U.S. patent application number 13/388657 was filed with the patent office on 2012-10-04 for stuffing box assembly.
This patent application is currently assigned to Millennium Oilflow Systems & Technology Inc.. Invention is credited to James Bentley, Andrew Wright.
Application Number | 20120247754 13/388657 |
Document ID | / |
Family ID | 43544722 |
Filed Date | 2012-10-04 |
United States Patent
Application |
20120247754 |
Kind Code |
A1 |
Wright; Andrew ; et
al. |
October 4, 2012 |
STUFFING BOX ASSEMBLY
Abstract
A stuffing box assembly (4) comprising a primary housing (8)
having a longitudinally oriented hollow bore (11) extending
therethrough, a hanger assembly (9) within the longitudinally
oriented hollow bore of the primary housing, and drive means (10)
received within the hollow bore of the hanger assembly. The hanger
assembly has a longitudinally oriented hollow bore extending
therethrough. The drive means has means (15) to releasably secure
the drive means to a pump rod such that the pump rod is hung from
and supported within the primary housing by the hanger assembly.
Rotation of the drive means causes a corresponding rotation of the
pump rod. The hanger assembly includes one or more seals (17) to
contain well fluids and to help prevent the flow of well fluids
into the bore of the hanger assembly.
Inventors: |
Wright; Andrew; (Leduc,
CA) ; Bentley; James; (Beaumont, CA) |
Assignee: |
Millennium Oilflow Systems &
Technology Inc.
|
Family ID: |
43544722 |
Appl. No.: |
13/388657 |
Filed: |
July 22, 2010 |
PCT Filed: |
July 22, 2010 |
PCT NO: |
PCT/IB2010/001787 |
371 Date: |
June 13, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61231887 |
Aug 6, 2009 |
|
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|
Current U.S.
Class: |
166/84.1 ;
166/75.13 |
Current CPC
Class: |
E21B 43/126 20130101;
E21B 33/085 20130101 |
Class at
Publication: |
166/84.1 ;
166/75.13 |
International
Class: |
E21B 33/08 20060101
E21B033/08; E21B 33/04 20060101 E21B033/04 |
Claims
1. A stuffing box assembly comprising: a primary housing having a
longitudinally oriented hollow bore extending therethrough; a
hanger assembly within said longitudinally oriented hollow bore of
said primary housing, said hanger assembly having a longitudinally
oriented hollow bore extending therethrough; and, drive means
received within said hollow bore of said hanger assembly, said
drive means having means to releasably secure said drive means to a
pump rod such that the pump rod is hung from and supported within
said primary housing by said hanger assembly and such that rotation
of said drive means causes a corresponding rotation of the pump
rod, said hanger assembly including one or more seals to contain
well fluids and to help prevent the flow of well fluids into said
bore of said hanger assembly.
2. The stuffing box assembly as claimed in claim 1 wherein said
hanger assembly includes bearings to facilitate the rotation of
said drive means, said hanger assembly further including one or
more seals to prevent the flow of fluid between said hanger
assembly and said primary housing.
3. The stuffing box assembly as claimed in claim 2 wherein said
drive means is a drive rod.
4. The stuffing box assembly as claimed in claim 3 further
including a pair of radially opposed blowout preventer rams
situated in transverse bores extending through said primary
housing, said transverse bores in communication with said
longitudinal bore through said primary housing such that said
blowout preventer rams sealingly engage the exterior surface of
said drive rod when said rams are advanced within said transverse
bores toward said drive rod.
5. The stuffing box assembly as claimed in claim 2 wherein said
longitudinally oriented hollow bore through said primary housing
includes a first diameter portion and a second reduced diameter
portion, said first and said second diameter portions connected by
a shoulder portion, said shoulder portion acting as a bearing
surface against which said hanger assembly is engaged, said
shoulder portion bearing the weight of said hanger assembly, said
drive means and a pump rod when attached thereto.
6. The stuffing box assembly as claimed in claim 2 wherein said
primary housing includes one or more locking mechanisms to retain
said hanger assembly within said primary housing.
7. The stuffing box assembly as claimed in claim 6 wherein said one
or more locking mechanisms comprise one or more lock down
screws.
8. The stuffing box assembly as claimed in claim 2 wherein said
drive means includes torque input means permitting for the
transference of rotational torque from a power source to said drive
means and to a pump rod attached thereto.
9. The stuffing box assembly as claimed in claim 8 wherein said
torque input means comprises a recess in the upper end of said
drive means and said power source comprises an electric or
hydraulic motor, said recess configured and sized to accept the
shaft of said electric or hydraulic motor such that the operation
of said motor causes a direct rotation of said drive means.
10. The stuffing box assembly as claimed in claim 2 wherein said
drive means comprises a rotatable mandrel.
11. The stuffing box assembly claimed in claim 10 wherein said
hanger assembly is hung and supported within the longitudinally
oriented hollow bore of said primary housing by a shoulder portion
on said primary housing.
12. The stuffing box assembly is claimed in claim 11 wherein said
rotatable mandrel has a longitudinally oriented hollow bore for
receiving a pump rod there through.
13. The stuffing box assembly as claimed in claim 12 wherein, the
hollow bore through said rotatable mandrel has a reduced diameter
portion, said mandrel including slips to engage a pump rod received
through said hollow bore in said mandrel, said slips engaging the
pump rod at said reduced diameter portion in order to hang the pump
rod from said mandrel such that rotation of said mandrel causes a
simultaneous rotation of the pump rod.
14. The stuffing box assembly as claimed in claim 12 including a
rod clamp, said rod clamp operatively securing the pump rod to said
rotatable mandrel such that rotation of said mandrel causes a
corresponding rotation of the pump rod, said rod clamp further
transferring the axial or longitudinal load of the pump rod to said
rotating mandrel.
