOSURE
[0008] These and other needs in the art are addressed by a pressure
control device having components configured to work together to
minimize damaging mechanical stresses and thereby to extend the
life of seals and decrease the likelihood that drilling operations
must be shut down in order to replace seals. In one embodiment, a
pressure control device for sealing about a tubular string
comprises: a flange disposed about a central axis, an annular
extension extending from the flange and having a radially-inward
facing surface; and an annular seal element coupled to the annular
extension. The seal member includes a through-passage for receiving
the tubular string and an annular recess in which the annular
extension is disposed. The radially-inward facing surface comprises
a tapered region that is nonlinear in an axial cross-section.
[0009] In some embodiments, the radially-inward facing surface
flares outwardly, away from the through-passage. The
radially-inward facing surface may, in some embodiments, include
first and second ends wherein the second end is further from the
central axis than the first end. In some embodiments, the
radially-inward facing surface comprises a first region extending
from the first end and a second region extending from the first
region, and wherein the second region is continuously curved in an
axial cross-section. The second region may include a constant
radius in an axial cross-section. Further, in some embodiments, the
radially-inward facing surface comprises a first region extending
from the first end and a second region extending from the first
region, and wherein the second region, in an axial cross-section,
has a radius that has a value selected from the range 0 to 30
inches.
[0010] In some embodiments the annular seal element comprises: a
seal first end adjacent the flange; a seal second end axially
spaced apart from the flange; and a radially outermost surface
having first and second regions, wherein the first region extends
from the seal first end and the second region extends from the seal
second end toward the seal first end and is frustoconical.
[0011] Also disclosed herein is a pressure control device for
sealing about a tubular string, comprising: a central axis; an
annular insert; and an annular seal element coupled to the annular
insert. The seal element comprises: a seal first end disposed
adjacent the annular insert; a seal second end axially spaced apart
from the annular insert; a through-passage extending through the
seal first and second ends for receiving the tubular string; and a
radially outermost surface including a first region extending from
the seal first end and a second region extending from the seal
second end toward the first region, wherein the second region
tapers as it extends in a direction away from the annular insert.
In some embodiments, the second region on the annular seal element
intersects the first region, and in some embodiments, the second
region is frustoconical. In some embodiments, the annular insert
comprises an annular flange disposed about the central axis; an
annular extension extending from the flange; and a radially-inward
facing surface extending along the annular extension, wherein the
annular seal element includes an annular recess in which the
annular extension is disposed, the annular recess extending from
the seal first end. The radially-inward facing surface of the
annular insert includes a tapered region that expands radially
outwardly as it extends axially away from the flange. The
radially-inward facing surface may, in some embodiments, further
include a generally cylindrical region extending from the flange to
the tapered region.
[0012] Another pressure control device for sealing about a tubular
string is disclosed and comprises: a central axis; an annular
insert, and an annular seal element. The insert includes a flange
disposed about the central axis, an annular extension concentric
with the flange and extending from the flange, and a
radially-inward facing surface extending along the annular
extension. The annular seal element is coupled to the annular
extension. The seal element includes: a seal first end disposed
adjacent the flange; a seal second end axially spaced apart from
the flange; a through-passage extending through the seal first and
second ends for receiving the tubular string; and an annular recess
in which the annular extension is disposed. The seal element
further includes a radially outermost surface having a first region
extending from the seal first end and a second region extending
from the seal second end toward the first region. The
radially-inward facing surface of the annular insert includes a
tapered region that expands radially outwardly as it extends
axially away from the flange.
[0013] In some embodiments, the second region on the annular seal
element intersects the first region and in some embodiments, the
tapered region is continuously curved. The tapered region of the
annular insert may have a constant radius as viewed in a profile on
an axial plane.
[0014] In some embodiments, the radially-inward facing surface of
the annular insert comprises: a first end coupled to the flange, a
second end spaced from the first end; and a cylindrical region
extending from the first end; wherein the tapered region extends
from the cylindrical region toward the second end. In some
embodiments, the tapered region of the radially-inward facing
surface intersects the second end at a fillet; and wherein the
tapered region intersects the fillet at a tangent line that is
disposed at angle between 5 and 45 degrees, inclusive, with respect
to the central axis.
