Note: Descriptions are shown in the official language in which they were submitted.
CA 02474418 2004-07-15
TITLE OF THE INVENTION
Tubing String Rotator
FIELD OF THE INVENTION
This invention relates to an apparatus that may be used to rotate a tubing
string within
an oil or water well, and in particular to such an apparatus that operates
without the need
for dedicated motors or other specifically dedicated sources of mechanical
energy that
are exterior to the well.
CA 02474418 2004-07-15
BACKGROUND OF THE INVENTION
When pumping oil (or for that matter water or other fluids) from wells driven
into the
ground, a downhole pump is often utilized wherein the pump is physically
located deep
within the well 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
stationary housing or stator. In most instances a rotating pump rod extends
from the
surface down through the well to the pump to drive the rotor. A power supply,
which
would typically be comprised of a gas or diesel engine, or an electric motor,
provides
the mechanism by which the pump rod, and hence the pump rotor, is rotated.
In most oil and water well applications a production tubing string is
positioned within
the well casing about the pump rod and is connected to the pump to provide a
conduit
for the extraction of oil or fluids from the well. Commonly the upper end of
the
production tubing string is held within the well casing through the use of a
variety of
flanges, hangers (often referred to as dognuts) or similar devices. The bottom
end of the
tubing string is often secured to the casing by means of an anchor or no-turn
tool. With
the rotation of the rotor in a downhole progressive cavity pump there is a
tendency to
impart what in many cases is a very significant torque to the production
tubing string.
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Accordingly, a swivel is typically inserted within the production tubing
string to prevent
torque from being earned throughout the length of the string to the surface of
the well.
It has been found that during production the type and quantities of fluids
passing through
the tubing string, as well as instances where the rotating pump rod comes into
contact
with the interior surface of the tubing string, can cause wear and erosion of
the surface
of the string. The degree of wear and erosion can increase significantly in
deep wells,
or in wells that are not perfectly vertical in orientation where the rod often
contacts the
string over a great distance. It is well know that through rotating the tubing
string in a
slow and constant manner, the wear that typically incurs on its inside surface
can be
more evenly distributed about the string, thereby significantly extending the
tubing
string's life and reducing the potential for equipment failure and the
resulting and
associated costs and lost production.
A variety of devices have been proposed by others to present a means to rotate
the
tubing string in order to more evenly distribute wear about the interior
surface of the
string. Commonly, such devices are mechanically operated tubing string
rotators that
comprise a housing that is bolted or otherwise attached to the wellhead.
Through a
mechanical linkage or gear system, an electric motor, a hydraulic motor, or
other form
of mechanical power source causes the tubing string rotator to slowly rotate
the string
within the casing. Such known tubing string rotators are described in U.S.
patents
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2,630,181, dated March 3, 1953; 5,139,090, dated August 18, 1992; 5,383,519,
dated
January 24, 1995; 5,427,178, dated June 27, 1995; 5,964,286, dated October 12,
1999;
and, 6,199,630, dated March 13, 2001.
While existing tubing string rotators have been relatively effective in
imparting a
rotational movement to a tubing string in the manner described above, they
also suffer
from a number of limitations that affect their performance, reliability and
cost. Not the
least of these limitations stems from the fact that existing rotators rely
upon a dedicated
source of mechanical power to rotate the string. In the majority of
applications a
dedicated electric or hydraulic motor is mechanically connected to the rotator
through
a gear reduction system. In other applications a mechanical linkage may be
utilized to
transfer energy from an alternate wellhead source to cause rotation of the
tubing string.
In either case, the mode of imparting mechanical energy to the tubing string
rotator adds
to the physical complexity of the wellhead equipment, increases capital cost,
presents
a further opportunity for equipment failure (particularly where an electric
motor is used)
and can add significantly to energy consumption and operating costs.
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CA 02474418 2004-07-15
SUMMARY OF THE INVENTION
The invention therefore provides a tubing string rotator that alleviates many
of the
problems associated with existing rotators through the provision of a
mechanism that
does not rely upon a traditional external power source. Rather, the present
invention
provides a tubing string rotator that harnesses the torque that is applied,
either directly
or indirectly, to the tubing string through the operation of a downhole pump.
Accordingly, in one of its aspects the invention provides a tubing string
rotator for
rotating a tubing string in a well having a downhole pump, the tubing string
rotator
comprising a housing having a first portion and a second portion, said second
portion
rotatable relative to said first portion, at least said second portion of said
housing
adapted to be operatively connected to the end of a length of the tubing
string such that
rotational torque applied to the tubing string through the operation of the
pump is
transferred to said second portion of said housing; and, means to permit the
controlled
rotation of said second portion of said housing, together with the tubing
string connected
thereto, relative to said first portion of said housing when the ability of
said first portion
to rotate is retarded or eliminated, and when rotational torque is supplied to
the tubing
string through the operation of the pump.
