WIRELINE/COILED TUBING RETRIEVABLE WELL PUMP

Abstract: A well pump assembly has an electric motor (21) that is secured to a lower end of a string of production tubing. The motor is powered by a power cable (25) that extends alongside the tubing to the surface. The motor has an upper end with a drive shaft coupling (29). The pump (37) for the motor is lowered through the productino tubing on a wireline, wire rope or coiled tubing. The pump has a lower end which has a driven shaft coupling (47) that makes up in stabbing engagement with the drive shaft coupling when the pump reaches the motor. A head (67) on the upper end of the pump assembly latches the pump in place.

Description: WIRELINE/COILED TUBING RETRIEVABLE WELL PUMP Technical Field This invention relates in general to well pumps, and in particular to a well pump which is operated by a submersible electric motor and is retrievable through tubing. Background Art Electrical submersible well pumps for deep wells are normally installed withing casing on a string of tubing. Usually the tubing is made up of sections of pipe screwed together. Coil tubing deployed from a reel is also used to a lesser extent. The motor is supplied with power through a power cable that is stapped alongside the tubing. The pump is typically located above the motor, is connected to the lower end of the tubing, and pumps fluid through the tubing to the surface. One type of a pump is a centrifical pump using a large number of stages, each stage having an impeller and a diffuser. Another type of pump, for lesser volumes, is a progressive cavity pump. This pump utilizes a helical rotor that is rotated inside an elastomeric stator which has double helical cavities. The stator is located inside a metal housing. Periodically, the pump assembly must be pulled to the surface for repair or replacement. This involves pulling the tubing, which is time consuming. A workover rig is necessary for production tubing, and a coiled tubing unit is needed to pull coiled tubing. Often, the electrical motor needs no service, rather the service needs to be performed only on the pump. Sometimes the only change needed is to change the size of the pump without changing the size of the motor. However, the motor, being attached to the lower end of the pump, is also pulled along with the tubing. Damage to the power cable is not uncommon when pulling the tubing. Summary of Invention In this invention, the motor is secured to and installed to the lower end of the tubing. The power cable to the motor is strapped alongside the tubing. The pump, however, is sized to be lowered through the tubing. The pump has a driven shaft extending downward from it that mates with a drive shaft extending upward from the motor. When the pump reaches the motor, the driven shaft will stab into the drive shaft. A head assembly is located at the upper end of the pump for engagement by a running tool to lower the pump through the tubing and retrieve it. The head may be secured to wireline, wire rope or coiled tubing which inserts through the production tubing. The head lands within a sub in the production tubing to latch the pump in place. The pump pumps well fluid up through the tubing. When it is desirable to change out or repair the pump, the operator lowers a running tool through the production tubing and latches it to the head. The operator pulls the pump, leaving the motor in place. Subsequently, the running tool lowers the repaired or replacement pump back through the tubing into engagement with the motor. Brief Description of Drawings Figures 1A and IB are partial sectional view of a pump assembly constructed in accordance with this invention. Figure 2 is an enlarged sectional view of an upper portion of the motor assembly and a lower portion of the pump of Figure 1A. Figure 3 is an enlarged partial sectional view of the head of the pump assembly of Figure 1A. Figure 4 is a sectional view similar to Figure 2, but showing the pump assembly out of engagement with the drive shaft of the motor. Best Mode for Carrying Out the Invention Referring to Figure 1, a string of production tubing 11 extends from the surface into a cased well. Production tubing 11 is a conduit made up of sections of pipe, for example four inches in diameter, screwed together. A tubular adapter 13 is located at and forms the lower end of tubing 11, adapter 13 being connected to tubing 11 by a threaded collar 15. A motor assembly is secured to adapter 13. The motor assembly includes a seal section 17 mounted to a gear reducer 19 which in turn is mounted to an AC electric motor 21. In the embodiment shown, motor 21 has a pressure sensor 23 secured to its lower end for sensing pressure in the well. A three-phase power cable 25 connects to motor 21 and extends alongside tubing 11 to the surface for receiving power. Motor 21 typically operates at about 3600 rpm, which is reduced by gear reducer 19 to a lower speed. Seal section 17 seals well fluid from the interior of motor 21 and also equalizes pressure differential between the lubricant in motor 21 and the exterior . A drive shaft 27 extends upward from and is driven by motor 21. As shown in Figure 2, drive shaft 27 has a coupling 29 on its upper end of which forms a part of drive shaft 27 and has a splined upper end 30. Coupling 39 is located within a reduced diameter portion of adapter 13. Bearings or bushings 31 rotatably support coupling 29 on the axis. Adapter 13 includes within it a receptcle 33 which has cylindrical walls leading to a lower tapered portion 33a which tapers downward. A drain hole 35 is located at the lower end of receptacle 33 for egress of debris . Referring again to Figure 1A, a progessing cavity pump 37 is driven by motor 21. Progressing cavity pump 37 is conventional, having a metal rotor 39 which has an exterior helical configuration. Rotor 39 orbitally rotates in an elastomeric stator 41. Stator 41 has double helical cavities located along its axis through which rotor 39 obits. A flexible shaft housing 43 is