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Title:
MOTOR REVERSAL SYSTEM FOR LINEAR DRIVE WELL PUMPS
Document Type and Number:
WIPO Patent Application WO/2016/057330
Kind Code:
A1
Abstract:
A reciprocating well pump assembly has a barrel (29), a plunger (34), a travelling valve (31), and a standing valve (33). A linear converter (41) has a rotating component (43) and an axially movable component (47), the axially movable component (47) being cooperatively engaged with the plunger (34) for stroking the plunger (34). A motor (23) rotates the rotating component (43). A reversing means (63 or 65, 67) reverses direction of the rotating component (43) at a top of the up stroke and at a bottom of the down stroke.

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WO/2005/015024GALVANIC CORROSION PROTECTION APPARATUS FOR A PUMP
WO/1992/012346PUMPS
WO/1986/000116A PUMP
Inventors:
TETZLAFF STEVEN K (US)
LAWSON PETER F (US)
Application Number:
PCT/US2015/053729
Publication Date:
April 14, 2016
Filing Date:
October 02, 2015
Export Citation:
Click for automatic bibliography generation   Help
Assignee:
BAKER HUGHES INC (US)
International Classes:
F04B47/00; F04B17/03; F04B47/06
Foreign References:
US20140105759A12014-04-17
US6497281B22002-12-24
US20090068026A12009-03-12
US20130186638A12013-07-25
US6497561B22002-12-24
Attorney, Agent or Firm:
HENDRYX, Thomas, N. (P.O. Box 4740Houston, TX, US)
Download PDF:
Claims:
Claims

1. A reciprocating well pump assembly, comprising: a barrel (29) having an axis; a plunger (34) reciprocally carried within the barrel (29) between an up stroke and a down stroke; a travelling valve (31) in the ban-el (29) that moves with the plunger (34) to lift well fluid during the up stroke; a standing valve (33) mounted to the barrel (29) through which the well fluid flows during the up stroke; a linear actuator (41 ) having a rotating component (43) and an axially movable component (47), such that rotation of the rotating component (43) moves the axially movable component (47) axially, the axially movable component (47) being cooperatively engaged with the plunger (34) for stroking the plunger (34) axially; and a motor (23) cooperatively engaged with the rotating component (43) of the linear actuator (41) for rotating the rotating component; characterized by: reversing means (63 or 65, 67) for reversing a direction of the rotating component (43) at a top of the up stroke and at a bottom of the down stroke.

2. The assembly according to claim 1, further comprising a controller (61) that supplies power to the motor (23), and wherein the reversing means comprises: a timer (63) selected to provide an estimated elapsed time for the up stroke and for the down stroke, and providing a signal to the controller (61) to reverse a direction of the power being supplied.

3. The assembly according to claim 1 , further comprising a controller (61 ) that supplies power to the motor (23), and wherein the reversing means comprises: an up stroke sensor (67) mounted to the assembly that senses when the plunger (34) nears the top of the up stroke; a down stroke sensor (65) mounted to the assembly that senses when the plunger (34) nears the bottom of the down stroke; and the up stroke and the down stroke sensors (67, 65) being in electrical communication with the controller (61) to reverse a direction of the power being supplied to the motor (23) upon receipt of a signal from the up stroke sensor (67) and a signal from the down stroke sensor (65).

4. The assembly according to claim 3, further comprising: a housing (40) in which the linear actuator (41) is located; and wherein the up stroke and the down stroke sensors (67, 65) are mounted to the housing (40).

5. The assembly according to claim 1 , wherein the liner actuator (41) comprises: a helical track rod(45) that rotates in unison with the rotating component (43), the helical track rod (45) having a single helical groove (46); and wherein the rotating component comprises a driver cage (47) carried on the helical track rod (45).

6. The assembly according to claim 1 , wherein the motor (23) is a three-phase electrical motor, and the assembly further comprises: a controller (61) that supplies alternating current to the motor (23); and the reversing means (63 or 56, 67) causes the controller (61) to supply the alternating current in one phase sequence during the up stroke and in another phase sequence during the down stroke.

7. The assembly according to claim 5, wherein: the controller (61) comprises a variable speed drive that varies a speed of the motor (23) by changing a frequency of power supplied to the motor; and the controller (61 ) is programmed to ramp down a speed of the rotating component (45) before each reversal and ramp up the speed after each reversal.

8. The assembly according to claim 1 , wherein the motor (23) is a three-phase electrical motor, and the assembly further comprises: a controller (61) that supplies alternating current to the motor (23); wherein the reversing means causes the controller (61) to supply the alternating current in one phase sequence during the up stroke and in another phase sequence during the down stroke; and wherein the reversing means comprises: a timer (63) selected to provide an estimated elapsed time for the up stroke and for the down stroke, and providing a signal to the controller (61) to change the phase sequence of the alternating current supplied to the motor (23).