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'The invention also concerns a tubing string rotator for rotating a tubing
string in a well
having a downhole pump, the tubing string rotator comprising a housing having
a first
portion and a second portion, said second portion rotatable relative to said
first portion,
at least said second portion of said housing adapted to be operatively
connected to the
end of a length of the tubing string such that rotational torque applied to
the tubing
string through the operation of the pump is transferred to said second portion
of said
housing; and, a hydraulic, mechanical or frictional brake to permit the
controlled
rotation of said second portion of said housing, together with the tubing
string connected
thereto, relative to said first portion of said housing when the ability of
said first portion
to rotate is retarded or eliminated, and when rotational torque is supplied to
the tubing
string through the operation of the pump.
In a further aspect the invention relates to a tubing string rotator for
rotating a tubing
string in a well having a downhole pump, the tubing string rotator comprising
a housing
having a first portion and a second portion, said second portion rotatable
relative to said
first portion, at least said second portion of said housing adapted to be
operatively
connected to the end of a length of the tubing string such that rotational
torque applied
to the tubing string through the operation of the pump is transferred to said
second
portion of said housing; and, braking means to permit the controlled rotation
of said
second portion of said housing, together with the tubing string connected
thereto,
relative to said first portion of said housing when the ability of said first
portion to rotate
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is retarded or eliminated and when rotational torque is supplied to the tubing
string
through the operation of the pump, said braking means including one or more
pistons
and one or more biasing means, said pistons received within one of said first
and said
second portions of said housing and said biasing means causing said pistons to
engage
one or more caromed surfaces on the other of said first and said second
portions of said
housing such that the interaction of said one or more pistons with said one or
more
caromed surfaces permits a controlled rotational movement of said second
portion of
said housing relative to said first portion of said housing.
The invention also concerns a tubing string rotator for rotating a tubing
string in a well
having a downhole pump, the tubing string rotator comprising a housing having
a first
portion and a second portion, said second portion rotatable relative to said
first portion,
at least said second portion of said housing adapted to be operatively
connected to the
end of a length of the tubing string such that rotational torque applied to
the tubing
string through the operation of the pump is transferred to said second portion
of said
housing; and, braking means to permit the controlled rotation of said second
portion of
said housing, together with the tubing string connected thereto, relative to
said first
portion of said housing when the ability of said first portion to rotate is
retarded or
eliminated and when rotational torque is supplied to the tubing string through
the
operation of the pump, said braking means including one or more pistons and
one or
more hydraulic cylinders received within at least one of said first and second
portions
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of said housing, said pistons received within said hydraulic cylinders and
engaging one
or more caromed surfaces on one of said first and said second portions of said
housing
such that the interaction of said one or more pistons with said one or more
caromed
surfaces permits a controlled rotational movement of said second portion of
said housing
relative to said first portion of said housing upon operation of the pump,
said one or
more hydraulic cylinders comprising one or more fluid filled cylinders
connected to a
fluid reservoir by way of one or more orifices, said one or more orifices
permitting the
controlled and retarded flow of fluid between said reservoir and said one or
more
cylinders to permit movement of said one or more pistons relative to said one
or more
caromed surfaces in a controlled manner.
The invention also pertains to a tubing string rotator for rotating a tubing
string in a well
having a downhole pump, the tubing string rotator comprising a housing having
a first
portion and a second portion, said second portion rotatable relative to said
first portion,
at least said second portion of said housing adapted to be operatively
connected to the
end of a length of the tubing string such that rotational torque applied to
the tubing
string through the operation of the pump is transferred to said second portion
of said
housing; and, braking means to permit the controlled rotation of said second
portion of
said housing, together with the tubing string connected thereto, relative to
said first
portion of said housing when the ability of said first portion to rotate is
retarded or
eliminated and when rotational torque is supplied to the tubing string through
the
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operation of the pump, said braking means including a bull gear operatively
connected
to said second portion of said housing and a torque limiter operatively
connected to said
bull gear, said torque limiter controlling the rotational movement of said
bull gear and
thereby controlling the rate of rotation of said tubing string.
In still a further aspect the invention concerns a tubing string rotator for
rotating a tubing
string in a well having a downhole pump, the tubing string rotator comprising
a housing
having a first portion and a second portion, said second portion rotatable
relative to said
first portion, at least said second portion of said housing adapted to be
operatively
connected to the end of a length of the tubing string such that rotational
torque applied
to the tubing string through the operation of the pump is transferred to said
second
portion of said housing; and, one or more gears operatively connected to said
second
portion of said housing to permit the controlled rotation of said second
portion of said
housing, together with the tubing string connected thereto, relative to said
first portion
of said housing when the ability of said first portion to rotate is retarded
or eliminated
and when rotational torque is supplied to the tubing string through the
operation of the
pump, the rate of rotation of said second portion of said housing controlled
through the
operation of said one or more gears.
An alternate embodiment of the invention encompasses a tubing string rotator
for
permitting the rotation of a tubing string connected directly or indirectly to
a downhole
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pump having a rotor that is rotated to pump fluids to the surface of a well,
the tubing
string rotator comprising a housing having a first portion, a second portion
and a
generally hollow bore to permit the passage of a pump rod and well fluids
through said
housing, said second portion of said housing rotatable relative to said first
portion of
said housing, at least said second portion of said housing adapted to be
operatively
connected to the end of a length of tubing string such that rotational torque
applied to
the tubing string through the operation of the pump is transferred to said
second portion
of said housing; and, a hydraulic, mechanical or frictional braking mechanism
to retard
the rotational movement of said second portion of said housing such that said
second
portion together with the tubing string connected thereto is permitted to
rotate at a
controlled rate relative to said first portion of said housing when the
ability of said first
portion of said housing to rotate within the well is restricted and when
rotational torque
is supplied to the tubing string through the rotation of the rotor of the
pump.