secured to the lower end of pump 37 and may be considered a part of pump 37. A flexible shaft 45 is located within housing 43 and is constructed in accordance with U.S. Pat. 5,501,580, March 26, 1996. Flexible shaft 45 flexes to allow orbiting at its upper end and pure rotation at its lower end. Flexible shaft 45 is connected on its upper end to rotor 39 and may be considered as part of a driven shaft of pump 37. Referring again to Figure 2, flexible shaft 45 has a driven shaft coupling 47 on its lower end which has a splined socket 49 that stabs into engagement with splined end 30 of drive shaft coupling 29. A guide 51 is attached to the lower end of housing 43 and surrounds coupling 47. Guide 51 comprises a plurality of radially extending blades, the inner edges of which are mounted to bushings 53 that allow rotation of driven shaft coupling 47 relative to guide 51. A key 55 serves as anti-rotation means for engaging the blades of guide 51 to prevent guide 51 from rotating. The outer edges of the blades of guide 51 circumscribe a diamter which matches receptacle 33, including a lower tapered portion that engages tapered portion 33a. As shown in Figure 4, guide 51 guides driven shaft coupling 47 into stabbing engagement with drive shaft coupling 29 and centralizes driven shaft coupling 47 once the makeup is achieved. A plurality of intake ports 59 are located in the lower portion of housing 43. A plurality of intake ports 61 are located in tubing 11 surrounding ports 59. Well fluid pumped by pump 37 is drawn in through intake ports 59, 61. Refering again to Figure 1A, a head assembly is mounted to the upper end 65 of pump 37. The head assembly includes spacing nipples 63, which are cylindrical sections of pipe through which well fluid will be discharged by pump 37. The head assembly also includes a head 67 mounted above spacing nipples 63. Head 67 is a tubular member having a passage through it for the passage of well fluid being discharged from pump upper end 65. Head 67 has an upper end that is adapted to be secured to a running tool (not shown) , which is deployed either by wireline, wire rope, or coiled tubing. Head 67 lands within a latch sub 69 which is connected into the string of tubing 11. Seals 71 located on head 67 seal the interior of latch sub 69. Latch sub 69 has an interior profile that cooperates with load bearing and locking members to land and retain pump 37 in place. Head 67 has a latch 73 which selectively latches head 67 to latch sub 69 to prevent upward movement of head 67. Head 67 also has a set of slips 75 which engage the profile of latch sub 69 to support the weight of and any downthrust from pump 37. Head 67, latch sub 69, latch 73 and slip 75 are shown schematically and are commercially available in general . Latch sub 69 also has a plurality of equalizing ports 77. A closure sleeve 79 is movable axially on sub 69 by a running tool to selectively open and close equalizing ports 77. When open, and when head 67 is retrieved, equalizing ports 77 allow fluid in tubing 11 to flow downward out equalizing ports 77 until reaching equilibrium with fluid in the casing. If it is necessary to pull tubing 11, this feature allows the fluid within tubing 11 to drain. In operation, during initial installation, the operator will connect the motor assembly together including pressure sensor 23, motor 21, gear reducer 19 and seal section 17. The operator connects this motor assembly to adapter 13, and connects adapter 13 to the lower end of a string of tubing 11. The operator connects latch sub 69 into tubing 11 above the drive shaft coupling 29 at a distance substantially equal to the length of the pump assembly. The operator then lowers the string of tubing 11 into the well to the desired depth. Power cable 25 is strapped alongside tubing 11 as tubing 11 is lowered into the well. The operator then makes up the pump assembly including pump 37, flex shaft housing 43, spacing nipples 63 and head 67. The operator latches head 67 to a running tool (not shown) . The running tool is fastened to a line, which may be wireline, wire rope, or coiled tubing. The operator lowers the pump assembly through tubing 11. Figure 4 shows guide 51 shortly before stabbing into engagement with drive shaft coupling 29. The operator lowers the pump assembly until the stabbing engagement is made up, as shown in Figure 2. Latch 73 and slips 75 (Fig. 3) will be actuated to support the weight of pump 37 and also prevent it from being pushed upward. The operator supplies power to power cable 25, which causes motor 21 to rotate, which in turn rotates flexible shaft 45 and rotor 39. Well fluid is drawn in through intake ports 61, 59. The well fluid pumps out upper end 65 and through head 67. The well fluid flows through production tubing 11 to the surface. When it is desired to change out pump 37 for repair or otherwise, the operator lowers the running tool on a line back into engagement with head 67. The running tool releases latch 73 and pulls upward on head 67. Pump 37 will move upward, bringing along with it flexible shaft 45 and guide 51 as illustrated in Figure 4. Motor 21 will remain in place while the operator pulls the pump assembly to the surface. Any debris contained within recepticle 33 may flow out through drain ports 35. The operator replaces the pump assembly in the same manner as discribed. The invention has significant advantages. By leaving the motor in place and retreiving only the pump, the operation to change out the pump is much faster. In the case of production tubing, a workover rig need not be employed for pulling the tubing. Damage to the power cable is avoided as the production tubing will remain in place. Reducing the expense of changing out the pump reduces the cost of using a pump of this nature in the well. While the invention has been shown only in one of its forms, it should be apparent to those skilled in the art that it is not so limited but is suseptable to various changes without departing from the scope of the invention.

