Note: Descriptions are shown in the official language in which they were submitted.
CA 02254391 1998-11-23
TITLE: Oil Well Tubing String Hanging Device And Lifting Assembly
FIELD OF THE INVENTION
This invention relates generally to devices used to hang a tubing string
within the casing
of an oil well.
BACKGROUND OF THE INVENTION
Even a slight deviation from the vertical will cause the sucker rod in an oil
well to
contact the inner wall surface of the production tubing string resulting in
wear to the
tubing string through rod movement. Such wear can form small holes in the side
of the
production string, or can reduce the tensile strength of the string to a point
where it will
fail under load. For that reason others have developed a variety of different
tubing
string rotators that slowly rotate the production tubing string about the
sucker rod in
order to more evenly distribute any frictional wear around the inside
circumference of
the string.
Traditionally, the production tubing string has been supported within the well
casing by
the rotator. However, that particular structure was found to suffer from a
variety of
limitations, not the least of which was a requirement to lift the entire
tubing string in
order to remove or service the rotator. As a result, more recently tubing
string hanging
devices have been developed that permit the production tubing string to be, in
effect,
hung from the well casing independently from the rotator. In such cases the
tubing
string is attached to a tubing string hanging device, which is itself then
hung or held
CA 02254391 1998-11-23
within the well casing. A variety of different mechanical structures can be
utilized to
transfer rotational movement from the rotator to the production tubing string.
While such tubing string hanging devices have proved useful in allowing for
the
independent removal of a rotator without the necessity of pulling the entire
production
tubing string from a well, they have not addressed all of the short comings of
prior
devices and suffer from their own inherent limitations. For example, a tubing
string
hanging device typically includes an outer shell, that is suspended from the
well casing,
and some form of inner rotatable mandrel or coupling device to which the
production
tubing string is attached. Between the inner and outer portions is usually
situated a
variety of different bearing mechanisms and seals. In the event that it
becomes
necessary to remove or lift the tubing string from the well those bearings and
seals often
become exposed to the elements of the well and can become clogged with sand
and
other debris which will significantly reduce their life span and operating
efficiency. In
addition, there are a large variety of devices or down-hole tools that are
employed at the
bottom of a production tubing string, deep within the well. Such devices
include
anchoring mechanisms, no-turn tools, and packers. Typically these devices are
attached
to the bottom end of the production tubing string and lowered into the well.
Once in
place down-hole tools are usually "set" through either rotating, or pulling
the tubing
string, or through a combination of rotational and pulling movements, to cause
arms or
other forms of engagement mechanisms to be deployed such that the tool becomes
locked to the well casing. At that point it often becomes necessary to lift
the production
tubing string in an upward direction so as to place the entire string, and the
tool, in
tension to complete the "setting" operation and allow proper functioning of
the down-
hole tool. The ability to set oil well tools in this manner, and to maintain a
production
tubing string in tension, is not available through use of current tubing
string hanging
devices.
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CA 02254391 1998-11-23
SiIMMARY OF THE INVENTION
The invention therefore provides a tubing string hanging device and lifting
assembly
which overcomes the shortfalls of such prior devices through the incorporation
of a
structure that allows for the production tubing string to be rotatably hung
from the well
casing, enables the string to be retained in tension, and in some instances
permits the
tubing string to be lifted within the oil well independent from the tubing
string hanging
device. The invention further provides for a mechanism to allow down-hole oil
tools
to be set while maintaining well control.
Accordingly, in one of its aspects the invention provides the invention
provides an oil
well tubing string hanging device and lifting assembly to hang a tubing string
within an
oil well casing, the device comprising a hanger shell suspended within or
connected to
the oil well casing, a mandrel mounted within said hanger shell, and, a
lifting assembly
releasably securable to said mandrel, said lifting assembly having means for
connecting
to and for hanging a production tubing string therefrom, said lifting assembly
including
engagement means for releasably securing said lifting assembly to said mandrel
such
that said lifting assembly, and a production tubing string attached thereto,
may be
independently lifted within the oil well without removal or lifting of said
mandrel or
said hanger shell.
In a further aspect the invention provides an oil well tubing string hanging
device and
lifting assembly to hang a tubing string within an oil well casing, the device
comprising
a hanger shell suspended within or connected to the oil well casing, and, a
lifting
assembly releasably securable to said hanger shell, said lifting assembly
having means
for connecting to and for hanging a production tubing string therefrom, said
lifting
assembly including engagement means for releasably securing said lifting
assembly to
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CA 02254391 1998-11-23
said hanger shell such that said lifting assembly, and a production tubing
string attached
thereto, may be independently lifted within the oil well without removal or
lifting of
said hanger shell.