15. The stuffing box assembly as claimed in claim 9 wherein said
shaft of said motor includes a longitudinal hollow bore extending
therethrough, when said shaft of said motor is received within said
recess in the upper end of said drive means said longitudinal bore
in said motor shaft is in fluid communication with a longitudinally
oriented hollow bore extending through at least the upper end of
said drive means, said bore in said drive means having at least one
transverse oriented exit port in communication with the exterior
surface of said drive means, said bore extending through said shaft
of said motor being at least partially filled with lubricant and
having associated therewith pressurization means to pressurize said
lubricant, said pressurization means forcing said lubricant through
said shaft of said motor into said bore within the upper end of
said drive means and through said transverse exit port, said
lubricant assisting in the lubrication of said seals and
pressurizing the interior of said stuffing box.
16. The stuffing box assembly as claimed in claim 15 wherein said
pressurization means pressurizes said lubricant to a level such
that the lubricant pressure within said stuffing box exceeds the
pressure of fluids within a well upon which said stuffing box is
mounted to help prevent the flow of well fluids into said stuffing
box.
17. The stuffing box assembly as claimed in claim 16 wherein the
upper end of said longitudinal bore extending through said shaft of
said electric or hydraulic motor is sealed, said pressurization
means situated within said longitudinal bore in said motor
shaft.
18. The stuffing box assembly as claimed in claim 17 wherein said
pressurization means comprises a spring or gas actuated piston.
19. The stuffing box assembly as claimed in claim 2 including an
external source of pressurized lubricant connected to the interior
of said hanger assembly, said pressurized lubricant lubricating
said one or more seals and pressurizing said hanger assembly to a
higher pressure than the pressure of a wellbore upon which said
stuffing box is mounted to help prevent the flow of well, fluids
into said hanger assembly.
20. The stuffing box assembly as claimed in claim 1 in combination
with a casing head, said casing head including one or more side
entry passageways to permit the introduction of coiled tubing or
other tubular or elongate member into the wellbore of a wellhead
onto which said stuffing box assembly is mounted, said introduction
of said coiled tubing or other tubular or elongate member occurring
at a point below said stuffing box assembly and without the removal
of said stuffing box assembly from the wellhead.
21. A casing head for securing to the upper end of the casing of a
well extending into an underground formation, the casing head
including one or more side entry passageways to permit the
introduction of coiled tubing or other tubular or elongate member
into the wellbore of the casing without the removal of wellhead
equipment positioned above said casing head.
22. The casing head as claimed in claim 21 including removable
plugs in said one or more side entry passageways to help prevent
the ingress of debris into the wellbore and the escape of fluids
from the wellbore.
23. The casing head as claimed in claim 22 wherein said one or more
side entry passageways are arranged with their longitudinal axes at
a shallow angle relative to the centerline of the wellhead to
permit the coiled tubing or other tubular or elongate member to be
inserted at a shallow angle of approach relative to the casing and
any tubing string that may be received therein.
24. A stuffing box assembly comprising: a primary housing; a
removable hanger assembly releasably and sealingly receivable
within a longitudinally oriented hollow bore extending through said
primary housing, said hanger assembly having a longitudinally
oriented hollow bore extending therethrough; and, drive means
sealingly receivable within said hanger assembly and extending
through said hollow bore within said primary housing when said
hanger assembly is received therein, said drive means including
torque input means permitting for the transference of rotational
torque from a power source to said drive means, said drive means
having means to releasably secure said drive means to a pump rod
such that rotation of said drive means causes a corresponding
rotation of the pump rod when secured thereto, said drive means
including one or more seals between said drive means and the pump
rod, when said hanger assembly is received within said primary
housing said hanger assembly hanging said drive means, and a pump
rod when attached thereto, from said primary housing, said hanger
assembly including bearings to facilitate the rotation of said
drive means, said hanger assembly including one or more seals to
seal against the exterior surface of said drive means to help
prevent the flow of fluid between said drive means and said hanger
assembly.
25. A stuffing box assembly comprising; a primary housing; a hanger
assembly within a longitudinally oriented bore extending through
said primary housing, said hanger assembly having a longitudinally
oriented bore extending therethrough; and, drive means sealingly
received within said hollow bore of said hanger assembly, said
drive means including torque input means permitting for the
transference of rotational torque from a power source to said drive
means, said drive means having means to releasably secure said
drive means to a pump rod such that rotation of said drive means
causes a corresponding rotation of the pump rod when secured
thereto, said hanger assembly hanging said drive means, and a pump
rod when attached thereto, from said primary housing, said hanger
assembly including bearings to facilitate the rotation of said
drive means, said hanger assembly including one or more seals to
contain well fluids and to help prevent the flow of well fluid into
said bore in said hanger assembly.
26. The stuffing box assembly as claimed in claim 25 wherein said
drive means is a rotating mandrel, said rotating mandrel having a
longitudinally oriented hollow bore for securedly receiving the
pump rod therein such that rotation of the rotating mandrel causes
a corresponding rotation of the pump rod.
Description
FIELD OF THE INVENTION
[0001] This invention relates generally to oil well production
equipment, and more particularly to a new and useful stuffing box
assembly for use on an oil or other well driven into an underground
formation.
