Drive assembly for a well site

A drive assembly for a tubing rotator comprising: a linear force to motive force convertor including an input for receiving a linear motion drive force and an output for outputting a rotary motion drive force, an arm for receiving a linear drive force and inputting it to the linear force to motive force convertor and an actuator couplable to a polish rod and configured for transmitting a linear drive from the polish rod to the arm.

FIELD OF THE INVENTION

This invention relates to an apparatus for driving devices at a well site. In particular, the drive apparatus employs the drive motion of a polish rod to drive other devices at a well site.

BACKGROUND OF THE INVENTION

At a wellsite, the production tubing string serves to support the rod pump and polish rod and provides a means to extract oil. During production on a rod pump system, the polish rod moves up and down with the stroke of a pump jack. In particular, the polish rod is driven up and down along its long axis to drive the pumping action of the rod pump. The polish rod extends up through the inner diameter of the production tubing string.

Many well sites have no source of grid power. However, they do have devices such as tubing rotators or chemical pumps that must be driven to operate.

As an example, the production tubing string is often rotated in order to more evenly distribute wear on its inside surface due to contact with the polish rod. Rotation may be via a tubing rotator. When a tubing rotator is used, it has a hanger body coupled to and supporting the tubing string. Rotation of the hanger body rotates the tubing string. The tubing rotator hanger body is driven to rotate within a housing of the tubing rotator by a gear assembly. If there is no grid power supply, power is provided by a generator but this requires refueling and considerable maintenance.

SUMMARY OF THE INVENTION

The invention provides a drive for a wellsite device.

In accordance with one broad aspect of the invention, there is provided a drive assembly for a wellsite device comprising: a linear to motive force convertor including an input for receiving a linear motion drive force and an output for outputting a motive drive force, an arm for receiving a linear drive force and inputting it to the linear to motive force convertor and an actuator couplable to a polish rod and configured for transmitting a linear drive from the polish rod to the arm.

In accordance with another broad aspect, there is provided a wellhead installation comprising: a polish rod drive, including a polish rod, for a downhole rod pump; a wellsite device; an actuator couplable to a polish rod and configured to move linearly with the polish rod; an arm free of connection to the polish rod and positioned adjacent to the polish rod for receiving a linear drive force by abutment with the actuator and a linear force to motive force convertor including an input, coupled to the arm and configured for receiving a linear motion drive force from the arm, and an output for outputting a motive drive force to the wellsite device.

In accordance with a further broad aspect, there is provided a method for driving a wellsite device at a wellsite, the method comprising: connecting an actuator to a polish rod such that the actuator moves up and down with the polish rod as it strokes; positioning an arm adjacent to but free of connection to the polish rod to be acted upon by the actuator, thereby to transfer an input of linear motion from the polish rod to the arm; connecting the arm to a convertor to convert the input of linear motion to a motive drive force and inputting the motive drive force to the wellsite device.

DESCRIPTION OF VARIOUS EMBODIMENTS

This invention is directed to a drive system for a wellsite device. The drive system is mechanical, not reliant on an input of electrical power or hydraulics. The drive system uses the linear drive of the polish rod and converts that linear drive to a drive for the wellsite device. In one embodiment, the drive system uses the downward linear motion of the polish rod to engage mechanisms that drive the wellsite device. It is useful to employ the downward motion, rather than the upstroke, because the downward movement of the polish rod, as driven by the horsehead of the pump jack, is known and limited to avoid mechanical contact between the pump components on the pump downhole. Since the polish rod and devices are important and expensive structures on the well, the drive system can be configured with mechanisms to prevent damage to the polish rod and to the device during use.

With reference to the Figures, the drive system is useful on a wellhead installation including: a polish rod10and a wellsite device, such as a tubing rotator12, that needs to be driven to operate. While the following focuses on a tubing rotator as the wellsite device, the technology can be applied to other devices, such as a chemical pump, that need to be driven to operate.

The polish rod10is linearly driven up and down (arrow L) such as by a pump jack, not shown. The linear drive of the polish rod drives a rod pump in a production tubing downhole.

The tubing rotator12is supported on the wellhead14and supports the production tubing that extends down into the well below the wellhead. The tubing rotator includes a hanger body (not shown) driven via a gear assembly16. Gear assembly16rotates the hanger body by receiving an input of motive force, in this embodiment, rotary motion. In this embodiment a shear coupling18is positioned at an input end of the gear assembly16to prevent overloading of the driven load.

The drive system includes a linear force to motive force convertor20including an input22for receiving a linear motion drive force indirectly from the polish rod10and an output24for outputting a motive drive force, such as a rotary drive force, directly or indirectly to the tubing rotator. The drive system also includes an arm26for receiving a linear drive force from the polish rod and inputting it to the linear force to motive force convertor20and an actuator28couplable to the polish rod and configured for transmitting the linear drive from the polish rod10to the arm26.