9. The assembly according to claim 1 , wherein the motor (23) is a three-phase electrical motor, and the assembly further comprises: a controller (61) that supplies alternating current to the motor (23); wherein the reversing means causes the controller (61) to supply the alternating current in one phase sequence during the up stroke and in another phase sequence during the down stroke; and wherein the reversing means comprises: an up stroke sensor (67) mounted to the assembly that senses when the plunger (34) nears the top of the up stroke; a down stroke sensor (65) mounted to the assembly that senses when the plunger (34) nears the bottom of the down stroke; and the up stroke and the down stroke sensors (67, 65) being in electrical communication with the controller (61) to change a phase sequence of the alternating current being supplied to the motor (23) upon receipt of a signal from the up stroke sensor and a signal from the down stroke sensor.

10. A method of pumping well fluid from a well, comprising: lowering into the well a reciprocating well pump assembly (1 1 ) comprising a barrel (29), a plunger (34) reciprocally carried within the barrel (29), a motor (23), and a linear actuator (41); powering the motor (23) to rotate a drive shaft (43) in a first direction; and with the linear actuator (41) converting the rotational movement of the drive shaft (43) into linear movement, causing the plunger (34) to move upward in an up stroke to lift well fluid up the well; characterized by: at a top of the up stroke, reversing a direction of the drive shaft (43) to a second direction, and with the linear actuator (41), causing the plunger (34) to move downward in a down stroke; and at a bottom of the down stroke, reversing the direction of the drive shaft (43) back to the first direction.

1 1 . The method according to claim 10, wherein reversing the direction of the drive shaft (43) at the top of the up stroke and at the bottom of the down stroke comprises signaling a controller (61) for the motor (23) based on estimated elapsed time for each of the strokes.

12. The method according to claim 10, wherein: reversing the direction of the drive shaft (43) at the top of the up stroke comprises sensing when the plunger (34) nears the top of the up stroke; and reversing the direction of the drive shaft (43) at the bottom of the down stroke comprises sensing when the plunger (34) nears the bottom of the down stroke.

13. The method according to claim 10, wherein: powering the motor (23) comprises providing three-phase alternating current to the motor; and reversing the direction of the rotating component (43) from the first direction to the second direction comprises changing a sequence of the phases of the alternating current supplied.

14. The method according to claim 10, further comprising: with a variable speed drive (61), controlling the motor (23) to ramp down a speed of the rotating component (43) when nearing the top and nearing the bottom of each of the strokes; and with the variable speed drive (61), controlling the motor (23) to ramp up the speed of the rotating component (43) after reversing the direction.

15. The method according to claim 10, wherein: powering the motor (23) comprises providing three-phase alternating current to the motor; reversing the direction of the drive shaft (43) at the top of the up stroke and at the bottom of the down stroke comprises sensing when the plunger (34) nears the top of the up stroke and nears the bottom of the down stroke and signaling a controller (61) for the motor (23); and with the controller (61), changing a phase sequence of the three-phase alternating current being supplied.

Description:
PATENT APPLICATION

Motor Reversal System For Linear Drive Well Pumps

Cross Reference to Related Application

This application claims priority to US provisional application 62/060,380, filed

October 6, 2014, the full disclosure of which is hereby incorporated by reference herein for all purposes.

Field of the Disclosure

This disclosure relates in general to linear actuator driven reciprocating well pumps and in particular to a system that reverses the direction of the motor at the top and the bottom of the stroke of the reciprocating pump.

Background

A reciprocating well pump normally has a barrel secured to a string of production tubing. A plunger located in the barrel strokes between a down stroke and an up stroke. A travelling valve mounted with the plunger opens a bore of the plunger during the down stroke to flow well fluid in the bore of the plunger into the barrel above the plunger. During the up stroke, the travelling valve closes to lift the well fluid from the barrel upward. A standing valve at an upper end of the barrel will be closed during the down stroke and opens on the up stroke to allow the well fluid being lifted to flow up into the production tubing.

A string of rods may extend down the tubing for stroking the plunger. Other types of stroking devices are known. For example, an electric motor may be installed below the barrel. A linear actuator coupled between the motor and the plunger converts rotary motion of an output shaft of the motor into linear motion of the plunger. The linear actuator may include a rotatable rod with helical grooves engaged by a ball nut that is restrained from rotating. The rotation of the linear actuator shaft causes the ball nut to move up one set of helical grooves until reaching a crossover at the top of the linear actuator shaft, then move down a second set of helical grooves. A linking member connects the ball nut with the plunger to move the plunger in unison. The linear actuator shaft rotates in only one direction.

