US20160123123A1

US20160123123A1 - Reciprocating electrical submersible well pump

Info

Publication number: US20160123123A1
Application number: US14/533,124
Authority: US
Inventors: Iain Maclean; Kenneth J. Sears
Original assignee: Zilift Holdings Ltd
Current assignee: Zilift Holdings Ltd
Priority date: 2014-11-05
Filing date: 2014-11-05
Publication date: 2016-05-05

Abstract

A downhole pump system includes a magnetically operated rotary to linear motion converter coupled at a rotary input to a drive source. A reciprocating action positive displacement pump having a reciprocating input thereto is coupled to a linear motion output of the magnetically operated rotary to linear motion converter. An intake of the pump is in fluid communication with a wellbore region and a discharge of the pump is in fluid communication with a well conduit extending to Earth's surface.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

Not Applicable.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not applicable.

BACKGROUND

This disclosure is related to the field of well pumps used to lift fluids from within subsurface wells to the Earth's surface. More specifically, the disclosure relates to reciprocating, positive displacement well pumps that may be powered by a rotary machine such as an electric motor.
Many subsurface wells used to extract hydrocarbons from subsurface formations are constructed with small diameter tubing in order to increase velocity of fluids as they are moved to the surface. For example, 3.5 inch (88.9 mm) outer diameter may be used, but the tubing may be as small as 2.375 inch (60.3 mm) outer diameter. Such wells may extend to, for example, 10,000 feet (3,048 m) or more in depth.
During the productive life of such wells, the natural pressure in the hydrocarbon productive formation(s) may decrease, and water and/or gas condensate (liquid) may accumulate in the tubing. Accumulated water or other liquid such as gas condensate may exert hydrostatic pressure against the formation(s) thus reducing or stopping the flow of hydrocarbons out of the well. To recover hydrocarbon production, some of the accumulated liquid has to be pumped out of the well to reduce the hydrostatic pressure exerted against the productive formation(s).
The use of centrifugal electrical submersible pumps (“ESPs”) in wellbores is well known, however, centrifugal pumps may not be suitable for generating high discharge pressures together with low flow rates. Also, the performance and efficiency of centrifugal pumps is related to the diameter of the rotating impeller, and it is therefore impractical to build effective centrifugal pumps of very small diameter.
Positive displacement pumps, on the other hand, are well suited to deliver relatively high pressure, and depending on the type of pump, at relatively low flow rates. Reciprocating pumps are a well-established class of positive displacement pumps. A well-known pump system for artificial lift and for dewatering gas wells, among other purposes, is a ‘sucker rod’ pump, driven by surface machinery (e.g., a “pump jack”, hydraulic lift or similar device) and a rod string extending into the well to a reciprocating pump. The maximum depth the pump can be placed in the well may be limited by the weight of the rod string. The power required to lift the rod string on each stroke may be many times the useful pumping power required. The movement of the rod string in the tubing to actuate the pump causes friction, and can wear the rod string and the bore of the tubing, such that both may have to be replaced from time to time. Such replacement is a costly operation. Further, rod strings may be impracticable to use in highly deviated wells.
In some instances while a sucker rod pump may suit a particular downhole application, this may in fact not be selected in practice due to the complexities of providing a suitable reciprocating drive from surface.
U.S. Pat. No. 4,687,054 issued to Russell et al. and U.S. Patent Application Publication No. 2014/0144624 filed by Camacho Cardenas disclose possible solutions to problems associated with surface driven sucker rod pumps by driving a downhole sucker rod pump with a downhole linear motor. However, such linear motors often require complex control systems which are not always readily preferred in downhole environments due to the added costs and risk of failure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows one example embodiment of deployment of an electrical submersible pump (ESP) system.

FIG. 2 is a schematic illustration of the example embodiment pump system of FIG. 1, shown deployed in a drilled wellbore.

FIGS. 3A and 3B are schematic illustrations of an embodiment of a magnetic rotary to linear (R2L) motion converter, shown in different configurations.

FIG. 4 is a schematic perspective view of the R2L motion converter of FIG. 3A.

FIG. 5 is a schematic illustration of another example embodiment of a R2L motion converter.

FIG. 6 shows another example embodiment of a (R2L) motion converter.

FIG. 7 shows an example embodiment of a (R2L) motion converter comprising multiple elements.

FIG. 8 shows an example electric motor, R2L converter and reciprocating pump assembly.

FIG. 9 shows another example embodiment of an assembly as in FIG. 7 wherein the rotating part and the reciprocating part of the R2L motion converter are reversed.

FIG. 10 shows an example embodiment of an electric motor and R2L motion converter rotating portion enclosed in a sealed, pressure compensated housing.

FIG. 11 shows an example embodiment as in FIG. 10 wherein the components forming the rotating part of the R2L motion converter are opposed to that of the embodiment of FIG. 10.

FIG. 12 shows one example embodiment of a valve body for a positive displacement pump.