The invention also relates to a method for rotating a tubing string in a well
within which
there is situated a downhole pump that is connected directly or indirectly to
the tubing
string, the method comprising the steps of (i) providing a tubing string
rotator, said
rotator having a housing with a first portion and with a second portion that
is rotatable
relative to said first portion; (ii) operatively connecting said second
portion of said
housing to the end of a length of the tubing string such that rotational
torque applied to
the tubing string through the operation of the pump is transferred to said
second portion
CA 02474418 2004-07-15
of said housing; (iii) retarding or eliminating rotational movement of said
first portion
of said housing when said second portion of said housing is rotated by the
tubing string;
and, (iv) providing a braking means to retard rotational movement of said
second
portion of said housing relative to said first portion of said housing and to
thereby permit
S the controlled rotation of said second portion of said housing and the
tubing string
connected thereto.
In an alternate embodiment the method of the present invention concerns a
method for
rotating a tubing string in a well within which there is situated a downhole
pump that
is connected directly or indirectly to the tubing string, the method
comprising the steps
of (i) providing a tubing string rotator, said rotator having a housing with a
first portion
and with a second portion that is rotatable relative to said first portion;
(ii) providing a
hollow interior bore through said rotator housing and inserting a pump rod
therethrough,
said pump rod connected to the downhole pump such that rotation of said pump
rod
causes rotational movement of a rotor of the pump; (iii) operatively
connecting said
second portion of said housing to the tubing string such that rotational
torque applied
to the tubing string through the rotation of the rotor of the pump is
transferred to said
second portion of said housing; (iv) retarding or eliminating rotational
movement of said
first portion of said housing when rotational torque is transferred to said
second portion
of said housing by the pump; and, (v) providing a braking means to retard
rotational
movement of said second portion of said housing relative to said first portion
of said
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housing and to thereby permit the controlled rotation of said second portion
of said
housing and the tubing string connected thereto, when rotational torque is
transferred
to said second portion of said housing by the operation of the pump.
Further aspects and advantages of the invention will become apparent from the
following description taken together with the accompanying drawings.
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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 sectional view of a typical oil well showing the tubing
string rotator
of the present invention;
Figure 2 is a cross-sectional view taken through the longitudinal axis of a
tubing string
rotator in accordance with one of the preferred embodiments of the present
invention;
Figure 3 is an enlarged detailed view of the lower portion of the tubing
string rotator
shown in Figure 2;
Figure 3A is an enlarged detailed view of one of the cylinders and pistons
shown in
Figure 3 having the fluid flow path of one of the preferred embodiments of the
invention
shown thereon;
Figure 4 is a sectional view taken along the line 4 - 4 of Figure 2;
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Figure 5 is a schematic view showing the operation of a plurality of pistons
within a
tubing string rotator constructed in accordance with one of the preferred
embodiments
of the present invention;
Figure 6 is an enlarged detailed view of the check valve assembly shown in
Figure 2;
Figure 7 is an enlarged detailed view of the lower end of one of the pistons
of the tubing
string rotator shown in Figure 2;
Figure 8 is a longitudinal sectional view of one of the pistons shown in the
tubing string
rotator of Figure 2;
Figure 9 is a side sectional view of an alternate embodiment of the rotator
shown in
Figure 2;
Figure 10 is a sectional view taken along the line 10 - 10 of Figure 9;
Figure 11 is a longitudinal sectional view of an alternate embodiment of the
rotator
shown in Figure 2;
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Figure 12 is a longitudinal sectional view of the rotator of Figure 11 showing
its
cammed surfaces riding over one another;
Figure 13 is a detail view of an alternate embodiment of the braking mechanism
of the
rotator shown in Figure 2;
Figure 14 is a detail view similar to Figure 13 wherein the upper and lower
portions of
the rotator housing have been rotated relative to one another;
Figure 15 is a detail view similar to Figure 14 wherein the upper and lower
portions of
the rotator housing have been rotated relative to one another;
Figure 16 is a partial longitudinal sectional view of a further alternate
embodiment of
the rotator shown in Figure 2; and,
Figure 17 is a sectional view taken along the line 17-17 of Figure 16.
CA 02474418 2004-07-15
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. For example, the drawings and the
description that are
set out below are directed specifically to an oil well application, however,
it should be
noted that the tubing string rotator of the present invention may be equally
applied to a
water well.
In Figure 1 there is shown in cross-section a relatively generic oil well as
it may be
configured during the production phase. The well will typically include of a
well casing
1 extending from the surface of the ground down into the oil bearing strata.