While reciprocating pumps with linear actuators and electric motors work well, wear and fatigue can eventually occur in the linear actuator. For example, wear and fatigue may occur between the ball nut and the helical grooves over time. The wear and fatigue may particularly occur at the top and bottom of the stroke where the ball nut moves from one set of helical grooves to the other set.

Summary

The reciprocating well pump assembly of this disclosure has a barrel and a plunger reciprocally carried within the barrel between an up stroke and a down stroke. A travelling valve in the barrel moves with the plunger to lift well fluid during the up stroke. A standing valve is mounted to the barrel for allowing well fluid to flow into the production tubing during the up stroke. A linear actuator has a rotating component and an axial ]y movable component. Rotation of the rotating component moves the axially movable component axially. The axially movable component is cooperatively engaged with the plunger for stroking the plunger. A motor is cooperatively engaged with the rotating component of the linear actuator for rotating the rotating component. A reversing means reverses a direction of the rotating component at a top of the up stroke and at a bottom of the down stroke. A controller supplies power to the motor. In one embodiment, the reversing means comprises a timer selected to provide an estimated elapsed time for the up stroke and for the down stroke. The timer provides a signal to the controller to reverse a direction of the power being supplied.

In another embodiment, the reversing means comprises an up stroke sensor mounted to the assembly that senses when the plunger nears the top of the up stroke. A down stroke sensor mounted to the assembly senses when the plunger nears the bottom of the down stroke. The up stroke and the down stroke sensors are in electrical communication with a controller to reverse a direction of the power being supplied to the motor upon receipt of a signal from the up stroke sensor and a signal from the down stroke sensor.

The assembly includes a housing in which the linear actuator is located. In the embodiment having up stroke and down stroke sensors, the sensors are mounted to the housing,

The liner actuator comprises a helical track rod that rotates in unison with the rotating component. The helical track rod has a single helical groove. The rotating component comprises a driver cage carried on the helical track rod.

The motor may be a three-phase electrical motor. A controller supplies alternating current to the motor. The reversing means causes the controller to supply the alternating current in one phase sequence during the up stroke and in another phase sequence during the down stroke.

The controller may comprise a variable speed drive that varies a speed of the motor by changing a frequency of power supplied to the motor. The controller may be programmed to ramp down a speed of the rotating component before each reversal and ramp up the speed after each reversal.

Brief Description of the Drawings

Figs. 1 A and IB comprise a side view of a pump assembly in accordance with this disclosure.

Figs. 2A and 2B comprise a sectional view of part of the pump assembly of Figs. 1 A and

IB.

Fig. 3 is a schematic view of the system of Figs 2A and 2B.

Fig. 4 is a partial schematic view of an alternate embodiment of a system for reversing the motor at the top and bottom of the stroke.

Detailed Description of the Disclosure

Referring to Fig 1 A, a well pump assembly 11 is illustrated suspended on a string of production tubing 13. In this example, well pump assembly 1 1 includes a tubular sub 15 with inlet ports 16. Sub 15, which may be considered to be a part of production tubing 13, secures by threads to the lower end of production tubing 13. Pump assembly 1 1 may be used in inclined and horizontal wells, thus the terms "upper" and "lower" are used only for convenience and not in a limiting manner. A tubular landing receptacle 17 secures by threads to the lower end of sub 15.

Referring to Fig. IB, landing receptacle 17 secures to the upper end of a seal or pressure equalizing section 19. A gear reducer 21 secures to the lower end of seal section 19 in this embodiment. An electrical motor 23 secures to the lower end of gear reducer 21. Motor 23 is filled with a dielectric lubricant. Seal section 19 has a movable component, such as a bag or bellows, that reduces a pressure differential between the dielectric lubricant in motor 23 and the hydrostatic pressure of the well fluid surrounding motor 23. A sensing unit (not shown) optionally may be attached to the lower end of motor 23 to provide readings of pressure, temperature, and other parameters. A power cable (not shown in Figs. 1 A, IB) will extend alongside tubing 13 from a wellhead or production tree at the top of the well to provide power to motor 23.

