Patent Application
20160193687
1. Field
Embodiments of the present disclosure generally relate to apparatus for connecting continuous sucker rods.
2. Description of the Related Art
In oil and gas wells, a “drive string” connects the pump, located down hole, to the drive system, located at the surface. Sucker rods are generally used in a drive string. A conventional drive string typically includes a sequence of conventional sucker rods with connecting mechanisms at each end of each conventional sucker rod which permit end-to-end interconnection of adjacent rods. Conventional sucker rods are elongated steel rods, 20 feet to 30 feet in length. Each interconnection point between two successive conventional sucker rods is a source of potential weakness and excess wear on the adjacent tubing and casing.
Alternatively, a drive string may include one continuous sucker rod to avoid weakness caused by interconnection points between conventional sucker rods. A continuous sucker rod is a unitary rod, consisting of one elongated continuous piece of steel. Continuous sucker rod is typically produced and stored for sale on large transport reels. These transport reels have a maximum diameter of about 19 to 20 feet and the diameter may be as small as 9-10 feet. A full reel can carry continuous sucker rod with lengths of over 6,000 feet depending on the diameter of the rod. However, the length of a drive string can vary from anywhere from as little as 500 feet to as much as 10,000 feet or more, depending on the depth of the well and desired location of the pump down hole. Therefore, connections are still needed with continuous rod, for example to attach driving and/or pumping equipment, to splice lengths of rod together, to create tapered drive strings, to repair parted drive strings, or to connect the continuous sucker rod to other auxiliary components.
Welding has been the predominant method for making continuous sucker rod connections. However, continuous sucker rod connections made by traditional sucker rod welding methods, such as flash-butt welding and gas-pressure welding, have failure frequencies higher than the industry tolerance.
Therefore, there is a need for apparatus and methods for connecting continuous sucker rods.
Embodiments of the present disclosure generally relate to apparatus and methods for connecting continuous sucker rods.
One embodiment provides a welding station. The welding station includes a first clamp die adapted to secure a first work piece, a second clamp die adapted to secure a second work piece, an actuator coupled to move the first clamp die and second clamp die relative to each other, and a controller coupled to the actuator.
Another embodiment provides a method for welding continuous sucker rod. The method includes preparing ends of a first work piece and a second work piece by reducing cross sections of the ends, and welding the first work piece and the second work piece at the prepared ends.
Another method provides a method for testing a weld in a rod. The method includes bending the rod at the weld to a pre-determined angle, and examining the weld to determine the quality of the weld.
So that the manner in which the above recited features of the present disclosure can be understood in detail, a more particular description of the various aspects, briefly summarized above, may be had by reference to embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of this disclosure and are therefore not to be considered limiting of its scope, for the disclosure may admit to other equally effective embodiments.
To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures. It is contemplated that elements disclosed in one embodiment may be beneficially utilized on other embodiments without specific recitation. The drawings referred to here should not be understood as being drawn to scale unless specifically noted. Also, the drawings are often simplified and details or components omitted for clarity of presentation and explanation. The drawings and discussion serve to explain principles discussed below, where like designations denote like elements.
In the following description, numerous specific details are set forth to provide a more thorough understanding of the present disclosure. However, it will be apparent to one of skill in the art that the present disclosure may be practiced without one or more of these specific details. In other instances, well-known features have not been described in order to avoid obscuring the present disclosure.
The resistance-butt welding system 100 includes a fixed clamp die 102 and a movable clamp die 106. The fixed claim die 102 may secure a first work piece 104 so that an end 124 of the work piece 104 faces the movable clamp die 106. The movable clamp die 106 may secure a second work piece 108 so that an end 126 of the work piece 108 faces the fixed clamp die 102. One or both of the work pieces 104, 108 may be continuous sucker rods.
The movable clamp die 106 may be connected to an actuator 110. The actuator 110 is configured to move the movable clamp die 106 relative to the fixed clamp die 102. The movable clamp die 106 may secure and move the second work piece 108 to make contact between the work pieces 104, 108 at the ends 124, 128 and to apply force between the work pieces 104, 108. The actuator 110 may be any suitable drive mechanism. In one embodiment, the actuator 110 may be a hydraulic cylinder. It must be noted that clamp dies 102, 106 are configured to allow relative movement between the work pieces 104, 108. In one embodiment, both claim dies 102, 106 may be movable, for example, the clamp die 102 may be configured to move by a second actuator.