[0015] Thus, embodiments described herein include a combination of
features and characteristics intended to address various
shortcomings associated with certain prior devices, systems, and
methods. The various features and characteristics described above,
as well as others, will be readily apparent to those of ordinary
skill in the art upon reading the following detailed description,
and by referring to the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] For a detailed description of the disclosed exemplary
embodiments, reference will now be made to the accompanying
drawings:
[0017] FIG. 1 shows a finite element analysis plot of stress
induced within a conventional packing element;
[0018] FIG. 2 shows cross-sectional side view of an embodiment of a
rotating control device having a pressure-responsive assembly
mounted in a rotating sleeve in accordance with principles
described herein;
[0019] FIG. 3 shows a perspective view of an embodiment of a
packing element configured for use in compatible with the rotating
control device of Figure, the packing element having an annular
insert and an annular seal element in accordance with principles
described herein 1;
[0020] FIG. 4 shows a cross-sectional view of the packing element
of FIG. 3;
[0021] FIG. 5 shows a cross-sectional view of the annular insert of
the packing element of FIG. 4;
[0022] FIG. 6 shows a cross-sectional view of another embodiment of
a packing element configured for use in compatible with the
rotating control device of FIG. 2 in accordance with principles
described herein;
[0023] FIG. 7 shows a cross-sectional view of still another
embodiment of a packing element configured for use and compatible
with the rotating control device of FIG. 2 in accordance with
principles described herein;
[0024] FIG. 8 shows a finite element analysis plot of an example
stress-loading within the packing element of FIG. 6; and
[0025] FIG. 9 shows a finite element analysis plot of an example
stress-loading within the packing element of FIG. 4.
NOTATION AND NOMENCLATURE
[0026] The following description is exemplary of certain
embodiments of the disclosure. One of ordinary skill in the art
will understand that the following description has broad
application, and the discussion of any embodiment is meant to be
exemplary of that embodiment, and is not intended to suggest in any
way that the scope of the disclosure, including the claims, is
limited to that embodiment.
[0027] The figures are not drawn to-scale. Certain features and
components disclosed herein may be shown exaggerated in scale or in
somewhat schematic form, and some details of conventional elements
may not be shown in the interest of clarity and conciseness. In
some of the figures, in order to improve clarity and conciseness,
one or more components or aspects of a component may be omitted or
may not have reference numerals identifying the features or
components. In addition, within the specification, including the
drawings, like or identical reference numerals may be used to
identify common or similar elements.
[0028] As used herein, including in the claims, the terms
"including" and "comprising," as well as derivations of these, are
used in an open-ended fashion, and thus are to be interpreted to
mean "including, but not limited to . . . ." Also, the term
"couple" or "couples" means either an indirect or direct
connection. Thus, if a first component couples or is coupled to a
second component, the connection between the components may be
through a direct engagement of the two components, or through an
indirect connection that is accomplished via other intermediate
components, devices and/or connections. The recitation "based on"
means "based at least in part on." Therefore, if X is based on Y,
then X may be based on Y and on any number of other factors. The
word "or" is used in an inclusive manner. For example, "A or B"
means any of the following: "A" alone, "B" alone, or both "A" and
"B."
[0029] In addition, the terms "axial" and "axially" generally mean
along or parallel to a given axis, while the terms "radial" and
"radially" generally mean perpendicular to the axis. For instance,
an axial distance refers to a distance measured along or parallel
to a given axis, and a radial distance means a distance measured
perpendicular to the axis. Furthermore, any reference to a relative
direction or relative position is made for purpose of clarity, with
examples including "top," "bottom," "up," "upper," "upward,"
"down," "lower," "clockwise," "left," "leftward," "right," and
"right-hand." For example, a relative direction or a relative
position of an object or feature may pertain to the orientation as
shown in a figure or as described. If the object or feature were
viewed from another orientation or were implemented in another
orientation, it may then be helpful to describe the direction or
position using an alternate term.