Figs. 2 A - 2C show the components normally located within sub 15, which has been removed from these figures for clarity. Referring to Fig. 2A, pump 27 has a barrel 29, a travelling valve 31, a standing valve 33, and a piston or plunger 34, all of which are shown schematically. Standing valve 33 secures to the upper end of barrel 29, and travelling valve 31 secures to plunger 34 for axial movement with plunger 34 within barrel 29 between an up stroke and a down stroke. An intake 35 located in barrel 29 below plunger 34 admits well fluid into barrel 29. During the down stroke, the well fluid flows through travelling valve 31 while travelling valve 31 moves downward. During the down stroke, standing valve 33 is closed, preventing well fluid in production tubing 13 from flowing downward past standing valve 33. During the up stroke, travelling valve 31 closes, causing the upward movement of plunger 34 to push the well fluid above plunger 34 upward through standing valve 33, thereby lifting the column of well fluid in production tubing 13 an increment. At the top of the stroke, standing valve 33 closes. The length of the stroke may be selected based on several factors, including the depth of pump 27 in the well. A typical stroke length may be from about 6 to 10 feet, for example. In this embodiment, a landing collar 37 on the upper end of pump 27 frictionally engages the interior of production tubing 13 (Fig. 1 A) to resist movement of barrel 29 once installed within tubing 13. An axially reciprocating rod 39 strokes plunger 34. Referring to Fig. 2B, reciprocating rod 39 is located within a tubular housing 40 that also contains a reversing linear actuator 41 for reciprocating rod 39. Housing 40 secures to barrel 29. Linear actuator 41 is engaged on its lower end by a rotating component or drive shaft 43, which is rotated by motor 23. Linear actuator 41 transforms the rotating movement of drive shaft 43 into axial movement of rod 39.

Linear actuator 41 has a helical tracked rod 45 that is rotated by drive shaft 43, but does not move axially. Helical tracked rod 45 has a single helical groove or rib 46 extending helically from a lower end to an upper end. An axially movable component or driver cage 47 fits around helical tracked rod 45 and is axially movable thereon. Driver cage 47 is restrained from rotating and has an engagement member, such balls, a diamond element, or a pawl, that rides in helical groove 46. If helical tracked rod 45 is rotating clockwise, driver cage 47 moves in a first axial direction, such as upward, relative to tracked rod 45. If helical tracked rod 45 is rotating counterclockwise, driver cage 47 moves axially in the opposite direction, such as downward. A non rotating tube 49 attaches to and extends upward from driver cage 47 for movement in unison. Helical tracked rod 45 extends through tube 49 and rotates relative to tube 49. A non rotating bearing 51 at the upper end of tube 49 slides axially along the inner diameter of housing 40 and facilitates axial non rotating movement of tube 49. Reciprocating rod 39 has a lower end fixed to bearing 51 for axial movement therewith.

In this example, motor 23, gear reducer 21 , and seal section 19 (Fig. IB) are secured to a lower end of landing receptacle 17, which in turn has an upper end secured to sub 15 of production tubing 13; thus these components are installed when production tubing 13 is run. Pump 27, linear actuator 41, and rotating drive shaft 43, are run through production tubing 13 into sub 15 after production tubing 13 has been installed. Alternately, rather than being installed within tubing 13, pump 27, linear actuator 41 and rotating drive shaft 43 could be mounted below the lower end of production tubing 13, along with motor 23, gear reducer 21 and seal section 19. Referring to Fig. 2C, a stabbing guide 53 on the lower end of rotating drive shaft 43 stabs into the drive shaft extending through seal section 19 within landing receptacle 17.

Alternately, motor 23 could be run through tubing 13, as well.

Motor 23 (Fig. 1) is preferably a three phase motor. Further, motor 23 may be a four pole motor, which can run at half speed compared to a three phase frame. Optionally, motor 23 could be a hydraulic motor rather than an electric motor. Motor 23 is capable being repetitively reversed in rotational directions. For example, when motor 23 is rotated clockwise, when viewed from above, rotating drive shaft 43 causes driver cage 47, tube 49, bearing 51 , reciprocating rod 39 and travelling valve 31 to stroke upward. When motor 23 is rotated counterclockwise, when viewed from above, rotating drive shaft 43 causes driver cage 47, tube 49, bearing 51 , reciprocating rod 39 and travelling valve 31 to stroke downward.

Referring to Fig. 3, a wellhead or tree 55 supports production tubing 13 in a cased well 57. A power cable 59, which normally includes a motor lead, extends alongside tubing 13 to motor 23. A controller or power source, which is preferably a variable speed drive 61, is adjacent tree 55 and connects to power cable 59 to supply electrical power to motor 23. Variable speed drive 61 supplies alternating current at frequencies that can be varied. The higher the frequency, the higher the rotational speed of motor 23. Also, the power supplied by variable speed drive 61 determines the direction of rotation of motor 23. The three conductors of power cable 59 are wound at a selected pattern through the stator of motor 23, and the sequence of each the three phases determines the direction of rotation. Variable speed drive 61 is configured to change the phase sequence to reverse the rotation at the top of the up stroke and the bottom of the down stroke. As an example, if the AC power is supplied to the phases in the order of phase A, phase B and phase C, the rotation of motor 23 is in one direction. If variable speed drive 61 supplies the power in another order, such as phase B, phase A, phase C, the rotation of motor 23 is in the opposite direction.

