Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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STUFFING BOX ASSEMBLY
FIELD OF THE INVENTION
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
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.
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
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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
December 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.
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.
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
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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.
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
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
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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.
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.
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.
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
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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
5 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.
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
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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.
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
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:
Figure 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;
Figure 2 is a side elevational view of the stuffing box assembly
shown in Figure 1, having an electric drive motor attached thereto;
Figure 3 is a side elevational view of the stuffing box assembly
shown in Figure 2, rotated 90 ;
Figure 4 is a cross-sectional view taken along the line of 4 - 4 of
Figure 2;
Figure 5 is a cross-sectional view taken along the line 5 - 5 of
Figure 3;
Figure 6 is an exploded view of the stuffing box assembly (with a
portion of its outer housing removed) shown in Figure 2;
Figure 7 is an enlarged detailed cross-sectional view taken along
the line 7 - 7 of Figure 6;
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Figure 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;
Figure 9 is an exploded view of the stuffing box assembly shown
in Figure 8;
Figure 10 is an enlarged detailed cross-sectional view taken along
the line 10 - 10 of Figure 9;
Figure 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;
Figure 12 is an enlarged view of the stuffing box assembly and
casing head shown in Figure 11 having the electric motor removed;
Figure 13 is an upper side perspective view of the casing head
shown in Figure 12;
Figure 14 is a side elevational view of the casing head shown in
Figure 13;
Figure 15 is a sectional view taken along the line 15-15 in Figure
14;
Figures 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;
Figures 17 and 17A are vertical cross-sectional views of a further
alternate embodiment to that shown in Figure 16;
Figure 18 is a vertical cross-sectional view of a further
embodiment to that shown in Figure 17;
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Figure 19A is a further alternate embodiment to that shown in
Figure 18; and
Figure 19B is a cross-sectional view taken along the line of 19B-
19B in Figure 19.
DESCRIPTION OF THE PREFERRED EMBODIMENT
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.
With reference to Figure 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 Figure 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.
Turning next to Figures 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
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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.
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.
In the embodiment of the hanger assembly shown in Figure 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
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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
5 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
10 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.
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
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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 Figure 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.
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
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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.
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.
As shown most clearly in Figures 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
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primary housing 8. In Figures 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.
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
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way. In any event, it will be appreciated that through mounting motor
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
5 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.
With reference to Figures 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 Figure
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
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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
5 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.
10 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
15 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.
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
Figures 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
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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.
In an alternate embodiment to that as shown in Figures 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 Figures 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.
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
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between the hanger and the internal bore of housing S. In the
embodiment shown in Figure 11, tubing string 45 has secured thereto a
downhole tubing rotator 46, such as that shown and described in US
Patent 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.
In the embodiment of the invention shown in Figures 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
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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.
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 , more preferably less than 30 and most preferably less
than 20 . 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.
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.
Figure 16 shows an alternate embodiment of the invention to that
shown generally in Figures 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 Figure 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)
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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.
With reference once again to Figure 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
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bearings within the hanger assembly with radial bearing facilitating the
rotational movement of the mandrel.
A slightly different variation to the embodiment shown in Figure
16 is depicted in Figure 17. The embodiment of Figure 17 is overall
5 generally similar to that shown in Figure 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
10 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
15 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 Figure 17, in this variation
the pump rod may also extend upwardly through the centre of motor 5.
The embodiment of the invention shown in Figure 18 is yet a
20 further version of that shown in Figures 16 and 17. Here, the pump rod
6 is shown as extending through the motor 5 (as in Figure 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.
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Figure 19 shows yet a further possible embodiment of the
invention to that shown in Figures 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.
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
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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.
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.