FIG. 13 shows another example of a valve body for a positive displacement pump.

FIG. 14 shows another example of a valve body for a positive displacement pump.

DETAILED DESCRIPTION

An aspect or embodiment of the present disclosure relates to a downhole pump system comprising a reciprocating action positive displacement pump having a fluid intake for providing fluid communication with a wellbore region and a fluid discharge for providing fluid communication with a well conduit.
A magnetically operated rotary to linear motion converter forming part of the system has a rotary motion input to be coupled to a downhole rotary drive source, and a linear reciprocating motion output coupled to a linear reciprocating motion input of the reciprocating action positive displacement pump.
In some embodiments, while in use, the reciprocating pump may be located within a wellbore such that the fluid intake is arranged in fluid communication with a region of the wellbore and the fluid discharge is arranged in fluid communication with a well conduit. A rotary drive may be applied to the input of the rotary to linear motion converter such that a reciprocating output from the motion converter may drive the reciprocating pump. In this way the pump may function to drive fluid from the wellbore region through the conduit.
In some embodiments the wellbore region may contain fluids originating from a fluid producing subsurface formation, such as a fluid producing formation surrounding the wellbore. In such a use the pump intake may provide fluid communication with the fluid producing subsurface formation. The pump system may function to remove the fluids from the wellbore region. Such removed fluids may be desirable and thus removed for subsequent use. Alternatively, or additionally, such fluids may be removed to facilitate appropriate recovery of other desirable fluids. In some embodiments the pump system may be for use in dewatering a gas well.
In some embodiments the well conduit may extend to a further wellbore region, such that the pump system may facilitate transfer of fluids from the wellbore region to the further wellbore region. Alternatively, or additionally, the well conduit may extend to the Earth's surface, for example to a top-side facility, such that the pump system may facilitate transfer of fluids from the wellbore region to surface. In some embodiments the well conduit, or at least a portion thereof, may form part of the pump system.
In some embodiments the well conduit may comprise a tubing string. The tubing string may be formed by multiple individual tubing sections secured together in end-to end relation. The tubing string may comprise coiled tubing.
In some embodiments the well conduit may provide support to the pump system within a wellbore.
In some embodiments the well conduit may be used as a conveyance device for deploying and/or retrieving the pump system, or portions thereof, into/from a wellbore.
In some embodiments the pump system may facilitate the use of a reciprocating pump without necessarily relying on a surface drive source and extended linear drive coupling. The reciprocating pump may facilitate a favorable pump duty cycle to be attained, for example by permitting a high head which may be largely independent of flow rate. In this respect the reciprocating pump may provide a flow rate which is associated with the pump reciprocation speed, while the head may be associated with the pump force. As the drive source does not necessarily need to drive an extended linear drive coupling (for example extending all the way to surface), more of the available work from the drive source will be converted to pump power, and thus increasing pump head.
In some embodiments the magnetically operated rotary to linear motion converter may function as a magnetic drivetrain interposed between the rotary drive source and the pump.
In some embodiments the use of a magnetically operated motion converter may assist minimizing energy losses, such as drive inertia losses, friction losses and the like within the drive path between the drive source and the reciprocating pump. Compared to mechanical drive systems, the requirement for lubricant and thus lubricant control may be minimized by using a magnetic drive. Furthermore, the use of a magnetically operated motion converter may facilitate a degree of movement compliance, such as axial movement compliance, between the rotary drive source and the pump. Also, in the event of pump overload, for example due to an increase in fluid viscosity, a degree of slip may be accommodated within the motion converter, assisting to reduce risk of damage to one or both of the pump and the rotary drive source.
In some embodiments the magnetically operated rotary to linear motion converter may define a longitudinal axis. In use, the longitudinal axis may be aligned with a longitudinal axis of the wellbore.
In some embodiments the magnetically operated rotary to linear motion converter may comprise a first magnet arrangement coupled to the rotary motion input and a second magnet arrangement coupled to the reciprocating linear output. The first and second magnet arrangements may comprise permanent magnets. Rotation of the first magnet arrangement may cause the second magnet arrangement to reciprocate by a magnetic field interaction therebetween.
In some embodiments the magnetically operated rotary to linear motion converter may comprise a pair of axially arranged outer magnet assemblies each having at least one pair of circumferentially arranged opposed magnetic poles. An inner magnet assembly may be positioned axially intermediate the outer magnet assemblies, wherein the inner magnet assembly may comprise at least one pair of circumferentially arranged opposed magnetic poles. The inner and outer magnet assemblies may be coaxially aligned. At least a portion of the magnetic field developed by each magnet assembly may extend in an axial direction. In such an arrangement, appropriate circumferential alignment between the respective magnetic poles of the outer and inner magnetic assemblies may generate an axial force between the outer and inner assemblies, in accordance with retraction and repulsion of the magnetic poles. Such an axial force may establish linear motion within the motion converter. Further, relative rotation between the outer and inner magnet assemblies may cause a cyclical alignment and misalignment between the magnetic poles of the inner and outer magnet assemblies, causing one of the inner and outer magnet assemblies to reciprocate.