The casing
maintains the well in an open condition and prevents caving and sloughing of
material
into the well. Situated within the casing is a production tubing string 2 that
is typically
hung within the well by means of a tubing string hanger or dognut 3. A variety
of
different types of production equipment may be positioned upon the wellhead
above the
tubing string hanger. Such equipment, amongst other devices, could include a
blowout
preventer 4 and a flow tee 5. In the embodiment shown in Figure 1, a downhole
pump
6 (which may be a progressive cavity, rotary, screw or other form of pump) is
connected
to the lower end of production tubing string 2. Here pump 6 is comprised
generally of
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CA 02474418 2004-07-15
a stator housing 7 and a rotor 8 that is turned by means of a rotating pump
rod 9
extending from a surface drive system down through the production tubing
string
(although it will be appreciated that other forms or methods of operating the
pump could
also be employed while remaining within the scope of the invention). A no-turn
tool 10
may be used to fix the downhole pump relative to the casing and a swivel 11
may be
inserted into the string above the no-turn tool in order to permit the string
to be rotated
so as to evenly distribute wear about its interior surface without disengaging
the no-turn
tool.
In accordance with one of the embodiments of the present invention both the
swivel 11
and no-turn tool 10 shown in Figure 1 are eliminated and a tubing string
rotator 12 is
inserted into the string, preferably at or near the surface. Upon a complete
and thorough
understanding of the invention it will be appreciated that while tubing string
rotator 12
may take any one of a wide variety of different forms, in each instance its
overall
1 S function will be the same; namely, to provide a means to permit the
controlled rotation
of the tubing string within the well through harnessing the rotational torque
applied to
the string by the operation of pump 6. That is, as the rotor in pump 6 is
turned by pump
rod 9, an element of rotational torque (which can vary but may be as high as
800 foot-
pounds) will be imparted to the stator, which will in turn be transmitted to
the tubing
string and ultimately to rotator 12. The rotator utilizes that rotational
energy applied to
the tubing string as a means to permit the string to rotate in a slow (for
example,
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CA 02474418 2004-07-15
typically one revolution per day) and controlled manner so that erosion and
wear of the
string is evenly distributed about its inner surface. It will be further
understood that
through harnessing the rotational energy applied to the tubing string, rotator
12 has no
need to rely upon external sources of mechanical, hydraulic or
electromechanical power,
as in the case of currently utilized tubing string rotators.
Referring now to Figure 2, there is depicted one of the preferred structures
for tubing
string rotator 12 in accordance with the current invention. In this
embodiment, rotator
12 is comprised generally of a housing 13 having a first portion 14 and a
second portion
1 S. In the Figure, first portion 14 is the upper end of the housing while
second portion
is the lower end of the housing. In alternate embodiments of the rotator the
relative
positions of the first and second portions may be reversed. Further, the first
and second
portions may also be concentric portions, or one portion may be otherwise
received
within the other. As is described in more detail below, in the embodiment
shown in
15 figure 2 second portion 15 is rotatable relative to first portion 14 and at
least the second
portion of the housing is adapted to be operatively connected to the end of a
length of
the tubing string such that rotational torque applied to the tubing string
through
operation of pump 6 is transferred to the second portion of the housing.
Typically the
connection between the second portion of the housing and the tubing string
will be
accomplished through a standard threaded connection, however, in some
instances other
forms of connection may be utilized. There may also be an intermediary nipple
or pup
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joint positioned between the upper and/or lower ends of the housing and the
tubing
stung.
Second portion 15 of housing 13 is itself formed of three general parts. The
bottom
most aspect of second portion 15 is comprised of a bottom sub 16 to which
there is
threadably secured a torque tube 17 that extends upwardly and comprises the
majority
of the exterior surface of the rotator. An upper top nut 18 is threadably
secured to the
upper end of the torque tube and serves to both facilitate the assembly of the
internal
components of the rotator, and to securely hold the first and second portions
of the
housing together. First portion 14 is generally comprised of a mandrel 19 that
is
rotationally received within top nut 18 and torque tube 17. The bottom end 20
of
mandrel 19 may extend into a hollow bore within the interior of bottom sub 16
in order
to enhance the overall rigidity of rotator 12 and its ability to endure a side
load.
As is also shown in Figure 2, both first and second portions 14 and 1 S
contain a
generally hollow interior, such that when the respective ends are assembled
together
their interiors are in fluid communication with the tubing string to permit
the passage
of the pump rod and well fluids therethrough. A series of upper seals 21 and
lower seals
22, situated between the first and second portions of the housing, help to
prevent fluid
passing through the tubing string from leaking into the interior of the
housing and fluid
exterior to the tubing string from leaking into the interior of the housing. A
back
19
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pressure value 61 may also be inserted into the hollow interior of the rotator
to seal the
tubing if necessary.