Actuator28is a structure that is couplable to the polish rod10and configured to communicate the linear movement of the polish rod to impart linear movement to the arm26. In one embodiment, the actuator is configured to only communicate linear downward movement of the polish rod to the arm. While the actuator could include a physical coupling between the arm and the actuator, in one embodiment, the actuator is free of any physical coupling to the arm. In such an embodiment, the actuator is separate from the arm and not directly connected via any connection (no hinge, link, cable, etc.) to the arm.

In one embodiment, actuator28is a clamp that clamps onto the polish rod10and creates an enlargement on the polish rod that can butt against a portion of the arm on the down stroke of the polish rod. In one embodiment, the actuator is a disk-shaped clamp, such as including clamp parts30a,30b. When clamped together the parts30a,30bdefine a ring shaped disk with a central opening31between them sized to accommodate the polish rod therein. The disk shaped body has a diameter larger than the polish rod diameter.

As noted, the polish rod is an expensive component of the well. Therefore, it is desirable that the actuator be couplable to the polish rod but not damage or score it. In one embodiment, the central opening31has a liner31aconstructed of a material such as plastic that is softer than the polish rod steel and, therefore, not capable of damaging the polish rod.

The actuator28is connected to the polish rod10to move with it and apply a force to the arm26when the actuator butts against the arm. The connecting force of the actuator to the polish rod may be selected to ensure that if excessive forces are encountered as the actuator bears against the arm, the actuator can release from its actuating position, such as slip along the polish rod or break off the polish rod. For example, the clamping force of the actuator on the polish rod can be selected to allow for normal operation to occur, but can be overcome to allow the actuator to slip up the polish rod if an excess amount of force is applied to the arm. The actuator, for example, can include an internal spring mechanism32through which the clamping force can be set to be capable of being overcome.

The arm26may also include a shear mechanism to ensure that it can be released if something in the drive assembly ceases. This shear mechanism takes the arm off line, for example disconnects the arm from its position adjacent the polish rod, disconnects the arm from its drive connection to the convertor or otherwise allows the arm to move freely, so that the polish rod can continue to function without the actuator being hindered by the arm.

To reduce shocks and reduce wear between the actuator and the arm, the actuator at least on its surface that contacts arm26may be plastic or elastomeric. In one embodiment, a lower pad33of plastic is connected on the lower end of the actuator.

Actuator28engages an upper portion of the arm26on each downward stroke of the polish rod. The arm can be positioned adjacent to the polish rod, and within the path of the actuator as it is moved by the polish rod. The arm generally is not coupled to or in contact with the polish rod to mitigate damage to the polish rod. The upper end of the arm in it highest position, also called it neutral position, is just below the actuator at the upper limit of its stroke length. The actuator, as it is stroked down, then, butts and pushes against the arm. Actuator28can be clamped onto the polish rod near the bottom of the polish rod stroke to be close to the tubing rotator. By placing the actuator28near the bottom of the polish rod stroke, the arm height can be minimized.

The arm26transfers the linear, for example downward linear, motion of the polish rod to the convertor20. In one embodiment, the arm26includes a main arm structure36that is rigid and elongate and is the main structure through which the linear motion is transmitted. Therefore, main arm structure36acts as a linear force transmission shaft. In another embodiment, the arm26includes the main arm structure36as a part of an arm assembly including a linkage and lever. In one embodiment, for example, arm26is configured as an assembly including a support post38and a lever40connected at its fulcrum42onto the post. A first, effort end40aof the lever is acted upon by the actuator28and the opposite, load end40bof the lever, on the other side of the fulcrum from the first end, is pivotally coupled to the main arm structure36. Thus, movement of the actuator down against the first end40aof the lever causes the main arm structure to be pulled up. The use of a lever and linkage to the main arm provides facilitates receiving and transmitted the linear force. The arm assembly with lever and linkage to the linear transmission arm36minimizes shocks and damage to the polish rod.

The arm26can further include a base44where post is mounted. Base44can be configured for securing to the ground or to a wellhead structure, such as to the wellhead or the tubing rotator. In the illustrated embodiment, the base includes receptacle that connects onto mounting bolt.

Support post38is height adjustable, for example, as by use of a telescoping and pinned adjustment. The main arm36is also length, and thereby stroke length, adjustable. Main arm36may for example, include a telescoping and pinned structure for length adjustment. The adjustments allow for different wellhead configurations and selection of stroke length.

The shear mechanism for arm29may be incorporated into various parts on arm36or connections between arm36and lever40. In one embodiment, the shear mechanism may be incorporated into the telescoping and pinned connection on arm36.

Lever40is positioned to be acted upon by the actuator, as the actuator is moved by the polish rod. In one embodiment, the lever is a dual arm structure with two parallel arms40′,40″. As such, the two arms can be positioned on either side of the polish rod, so that the lever stays in a position to be acted upon by the actuator. The space between the arms40′,40″ is smaller than the diameter across the actuator. While a connector could be employed between arms40′,40″ at end40a, the connector may be omitted for various reasons but for example, to avoid the arm26contacting the polish rod and to facilitate installation of the lever40onto a well.