In a further aspect the invention provides an oil well tubing string hanging
device and
lifting assembly to hang a tubing string within an oil well casing, the device
comprising
a hanger shell suspended within the oil well casing, a lifting assembly
releasably
suspendable from said hanger shell, said lifting assembly containing means to
hang a
production tubing string therefrom, and, engagement means to releasably
suspend said
lifting assembly from said hanger shell, said engagement means allowing said
lifting
assembly to be suspended from hanger shell and allowing said lifting assembly,
and a
production tubing string attached thereto, to be independently lifted within
the oil well
casing without removal or lifting of said hanger shell.
In a yet further aspect the invention provides a method of retaining an oil
well tubing
string in tension within an oil well casing, the method comprising (i)
lowering an oil
well tubing string, having a lifting assembly attached to its upper end, into
an oil well
casing; (ii) anchoring a lower portion of the oil well tubing string within
the oil well
casing; (iii) applying a lifting force to the tubing string to place the
tubing string in
tension and bringing the lifting assembly into engageable contact with a
tubing string
hanger such that engagement means on the lifting assembly are releasably
securable to
the tubing string hanger; and, (iv) releasing the lifting force applied to the
tubing string
and causing the engagement means to secure the lifting assembly within the
tubing
string hanger thereby causing the tubing string to be held and retained in
tension.
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CA 02254391 1998-11-23
Further objects ands 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 side elevational view in longitudinal section of an oil well
tubing string
hanging device and lifting assembly in accordance with the present invention;
Figure 2 is a side elevational view in longitudinal section of the lifting
assembly of the
1 S device shown in Figure I ;
Figure 3 is a side elevational view in longitudinal section of the mandrel
portion of the
device shown in Figure I ;
Figure 4 is a sectional view of the lifting assembly of Figure 2 taken along
the line 4-4
of Figure 2;
Figure 5 is a side elevational view in longitudinal section of an alternate
embodiment
of the device shown in Figure 1;
Figure 6 is a side elevational view in longitudinal section of an alternate
embodiment
of the lifting assembly of the device shown in Figure I;
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CA 02254391 1998-11-23
Figure 7 is a side elevational view in longitudinal section of a further
alternate
embodiment of the present invention;
Figure 8 is a side elevational view in longitudinal section of a further
alternate
S embodiment of the present invention having a modified rotator design; and,
Figure 9 is a side elevational view in longitudinal section of yet a further
embodiment
of the invention.
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
1 S in the claims that follow herein.
The oil well tubing string hanging device and lifting assembly pursuant to the
present
invention is shown in the attached drawings and noted generally by reference
number
1. Device 1 is comprised generally of a hanger shell 2, a mandrel 3 and a
lifting
assembly 4. Hanger shell 2 includes means to engage an oil well casing S such
that the
hanger shell is retained or suspended within the casing. While it will be
appreciated that
a variety of different structures could be utilized to engage the well casing
so as to
suspend the hanger shell therein, in the preferred embodiment, and as shown in
Figure
1, hanger shell 2 has an inwardly tapered exterior surface 6 that engages an
inwardly
tapered shoulder 7 on the inner surface of well casing 5. Since the diameter
of hanger
shell 2 is greater than the internal diameter of well casing 5, hanger shell 2
effectively
acts as a plug and engages the side of the well casing to suspend itself
therein.
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CA 02254391 1998-11-23
Mandrel 3 may be constructed so as to be either stationary or rotatably
mounted within
hanger shell 2. In the attached drawings the mandrel is rotatably mounted
within the
hanger shell and has an upper end 8 and a bottom or lower end 9. In the
embodiment
shown in Figure l, mandrel 3 further includes, at or near its upper end, an
outwardly
extending radial flange 10 that bears against bearing means 11 disposed
between the
hanger shell and the mandrel. Bearing means 11 facilitates in the rotation of
mandrel
3 within hanger shell 2 through a reduction in friction between the respective
parts.
Bearing means 11 preferably comprises both a thrust bearing 12 and a radial
bearing 13,
and is configured such that vertical loading of the mandrel is transferred
through thrust
bearing 12 to hanger shell 2. Radial bearing 13 facilitates in the rotational
movement
of the mandrel and carries side loading where the mandrel is subjected to non-
vertical
loading in deviated well situations.