BACKGROUND OF THE INVENTION
[0002] When pumping oil (or for that matter water or other fluids)
from underground formations, typically a downhole pump is utilized
wherein the pump is physically located deep within the well and
used to pump the oil or fluid to the surface. In many such
applications the downhole pump of choice is a screw or progressive
cavity pump. Screw or progressive cavity pumps generally operate
through the revolution of a pump rotor within a stator. A rotating
pump rod extends from the surface to the downhole pump and is used
to drive or rotate the rotor. A power supply, which most commonly
would be comprised of a gas, diesel, hydraulic or electric motor,
provides the means to rotate the pump rod, and hence the pump
rotor. A series of seals are used to engage the rotating pump rod
at or near the point where it exits the top of the well to prevent
downhole fluids from leaking into the environment. Traditionally
these seals and their related structural components have been
referred to as a stuffing box.
[0003] In older reciprocating-type wells, a single stationary
stuffing box was typically provided. In such applications packing
material would normally be inserted into the stuffing box and
compressed against a dedicated portion of the pump rod (that may be
polished to present a smooth sealing surface) in order to minimize
the leakage of well fluids. With the introduction of rotary or
progressive cavity pumps, others have suggested the use of a
rotating stuffing box as a means to help guard against a premature
failure of packing material that can sometimes occur when using a
more traditional stuffing box in a rotary pump application (for
example see Canadian patent 2,095,937 issued Dec. 22, 1998). Such
rotary stuffing boxes commonly employ a rotating or hollow shaft
structure that is received about the pump rod such that the hollow
shaft rotates in unison with the pump rod. The exterior portion of
the hollow shaft can be hardened and machined to provide a smooth
surface against which one or more seals act in order to help
prevent leakage of fluid from the well. While these hollow shaft
structures can be effective, they also add to the complexity of the
stuffing box, its costs and weight.
[0004] In addition to stuffing boxes, the wellhead equipment on
most oil wells includes a blowout preventer that may be used to
seal around the pump rod in order to contain well fluids and
maintain well control, particularly when pumping ceases. Blowout
preventers have been produced in a wide variety of different
configurations and, using an equally wide variety of different
mechanical structures. Most commonly, blowout preventers are
comprised of a pair of radially opposed rams having sealing
surfaces on their inner ends such that when the rams are driven
inwardly toward the pump rod they sealingly engage the exterior of
the rod surface, thereby preventing the escape of fluids from the
well. In some instances the blowout preventer, rams may include
gripping inserts or gripping surfaces that serve the further
function of engaging the surface of the pump rod to a degree that
allows the rams to securely hold and retain the pump rod in
place.
[0005] The surface equipment on an oil well will often include a
number of additional components, such as casing heads, tubing
string hangers, tubing string rotators, flow-tees, backspin
inhibiting devices, drive heads etc. In many applications it is
also necessary to employ some form of pump rod hanging device that
serves the function of accepting the vertical load of the pump rod
(which in deep wells can be significant) and transmitting that load
to the well casing. Often the pump rod hanging device takes the
form of a rod clamp that is secured or compressed about the
exterior surface of the pump rod, typically at the top or upper end
of the rod. Pump rod clamps are commonly designed to fit or mate
within correspondingly shaped recesses in a drive gear or
equivalent structures, such that rotation of the drive gear causes
rotational movement of the rod clamp and thus the pump rod.
[0006] As a result of the need for a substantial number of
mechanical components at the surface of an oil well, the height of
the wellhead equipment can often become significant. As the height
of the surface equipment (sometimes referred to as a Christmas
tree) increases, so does its weight and the general necessity for
larger and stronger flanges, bolts, threads and other such means
that are used to hold adjacent components together. The height and
weight of the wellhead components is even more significant where
the well is not vertical, in which case the assembled equipment
must be capable of accommodating the resulting bending moment.
There is thus a desirability to minimize the height of surface
production equipment that extends out of the ground above the well
casing. There is also the need for the use of highly effective
stuffing boxes and sealing mechanisms, and the need to simplify the
mechanical systems that are utilized to hang and to rotate a pump
rod within a well, and to seal against the rod when the pumping
operation ceases.
SUMMARY OF THE INVENTION
[0007] The invention therefore, in one of its aspects, provides a
stuffing box assembly that helps to address some of the
deficiencies in currently available wellhead equipment. The
stuffing box is contained within a housing that provides an
effective means to seal against the pump or drive rod, and that
contains a pump rod hanger with related bearing components and a
mechanism that presents a simplified mechanical structure for
driving the pump rod. In one embodiment the stuffing box may also
contain an integrated blow out preventer. The invention also
concerns a new and novel casing head.
[0008] Accordingly, in one of its aspects the invention provides a
stuffing box assembly comprising a primary housing having a
longitudinally oriented hollow bore extending therethrough; a
hanger assembly within said longitudinally oriented hollow bore of
said primary housing, said hanger assembly having a longitudinally
oriented hollow bore extending therethrough; and, drive means
received within said hollow bore of said hanger assembly, said
drive means having means to releasably secure said drive means to a
pump rod such that the pump rod is hung from and supported within
said primary housing by said hanger assembly and such that rotation
of said drive means causes a corresponding rotation of the pump
rod, said hanger assembly including one or more seals to contain
well fluids and to help prevent the flow of well fluids into said
bore of said hanger assembly.
[0009] In a further aspect the invention provides a casing head for
securing to the upper end of the casing of a well extending into an
underground formation, the casing head including one or more side
entry passageways to permit the introduction of coiled tubing or
other tubular or elongate member into the wellbore of the casing
without the removal of wellhead equipment positioned above said
casing head.