The resistance-butt welding system 100 further includes a power supply 112. The power supply 112 may be connected to deliver electric current across an interface 128 of the work pieces 104, 108 when the work pieces 104, 108 are in contact. In one embodiment, the power supply 112 may be coupled to the fixed clamp die 102 and the movable clamp die 106. The power supply 112 may be direct current (DC) power source or alternate current (AC) power source. In one embodiment, the power supply 112 may be adjustable to deliver variable current and/or variable voltage to the work pieces 104, 108. A switch 114 may be used to switch on and off the power supply 112.
The resistance-butt welding system 100 further includes a controller 116. The controller 116 may be connected to the actuator 110 to control the movement of the movable clamp die 106. In one embodiment, a sensor 120 may be configured to sense motion and/or location of the movable clamp die 106. The sensor 120 may be connected to the controller 116. The controller 116 may receive signals from the sensor 120 to determine the position and/or speed of the movable clamp die 106. The controller 116 may then send a command to the actuator 110 according to the determined position and/or speed information.
The controller 116 may be configured to control the power supply 112. For example, the controller 116 may control the switch 114 to turn on and off the power supply 112. In one embodiment, the power supply 112 may be adjustable. The controller 116 may adjust at least one of the current and the voltage of the power supply 112. The resistance-butt welding system 100 may include a sensor 118 connected to monitor one or more parameters of the power supply 112. The controller 116 may receive and monitor input signals of the sensor 118 and control the power supply 112, the actuator 110, or both, in response to the signal from the sensor 118. In one embodiment, the sensor 118 may be a current sensor.
The resistance-butt welding system 100 may also include additional sensors to monitor operating parameters, such as pressure, force, temperature, and combinations thereof. In one embodiment, a force sensor 122 may be connected to measure the force applied between the first and second work pieces 104, 108. The controller 116 may monitor the measurement of the force sensor 122 and control the power supply 112 and/or the movable clamp die 106. During resistance-butt welding, the size of the cross section of the contact area between the two work pieces 104, 108 changes continuously. Since the force applied between the two work pieces 104, 108 is not affected by the change in size of the contact area, the force sensor 122 provides a direct measurement for the controller 116 to control the power supply 112 and/or the movable clamp die 106. Alternatively, a pressure sensor may be used in place of a force sensor 122. The measured pressure may be used by the controller 116 to control the power supply 112 and/or the movable clamp die 106.
According to one embodiment of the present disclosure, the resistance-butt welding system 100 may be installed on the back of a truck to operate in the field. The power supply 112 may be a group of 12 Volt batteries that may be recharged. The power supply 112 may be recharged by the motor of the truck, for example from an oversized alternator of the truck, or from a hydraulic driven generator of the truck. Alternatively, the power supply 112 may be charged from an independent generator disposed on the truck or from land power when the truck is parked at the base or a location with access to land power.
Ends 124, 126 of the work pieces 104 and 108 may be prepared to improve heating uniformity during welding, avoid arcing, and reduce contamination in the weld line. In one embodiment, the ends 124, 126 of the first and second work pieces 104, 108 may be prepared to be tapered ends, wherein areas of cross sections of the work pieces 104, 108 gradually reduce from the bodies of the work pieces 104, 108 to the tips. The tapered ends 124, 126 allow a contact surface 128 that is smaller than the cross sections of the first and second work pieces 104, 108. The smaller contact surface 128 enables a more planar contact than a larger contact surface, thus, providing a more uniform heating and resulting in a uniform weld. In one embodiment, the contact surface 128 may be less than about 25% of the cross section of the work pieces 104, 108. The contact surface 128 may be between about 15% to about 25% of the cross section of the work pieces 104, 108.
During process, the tapered ends 126, 128 are pushed into each other to form a weld.