According to the invention, rotator 12 includes means to permit the controlled
rotation
of second portion 15 of housing 13, together with the tubing string connected
thereto,
relative to first portion 14 of the housing when the ability of the first
portion to rotate
is retarded, restricted or eliminated. In the embodiment of the invention
shown in Figure
2, such means is a braking means or braking mechanism 23. Braking mechanism 23
may be comprised of a hydraulic, mechanical or frictional brake, or for that
matter a
wide variety of other structures that assist in retarding, slowing or
otherwise controlling
the rotational movement of the second portion of the housing. The particular
braking
mechanism shown in Figure 2 is comprised generally of one or more pistons 24
that
interact with one or more rammed surfaces 25. Pistons 24 may be received
within
second portion 1 S of housing 13 with rammed surfaces 25 positioned on first
portion
1 S 14 of housing 13. One or more biasing means 26 cause the pistons to engage
rammed
surface 25 so that the interaction of the pistons with the rammed surface
permits a
controlled rotational movement of the second portion of the housing when
tordue is
applied thereto. As will be discussed in more detail below, biasing means 26
may
comprise a spring 27 and/or one or more hydraulic cylinders 28. In the
embodiment
shown in Figures 1 through 8 both a spring 27 and a cylinder 28 are utilized,
with the
spring situated within the cylinder. The cylinders may be integral parts of
the rotator
CA 02474418 2004-07-15
housing or may be separate components received within the first and/or second
portions
of the housing.
Referring to Figures 2 and 3, mandrel 19 of first portion 14 includes a cam
nut 29, the
lower surface of which comprises caromed surface 25 against which pistons 24
interact.
Cam nut 29 is received within torque tube 17 with sufficient clearance between
the
exterior of the cam nut and the interior of the torque tub to permit free
rotation of the
torque tube about the cam nut. The upper surface 59 of the cam nut comprises a
radial
flange 30 which serves as a lower shoulder upon which one or more bearings 31
may
act in order to facilitate rotational movement between the first and second
portions of
the housing. The lower interior surface 60 of top nut 18 acts as an upper
shoulder to
define a containment chamber for bearings 31. Under the above described
structure the
weight of the tubing string that is transferred to the second portion of the
housing will
be borne by top nut 18 and transferred through bearings 31 to radial flange 30
upon cam
nut 29. Since the cam nut is an integral part of mandrel 19, the weight of the
string will
thereby be transferred to the mandrel and ultimately to a tubing string
hanger, dognut
or other device used to suspend the string within the well. An upper bushing
32,
positioned between mandrel 19 and top nut 18, together with a lower bushing
33,
positioned between the bottom end 20 of mandrel 19 and bottom sub 16, help to
facilitate rotary movement between the first and second portions of the
housing. The
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CA 02474418 2004-07-15
bushings also help to accommodate any side loading or bending moment applied
to the
rotator.
In the embodiment of the invention shown in Figure 2, one or more pistons 24
may be
utilized. While the interaction of a single piston with the caromed surface of
cam nut
29 will permit a controlled rotation of the second portion of the housing
relative to the
housing's first portion, as the end of the piston rides over the caromed
surface movement
of the second portion of the housing will tend to be rough or "jerky".
Increasing the
number of pistons and increasing the undulations in the caromed surface of cam
nut 29,
so that at any point in time the ends of individual pistons interact with
various parts of
the undulating caromed surface, will tend to smooth out the rotary movement of
the
second portion of the housing. In the embodiment shown (see Figure 4) 16
pistons are
utilized. It will, however, be appreciated that in alternate embodiments more
or fewer
than 16 pistons could equally be incorporated into the structure while having
little effect
I S upon the rotator's operation.
With reference to Figures 3, 7 and 8, the structure of the pistons used in one
of the
preferred embodiments of the invention that is illustrated will now be
described in
further detail. Generally, pistons 24 are comprised of elongate cylinders
having an
upper or leading end 34 that interacts with caromed surfaces 25, and a lower
or trailing
end 35 that, in the case of the embodiment shown in the attached drawings, is
received
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within a piston cylinder 36 situated within second portion 1 S of housing 13.
As will
become apparent from an examination of the enclosed drawings, lower end 35 of
piston
24 is also operatively connected, or otherwise in communication, with one of
the
hydraulic cylinders 28. Situated within hydraulic cylinder 28 may be a spring
27 having
an upper end 37 received against a spring cap 38, that is in turn received
about lower end
35 of piston 24. Spring 27 further includes a lower end 39 that abuts a spring
stop 40.
The combined function of spring 27, spring cap 38, and spring stop 40 is to
create a
biasing force that is applied to lower end 35 of piston 24 tending to drive
the piston in
an upward direction, and to maintain contact between the piston's upper end
and
cammed surface 25.
Preferably a hydraulic flow path places hydraulic cylinders 28 in fluid
communication
with a fluid reservoir 41 such that when the cylinders are filled with
pressurized fluid
the fluid will migrate from the cylinders to the reservoir. To accomplish
this, within the
hydraulic flow path connecting the reservoir and each cylinder 28 there is
positioned one
or more orifices 63 that control and retard the flow of fluid from the
cylinders to the
reservoir. Fluid is prevented from escaping through the upper end of hydraulic
cylinder
28 through the use of a seal 42. Similarly, a seal 43 prevents the escape of
fluid through
the bottom of the cylinder. Through the operation of seals 42 and 43 the only
manner
of movement of fluid out of hydraulic cylinder 28 is by way of the one or more
orifices
mentioned above. The reservoir may also include a magnet to trap and collect
metal
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CA 02474418 2004-07-15
particles that may be present in the fluid, particularly following break-in of
the tool.