[0010] In yet a further aspect the invention concerns a stuffing
box assembly comprising a primary housing; a removable hanger
assembly releasably and sealingly receivable within a
longitudinally oriented hollow bore extending through said primary
housing, said hanger assembly having a longitudinally oriented
hollow bore extending therethrough; and, drive means sealingly
receivable within said hanger assembly and extending through said
hollow bore within said primary housing when said hanger assembly
is received therein, said drive means including torque input means
permitting for the transference of rotational torque from a power
source to said drive means, said drive means having means to
releasably secure said drive means to a pump rod such that rotation
of said drive means causes a corresponding rotation of the pump rod
when secured thereto, said drive means including one or more seals
between said drive means and the pump rod, when said hanger
assembly is received within said primary housing said hanger
assembly hanging said drive means, and a pump rod when attached
thereto, from said primary housing, said hanger assembly including
bearings to facilitate the rotation of said drive means, said
hanger assembly including one or more seals to seal against the
exterior surface of said drive means to help prevent the flow of
fluid between said drive means and said hanger assembly.
[0011] In still a further aspect the invention provides a stuffing
box assembly comprising a primary housing; a hanger assembly within
a longitudinally oriented bore extending through said primary
housing, said hanger assembly having a longitudinally oriented bore
extending therethrough; and, drive means sealingly received within
said hollow bore of said hanger assembly, said drive means
including torque input means permitting for the transference of
rotational torque from a power source to said drive means, said
drive means having means to releasably secure said drive means to a
pump rod such that rotation of said drive means causes a
corresponding rotation of the pump rod when secured thereto, said
hanger assembly hanging said drive means, and a pump rod when
attached thereto, from said primary housing, said hanger assembly
including bearings to facilitate the rotation of said drive means,
said hanger assembly including one or more seals to contain well
fluids and to help prevent the flow of well fluid into said bore in
said hanger assembly.
[0012] Further aspects and advantages of the invention will become
apparent from the following description taken together with the
accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] For a better understanding of the present invention, and to
show more clearly how it may be carried into effect, reference will
now be made, by way of example, to the accompanying drawings which
show the preferred embodiments of the present invention in
which:
[0014] FIG. 1 is a vertical cross-sectional view through a typical
oil well that employs a progressive cavity pump and having attached
to the wellhead a stuffing box assembly generally constructed in
accordance with one of the preferred embodiments of the present
invention;
[0015] FIG. 2 is a side elevational view of the stuffing box
assembly shown in FIG. 1, having an electric drive motor attached
thereto;
[0016] FIG. 3 is a side elevational view of the stuffing box
assembly shown in FIG. 2, rotated 90.degree.;
[0017] FIG. 4 is a cross-sectional view taken along the line of 4-4
of FIG. 2;
[0018] FIG. 5 is a cross-sectional view taken along the line 5-5 of
FIG. 3;
[0019] FIG. 6 is an exploded view of the stuffing box assembly
(with a portion of its outer housing removed) shown in FIG. 2;
[0020] FIG. 7 is an enlarged detailed cross-sectional view taken
along the line 7-7 of FIG. 6;
[0021] FIG. 8 is a vertical cross-sectional view of an alternate
embodiment of the stuffing box assembly of the current invention
having mounted thereon an electric motor;
[0022] FIG. 9 is an exploded view of the stuffing box assembly
shown in FIG. 8;
[0023] FIG. 10 is an enlarged detailed cross-sectional view taken
along the line 10-10 of FIG. 9;
[0024] FIG. 11 is a vertical cross-sectional view of one embodiment
of the stuffing box assembly in accordance with the present
invention shown in association with an electric motor and a casing
head, and further including a separate scrap view of the tubing
(with a tubing rotator attached thereto) and the stuffing box
assembly (with a rod assembly) shown removed from the vertical
cross-sectional view;
[0025] FIG. 12 is an enlarged view of the stuffing box assembly and
casing head shown in FIG. 11 having the electric motor removed;
[0026] FIG. 13 is an upper side perspective view of the casing head
shown in FIG. 12;
[0027] FIG. 14 is a side elevational view of the casing head shown
in FIG. 13;
[0028] FIG. 15 is a sectional view taken along the line 15-15 in
FIG. 14;
[0029] FIGS. 16 and 16A are vertical cross-sectional views of an
alternate embodiment of the stuffing box assembly of the current
invention having mounted thereon an electric motor;
[0030] FIGS. 17 and 17A are vertical cross-sectional views of a
further alternate embodiment to that shown in FIG. 16;
[0031] FIG. 18 is a vertical cross-sectional view of a further
embodiment to that shown in FIG. 17;
[0032] FIG. 19A is a further alternate embodiment to that shown in
FIG. 18; and
[0033] FIG. 19B is a cross-sectional view taken along the line of
19B-19B in FIG. 19.
DESCRIPTION OF THE PREFERRED EMBODIMENT
[0034] The present invention may be embodied in a number of
different forms. However, the specification and drawings that
follow describe and disclose only some of the specific forms of the
invention and are not intended to limit the scope of the invention
as defined in the claims that follow herein.
[0035] With reference to FIG. 1 there is shown in vertical cross
section a typical oil well 1 that employs a progressive cavity pump
2 to lift oil to the surface. At the surface of the oil well the
wellhead 3 has attached to it a stuffing box assembly 4 constructed
in accordance with one of the preferred embodiments of the present
invention. In the embodiment of the well shown in FIG. 1, an
electric or hydraulic motor 5 provides the means by which a pump
rod 6 is rotated in order to turn the rotor 7 of the progressive
cavity pump. In this embodiment motor 5 is in a direct drive
configuration with rotor 7.