DETAILED DESCRIPTION OF THE DISCLOSED EXEMPLARY EMBODIMENTS
[0030] The present disclosure involves sealing between a rotatable
conduit and a stationary conduit to prevent fluid leakage. The
sealing is achieved by a packing element(s), which serves as a
pressure control device and may rotate with the rotatable conduit
or may remain stationary with the stationary conduit. Each packing
element includes an annular insert having a mounting flange and an
annular seal element that surrounds and contacts the pipe. Axial
movement of a drill pipe or another tubular string through the
packing element may cause the annular seal element, which includes
a resilient portion, to deform as it expands and contracts in
response to varying outside diameter of the tubular string and its
joints. Deformation causes stress in the resilient portion. The
packing element embodiments disclosed herein are configured to
reduce stress within the seal element as a drill pipe or another
tubular string slides into or through the packing element or
remains sealingly coupled within the packing element.
[0031] Referring to FIG. 2, in an exemplary embodiment, a rotating
control device (RCD) 100 extends along a central axis 101 and is
configured to receive sealingly a tubular member, which in this
example is a pipe 102. Device 100 is suitable as a member of a
wellhead over a borehole of a well, such as a hydrocarbon well, for
controlling or isolating fluid pressures. As such, RCD 100 is a
type of pressure control device. Device 100 includes an outer
housing 110 holding a sensor 120 and includes a rotating sleeve
assembly (RSA) 125 received within housing 110.
[0032] Housing 110 includes a housing wall or tubular body 111
extending along the central axis 101 from a lower end 112 to an
upper end 113, having an outer surface and a through-bore 114.
Through-bore 114 is centered on axis 101 and defines an inner
wall.
[0033] RSA 125 extends at least partially within the through-bore
114 of housing 110. RSA 125 includes a rotatable sleeve 130
received within a bearing assembly 180 to rotate about axis 101
relative to the housing 110, a speed indicator 131 received in
sleeve 130 at a location along axis 101 that is aligned with sensor
120 of outer housing 110. Sleeve 130 and pipe 102, when installed,
are configured as a rotatable conduit, and housing 110 is
configured as a stationary conduit. Sensor 120 is configured to
detect the periodic presence of speed indicator 131 as sleeve
assembly 125 rotates relative to housing 110 and sensor 120.
[0034] In FIG. 2, speed indicator 131 includes a magnet, and sensor
120 is includes Hall Effect sensor; although, various other
embodiments include another type of speed indicator 131or another
type of sensor 120.
[0035] Rotating sleeve 130 includes a sleeve outer surface 134 and
a bore 136 extending from a lower end 132 to an upper end 133. In
FIG. 2, rotating sleeve 130 is formed from an upper sleeve member
140 coupled to a lower sleeve member 160 by a sleeve coupling 165.
Referring to FIG. 2, a collar 168 is coupled to sleeve member 140
at upper end 133, and an upper packing element 170A extends
downward from the bottom of collar 168, into member 140. Collar 168
is generally tubular, being open at both ends to receive pipe 102
therethrough. A lower packing element 170B extends downward from
sleeve member 160 at lower end 132. Each packing element 170A,B
includes annular insert 172 bonded or otherwise coupled to an
annular seal element 174 extending axially from insert 172. Annular
inserts 172 are fastened to collar 168 and sleeve member 160,
respectively. The annular seal element 174 of packing element
170A,B are configured to seal around the circumference of pipe 102,
isolating the bore 136 from an upper portion of collar 168 and from
upper and lower portions of bore 114 in housing 110, to prevent
fluid leakage from these regions. Thus, these and other packing
elements disclosed herein are pressure control devices. The sealing
configuration of packing elements 170A,B is maintained even as
sleeve 130 and pipe 102 rotate relative to housing 110 during
operation. In at least some modes of operation, rotation of pipe
102 causes sleeve 130 to rotate due to the gripping action of
packing elements 170A,B. Collar 168, packing elements 170A,B, and
bore 136 provide a sealable through-passage for a tubular member,
e.g. pipe 102, to extend or pass through housing 110, which in some
arrangements leads into a borehole. Bore 136 is configured to be an
isolated chamber when a tubular member is installed.