The orifice or orifices that connect fluid reservoir 41 to hydraulic cylinders
28 may have
various different physical structures. In the embodiment shown in Figures 2
through 8
lower end 35 of piston 24 has a reduced diameter portion 44 about the
circumference of
which is positioned a helical channel 45. Encompassing reduced diameter
portion 44
is a flow ring 46 that is press fit over the reduced diameter portion. Press
fitting flow
ring 46 over reduced diameter portion 44 has the effect of forming a helical
flow
passageway or orifice that presents a means for fluid to pass out of hydraulic
cylinder
28. In one version of the invention, the operation of check valves (described
in more
detail below) results in the helical flow passageway formed between reduced
diameter
portion 44 and flow ring 46 being the only manner for fluid to flow out of
cylinders 28.
I S As shown in Figures 3 and 7, once fluid from hydraulic cylinder 28 flows
through the
helical orifice and passes seal 42, it is allowed to escape into that portion
of piston
cylinder 36 that surrounds the outside diameter of piston 24 by flowing
through
openings in the top 62 of flow ring 46. From that point the fluid is free to
flow into fluid
reservoir 41. It should also be noted that in an alternate embodiment of the
invention
the reduced diameter portion of the pistons, the flow ring and the seal may be
incorporated into a single structure having one or more orifices therethrough
that permits
24
CA 02474418 2004-07-15
the controlled flow of pressurized fluid out of cylinders 28.
Figure 6 depicts a check valve 47 which effectively forms the bottom of
hydraulic
cylinder 28. Check valve 47 is dimensioned so as to be received within
cylinder 28 and
presents a mechanism upon which seal 43 may be carried. The check valve
includes a
fluid intake 48, a vent hole 49, a ball 50, and a spring 51. The purpose of
the check
valve is to enable fluid to be pumped or otherwise delivered into hydraulic
cylinder 28,
and to thereafter prevent or limit the escape of fluid through the bottom
portion of the
cylinder when it is pressurized. When the cylinders are in a vacuum state or
are being
filled with fluid (which it is expected in most instances will be hydraulic
oil) fluid is
drawn from reservoir 41, through a connecting passageway 76, through fluid
intake 48,
and out vent hole 49 into cylinder 28 (see Figure 3A). When no longer under a
state of
vacuum, spring 51 forces ball 50 to seat against the fluid intake passageway
forming a
seal therebetween to prevent leakage of fluid out of the bottom of the
hydraulic cylinder.
In an alternate embodiment to that shown in the attached drawings, orifices 63
may be
contained within the check valves rather than being incorporated within the
lower end
of the pistons, such that fluid flowing out of the cylinders must pass through
the orifices
within the check valves prior to entering reservoir 41.
The operation of pistons 24 and their interaction with caromed surface 25 will
now be
described in further detail with specific reference to Figure 5. As mentioned,
preferably
CA 02474418 2004-07-15
a plurality of pistons are situated within second portion 1 S of housing 13
such that the
upper ends of the pistons contact the cammed surface on first portion 14 of
the housing
at various points along the cam profile. In Figure 5, if a torque is applied
to the second
portion of the housing in a direction toward the left, the upper ends 34 of
pistons 24 will
tend to engage caromed surface 25 of cam nut 29 causing the pistons to move in
a
upward and downward direction as they ride over the cam's profile. When being
pushed
downwardly along the sloping surface of the cam nut a piston will tend to
compress the
fluid within its associated hydraulic cylinder, forcing fluid to flow through
orifice 63 and
into fluid reservoir 41. Pushing the fluid through the orifice into the
reservoir has a
retarding effect on its flow, which in turn results in a slow and controlled
movement of
the piston in a downward direction.
Once enough fluid has been forced from cylinder 28 to allow the tip of the
piston to
clear the lower most portion of the caromed surface, further rotation of the
second
portion of the housing will allow the piston come into contact with the upward
sloping
portion of the cam profile. At that point the pressure forcing fluid from
cylinder 28 will
be relieved and spring 27 will tend to drive the piston upwardly, which will
in turn have
the effect of drawing fluid back through the check valve and into the
cylinder. Once
rotation of the second portion of the housing has advanced far enough to allow
the
piston to move upwardly to the point where its tip contacts the trough of the
caromed
surface, the piston will be restricted from further upward movement. Continued
rotation
26
CA 02474418 2004-07-15
of the second portion of the housing will at that point cause the process to
repeat itself
with the piston once again being driven in a downward direction, with fluid
slowly
forced from cylinder 28 through the orifice into reservoir 41, as the upper
end of the
piston rides along the downwardly sloping cam surface.
By way of the above piston movement, and through the use of a plurality of
pistons
contacting various portions of the cam profile, a smooth, slow and controlled
rotational
movement of the second portion of the rotator housing relative to the
rotator's first
portion is achievable. The structure also helps to balance the hydraulic flow
within the
rotator since some of the pistons will be moving downward and forcing fluid
from the
hydraulic cylinders while others will be moving upward and drawing fluid into
the
hydraulic cylinders. It will also be appreciated that through a modification
of the cam
profile, by altering the size of the orifice between hydraulic cylinders 28
and fluid
reservoir 41, andlor through the utilization of fluids having different
viscosities, the
retarding effect that the braking mechanism has upon the rotation of the
second portion
of the housing will be altered. In this manner the rotator's components can be
constructed to permit a controlled rotation of the second portion of the
housing at a pre-
determined rate.
