CA2802720A1 - Method and device for reversing polished rod rotator action - Google Patents

Abstract

A polished rod rotator reversing device that functions to reverse the action of a polished rod rotator, causing the polished rod rotator to rotate the polished rod and rod strings on upstroke as opposed to the downstroke. The preferred polished rod rotator reversing device is adapted for retrofit installation on a reciprocating plunger pump as a replacement for the actuator arm of the existing polished rod rotator. The polished rod rotator reversing device has a lever arm, one end of which is configured for attachment to the actuator arm attachment shaft on the polished rod rotator, and the other end is adapted for connection to a pull cable mounted on the pump. An actuator arm is attached to the one end of the lever arm at substantially a 90° angle. The other end of the actuator arm carries a weight. When the pump strokes down, it causes the cable to pull the lever arm away from a first position, pivoting the actuator arm up, which rotates the shaft in a first direction and lifts the weight upward.
When the pump strokes up, the cable slackens allowing the weight to pivot the actuator arm down, which rotates the shaft in a second direction opposite the first direction, and returns the lever arm to the first position. Rotation of the shaft in the second direction activates the internal mechanism of the polished rod rotator, causing the polished rod rotator to rotate the polished rod and rod strings using the weight of the polished rod and rod strings.

Description

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.

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 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.

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 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 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 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 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 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 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 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 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.

Claims (2)

1. A polished rod rotator reversing device for a reciprocating oil or gas well pump substantially as shown and described.

2. A method for reversing the action of a polished rod rotator on an existing reciprocating oil or gas well pump substantially as shown and described.