[0036] Upper sleeve member 140 includes a threaded lower end 142
attached to sleeve coupling 165 and an upper end 133 attached to
collar 168. Sleeve member 140 includes a radially protruding
annular shoulder 146 located between ends 142, 133 and a port 148
extending into shoulder 146 along a central axis 149 coplanar with
central axis 117 of port 116. Some misalignment between axis 149
and 117 is acceptable in various embodiments depending on the
sensitivity of sensor 120. Port 148 is configured to receive speed
indicator 131 at a fixed position along port axis 149, disposing
speed indicator 131 at a fixed distance from axis 101, being
generally flush or adjacent to outer surface 134. Whenever sleeve
130 rotates the indicator 131 to the circumferential position of
sensor 120, the magnet of indicator 131 is at a fixed distance from
sensor 120 within its detection range (e.g. a prescribed distance).
Repeated movement of speed indicator 131 past sensor 120 provides a
measurement of the rotational speed of sleeve 430 with respect to
housing 110. Thus sensor 120 is configured as a speed sensor.
[0037] Referring again to FIG. 2, bearing assembly 180 includes a
bearing housing 182 that is coupled within housing 110 to remain
stationary, a bearing sleeve 184 coupled to sleeve 130 to grasp and
rotate with sleeve 130, and bearing 186 coupled between housing 182
and sleeve 186. In this example, bearing 186 includes two opposing
sets of tapered roller bearings to resist axial thrust in either
vertical direction from, for example, pipe 102.
[0038] FIG. 3 presents a packing element 200. One or more packing
element 200 may be installed or used as either or both packing
elements 170A, 170B in RSA 125 of FIG. 2 to perform as a pressure
control device for sealing about a tubular string. Packing element
200 includes an axis 202, an annular insert 204 centered on axis
202, and an annular, resilient seal element 205 extending from
insert 204 and centered on axis 202. Annular insert 204 includes a
flange 206 with a plurality of fastener holes 208. Seal element 205
includes a radially outermost surface 212 having a plurality of
axial slots 214. Each slot 214 is circumferentially aligned with an
axially extending, fastener hole 208 in flange 206 to allow a
fastener to extend therein.
[0039] FIG. 4 shows a cross-sectional view of packing element 200,
the cross-sectional view formed along a geometric plane 215 that
intersects central axis 202. Insert 204 includes a first end 222, a
second end 224 spaced apart from first end 222 along axis 202, a
flange 206 disposed about axis 202 at end 222, an annular extension
226 concentric with flange 206 extending from the flange 206 to end
224, and a radially-inward facing surface 230 extending along
flange 206 and annular extension 226. In this example, and as shown
in profile view in FIGS. 4 and 5, surface 230 is nonlinear along
axial plane 215.
[0040] FIG. 5 shows a closer view of insert 204 from FIG. 4. From
end 222 to end 224, insert 204 has a height 232. Extension 226 has
an outside diameter (OD) 233 at least at second end 224 and has an
inside diameter (ID) 234 at first end 222. At first end 222,
inward-facing surface 230, starting with the ID 234, extends from
flange 206. Surface 230 expands and has an inner diameter at second
end 224 that is greater than ID 234 at first end 222. Consequently,
surface 230 is further from central axis 202 at second at end 224
than it is at the first end 222. Radially-inward facing surface 230
comprises a cylindrical region 236 (i.e. flat along plane 215, i.e.
when viewed in the cross-section) extending from the first end 222
and a tapered region 238 extending from the region 236, starting at
an axial distance 245 from end 222. Region 238 tapers radially
outward from axis 202 as surface 230 extends away from the flange
206. In various embodiments including that of FIG. 4, distance 245
is selected from the range 0 to 90% of height 232. Embodiments
having a distance 245 equal to 0 inches lack a cylindrical region
236.
[0041] Continuing to reference FIG. 5, tapered region 238 is
continuously curved in this embodiment, lacking any radially inward
annular protrusion. Tapered region 238 intersects or joins the
second end 224 at a fillet 242. In this example, with tapered
region 238 shown in profile view, region 238 has a constant radius
244 on axial plane 215. In various embodiments including FIG. 5,
radius 244 has a value selected from the range 1/8 inch to ten
times OD 233. In various embodiments, including FIG. 5, radius 244
has a value selected from the range 1/8 to 30 inches. In some
embodiments, radius 244 has a value selected from outside these
ranges. In some embodiments, tapered region 238 has a varying
radius along plane 215. In some embodiments, tapered region 238 is
flat rather than curved.