In the embodiment of the invention shown in Figure 2 the first portion of the
rotator
housing is preferably held or otherwise secured within the well in order to
retard (or
27
CA 02474418 2004-07-15
preferably eliminate) rotational movement of the first portion when the second
portion
is subjected to rotational torque by the tubing string. The second portion of
the rotator
and the string are allowed to rotate relative to, and independently from, the
first portion
of the rotator housing. To hold or secure the first portion 14 of the housing
within the
well the first portion may be operatively connected to the well casing through
bolting
it directly to the wellhead. Alternately, a splined or similar mechanical
connection may
be utilized that provides for easier extraction of the rotator from the well
should it
become necessary. As mentioned previously, in a further embodiment the first
portion
of the rotator may be held and secured within the well through the use of a
tubing string
hanger that suspends both the housing and the tubing string. Where a tubing
string
hanger is utilized, it may take the form of an integral part of rotator 12
that is connected
to mandrel 19. Alternately, a dedicated tubing string hanger could be utilized
to which
mandrel 19 may be secured directly, by means of an intermediary length of
tubing, or
through a short pup joint. While it is only necessary to retard or restrict
the rotational
1 S movement of first portion 14 to an extent that enables braking mechanism
13 to operate
and to permit a controlled rotation of second portion 15 relative to first
portion 14, in
most instances it is anticipated that first portion 14 of housing 13 will be
held securely
in position so that it does not rotate,
One of reasonable skill in the art will understand that a variety of different
braking
mechanisms could be used in rotator 12 while remaining within the broad scope
of the
28
CA 02474418 2004-07-15
invention. For example, in an alternate embodiment to that as shown in Figures
2
through 8, the caromed surfaces may be positioned upon the outside diameter of
the cam
nut with the pistons situated and operating in a generally horizontal plane.
The relative
location of the caromed surface and the pistons could also be reversed, with
the pistons
received within first portion 14 of housing 13 and the caromed surface forming
part of
second portion 15.
In a further embodiment of the invention, rotator 12 may be of a more
traditional
configuration that includes a bull gear drive (see Figures 9 and 10). In this
embodiment
the tubing string is operatively connected to a mandrel or dognut 52 suspended
within
a gear housing 53 that is in turn rotatably positioned with a rotator shell
54. In a slightly
varied structure the mandrel many be rotatably suspended directly within the
rotator
shell without the use of the gear housing. Where is gear housing is utilized,
the mandrel
is preferably secured to the gear housing through a splined, friction or
similar connection
that allows for rotation of the gear housing upon rotation of the mandrel. The
splined or
similar connection between the mandrel and the gear housing also permits the
mandrel
and the tubing string to be readily pulled from the well if necessary. It will
be
appreciated that the mandrel and the gear housing together (or the mandrel
independently where no gear housing is utilized) effectively function as
second portion
15 of the rotator housing while the rotator shell functions as the rotator's
first portion
14.
29
CA 02474418 2004-07-15
In the embodiment shown in Figure 9, a bull gear 55 is positioned on the
exterior surface
of gear housing 53 and engages a corresponding and mating gear 56 (which may
be a
worm gear or other form of gear) such that rotation of mandrel 52 and gear
housing 53
causes rotation of gear 56. Of course where no gear housing is used, bull gear
55 is
preferably positioned on the exterior of mandrel 52. A shaft 57 may extend
from gear
56 to a torque limiter 58. Where utilized, torque limner 58 provides a braking
or
retarding effect upon both shaft 57 and gear 56, which in turn permits a slow
and
controlled rotation of mandrel 52 and the tubing string attached thereto.
Torque Iimiter
58 can take any one of a wide variety of different structures from purely
frictional
devices that dissipate torque generated by the pump rotor to mechanical
devices that
may direct the excess energy for use in other applications. In a further
alternate
embodiment one or more gears may be driven by the rotating mandrel without the
use
of a torque limiter. In such an instance the configuration of the one or more
gears will
be relied upon to retard or control rotation of the mandrel and hence the
tubing string.
Figures 11 through 17 show yet further embodiments of the invention that
employ
alternate braking mechanisms to those shown in Figures 1 through 10. In
Figures 11 and
12 there is depicted a tubing string rotator 12 having a braking mechanism 23
that
includes an upper cam nut 64 and a lower cam nut 65. Cam nuts 64 and 65 have
corresponding caromed surfaces 66 and 67, respectively. In this particular
embodiment
CA 02474418 2004-07-15
of the invention lower cam nut 65 is secured to the lower end 1 S of housing
13 through
threading the cam nut to the housing or otherwise securing the two parts
together.
Upper cam nut 64 is slidably received over mandrel 19 and biased towards lower
cam
nut 65 through the operation of a plurality of belleville washers 68. It
should, however,
be noted that a variety of other mechanisms may be utilized to bias the two
cam nuts
together (including traditional coil springs, leaf springs, hydraulic or
pneumatic pistons,
etc) and that the relative positions of the cam nuts may be reversed within
housing 13.