[0036] Turning next to FIGS. 2 through 7, there is shown from
various angles and with various degrees of cross sectioning the
internal and external features and components of stuffing box
assembly 4. As will be appreciated from an examination of those
Figures, stuffing box 4 is comprised generally of a primary housing
8, a hanger assembly 9 (that in this embodiment is shown as being
removable but that also may be permanently fixed to housing 8), and
a drive means 10 (that in this embodiment is a drive rod but that,
as discussed below, may also be a rotating mandrel). Primary
housing 8 has a longitudinally oriented hollow bore 11 extending
generally through its middle portion into which hanger assembly 9
is releasably receivable. As shown, hanger assembly 9 also has a
longitudinally oriented bore 12 extending therethrough that is
capable of sealingly receiving drive rod 10. Drive rod 10 is an
elongate member that, when received within hanger assembly 9 with
the hanger assembly situated within hollow bore 11 of primary
housing 8, will preferably extend through the bottom of the primary
housing. Drive rod 10 further has an upper end 13 and a lower end
14, with lower end 14 having means 15 thereon to releasably secure
the drive rod to a pump rod such that rotation of the drive rod
will cause a corresponding rotation of the pump rod. It will be
appreciated that means 15 could be any one of a variety of
different mechanisms that could be used to secure the drive rod to
the pump rod, however, in most instances it is expected that means
15 will be a threaded connection that allows the two rods to be
threaded together.
[0037] Hanger assembly 9 is designed and configured to hang drive
rod 10, and a pump rod that may be attached thereto, from primary
housing 8 when the hanger assembly is received within the primary
housing. In order to facilitate the rotation of the drive rod and
pump rod, the hanger assembly preferably includes bearings 16 as
well as one or more seals 17 that seal against the exterior surface
of the drive rod to prevent the flow of fluid between the drive rod
and the hanger assembly. To help facilitate the seal between drive
rod 10 and seals 17, the surface of the drive rod adjacent the
seals may be polished or may have a smooth ceramic or other coating
applied. Polishing or coating the rod not only helps to enhance the
seal between the rod and seals 17 but also potentially extends the
useful life of the rod.
[0038] In the embodiment of the hanger assembly shown in FIG. 7,
bearings 16 include an upper bearing 32, a middle bearing 33 and a
lower bearing 34. It will be understood that other configurations
of bearings could also be used and that the various bearings
generally accommodate thrust and/or rotary loads. It will also be
apparent that the hanger assembly in this embodiment is
manufactured in two primary sections; namely, a bottom portion 35
and a lock down nut 36 that are threaded together once the various
bearings and seals have been put in place. A cap 43 may be screwed
or bolted to the lock down nut and/or the bottom portion. The upper
portion of the hanger assembly may include a grease nipple or
lubrication port 37 to permit the introduction of grease or
lubricants into the hanger assembly to help lubricate the various
bearings and seals. In addition to seals 17 positioned in the lower
portion of the hanger assembly to seal against the drive rod and
maintain well control (two of which are shown, however, more or
fewer of which may be utilized), the hanger assembly may also
include an upper seal 38 to seal between the upper or top portion
of the hanger assembly and the top portion of the drive rod. When
received within the primary housing, hanger assembly 9 will be
static while permitting drive rod 10 to be rotated. Accordingly,
seals 17 and 38 are preferably dynamic seals that seal against the
rotating exterior surface of the drive rod when it is received
within the hanger assembly. A series of static seals 39 are used to
seal the hanger assembly with housing 8 and to seal lock down nut
36 within bottom portion 35.
[0039] While hanger assembly 9 may be hung within hollow bore 11 of
primary housing 8 in a number of different manners, in the
embodiment shown in the attached drawings longitudinally oriented
hollow bore 11 through the primary housing includes a first
diameter portion 18 at its upper end in order to receive the hanger
assembly and a second or lower, reduced diameter, portion 19. In
this embodiment the first and second diameter portions 18 and 19
are connected by a sloped shoulder portion 20 that acts as a
bearing surface against which a sloped exterior portion 21 of
hanger assembly 9 bears when the hanger assembly is received within
hollow bore 11 of the primary housing. The engagement of the sloped
exterior surface 21 of the hanger assembly with the sloped shoulder
20 of hollow bore 11 results in a friction fit between the hanger
assembly and the primary housing that securely and statically holds
the hanger assembly within the housing such that the weight of the
drive rod, and the pump rod attached thereto, that is borne by the
hanger assembly is transmitted, via the sloped shoulder contact, to
the body of the primary housing. One or more of the static seals 39
(see FIG. 7) are preferably placed between the exterior surface of
the hanger assembly and the interior of hollow bore 11 of the
primary housing in order to help prevent the flow of fluid between
the primary housing and the hanger assembly. The hanger assembly
may also include one or more lock pins to prevent the hanger
assembly (and hence the drive rod) from rotating and/or lifting
with primary housing 8, particularly in the event of a power loss,
pump shut down or in a high pressure well. In a further embodiment
sloped shoulder portion 20 could be a square or other shaped
shoulder. It will also be appreciated that there could exist teeth,
splines or other structures between the hanger assembly and the
primary housing to prevent the hanger assembly from rotating.
Alternately, the hanger assembly could be prevented from rotating
by frictional engagement with the primary housing.
[0040] In the embodiment of the invention shown, stuffing box
assembly 4 further includes a pair of radially opposed blowout
preventer rams 23 that are situated in transverse bores 24 that
extend through the primary housing. Transverse bores 24 are in
communication with the exterior of the housing and with hollow bore
11 such that when driven inwardly towards the center of the
housing, the blowout preventer rams sealingly engage each other and
the exterior surface of drive rod 10. It will be appreciated by
those skilled in the art that the particular form of rams used
could vary from application to application. In most instances it is
expected that the interior surfaces of the rams will be fitted with
a seal that generally has a shape that conforms to the exterior
surface of the drive rod. When the rams are driven inwardly and
compressed up against the surface of the drive rod the seals will
pack off the open area of the hollow bore in order to prevent the
escape of well fluids past the rams.