[0042] Considering surface 230 in FIG. 5 further, tapered region
238 intersects the fillet 242 at a tangent line 246. In various
embodiments including FIG. 5, tangent line 246 is disposed at angle
247 having a value between 5 and 45 degrees, inclusive, with
respect to central axis 202 on plane 215. In three dimensions,
tangent line 246 extends circumferentially as a conical surface
about axis 202.
[0043] Referring again to FIG. 4, annular seal element 205,
includes a seal first end 262 coupled to annular extension 226 and
disposed adjacent flange 206 and includes a seal second end 264
axially spaced apart from flange 206. Seal element 205 further
includes a through-passage 266 extending through the seal first and
second ends 262, 264, an annular recess 268 extending from seal
first end 262, and radially outer or outermost surface 212, which
extends from first end 262 to second end 264. Through-passage 266
is configured to receive a tubular member or string. Annular
extension 226 of insert 204 is disposed and held in annular recess
268. The resiliency of seal element 205 allows a portion of element
205 to expand and contract in response to varying outside diameter
or alignment of a tubular string and its joints that may move
within the through-passage 266.
[0044] Outermost surface 212 includes a first region 272 extending
axially from the seal first end 262 at a taper angle 273 with
respect to axis 202 and a second region 274 extending from the seal
second end 264 toward the first region 272. In FIG. 4, slots 214
extend primarily through region 272 but also region 274. Region 274
becomes smaller as it extends in an axial direction from region 274
toward end 264. Conversely, region 274 becomes larger as it extends
in an axial direction from end 264 toward region 274 and annular
insert 204. In FIG. 4, the second region 274 is frustoconical,
extending at a taper angle 275 with respect to axis 202. Region 274
intersects the first region 272 at a fillet and intersects seal
second end 264 at a fillet 276. Thus, in this example, outermost
surface 212 includes two regions defined by their axially-extending
character, i.e. regions 272, 274 located between ends 262, 264, but
not a third region; wherein the fillets are considered to be
portions of these regions 272, 274 and not regions in their own
right. Region 274 extends from region 272 to end 264 without an
intervening cylindrical region. In FIG. 4, taper angle 273 is equal
to 2 degrees; thus, the outer extent of region 272 (radially beyond
slots 214) is mildly frustoconical. Some embodiments have a greater
or lesser value for taper angle 273, and in some embodiments, taper
angle 273 may be zero degrees such that the outer extent of region
272 is generally cylindrical. The size of the other taper angle,
taper angle 275, may also vary. In various embodiments including
FIG. 4, taper angle 275 is selected from a value between 5 and 85
degrees, inclusive. More specifically, in FIG. 4, taper angle 275
is 20 degrees. Axial slot 214 extends from first seal end, along
the first region 272, and into the second region 274 of surface
212. For packing element 200, the radially-inward facing surface
230 of insert 204 expands or flares outwardly, away from the
through-passage 266 as surface 230 extends axially from flange 206.
Packing element 200 has a total height 280 from end 222 to end 264.
In various embodiments including FIG. 4, the height 282 of second
region 274 of seal element 205, measured from end 264, is selected
from a value in the range 10% to 75% of height 280, inclusive. In
some embodiments, second region 274 is curved along axis 202 rather
than being frustoconical and straight along axis 202 on plane
215.
[0045] FIG. 6, in another embodiment, shows a cross-sectional view
of packing element 300. One or more packing element 300 may be
installed or used as either or both packing elements 170A, 170B in
RSA 125 of FIG. 2 to perform as a pressure control device for
sealing about a tubular string. Packing element 300 includes an
axis 302 located on a geometric plane 303, an annular insert 204
centered on axis 302, and an annular seal element 305 extending
from insert 204 and centered on axis 302. Annular insert 204 is the
same as previously described with respect to FIGS. 3 and 4,
including a radially-inward facing surface 230 extending along a
flange 206 and an annular extension 226 from a first end 222 to a
second end 224. As shown in the profile view of FIG. 6, surface 230
is nonlinear along axial plane 215.