The tapered ends 208, 210 may be prepared by chamfering. As shown in
The size of the end surfaces 220, 222 may be smaller than the cross sections of the work pieces 204, 206. In one embodiment, the size of the end surfaces 220, 222 may be less than 80% of the size of the cross section of the body of the work pieces 204, 206. In another embodiment, the size of the end surfaces 220, 222 may be between about 15% to about 25% of the size of the cross section of the body of the work pieces 204, 206. Without being bound by theory, it is believed the reduced size of the end surfaces 220, 222 eliminates air pockets between the work pieces 204, 206 when in contact, thus improving heating uniformity. The tapered ends 208, 210 allow the area of the contact surface to gradually increase during welding resulting in uniform weld.
Cross section of continuous sucker rods may have different shapes, for example, circular, elliptical, semi-elliptical.
Box 310 of the method 300 includes preparing the ends of the two work pieces to be connected. For example, the ends of the work pieces may be prepared to include a gradually increased sectional area so that the contact areas of the two work pieces increase during the course of butt welding. In one embodiment, preparing the ends includes forming an abutting surface on a tip of the end of each work pieces. The abutting surfaces may be planar to enable a planar contact between the two work pieces, thus, avoid arc between the work pieces when electrical power is applied to the two work pieces. The ends of the work pieces may be prepared as shown in
Box 320 of the method 300 includes positioning the first and second work pieces to establish contact at the prepared ends of the two work pieces. In one embodiment, the first and second work pieces may be secured to a stationary clamp die and a movable clamp die respectively, such as the first clamp die 102 and the second clamp die 106 of the resistive-butt welding system 100. A planar contact between the ends of the two work pieces may be established by moving the movable clamp die towards the stationary clamp die. The first and second work pieces may be in planar contact at the abutting surfaces and aligned axially.
Box 330 of the method 300 includes applying a weld current across the first and second work pieces to generate a resistive heat at the abutting ends. The weld current may be applied by switching on a power source 116 of the resistive-butt welding system 100 that is connected to the clamp dies in which the work pieces are secured. The weld current may be direct current (DC) or alternating current. In one embodiment, the weld current may be applied by applying a constant voltage between the two work pieces. The planar contact at the abutting surfaces of the prepared ends of the work pieces prevents any arc or flashing from occurring between the work pieces and to maintain a minimum contact force between the work pieces when the weld current is applied. When the weld current is applied, the electrical resistance at the interface of the two work pieces causes heat to generate at the interface. In one embodiment, the weld current is tailored to generate enough heat to soften but not melt the prepared ends of the work pieces.
In one embodiment, a force is applied to urge the work pieces towards each other while applying the current. As the heat from the weld current softens the prepared ends of the work pieces, the force moves the work pieces into each other whereby the prepared ends upset. Because the prepared ends have gradually increased cross sections, the area of cross section at the interface of the two work pieces increases as the two work pieces move towards each other. The force may be applied using any suitable devices. In one embodiment, the force may be applied by an actuator, such as the actuator 110, coupled to the movable clamp die to which one of the work piece is secured.
Without being bound by theory, it is believed the small contact area at the beginning of applying the weld current allows uniform current distribution across the abutting surfaces. The gradual increase of the contact area helps maintain the uniform current distribution, thus resulting in a high quality weld.
Box 340 of the method 300 includes ceasing or reducing the weld current while continuously moving the two work pieces towards each other to form the weld. In one embodiment, the weld current may cease when the interface of the work pieces reaches a desired temperature such that no additional heat is needed to complete the welding process.
Box 350 of the method 300 includes stopping movement of the work pieces. As the work pieces are moved towards each other, the contact area between the ends increases. The movement of the work pieces may be stopped at a predetermined time, at a predetermined load, at a predetermined contact force, or at a predetermined contact pressure.