Mandrel 3 also includes means to engage a tubing string rotator 17 so as to
impart a
rotational movement to the mandrel. In the embodiment shown in Figure 1, the
engagement with tubing string rotator 17 is accomplished through the use of a
series of
inwardly directed splines 14 situated at the upper end 8 of mandrel 3. Splines
14 mesh
with similarly shaped splines on a coupling member 1 S that is attachable to
the shaft 16
of tubing rotator 17. As shown in Figure I, coupling member 15 is preferably
of a
dimension that allows it to be inserted into the upper opening of mandrel 3
such that the
splines on the coupling member mesh with splines 14 on mandrel 3 to
effectively "lock"
the structures together. It will therefore be appreciated that when coupling
means I S is
inserted into the upper portion of mandrel 3, rotation of tubing rotator shaft
16 will
result in the transmission of rotational movement through coupling member 1 S
to
splines 14, and thus cause the rotation of mandrel 3 within hanger shell 2. It
will also
be appreciated that a variety of other mechanical structures could equally be
used to
rotate the mandrel.
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CA 02254391 1998-11-23
To hold mandrel 3 securely within hanger shell 2, a retaining nut 18 is
preferably
threaded onto the top portion of hanger shell 2. When retaining nut 18 is
threaded onto
hanger shell 2 it is positioned in close proximity the exterior surface of the
mandrel such
that the mandrel is effectively held within the hanger shell and yet is still
able to freely
rotate. In order to prevent the seepage of dirt or debris into bearing means
11, a seal 19
is positioned near the top of hanger shell 2, and between retaining nut 18 and
mandrel
3. Similarly, seals 20 are positioned between hanger shell 2 and mandrel 3 at
a point
below bearing means 11. To help ensure full well control a further set of
seals 21 is
preferably positioned on the exterior surface of hanger shell 2 such that they
bear against
the interior of oil well casing 5. Seals 21 will help to preventing the escape
of oil and
gases from between the hanger shell and the well casing.
Referring specifically to Figures l, 2 and 4, lifting assembly 4 is shown as
comprised
of a generally cylindrical structure having an upper end 22 and a lower end
23. Lower
1 S end 23 of lifting assembly 4 includes means for connecting the lifting
assembly to a
production tubing string and hanging the tubing string therefrom. In the
preferred
embodiment the production tubing string is threadably received within a
threaded
internal bore 24 within lower end 23 of lifting assembly 4, however, it will
be
appreciated that other forms of connections between the lifting assembly and
the
production tubing string could equally be employed. Lifting assembly 4 further
includes
engagement means 25 for releasably securing the assembly within mandrel 3.
Engagement means 25 operates such that when lifting assembly 4 is releasably
secured
to mandrel 3 rotational movement of the mandrel results in rotational movement
of the
lifting assembly, and hence the production tubing string attached thereto.
When engagement means 25 is disengaged from the mandrel, lifting assembly 4,
and a
production tubing string attached thereto, may be independently lifted,
through a limited
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CA 02254391 1998-11-23
vertical range, within oil well casing 5 without the removal or lifting of
either the
mandrel or the hanger shell. That is, through hanging lifting assembly 4 from
mandrel
3 by way of the interaction of engagement means 25 with the mandrel, lifting
assembly
4 may be releasably secured to the mandrel so as to enable the entire
production tubing
S string to be quickly and easily lifted or lowered within the well casing
without
interfering, lifting or disturbing hanger shell 2 or mandrel 3. In this way
well control
can be maintained. In addition, the raising or lowering of lifting assembly 4
will not
expose any of the internal mechanisms of device 1, including bearing means 11,
to
contamination from dirt and debris that may otherwise be present within the
oil well.
At all times the bearings will remain sealed between the hanger shell and the
mandrel
regardless of the position of lifting assembly 4.
Raising or lowering lifting assembly 4 within the well is facilitated through
the use of
lifting threads 26 positioned at upper end 22. Lifting threads 26 permit a
rod, pipe or
1 S other tool to be threadably received within lifting assembly 4 to enable
the assembly to
be lifted or lowered. In the preferred embodiment seals 27 are positioned
between
lifting assembly 4 and mandrel 3 and prevent the by-pass of oil and gases
between the
lifting assembly and the mandrel to maintain full well control.
It will be appreciated by those skilled in the art that a wide variety of
different
engagement means 25 could be utilized in order to releasably secure lifting
assembly 4
within mandrel 3 while staying within the scope of this invention. However,
for
purposes of explanation the particular embodiments shown in the attached
drawings will
now be described and discussed in more detail. Referring again to Figures I, 2
and 4,
engagement means 25 is shown as comprising outwardly extending pins 28. Pins
28 are
located on the outer surface of the lifting assembly and are releasably
receivable within
slots 29 on mandrel 3. Slots 29 may be either positioned on the interior
surface of
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CA 02254391 1998-11-23
mandrel 3 and recessed into the mandrel body or may extend completely through
the
mandrel. Preferably slots 29 are positioned at or near lower end 9 of mandrel
3 in order
that they provide no interference to the operation of bearing means 11 or the
numerous
seals positioned on the lifting assembly, mandrel and hanger shell.
