Note: Descriptions are shown in the official language in which they were submitted.
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Title: METHOD AND DEVICE FOR REVERSING POLISHED ROD ROTATOR
ACTION
FIELD OF THE INVENTION
The present invention relates to the field of oil and gas surface wellhead
equipment. More particularly, the present invention relates to devices for
rotating the rod string of a sucker rod during operation of a reciprocating
plunger
pump.
BACKGROUND OF THE INVENTION
Reciprocating plunger pumps are commonly used for oil and gas well recovery
or extraction projects. This type of pump is used to lift fluid from oil and
gas
wells where there is not enough reservoir pressure to lift the produced fluids
to
surface. Reciprocating plunger pumps operate by lifting the fluids to the
surface
by a reciprocating plunger which traps a quantity of fluid with the use of
ball
valves and forces the trapped fluid incrementally upward in a reciprocating
manner to the surface via production tubing. The plunger is connected to the
above ground wellhead stroking unit via a series of rod, sucker rod, co-rod,
and
polished rod strings positioned inside the production tubing.
A common problem with reciprocating plunger pumps is that over time, the
reciprocating movement of the rod string causes severe sliding wear, also
known as rod wear. Also these wells are potentially left with a paraffin or
build-up of sand or permeable production content on one side of the production
tubing choking back or restricting maximum production output resulting in
pump,
rod, or tubing failures. This in turn leads to premature oil well failures and
costly
repairs.
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Attempts to overcome these common problems resulted in development of
polished rod rotators which are used to decrease the wear of sucker rods and
production tubing, prevent unwanted unscrewing of sucker rods, and reduce the
deposit of wax and paraffin on the surfaces of sucker rods and production
tubings.
U.S. Pat. No. 7,857,043 to Ali-zada discloses one such attempt at a polished
rod rotator, which uses a mechanism to rotate a string of sucker rods relative
to a string of oil well tubing to high degrees of rotational angle and achieve
large
rotator torque. The activation and resulting rotation torque is achieved
through
axial impact directly by the weight of the sucker rod string at the end of the
downward movement of the pumping equipment. The rotator is described as
a two-part assembly, one part is attached to a well-head stuffing box and the
other is attached to a polished rod, having a hollow body with spiral slots
with
rollers. With the downward movement of a beam, the two parts dock through
their docking surfaces, while the weight of sucker rods forces the rotator to
move down using rollers in spiral slots rotating the polished rod along with
the
sucker rods until the beam's movement is complete. With the upward
movement of the beam, the parts undock rod rotator is static waiting for the
completion of pumping cycle.
However, one problem with the Ali-zada device and other prior art polished rod
rotators is that they occasionally fail to function properly. This stems from
the
fact that these prior devices are designed to utilize the weight of the rod
string,
when the polished rod reaches the bottom of the downstroke, to effect the
rotation. It has been discovered that it is not uncommon for the rod string to
hang up, or float on the down stroke due to heavy viscosity or partially sand
mixed production fluid which is restricted by the bypass allowed in the ball
valves of plunger or reciprocating pumps. Thus when the rod string hangs or
floats on the downstroke, there is insufficient weight on the device to effect
the
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rotation and the device fails to rotate the polished rod.
Another problem with prior art polished rod rotators is that they are
integrated
into wellhead equipment as whole systems which makes them difficult to and
costly to replace.
Other prior art patents of general interest in the field of polished rod
rotators
include: U.S. Pat. Nos. 2,471,198 to Cormany; 2,932,204 to Johnson;
6,293,347 to Cahill; 1,681,789 to Sargent; 1,667,240 to Boynton; 2,599,869 to
Sheltonvborger; 2,603,098 to Cremeens; 1,686,261 to Boynton; and 2,702,690
to Bradford; and U.S. Pat. App. Pub. No. 2009/0065190 to Smith.
However there is a continued need for improvement in polished rod rotators.
SUMMARY OF THE INVENTION
What is desired is a device and method to reverse the action of the rotation
of
a polished rod rotator to overcome at least some of the problems associated
with prior art polished rod rotators.