[0046] Annular seal element 305 extends from a seal first end 362
coupled to annular extension 226, adjacent flange 206 to a seal
second end 364 axially spaced apart from flange 206. Seal element
305 further includes a through-passage 266 extending through the
seal first and second ends 362, 364, an annular recess 268
extending from seal first end 362, and a radially outermost surface
312 extending from first end 362 to second end 364, and having a
plurality of axial slots 214, in surface 312. Each axial slot 214
is aligned with a fastener hole 208 in flange 206. Only one pair of
aligned slot 214 and hole 208 is shown in FIG. 6. Through-passage
266 is configured to receive a tubular member or string. Annular
extension 226 of insert 204 is disposed and held in annular recess
268. Seal element 305 includes flexible or resilient material to
expand and contract in response to varying outside diameter or
alignment of a tubular string and its joints that may move within
the through-passage 266.
[0047] Outermost surface 312 includes a first region 372 extending
from the seal first end 362 at a mild taper with respect to axis
302, a tapered second region 374 extending from the first region
372, and a cylindrical, third region 376 extending from the second
region 374 to the seal second end 364. Second region 374 and third
region 376 intersect at an obtuse angle 377. In FIG. 6, second
region 374 is frustoconical, having taper angle 375 that is
substantially greater than the taper of region 372, and the
cylindrical, third region 376 intersects seal second end 364 at a
fillet 378. Taper angle 375 of second surface region 374 is 30
degrees, but angle 375 could vary in other embodiments. For
example, angle 375 may have a value between 5 and 85 degrees. In
some embodiments, third region 376 is mildly tapered, frustoconical
with respect to central axis 302. For packing element 300, the
radially-inward facing surface 230 of insert 204 expands or flares
outwardly, away from the through-passage 266 as surface 230 extends
axially away from flange 206.
[0048] FIG. 7 shows a cross-sectional view of in another
embodiment, a packing element 400. One or more packing element 400
may be installed or used as either or both packing elements 170A,
170B in RSA 125 of FIG. 2 to perform as a pressure control device
for sealing about a tubular string. Packing element 400 includes an
axis 402 located on a geometric plane 403, an annular insert 404
centered on axis 402, and an annular seal element 205 extending
from insert 404 and centered on axis 402.
[0049] Annular insert 404 includes a first end 422, a second end
424 spaced apart from first end 422 along axis 402, a flange 206
disposed about axis 402 at end 422, an annular extension 426
concentric with flange 206 extending from the flange 206 to end
424, and a cylindrical radially-inward facing surface 430 extending
along flange 206 and annular extension 426, and a plurality of
axially extending fastener holes 208. The profile view of FIG. 7
shows that surface 430 is linear along axial plane 215 and includes
an annular protrusion 431 proximal end 424. Protrusion 431 may aid
in keeping seal element 205 coupled to insert 404.
[0050] Annular seal element 205 is the same as previously described
with respect to FIG. 3, including the possible embodiments thereof.
For example, seal element 205 extends from a seal first end 262
coupled to annular extension 426 adjacent flange 206 to a seal
second end 264 axially spaced apart from flange 206. Seal element
205 also includes a through-passage 266 to receive a tubular member
or string, an annular recess 468 extending from seal first end 262,
and a radially outermost surface 212, which extends from first end
262 to second end 264. Annular extension 426 of insert 404 is
disposed and held in annular recess 468, which is contoured to
match this extension 426. For example, recess 468 is generally
cylindrical and includes a radially-inward, annular indentation 469
to receive protrusion 431. As previously described, surface 212
includes a tapered first region 272 and a tapered second region 274
extending from region 272 to seal second end 264, and a plurality
of axial slots 214.
[0051] FIG. 8 shows an FEA plot of stress induced within a
resilient, annular seal element 305 of a packing element 300 (FIG.
6). The plot shows stress results for regions along a
cross-section; even so, the results are representative of
volumetric portions of seal element 305. As described previously,
seal element 305 extends from a first end 362 to a second end 364
and includes a through-passage 266, an annular recess 268 extending
inward from first end 362, and a radially outermost surface 312.