Through receipt of pins 28 on lifting assembly 4 into slots 29 within mandrel
3, the
lifting assembly may be hung from the mandrel in such a manner that the weight
of both
the lifting assembly and the production tubing string attached thereto is
fully transferred
to the mandrel and borne by bearings means 11. Typically the weight will be
supported
by thrust bearings 12, however, in the event of a deviated well a portion of
the load will
be transferred to radial bearings 13 as well. When pins 28 are received within
slots 29
there will also be a transference of rotational movement from the mandrel to
the lifting
assembly when the mandrel is rotated by tubing string rotator 17. Slots 29 are
preferably configured so as to enable the mandrel to be rotated in either a
clockwise or
1 S counter clockwise direction while transferring rotational movement to the
lifting
assembly. In this manner the production tubing string may also be rotated in a
clockwise or counterclockwise manner. To accomplish this function, slots 29
are of a
generally "J"-shaped configuration having an open longitudinal portion 30, and
a hook
portion 31 that defines an open bowl portion 32.
As shown in Figures 2 and 4, when pins 28 are received and secured within
bowls 32
of slots 29, the disengagement of the pins will require the application of
both a lifting
and rotational force. That is, to remove pins 28 from open bowls 32 of slots
29, lifting
assembly 4 will first have to be lifted in an upward manner until pins 28 are
able to clear
the ends of hook portions 31. At that point either lifting assembly 4 and/or
mandrel 3
may be rotated to allow the pins to move rotationally beyond the ends of hook
portions
31 and to enable lifting assembly 4 to the lowered downwardly, past the
mandrel and
CA 02254391 1998-11-23
into the well casing. Where the lifting assembly is rotated locking keys are
inserted into
slots 24 on the upper end of the mandrel to hold the mandrel stationary and
allow
independent rotation of the lifting assembly. Engaging pins 28 within slots 29
will
require the exact opposite series of movements. That is, the lifting assembly
is first
pulled upwardly to a point where pins 28 are raised above hook portions 31 of
slots 29.
Thereafter rotational movement of the lifting assembly and/or the mandrel will
allow
the pins to pass around the ends of hook portions 31. Lifting assembly 4 may
then be
lowered downwardly so as to seat pins 28 within open bowls 32.
Rather that being formed as a single unit, as shown in Figure 3 the mandrel
may be
comprised of upper and lower portions, 41 and 42 respectively, that are
threaded
together. In this manner manufacture and assembly of the parts of the
invention may
be simplified. Further, mandrel 3 may also include an external sleeve 36 that
both
encloses slot 29 and helps to support hook portion 31. To this extent, sleeve
36 is
preferably fixed to the outer surface of the mandrel through pinning or by use
of plug
welds 43.
In the attached drawings pins 28 are shown as positioned on the exterior
surface of
lifting assembly 4 with slots 29 situated within mandrel 3. A reversed
structure, where
the slots are positioned on the exterior surface of the lifting assembly and
the pins
extend outwardly from a sleeve 35 attached to the lower portion 9 of the
mandrel (see
Figure 5), could equally be utilized and would function and operate generally
in the
same manner as that described above. Regardless of which configuration of pins
and
slots is utilized, engagement and disengagement of the lifting assembly from
the
mandrel will require the application of both a lifting and a rotational force.
For that
reason, it will be understood that other configurations of slots may be used
while
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CA 02254391 1998-11-23
performing the same functions. For example, a "U" or "L" shaped slot could be
used in
the substitution for the "J"-shaped slot depicted in the attached Figures.
By way of the foregoing structure, lifting assembly 4 can be utilized to help
set down-
S hole oil tools within the well casing. Doing so generally requires lowering
lifting
assembly 4 such that pins 28 are no longer engaged within slots 29, and then
"setting"
the down-hole tool within the well casing. The method of "setting" the down-
hole tool
will be dependant upon the tool itself but typically will require the tubing
string to be
dropped below the lifting assembly by the amount of desired string stretch and
thereafter
setting the tool through a rotational and/or lifting movement. Once the tool
has been
"set", lifting assembly 4 can be pulled upwardly within mandrel 3 until pins
28 have
sufficiently cleared the ends of hook portions 31 of slots 29 to enable the
lifting
assembly and/or the mandrel to be rotated so that the pins are vertically
aligned with
open bowl portions 32. At that point the lifting assembly can be lowered back
downwardly into the well casing until the pins rest within bowl portions 32.