Claims: We claim : 1. An apparatus for pumping fluid from a well, comprising in combination: a conduit adapted to extend into a well; an electric motor assembly which has a drive shaft, the motor assembly being carried by the conduit and lowered into and suspended in the well by the conduit; a pump assembly carried inside the conduit; a head at the upper end of the pump assembly for lowering the pump assembly through the conduit into engagement with the motor assembly and for retrieving the pump assembly while the motor assembly remains stationary; the pump assembly having a driven shaft which has a lower end that makes a stabbing engagement with the drive shaft as the pump assembly is lowered into engagement with the motor assembly; and an intake port in the conduit for entry of well fluid to the pump assembly for pumping the well fluid through the conduit to the surface. 2. The apparatus according to claim 1, wherein the pump assembly comprises a progressing cavity pump having a helical rotor which rotates within an elastomeric stator. 3. The apparatus according to claim 1 further comprising a latch which selectively latches the head to the conduit for preventing upward movement of the pump assembly after the pump assembly has engaged the motor assembly. 4. The apparatus according to claim 1 further comprising a power cable extending from the motor assembly alongside the conduit for connection to a power source at the surface. 5. A well pump assembly for mounting to a conduit extending into a well, comprising in combination: an electric motor which rotates a drive shaft; an adapter for connecting the motor to a lower end of the conduit such that the motor is lowered into and suspended in the well by the conduit; a power cable adapted to be strapped alongside the conduit from the motor to the surface for connection to a power source; a progressing cavity pump, the pump having a helical rotor which rotates within an elastomeric stator; a head at the upper end of the pump for lowering the pump through the conduit into engagement with the motor and for retrieving the pump through the conduit while the motor remains at the lower end of the conduit; and the pump having a driven shaft extending downward from the rotor of the pump which makes a stabbing engagement with the drive shaft as the pump is lowered into engagement with the motor. 6. The well pump assembly according to claim 5 further comprising a latch which selectively latches the head to the conduit for preventing upward movement of the pump after the pump is in engagement with the motor. 7. The well pump assembly according to claim 5, further comprising: a receptacle located in the adapter and surrounding an upper portion of the drive shaft, the receptacle having a tapered lower portion; a guide surrounding a lower end of the driven shaft, the guide having a lower tapered portion which mates with the tapered portion of the receptacle; and an anti-rotation key which locks the guide to the receptacle for preventing rotation of the guide relative to the receptacle. 8. A method for installing a pump for a well, comprising in combination: providing an electric motor assembly which has a drive shaft at an upper end of the motor assembly; providing a pump assembly which has a driven shaft at a lower end of the pump assembly; securing the motor assembly to a lower end of the conduit and lowering the motor assembly into the well on the conduit; then lowering the pump assembly through the conduit and stabbing the driven shaft of the pump assembly into engagement with the drive shaft of the motor assembly. 9. The method according to claim 8, further comprising latching the pump assembly to the conduit as the pump assembly reaches the motor assembly to prevent upward movement of the pump assembly. 10. The method according to claim 8, wherein the method also includes operating the pump assembly by supplying power to the motor assembly to operate the pump assembly, causing the pump assembly to pump well fluid through the conduit to the surface. 11. The method according to claim 10 further comprising extending a power cable from the motor assembly alongside the conduit to the surface; and the step of supplying power comprises supplying power to the power cable. 12. The method according to claim 8, wherein the method further comprises retrieving the pump assembly by the step comprising: pulling the pump assembly upward through the conduit while leaving the motor assembly secured to the conduit.

Inventors: COZZENS KENT H, TETZLAFF STEVEN K, COZZENS, KENT, H., TETZLAFF, STEVEN, K.
Applicants: BAKER HUGHES INC, BAKER HUGHES INCORPORATED
Application year: 1997
Main classification: E21B43
IPC codes: E21B43