Box 360 of the method 300 includes performing a heat treatment to the weld. While the work pieces move to form the weld, microstructures in the ends of the work pieces may be disrupted. A heat treatment may be performed on the weld to achieve desired mechanical properties in the weld. In one embodiment, a heat treatment current is applied for a short period of time. The heat treatment current may be applied by switching on a power source that is connected to the clamp dies, such as the power source 116 of the resistive-butt welding system 100. The heat treatment current may be direct current (DC) or alternating current (AC). In one embodiment, the heat treatment current may be applied by applying a constant voltage between the two work pieces. In one embodiment, the weld may be quenched after the heat treatment current is applied. For example, high pressure gas quenching may be applied after the heat treatment supply. In one embodiment, a gas pressure between about 15 psi to about 20 psi may be applied to perform high pressure gas quenching. In one embodiment, a gas pressure between about 20 psi to about 25 psi may be applied to perform high pressure gas quenching. In one embodiment, a gas pressure between about 50 psi to about 60 psi may be applied to perform high pressure gas quenching. In one embodiment, a gas pressure between about 65 psi to about 75 psi may be applied to perform high pressure gas quenching.
In
The lines 406, 407, 408, and 409 relate to a second set of sucker rods that are thicker than the first set of sucker rods. Line 406 shows the current applied across the two sucker rods over time. Line 407 shows the heat treatment current applied to the sucker rods. Line 408 shows the position of the second sucker rod over time. Line 409 shows the gas pressure applied during high pressure gas quenching. Between time t0 to t1, a welding current is applied as the second sucker rod moves toward the first sucker rod. The weld current for the second set of sucker rods is higher than the weld current for the first set of sucker rods. Between time t1 and t6, the weld current is switched off while the second sucker rod continues to move and reaches distance d2. During the time between t6 and t7, a heat treatment current is applied while the second sucker rod remains substantially stationary. During the time t8 and t9, a high pressure gas is applied to the weld to quench the weld.
The resistance-butt welding may be performed manually and the parameters may be controlled by operator's in response to observation. In one embodiment, the resistance-butt welding may be automatically controlled to achieve repeatable quality.
Box 510 of the method 500 includes establishing ranges of parameters empirically. The parameters may include one or more of value and duration of the weld current, speed and distance of movable sucker rod, and timing, duration and value of the heat treatment current. For each setting, such as a combination of size, shape, and material of sucker rods, ranges of parameters may be established by conducting resistance-butt welding under various process parameters and performing a test to determine whether the process parameters yield an acceptable weld. In one embodiment, a bend test (to be discussed with
Box 520 of the method 500 includes preparing ends of work pieces to be welded together. Box 520 may be similar to Box 310 of the method 300. In one embodiment, the size, shape and dimension of prepared ends may be prepared according to empirical tests.
Box 530 of the method 500 includes loading the prepared work piece onto an automatic resistance-butt weld station, such as the resistance-butt weld system 100.
Box 540 of the method 500 includes setting weld parameters according to the established range of parameters. In one embodiment, the parameters may be set by selecting size and shape of the work pieces in a controller which determines the parameters according to stored ranges of parameters.
Box 550 of the method 500 includes starting the automatic weld station to perform the resistance-butt weld, for example, from box 320 to box 350, automatically. The welding process may be completed in less than one minute, for example about 30 seconds.
The automatic weld may be performed by monitoring and controlling various parameters, such as force, distance, current, and speed. The parameters may be measured by corresponding sensors and monitored by a controller to achieve a closed loop control.
Embodiments of the present disclosure provide a bend performance test to detect weld line defects. Traditional tensile performance tests are performed to determine whether a weld line in a continuous sucker rod is defective. However, traditional tensile performance tests are inefficient for investigating weld line defects.
Embodiments of the present application may include a method for testing a weld in a rod. The method may include bending the rod at the weld to a pre-determined angle, and examining the weld to determine the quality of the weld.
In one embodiment, the per-determined angle is about 90 degrees.
In one embodiment, examining the weld includes examining presence of ductile tearing.
In another embodiment, examining the weld includes examining presence of rapid brittle failure.
In one embodiment, the method further includes forming the weld by preparing ends of a first work piece and a second work piece by reducing cross sections of the ends, and welding the first work piece and the second work piece at the prepared ends.
While the foregoing is directed to embodiments of the present disclosure, other and further embodiments may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.
This application claims benefit of U.S. Provisional Patent Application No. 62/100,139, filed Jan. 6, 2015, and entitled “Resistance Welding Method for Sucker Rod” which is herein incorporated by reference in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| 62100139 | Jan 2015 | US |