In this manner lifting assembly 4 will effectively be hung from mandrel 3 such
that
rotation of the mandrel will cause rotation of the lifting assembly and the
production
tubing string attached thereto. At the same time, the entire production tubing
string may
be held in tension since it will be anchored at the bottom of the well casing
by the down-
hole tool and will be hung from and secured to the mandrel through the
engagement of
pins 28 within slots 29. Accordingly, the described structure will readily
allow for
down-hole tools to be set and reset as required, without having to pull the
tubing string
from the well, remove or disturb the hanger shell or mandrel, and without
losing well
control.
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CA 02254391 1998-11-23
In the further alternate embodiment as shown in Figure 6, lifting assembly 4
is
releasably secured directly to hanger shell 2. To accommodate and support
lifting
assembly 4, hanger shell 2 contains slots 33 on its interior surface that
releasably receive
pins 28 of the lifting assembly. The function and operation of lifting
assembly 4 will
thus be essentially the same as that described above for the other embodiments
of the
invention except that, as the lifting assembly is secured directly to the
hanger shell, once
in place within the well casing it will remain stationary such that neither
the lifting
assembly nor a production tubing string attached thereto will be rotated.
In Figure 7 a variation to the embodiment of Figure 1 is show. Here external
sleeve 36
is positioned around the lower portion 9 of mandrel 3 so as to enclose slots
29. As
discussed previously, sleeve 36 serves to help prevent the ingress of debris
into slots 29
and may also be fixed, by way of welding, pinning, or otherwise, to hook
portion 31 of
slot 29 and to the upper and lower portions of the mandrel to increase the
load bearing
capabilities of the assembly. In Figure 7, mandrel 3 is comprised of upper and
lower
portions that are threaded to together.
In Figure 8 a variation of the present invention is shown having a modified
rotator
design. In this embodiment rotator 17 includes a worm gear 37 which drives a
radial
gear 38 connected to mandrel 3. It will thus be appreciated that in this
embodiment the
means for driving or rotating mandrel 3 are somewhat different, however, the
function
and the operation of lifting assembly 4 will be the same.
In yet a further embodiment of the invention as shown in Figure 9, lifting
assembly 4
is releasably suspendable from hanger shell 2 and contains means to hang a
production
tubing string therefrom. In the preferred form of this variation, lifting
assembly 4
supports mandrel 3, to which the production tubing string is connected. There
may be
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CA 02254391 1998-11-23
positioned between mandrel 3 and lifting assembly 4 thrust and radial
bearings, 12 and
13 respectively, to assist in rotational movement of the mandrel and the
transference of
axial and radial loading from the mandrel to the lifting assembly. A retaining
nut 18
secures the mandrel within lifting assembly 4. As in the case of the
previously
described embodiments, a tubing rotator 17 may be utilized to supply
rotational energy
to the mandrel.
The embodiment of Figure 9 further includes engagement means to releasably
suspend
lifting assembly 4 from hangerlshell, 2., The engagement means preferably
comprise a
series of slots 39, on the exterior surface of the lifting assembly, that are
engaged by
pins 40 extending outwardly from~the interior surface of hanger shell 2. As
shown in
Figure 9, pins 40 are preferably threadably engaged within the walls of the
hanger shell.
It will therefore be appreciated that through the interaction of pins 40 and
slots 39,
lifting assembly 4 may be releasably suspended within the hanger shell.
Furthermore,
formation of slots 39 such that they have a generally "J"or "L"-shaped
configuration
will enable the lifting assembly, and a production tubing string attached
thereto, to be
independently lifted within the well casing without lifting or disturbing the
hanger shell.
In a similar fashion as described previously with respect to slots 29 and pins
28, it will
equally be appreciated that slots 39 and pins 40 of Figure 9 will enable the
tubing string
to be held in tension following the setting of a down-hole tool or anchor.
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 variat;~"~ have
1,PP.,
discussed while others will be readily apparent to those skilled in the art.
For example,
whereas the attached drawings show the use of three pins 28 upon lifting
assembly 4,
it will be understood that if desired four or more pins could equally be
employed. In
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CA 02254391 1998-11-23
addition while "J"-shaped slots 29 are described and shown in the drawings a
wide range
of alternate slot configurations could equally be used.
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