Although not shown, the FEA includes boundary conditions that
assume rigid flanged, annular insert 204 is located along the
radially outer portion of first end 362 and within annular recess
268 as shown in FIG. 6. In the plot, a box end 20 of a drill pipe
22 is located within through-passage 266 of seal element 305 with a
neck 24 of box end 20 axially aligned with the innermost end of
recess 268. More specifically, the plot represents a situation in
which drill pipe 22 is being pulled upward through seal element
305. In the plot, stress levels are normalized and labeled as
previously explained with respect to FIG. 1. In the scenario of
FIG. 8, a region of low stress SL1 in seal element 305 occurs
throughout a majority of seal element 305. A region of elevated
stress SL2 occurs around the innermost end of recess 268 and neck
24. Highest stress SL3 extends radially between the innermost end
of recess 268 and the intersection of box end 20 and neck 24 but
not spanning the entire distance therebetween, unlike the scenario
of FIG. 1. Thus, the configuration of a packing element 300 with an
annular insert 204, which includes a tapered or curved
radially-inward facing surface 230 (FIG. 5), results in a smaller
portion of its seal element 305 experiencing highest stress SL3 as
compared to the seal element of a conventional packing element,
which is analyzed in FIG. 1.
[0052] FIG. 9 shows an FEA plot of stress induced within a
resilient, annular seal element 205 of a packing element 200 (FIG.
4). The plot shows stress results for regions along a
cross-section; even so, the results are representative of
volumetric portions of seal element 205. As described previously,
seal element 205 extends from a first end 262 to a second end 264
and includes a through-passage 266, an annular recess 268 extending
inward from first end 262, and a radially outermost surface 212.
Although not shown, the FEA includes boundary conditions that
assume a rigid flanged, annular insert of the packing element is
located along the radially outer portion of first end 262 and
within annular recess 268 as shown in FIG. 4. Annular recess 268 is
cylindrical, having axially extending walls. In the plot, a box end
20 of a drill pipe 22 is located within a seal element 205 with
neck 24 of box end 20 axially aligned with the innermost end of
recess 268. The plot represents a situation in which drill pipe 22
is being pulled upward through seal element 205. In the plot,
stress levels are normalized and labeled as previously explained
with respect to FIG. 1. In the scenario of FIG. 9, a region of low
stress SL1 in seal element 205 occurs throughout a majority of seal
element 205. A region of elevated stress SL2 occurs around the
innermost end of recess 268 and neck 24. Disposed between the
innermost end of recess 268 and the intersection of box end 20 and
neck 24, a region of highest stress SL3 extends radially inward
from recess 268 and radially inward from the through-passage 266,
but spanning only a relatively small portion of the entire distance
therebetween, unlike the scenario of FIG. 1. The size of the
regions of the seal element in FIG. 9 that experience the highest
stress SL3 and the regions that experience elevated stress SL2 are
both reduced as compared to the seal element of a conventional
packing element analyzed in FIG. 1, and as compared to packing
element 300 analyzed in FIG. 8. Thus, as shown in FIG. 9, packing
element 200 includes an annular insert 204 having a tapered or
curved radially-inward facing surface 230 (FIG. 5) and also
includes a seal element 205 having a radially outermost surface
212, and this configuration is understood to be a reason that seal
element 205 is subjected to lower stress when a box end 20 is in
seal element 205 as compared to stress experience by a seal element
of a conventional packing element and as compared to some other
packing element embodiments disclosed herein.
[0053] Some embodiments of packing elements in accordance with
principles described herein include an annular seal element having
an outer surface region defined by a single axially-extending
character, such as being entirely frustoconical or entirely
cylindrical, as examples. Some of these embodiments include slots
214.
[0054] While exemplary embodiments have been shown and described,
modifications thereof can be made by one of ordinary skill in the
art without departing from the scope or teachings herein. The
embodiments described herein are exemplary only and are not
limiting. Many variations, combinations, and modifications of the
systems, apparatuses, and processes described herein are possible
and are within the scope of the disclosure. Accordingly, the scope
of protection is not limited to the embodiments described herein,
but is only limited by the claims that follow, the scope of which
shall include all equivalents of the subject matter of the claims.
The inclusion of any particular method step or operation within the
written description or a figure does not necessarily mean that the
particular step or operation is necessary to the method. The steps
or operations of a method listed in the specification or the claims
may be performed in any feasible order, except for those particular
steps or operations, if any, for which a sequence is expressly
stated. In some implementations two or more of the method steps or
operations may be performed in parallel, rather than serially.
* * * * *