In this example, a timer 63 provides a signal to variable speed drive 61 when to reverse the direction of rotation of motor 23. Timer 63, which would be incorporated with variable speed drive 61 , can be set for a desired stroke length. The operator empirically determines how many seconds are required to complete movement from the bottom of the stroke to the top at a selected rate, and inputs that value to timer 63. The operator also selects how much time would be required to complete movement from the top of the up stroke to the bottom of the down stroke. These time values cause reciprocating axial movement of travelling valve 31 (Fig. 2A) from a known point to a second known point. Preferably, variable speed drive 61 will slow the rotation before reversal when nearing the top and bottom of the stroke. Also, variable speed drive 61 may ramp up the rotational speed at a desired rate after each reversal. Although a variable speed drive is preferable, other surface controllers could be fitted with timer type devices. The time selected for the down stroke could differ from the time selected for the up stroke. A delay of selected duration with motor 23 not rotating in either direction could occur before each reversal at the top of the stroke and the bottom of the stroke. The time selected for each up stroke and each down stroke could be about 10 seconds to one minute, for example. In the operation of the first embodiment, variable speed drive 61 supplies power to rotate motor 23 in a direction to cause an up stroke. Motor 23 rotates tracked rod 45 in a direction that causes non rotating driver cage 47 to move upward on tracked rod 45. Driver cage 47 pushes upward reciprocating rod 39, plunger 34 and travelling valve 3 1 , which is closed. Travelling valve 31 lifts well fluid in barrel 29 up through open standing valve 33 and into production tubing 13. The upward movement lifts the column of well fluid in production tubing 13 an increment, causing well fluid to flow out the production tree 55. During the up stroke, well fluid flows through intake 35 into barrel 29 below travelling valve 31.

At or near the top of the up stroke, timer 63 will signal variable speed drive 61 to reverse the direction of rotation of motor 23. Motor 23 begins rotating helical tracked rod 45 in the reverse direction. Driver cage 47 begins moving downward, causing standing valve 33 to close and travelling valve 31 to open. The well fluid contained in barrel 29 flows upward through travelling valve 31 to refill barrel 29. Timer 63 again reverses motor 23at the bottom of the down stroke.

In a second embodiment, illustrated in Fig. 4, components that are the same as in the first embodiment employ the same reference numerals. A lower sensor 65 at least partially mounted within housing 40 senses when travelling valve 31 is nearing the bottom of the stroke and provides a signal to variable speed drive 61 (Fig. 3) to cause the rotational direction of motor 23 (Fig. IB) to reverse. An upper sensor 67 senses when travelling valve 31 is nearing an upper end of the up stroke and provides a signal to variable speed drive 61 (Fig. 3), causing the rotation direction of motor 23 to reverse. Variable speed drive 61 will ramp up and down the rotational speed with each reversal. Some variable speed drives have a capability to slow and change direction without actually coming to a complete stop. Sensors 65, 67 are mounted at fixed locations axially apart from each other. Sensors 65, 67 may be mounted in various places to sense the approach of one of the components that moves axially during the strokes. In the example shown, both sensors 65, 67 are mounted within housing 40 to sense the approach of bearing 51 at the top and bottom of the stroke. Sensor 67 is mounted near the upper end of housing 40 and sensor 65 a distance below that is based on the desired length of the stroke.

Sensors 65, 67 may be a variety of types, including proximity sensors using magnets and Hall effect types.

Sensors 65, 67 may connected to a separate instrument wire that is a part of power cable 59 leading to the surface. Alternately, the signals from sensors 65, 67 could be superimposed on the three electrical conductors of power cable 59 that supply three-phase power to motor 23 (Fig. 3) and extend alongside linear actuator 41. In the embodiment of Figure 4, unlike the first embodiment, linear actuator 41 and pump 27 (Fig. 2) are optionally not installed within sub 15 (Fig 1 A) of production tubing 13. Rather the lower end of production tubing 13 (Fig. 1A) will be at the discharge of pump 27 (Fig. 2A).

While the disclosure has been described in only two of its forms, it should be apparent to those skilled in the art that various changes may be made. For example, the standing and travelling valves may have a variety of configurations.