According to the preferred embodiment of the present invention, the polished
rod rotator reversing device functions to reverse the action of a polished rod
rotator, causing the rotator to rotate the polished rod at the top of the
upstroke
as opposed to the bottom of the downstroke, which decreases the wear of
sucker rods and production tubing, prevents unwanted unscrewing of sucker
rods, and reduces the deposit of wax and paraffin on the surfaces of sucker
rods and production tubings. Furthermore, the preferred polished rod rotator
reversing device is adapted for easy retrofit installations on existing
wellhead
equipment, to provide a more cost effective update to older wellhead equipment
than was previously possible.
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BRIEF DESCRIPTION OF THE DRAWINGS
Reference will now be made to the preferred embodiments of the present
invention with reference, by way of example only, to the following drawings in
which:
Figure 1 is a diagram of a prior art polished rod rotator on a walking
beam type reciprocating plunger pump;
Figure 2 is a diagram of a polished rod rotator reversing device installed
on a walking beam type reciprocating plunger pump according to an
embodiment of the present invention;
Figure 3 is a side view of the polished rod rotator reversing device of
Figure 2; and
Figure 4 is a top view of the polished rod rotator reversing device of
Figure 2.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The present invention is described in more detail with reference to exemplary
embodiments thereof as shown in the appended drawing. While the present
invention is described below including preferred embodiments, it should be
understood that the present invention is not limited thereto. Those of
ordinary
skill in the art having access to the teachings herein will recognize
additional
implementations, modifications, and embodiments which are within the scope
of the present invention as disclosed and claimed herein.
Figure 1 shows a typical walking beam type reciprocating plunger pump 10
including a polished rod rotator 12. The polished rod rotator 12 is of the
type
having a mechanism that rotates the polished rod 14 and rod strings 16 using
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the weight of the rod strings 16 on the downstroke of reciprocating plunger
pump 12. An example of a common polished rod rotator 12 is the T-302Tm by
Hercules . These types of polished rod rotators have an existing actuator arm
18 attached to an actuator arm attachment shaft 20. For the purposes of this
example, rotating the shaft 20 in a counter-clockwise direction activates the
internal mechanism of the polished rod rotator 12 to utilize the weight of the
polished rod 14 and rod strings 16 to turn the polished rod 14 and rod strings
16. Rotating the shaft 20 in a clockwise direction deactivates the internal
mechanism of the polished rod rotator 12 until the next cycle. The shaft 20 is
normally biassed toward the clockwise direction to return the actuator arm 18
to its inactive position. One end of a pull cable 22 is attached the walking
beam
24 of the reciprocating plunger pump 10 at an end 26 opposite the horsehead
28, while the other end of cable 22 is connected to the existing actuator arm
18
of the polished rod rotator 12.
As will be appreciated, on the downstroke of the reciprocating plunger pump
10,
the end 26 of the walking beam 24 opposite the horse head 28 of the
reciprocating plunger pump 10 moves upward. As it moves upward the end 26
pulls with it the cable 22, which tightens an causes the existing actuator arm
18
to turn the shaft 20 of the polished rod rotator 12 in a counter-clockwise
direction. The counter-clockwise rotation of shaft 20 activates the internal
mechanism of the polished rod rotator 12 to utilize the weight of the polished
rod 14 and rod stings 16 to turn the polished rod 14 and rod strings 16. On
the
upstroke, the end 26 of the walking beam 24 opposite the horsehead 28 of the
reciprocating plunger pump 10 moves downward, releasing the tension in the
cable 22. As the tension in cable 22 is released, shaft 20 is allowed to turn
in
a clockwise direction which deactivates the internal mechanism of the polished
rod rotator 12 and returns the actuator arm 18 back to its inactive position.
Referring now to Figure 2, there is shown a polished rod rotator reverser
device
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30 according to an embodiment of the present invention is shown installed on
a walking beam type reciprocating plunger pump 10. As shown, the preferred
polished rod rotator reversing device 30 is attached to the shaft 20 of an
existing polished rod rotator 12, with for example a bolt 32. One end of cable
22 is attached to the walking beam 24 at the end 26 opposite the horsehead 28,
while the other end of cable 22 is connected to the polished rod rotator
reverser
device 30.