[0041] In some instances it may be desirable for the interior
surfaces of the rams to have gripping faces or, alternatively,
gripping inserts (not shown) that can physically contact the
exterior surface of the drive rod in order to securely hold it in
place. The gripping faces or gripping inserts would typically be
capable of holding both the vertical load of the drive rod and the
pump rod attached thereto, as well as rotational torque that may be
built up within the drive rod and pump rod on account of either the
operation of the compressive cavity pump or the tendency for the
pump rod to exhibit back spin when the pumping operation ceases and
the weight of oil or fluid in the well bears directly upon the pump
rotor. It will equally be appreciated that the blowout preventer
rams will, typically include various other features and elements
that are commonly used in blowout preventers, including ram stems
and a mechanism to actuate the rams, whether it be through manually
turning the stems or through the use of hydraulic, electric or
pneumatic actuators.
[0042] As shown most clearly in FIGS. 2, 3 and 4, in one
embodiment, stuffing box assembly 4 includes one or more locking
mechanisms 25 that assist in retaining hanger assembly 9 within
hollow bore 11 of primary housing 8. In FIGS. 2, 3 and 4, the
locking mechanisms are comprised of a plurality of lock down or
hold down screws 26 that are threadably received within the primary
housing 8 of the stuffing box. Lock down screws 26 have interior
ends that engage the exterior surface of hanger assembly 9 in order
to prevent the hanger assembly from being lifted within the primary
housing, particularly in the case of high pressure wells.
Employment of lock down screws 26 maintains the seating of sloped
exterior surface 21 of the hanger assembly with shoulder 20 of
hollow bore 11, and in so doing also maintains the seating of seals
39 with the interior surface of hollow bore 11 to prevent the
leakage of well fluids between the hanger assembly and the primary
housing.
[0043] Rotational torque may be applied to drive rod 10 through the
use of a variety of different mechanical and electro-mechanical
means. The example of one of the preferred embodiments of the
invention that is shown in the attached drawings is a direct drive
system where drive rod 10 is driven directly by electric or
hydraulic motor 5. In this instance the upper end of the drive rod
includes a torque input means 27 that permits the transference of
rotational torque from a drive source (in this case motor 5) to the
drive rod, which in turn transfers rotational torque to a pump rod
attached thereto. While input means 27 could itself take different
forms, in the embodiment shown the input means comprises a recess
within the upper end of the drive rod which is of a configuration
and size such that the recess accepts the end of the shaft of motor
5 when the motor is mounted on top of primary housing 8. To permit
the transference of rotational torque from the motor shaft to the
drive rod, the motor shaft may be splined with the recess and the
drive rod having a similar configuration or, alternatively, the
motor may be equipped with a keyed shaft with the recess machined
with an appropriate key way. In any event, it will be appreciated
that through mounting motor 5 directly upon the upper surface of
primary housing 8 such that the shaft of the motor is received
within a corresponding configured recess in the upper end of drive
rod 10, operation of motor 5 will result in a direct rotation of
the drive rod and the pump rod attached thereto. It will also be
appreciated that such a direct drive structure presents a number of
advantages, not the least of which includes a more compact and
simplified wellhead design, a more efficient drive structure (that
eliminates the need for belts, chains, gears, pulleys etc.), the
ability to more accurately control the speed of rotation of the
drive rod and pump rod (particularly where a DC motor is utilized),
a simplified structure that permits for the easy removal and
replacement of the motor, a reduced wellhead height, and a
mechanism by which backspin of the pump rod can be controlled
and/or dissipated easily, economically and in a safe manner.
[0044] With reference to FIGS. 8, 9 and 10, there is disclosed
therein an embodiment of stuffing box assembly 4 that includes
means to pressurize the interior of the stuffing box for purposes
of helping to lubricate seals 17 and also, if desired, to help
maintain the pressure within the stuffing box above wellbore
pressure as a means to deter the influx of well fluids into the
stuffing box. In this embodiment the shaft of motor 5 includes a
longitudinal hollow bore 28 that extends therethrough. Similarly, a
longitudinally oriented hollow bore 29 extends through at least the
upper end of drive rod 10 such that when the shaft of the motor is
received within input means 27 longitudinal bore 28 within the
motor shaft is in fluid communication with longitudinal bore 29 of
the drive rod. As shown most clearly in FIG. 10, drive rod 10 is
also formed with at least one transverse oriented exit port 30 that
extends from the exterior surface of the drive rod to bore 29 such
that bore 29 is effectively in fluid communication with the drive
rods' exterior surface. Such a structure of hollow bores extending
through the motor shaft and into the upper end of the drive rod, in
combination with one or more exit ports 30, permits bore 28 within
the motor shaft to be at least partially filed with oil and to have
connected to, or associated therewith, a pressurization means to
pressurize the oil. The pressurized oil (or for that matter other
lubricant) is forced through the motor shaft, into the bore in the
upper end of the drive rod, through the transverse passage, and
into the interior of hanger assembly 9. Transverse exit ports 30
deliver pressurized oil to the exterior surface of the drive rod
adjacent to, or in the general vicinity of, dynamic seals 17,
thereby helping to lubricate the seals, pressurizing the interior
of the stuffing box, and helping to maintain well control by
deterring the influx of well fluids into the interior portions of
the stuffing box. As mentioned, if desired the pressurization means
can be designed so as to pressurize the oil or fluid injected into
the stuffing box to such a level that the pressure within the
interior of hanger assembly 9 exceeds the pressure of the
wellbore.
[0045] The source of pressurization used to pressurize the interior
of the stuffing box could be an exterior source of pressurized
fluid (such as a hydraulic pump or accumulator) that is piped or
otherwise connected to one or the other of bores 28 and 29. In the
embodiment shown in FIGS. 8, 9, 10 the upper end of bore 28 within
the motor shaft is sealed and a pressurization piston 31 is
received therein. Piston 31 may be either spring or gas actuated.