Biasing the caromed surfaces of upper and lower cam nuts 64 and 65 toward one
another
will effectively prevent rotational movement between the upper and lower ends
of the
housing until such time as the torque applied to the housing by the action of
pump 6 is
sufficient to overcome the biasing force applied by the belleville washers (or
such other
means as are employed). When sufficient torque is applied the caromed surfaces
of the
cam nuts will "ride" over one another and permit a stepped rotational movement
1 S between the upper and the lower ends of the rotator housing. The described
structure
will therefore provide for a controlled and stepped rotational movement of the
lower end
of the housing through the utilization of the torque applied to the rotator by
the operation
of pump 6.
Figures 13 through 1 S illustrate a variation to the embodiment of the
invention shown
in Figures 2 through 8. Here the operation of piston 24 is essentially the
same as
31
CA 02474418 2004-07-15
described above with respect to the embodiment shown in Figures 2 through 8,
with the
exception that the upper or leading ends 34 of pistons 24 do not contact
caromed surface
25 directly. Instead, positioned above each piston 24 within the lower end 15
(or the
upper end as the case may be) of the rotator housing is a lifter 69. Lifter 69
has a lower
end 70, that engages the upper end 34 of piston 24, and an upper end 71, that
engages
caromed surface 25 of cam nut 29. As shown, lifter 69 is rotatable about an
axis 72 that
is generally perpendicular to piston 24 in such a manner that longitudinal
movement of
the piston causes the upper end 71 of the lifter to either engage or to be
withdrawn from
caromed surface 25. Figures 13, 14 and 15 show lifter 69 in three positions.
In Figure
13 piston 24 is being moved toward the cam nut and effectively driving the
upper end
of the lifter into the surface of the cam nut. In Figure 14 the piston has
reached its
upper-most position with upper end 71 of lifter 69 positioned within a valley
of caromed
surface 25. Finally, in Figure 15 the piston has been retracted permitting the
lifter to be
rotated away from the caromed surface and allowing the upper end 71 of the
lifter to ride
over the peak surface of the cam. When piston 24 is retracted, the lifters are
rotated
away from caromed surface 25 through the operation of gravity or through the
use of a
spring (not shown). It will therefore be appreciated that the engagement of
lifters 69
with caromed surface 25 permits a controlled rotational movement of the lower
end of
the rotator housing relative to its upper end through harnessing and
controlling torque
applied to the rotator by the operation of pump 6.
32
CA 02474418 2004-07-15
Yet a further form of a braking mechanism that may be employed in the present
invention is shown in Figures 16 and 17. Here, braking mechanism 23 is
comprised
generally of a hydraulic vane pump or motor 73 having a vane pump rotor 74 and
a vane
pump stator 75. In the embodiment shown in Figure 16, vane pump rotor 74 forms
part
of upper end 14 of housing 13 whereas stator 75 forms part of the housing's
lower end
15. It should be appreciated that the relative positions of the vane pump
rotor and stator
could be reversed while not detracting from their function. Through the
placement of a
fluid having a relatively low viscosity within the vane pump housing
surrounding its
rotor and stator, a retarding or braking affect will be applied between the
upper and loser
ends of housing 13 when torque is applied to the rotator through the operation
of rotary
pump 6. It will thus be appreciated that through adjustment of the tolerances
between
the vane pump rotor and stator, and by utilizing fluids of different
viscosity, the amount
or degree of the braking or retarding affect that may be applied can be
altered. The
embodiment of the invention shown in Figure 16 may be particularly adaptable
to
shallow wells, when pumping light crude oil, or in situations where lower
levels of
torque are applied to the rotator through the operation of the rotary pump.
It will thus be appreciated from a complete understanding of the invention
that there is
provided a tubing string rotator capable of harnessing the torque that is
applied to the
33
CA 02474418 2004-07-15
tubing string through rotation of the rotor in a progressive cavity pump as a
source of
mechanical energy to impart a slow and controlled rotational movement to the
string.
Through the incorporation of a braking mechanism operatively connected to the
tubing
string there is provided a means to slow and control the rotation of the
string without the
need to utilize external power sources, including hydraulic, pneumatic,
electrical and
other drive mechanisms. The braking mechanism may comprise one or more
hydraulically actuated pistons, a mechanical gear system, or any one of a wide
variety
of braking or friction inducing structures. Depending upon the nature of the
braking
mechanism, the rotator may take the form of an in-line rotator (such as that
shown in
Figure 2) or may be of a structure more similar to existing tubing string
rotators (see
Figure 9). In either case, a controlled rotation of the tubing string is
achieved without
recourse to external sources of power, thereby reducing operating costs for
the well. The
invention also removes the necessity for the use of a no-turn tool and swivel
as is
required when using traditional tubing string rotators.
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,
in one embodiment of the invention one or more pistons engage a cam nut having
a cam
surface or profile on one side. In an alternate embodiment the cam nut may
have a cam
34
CA 02474418 2004-07-15
profile on two sides which may be engaged by one or more pistons. In addition,
multiple
cam nuts or cam nuts having multiple cam surfaces on one or more sides could
be
utilized.
35