Referring now to Figure 3, the polished rod rotator reversing device 30 is
shown
attached to a side of the polished rod rotator 12. As can be seen the polished
rod rotator reversing device 30 has a lever arm 34 having one end 36 attached
to the shaft 20 of the polished rod rotator 12, and the other end 38 is
attached
to the cable 22. As mentioned above, the other end of the cable 22 is attached
to the walking beam 24 at the end 26 opposite the horsehead 28. An actuator
arm 40 is attached to the one end 36 of the lever arm 34 at the shaft 20,
substantially at a 900 angle to the lever arm 34. The other end 44 of the
actuator arm 40 is attached to a weight 42. Good results have been obtained
with the lever arm 34 having a length of nine inches, the actuator arm having
a length of four inches, and the weight 42 having a weight of three to ten
pounds. What is required is to provide enough torque, by means of the
combination of lever arm 34 and weight 42 to achieve the desired rotation as
set out below. Thus, it will be appreciated that the polished rod rotator
reversing device 30 may be provided with other dimensions and weights and
still operate as described herein. All such other dimensions and weights are
covered by the present invention.
With reference to Figures 3 and 4, the polished rod rotator reversing device
30
is installed on the shaft 20 of the existing polished rod rotator 12 as a
replacement for the existing actuator arm 18. The polished rod rotator
reversing device 30 is configured to reverse the action of the polished rod
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rotator 12 so that it turns the polished rod 14 and rod strings 36 at the top
of the
upstroke of the reciprocating plunger pump 10 as opposed to the bottom of the
downstroke.
As the reciprocating plunger pump 10 strokes downward, the cable 22 is pulled
tight by the movement of the one end 36 of the walking beam 24. The
tightening cable 22 pulls the other end 38 of the lever arm 34, causing the
attached actuator arm 40 to pivot upwards in a clockwise direction. As above,
in this example, rotating the shaft 20 in a clockwise direction deactivates
the
internal mechanism of the polished rod rotator 12. In other words, on the
downstroke, the cable 22 pulls on the lever arm 34, causing the actuator arm
40 to pivot upward effecting a clockwise rotation on the shaft 20, and lifting
the
weight 42, without causing the polished rod rotator 12 to rotate the polished
rod
14 and rod strings 16.
Then as the reciprocating plunger pump 10 strokes upward, the movement of
the one end 36 of the walking beam 24 slackens the cable 22, allowing the
weight 42 to force the actuator arm 40 to pivot downwards. The downward
movement of the actuator arm 40 effects a counter-clockwise rotation on the
shaft 20 which causes the internal mechanism of the polished rod rotator 12 to
activate and rotate the polished rod 14 and rod strings 16 utilizing the
weight of
the polished rod 14 and rod strings 16.
It will now be appreciated that by utilizing the weight 42 to activate the
polished
rod rotator 12 on the upstroke there will always be enough weight from the
polished rod 14 and rod strings 16 to effect the rotation of the polished rod
14
and rod strings 16, and the polished rod rotator 14 will function consistently
even if the rod strings 38 float or get hung up on the downstroke. In other
words, when the lever arm 34 is pulled by the cable 22, the internal mechanism
of the polished rod rotator 12 allows the parts to slip past one another
without
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engagement and when the actuator arm 40 is tipped by the weight 42, the parts
engage and the weight of the polished rod 14 and rod strings 16 causes the
internal mechanism of the polished rod rotator 12 to move or rotate to change
the position of the polished rod 14 and rod strings 16 within the production
tubing.
Although the present invention has been described in the context of a walking
beam type reciprocating plunger pump 10, it will be appreciated that the
invention may be used on other types of reciprocating plunger pumps such as
hydraulic pump jacks and cable jacks. All such embodiments are covered by
the broad scope of the claims.
While reference has been made to various preferred embodiments of the
invention other variations, implementations, modifications, alterations and
embodiments are comprehended by the broad scope of the appended claims.
Some of these have been discussed in detail in this specification and others
will
be apparent to those skilled in the art. Those of ordinary skill in the art
having
access to the teachings herein will recognize these additional variations,
implementations, modifications, alterations and embodiments, all of which are
within the scope of the present invention, which invention is limited only by
the
appended claims.