As noted, lever40is acted upon by the actuator28on the down stroke of the polish rod. Lever40is moved from a high position to a lower position by this action. Lever40is biased to return to the high position after each downward stroke. In one embodiment, the lever has a weight46on its load end40bthat biases the lever back into the high position. Biasing could alternatively be achieved by use of torsion, tension or compression springs, or gas shocks, for example.

Arm26may include a stop47to control the maximum upward movement, such as a stop near fulcrum46to limit the upward rotation of the lever. The stop may be adjustable to allow for different wellhead configurations.

Arm26transmits the linear drive force from the polish rod to the linear force to motive force convertor20. In one embodiment, arm26, for example, main arm36, is connected to convertor20at input22by a pivoting connection46.

The convertor may be any mechanism that converts a linear force input to a motive force suitable for the device to be driven. In one embodiment, such as for a tubing rotator, the linear force input is converted to a rotary force output. The convertor may include a gear rate adjuster, such as a reducer. This is useful where the frequency of the polish rod actuation is too rapid/great or too slow/small for the device. For example, in a tubing rotator embodiment, a gear reducer may be of interest to ensure the tubing rotator is turned slowly. The converter may also have an output directional change, such as a right hand or left hand gear mechanism.

In some embodiments, the device only requires a one way motive force. As such a clutch or ratchet may be required to transmit only a one way motive force to operate the device. The device may have the one way mechanism. If not or as a failsafe, the convertor may be configured to output only a one way motive force. For example, the convertor may have a mechanism to output rotary drive only in one direction. For example, there may be a release, ratchet, backspin preventor or other means to prevent reverse rotation from being output from the convertor. Therefore, convertor20can accommodate the reverse movement of arm26as it returns to a start, neutral position without any reverse rotational drive being output into the device. Converter20may, for example, operate using a clutch with backspin preventer20a(FIG.3) or a ratcheting wrench mechanism20b.

In one embodiment, for example as shown inFIG.3, the convertor includes a clutch with a backspin preventer20b. Arm36is connected by a pivoting connection to input linear motion to the converter and the linear motion is received by a main shaft50and clutch. The backspin preventor ensures that the convertor only outputs rotary motion in one direction (see the arrow), when arm36is pulled up by the lever. When the arm moves back down, that reverse movement is not transmitted through to coupling18and the gear of the tubing rotator. The clutch and preventer may be roller style mechanisms. This convertor also includes a right hand, reducing gear box52.

In another embodiment, the linear force to motive force convertor employs a ratcheting mechanism20b. For example, the adjustable connecting arm36is pivotally connected to and turns an attached ratcheting wrench by approximately 90 degrees with each downward stroke. The ratcheting wrench transfers that motion through a right-angle gearbox reducer through to the shear coupling, and thus through to the tubing rotator12, thereby turning the production tubing. When arm36returns to the upper position, the ratcheting mechanism allows the wrench to reverse back without imparting reverse drive to the output of the convertor.

The total allowable swing of the wrench may be adjusted with a bolt-type stop47attached to the lever which limits the motion of the lever around its fulcrum46and acts as a positive stop against the central support post.

The drive actuates the rotator during the downward stroke rather than the upstroke. This is useful since the downward extent of the horsehead is limited to avoid mechanical contact between the plunger and the pump downhole.

FIGS.2A,2B and2Cshow the functioning of the drive assembly. Overall, the operation includes connecting actuator28to a polish rod10such that the actuator moves up and down with the polish rod as it strokes. Then, arm26is positioned adjacent to but free of connection to the polish rod. In this position, the arm is in the path to be acted upon by the actuator, thereby to receive an input of linear motion from the polish rod through interaction with the actuator. The arm is then connected to a convertor to input the linear motion to the convertor. The convertor converts the input of linear motion to a motive drive force. The motive drive force is input from the convertor to the wellsite device.

FIG.2Ashows lever40and arm36in a neutral position, where the effect end of lever40is in a high position awaiting actuator28to be moved down with the polish rod, wherein actuator28makes contact with the lever and linearly moves arm36.

FIG.2Bshows the contact position, where actuator28is driven to make contact with the lever40. At this point, polish rod10and actuator28are moving down. Contact between actuator28and lever drives the effort end40aof the lever down (arrow A). This downward force moves arm36linearly up (arrow B). This upward movement is communicated to convertor20and the upward pull causes convertor20to generate a rotational force (arrow R).

FIG.2Cshows the full down position of the drive assembly. In this position, actuator28is at its lowest position, timed to the pump jack and polish rod10lowest positions. Lever40effort end40ais fully pushed down and arm36has reached the peak of its linear pull force on convertor20.

AfterFIG.2C, the polish rod10and actuator28are stroked back up. Lever40is also biased to return to the neutral, highest position (FIG.2A). This movement moves arm36back to its neutral, position. This upward movement does not rotationally reverse the convertor20. Instead, the convertor permits this reverse movement via a ratchet, slip or backspin preventor.

It is to be understood that what has been described are 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.