Regardless, in either instance the piston exerts a compressive
force upon the oil received within bore 28. If desired the sealing
of the upper end of bore 28 within the motor shaft can be
accomplished through the use of a removable cap or nut 42 that
permits an increase in the compression of the spring 41 used to
energize piston 31. Alternately, when the piston is gas actuated a
valve (such as a snifter valve) can be mounted in the top of the
shaft to permit the addition of further gas in order to more highly
pressurize the piston and thereby enhance or increase the
pressurization of the oil within bores 28 and 29. A removable cap
at the top of bore 28 will also allow for the level of oil within
the bore to be checked periodically.
[0046] In an alternate embodiment to that as shown in FIGS. 8 and
10, an external source of pressurized oil or lubricant may be
connected to a lubrication port 37 to permit the introduction of
lubricant into the hanger assembly in order to lubricate the
various bearings and seals. In such an embodiment the drive rod
and/or the hanger assembly may be fitted with specialized
lubrication ports to direct lubricant to particular seals,
bearings, or other areas where lubrication may be desired. Whether
it be through the use of a lubrication system such as that shown in
FIGS. 8, 9 and 10, or a separate stand-alone lubrication system
connected to the hanger assembly, it is expected that during
operation the lubricant will be pressurized to the point where it
will slowly seep past dynamic seals 17 and leak into the well. This
will help to ensure that the seals are adequately lubricated, will
assist in flushing debris from the bearing and keeping the bearings
free of contaminants, and will also help to prevent the ingress of
well fluids into the stuffing box. In most instances it is expected
that the leakage of lubricant into the well will be something in
the range of a few cubic centimeters per day, making the loss of
lubricant negligible under the circumstances.
[0047] In a further embodiment of the invention, stuffing box
assembly 4 includes a tubing hanger 44 that effectively hangs a
tubing string 45 from primary housing 8. The tubing hanger may be
any one of a wide variety of commonly utilized tubing hangers that
permit tubing to be securely held within the wellhead while
preventing the loss of fluids between the hanger and the internal
bore of housing 8. In the embodiment shown in FIG. 11, tubing
string 45 has secured thereto a downhole tubing rotator 46, such as
that shown and described in U.S. Pat. No. 7,306,031. It will be
appreciated by those having a thorough understanding of the
invention that through permitting the incorporation of tubing
hanger 44 within stuffing box assembly box 4, the overall height of
the wellhead can be reduced; once again having associated
beneficial effects. Furthermore, the utilization of a downhole
rotator eliminates the need for an external tubing rotator and
further reduces the size and weight of the exterior wellhead
components.
[0048] In the embodiment of the invention shown in FIGS. 1 and 11
through 15, stuffing box assembly 4 is mounted upon a unique and
novel casing head 47. In this embodiment the casing head contains
one or more side entry passageways 48. In the attached Figures two
such side entry passageways are incorporated within the casing
head. During normal pumping operations side entry passageways 48
would typically be closed off through the use of removable plugs
49. Alternately, valves could be used in place of the plugs. Plugs
49 keep debris out of passageways 48 and also maintain well
control. However, if for any reason (for example formation
stimulation purposes) it should become necessary to insert coiled
tubing or other tubular or elongate members into the well, plug 49
can be removed from one of the side entry passageways permitting
the coiled tubing or other device to be inserted into the well
without the need to disassemble wellhead equipment and without the
need to pull the tubing from the well. It will be appreciated that
particularly where a downhole tubing rotator 46 is utilized, the
advantage provided by casing head 47 is significant in that it
allows for the insertion of coiled tubing below the position of the
tubing rotator. Otherwise, any activities requiring the insertion
of coiled tubing or similar devices into the well would necessitate
the removal of wellhead equipment, the pulling of the tubing string
(at least to the point where the rotator is clear of the well head)
and then the insertion of the coiled tubing, all of which increase
costs and downtime of the well.
[0049] As shown in the attached Figures, in a preferred embodiment
passageways 48 are arranged with their longitudinal axes at a
"shallow" angle relative to the centre line of the wellhead to
permit the coiled tubing or other tubular or elongate member to be
inserted at a shallow angle of approach relative to the casing and
any tubing string that may be received therein. In these regards,
the "shallow" angle is preferably less than 45.degree., more
preferably less than 30.degree. and most preferably less than
20.degree.. That is, a shallow angle of approach between the
passageways and the tubing string will allow the coiled tubing or
other member to be inserted while minimizing the potential for
damage to either the coiled tubing or the tubing string.
[0050] Casing head 47 may also be configured to accept the tubing
string hanger 44 or, alternately, and as shown in the attached
Figures, the tubing string hanger may be located in primary housing
8. Lock down or hold down screws for the tubing string hanger may
be located in the upper flange of the casing head.
[0051] FIG. 16 shows an alternate embodiment of the invention to
that shown generally in FIGS. 8 through 10. In this embodiment, the
drive means is not a drive rod but is instead a rotating mandrel 51
through which the pump or polished rod 6 is received. In the
embodiment depicted in FIG. 16, the energy to drive the pump rod is
provided by an electric or hydraulic motor 5 that is situated in a
direct-drive configuration. In this particular embodiment the motor
shaft 50 is preferably hollow (or at least the lower portion of it
is preferably hollow) to be received about the upper end of the
pump rod 6 and into rotating mandrel 51. A drive connection exists
between the motor shaft 50 and the rotating mandrel that permits
the transference of rotational energy from the motor shaft to the
mandrel. In most instances it is expected that that drive
connection will be in a form of a series of splines 52 on the motor
shaft and the rotating mandrel, wherein the splines mesh together
in order to allow for the transference of rotational torque. In
other cases keys, shaped shafts and other drive connection
mechanisms could equally be used in place of splines 52.
[0052] With reference once again to FIG. 16, it will be understood
that when the pump rod extends through the hollow interior 53 of
rotating mandrel 51, it will be necessary to transfer rotational
energy from the mandrel to the pump rod in order to cause the rod
to rotate. In this embodiment of the invention, the preferred
mechanism for doing so comprises slips 54 that are inserted between
the exterior surface of the pump rod and the interior diameter of
mandrel 51. As shown, the lower portion of the hollow interior 53
of rotating mandrel 51 preferably decreases in diameter forming a
generally conical shape into which slips 54 are received. The
weight of pump rod 6 bearing against slips 54 will thus have the
tendency to enhance the grip between the slips, the pump rod and
the interior surface of the mandrel, to the point where rotation of
the mandrel by motor shaft 50 will cause the simultaneous rotation
of pump rod 6. In this manner the motor shaft, rotating mandrel and
pump rod will all rotate in unison, effectively as a single
component. Static seals 55 (for example o-rings) are preferably
inserted between the bottom portion of the rotating mandrel and the
pump rod to prevent the influx of well fluids into hollow interior
53. Otherwise, rotating mandrel 51 generally functions in a similar
fashion to drive rod 10 in that it transfers the load of the pump
rod onto thrust bearings within the hanger assembly with radial
bearing facilitating the rotational movement of the mandrel.
[0053] A slightly different variation to the embodiment shown in
FIG. 16 is depicted in FIG. 17. The embodiment of FIG. 17 is
overall generally similar to that shown in FIG. 16 with the primary
exception being that pump rod 6 is secured to rotating mandrel 51
through the use of a rod clamp 56 rather than slips 54. In this
embodiment, rod clamp 56 has an outside diameter that is smaller
than the inside diameter of hollow motor shaft 50 to allow the
clamp to at least be partially received within the motor shaft. Rod
clamp 56 will be securely held about the exterior surface of pump
rod 6 (preferably through frictional engagement such as what would
occur as a result of a conical shaped interior of rotating mandrel
51 and elements on the rod clamp that are able to deflect inwardly
towards a rod when wedged against the conical sloping shape of the
mandrel). Mandrel 51 also preferably contains splines (or drive
dogs) 57 that transfer rotational movement of the mandrel to the
pump rod. As shown in FIG. 17, in this variation the pump rod may
also extend upwardly through the centre of motor 5.
[0054] The embodiment of the invention shown in FIG. 18 is yet a
further version of that shown in FIGS. 16 and 17. Here, the pump
rod 6 is shown as extending through the motor 5 (as in FIG. 17),
however, rod clamp 56 is a more traditional polished rod clamp and
it has been moved to a position above the motor as is more common
in current drive heads. The weight of the pump rod is thus
transferred from the rod to clamp 56, to motor shaft 50, and then
ultimately to rotating mandrel 51 which, as is in case of the
previously described embodiments, engages both thrust and radial
bearings within hanger assembly 9.
[0055] FIG. 19 shows yet a further possible embodiment of the
invention to that shown in FIGS. 16 through 18. Here the hollow
motor shaft has a splined connection with a torque coupling 57
which transmits rotational torque from the motor shaft to rod clamp
56. Clamp 56 physically bears against the upper surface of rotating
mandrel 51 and also contains in its lower end a rotating sleeve 57
that rotates with rod clamp 56 and that is splined to mandrel 51.
Accordingly, rotation of motor shaft 50 causes torque coupling 57,
rod clamp 56, rotating sleeve 58, rotating mandrel 51 and pump rod
6 to rotate in unison with the motor shaft. In this embodiment
motor 5 can be more easily removed from the wellhead.
[0056] From a thorough understanding of the invention described
herein and shown in the attached drawings it will become clear that
the stuffing box assembly of the present invention presents a
highly efficient, compact, structure that is capable of sealingly
hanging a drive rod, and a pump rod attached thereto, within a well
using a minimum number of well head components to reduce the
overall height and weight of the wellhead. The design and structure
of the stuffing box assembly and its primary housing allows for the
integration of a blowout preventer/rod clamp within the same
compact unit, thereby eliminating the need for a separate BOP and
rod clamp. A simplified manner of applying rotational torque to the
drive and pump rods is also provided that allows for the direct
mounting of an electric or hydraulic motor on top of the stuffing
box, hence eliminating the need for more complex drive gear systems
that add to the weight of the wellhead equipment, increase expense,
and in many instances provide off-balanced non-symmetrical loading
of wellhead equipment. Where a hydraulic or DC motor is used to
rotate the drive rod, there is greater ability to control the
rotational speed of the drive and pump rods in a safe and
inexpensive manner that can also be used to control back spin. As
has also been described, the stuffing box assembly of the present
invention provides a manner to easily and effectively pressurize
the internal portion of the stuffing box in order to lubricate and
enhance the effectiveness and longevity of its bearings and seals.
The novel and unique casing head design of the invention presents a
simple, fast and efficient means for coiled tubing to be inserted
into the well without the need to disassemble wellhead components
and without the need for cranes or boom trucks to pull the tubing
string.
[0057] It is to be understood that what has been described are the
preferred embodiments of the invention and that it may be possible
to make variations to these embodiments while staying within the
broad scope of the invention. Some of these variations have been
discussed while others will be readily apparent to those skilled in
the art. For example, while the invention has been described as
used in association with a direct drive electric or hydraulic
motor, it will be appreciated that the motor could equally be
off-set from the centerline of the stuffing box with the rotation
of the drive or pump rod accomplished through the use of
conventional pullies and gears.
* * * * *