In some embodiments at least one pair of opposed poles of the outer magnet assemblies may be provided by opposed poles on a common magnet member. At least one pair of opposed poles of the outer magnet assemblies may be provided by opposed poles on separate magnet members.
In some embodiments the circumferential separation between opposed poles in one outer magnet assembly may be substantially the same as that in the other outer magnet assembly.
In some embodiments the opposed poles of one outer magnet assembly may be circumferentially aligned or in-phase with the opposed poles of the other outer magnet assembly.
In some embodiments the opposed poles of one outer magnet assembly may be circumferentially misaligned or out-of-phase with the opposed poles of the other outer magnet assembly.
In some embodiments the circumferential separation between opposed poles in the inner magnet assembly may be substantially the same as in one or both of the outer magnet assemblies.
In one embodiment the outer and inner magnet assemblies may each comprise a single pair of opposed magnetic poles. In such an arrangement a full 360 degrees of relative rotation between the outer and inner magnet assemblies may provide a single reciprocation motion within the motion converter. The opposed poles may be diametrically opposed.
In one embodiment one or each outer magnet assembly may comprise multiple pairs of circumferentially arranged opposed magnetic poles. Similarly, the inner magnet assembly may comprise multiple pairs of circumferentially arranged opposed magnetic poles. In one embodiment each outer magnet assembly and the inner magnet assembly may comprise an equal number of pairs of circumferentially arranged opposed magnetic poles. The provision of multiple pairs of opposed magnetic poles may facilitate multiple reciprocations within the motion converter for a full 360 degree of relative rotation between the outer and inner magnet assemblies. In some instances the number of reciprocations for each 360 degrees of relative rotation may be equal to the number of pairs of opposed magnetic poles.
In some embodiments the magnetically operated rotary to linear motion converter may comprise multiple inner magnet assemblies positioned intermediate a pair of outer magnet assemblies. At least two inner magnet assemblies may be arranged axially adjacent to each other. The opposed poles of one inner magnet assembly may be circumferentially misaligned or out-of-phase with the opposed poles of the other inner magnet assembly. Alternatively, the opposed poles of one inner magnet assembly may be circumferentially aligned or in-phase with the opposed poles of the other inner magnet assembly.
In some embodiments one or each outer magnet assembly may include a radially polarized magnetic ring having two or more radially polarized, opposed polarity magnet segments. The inner magnet assembly may include a plurality of longitudinally polarized magnet segments coupled to each other in opposed polarity.
In some embodiments multiple pairs of axially spaced outer magnet assemblies may be provided, wherein at least one inner magnet assembly is positioned between each pair of outer magnet assemblies. In some embodiments a single outer magnet assembly may be common to two adjacent pairs of outer magnet assemblies.
In some embodiments the rotary input to the magnetically operated rotary to linear motion converter may be coupled to the outer magnet assemblies, and the linear reciprocating motion output may be coupled to the inner magnet assembly. Alternatively, the rotary input to the magnetically operated rotary to linear motion converter may be coupled to the inner magnet assembly, and the linear reciprocating motion output may be coupled to the outer magnet assemblies.
In some embodiments the downhole pump system may comprise a magnetic control arrangement for directing or assisting to direct a magnetic field associated with the magnetically operated rotary to linear motion converter. The magnetic control arrangement may comprise one or more pole pieces, laminations or the like.
In some embodiments the downhole pump system may comprise the downhole rotary drive source. The downhole rotary drive source may comprise a drive shaft, wherein said drive shaft is coupled to the rotary input of the magnetically operated rotary to linear motion converter. At least a portion of the magnetically operated rotary to linear motion converter may be mounted on the drive shaft. For example, one or more magnet assemblies may be mounted on the drive shaft.
In some embodiments the downhole rotary drive source may comprise a motor, such as an electric motor.
In one embodiment the downhole rotary drive source may comprise a rotary permanent magnet electric motor. Such a rotary permanent magnet electric motor may provide a compact drive source with a relatively high power density.
At least a portion of the downhole rotary drive source, such as an electric motor, and the rotary input to the magnetically operated rotary to linear motion converter may be disposed in a sealed housing on some embodiments. In some embodiments the housing may be at least partially filled with a dielectric fluid.
An interior of the housing may be pressure compensated to equalize pressure therein to an external fluid pressure.
The housing may be made from a non-magnetic metal.
In some embodiments the reciprocating pump may comprise a reciprocating drive rod assembly, wherein said drive rod assembly is coupled to the linear reciprocating motion output of the magnetically operated rotary to linear motion converter. At least a portion of the magnetically operated rotary to linear motion converter may be mounted on the drive rod assembly. For example, one or more magnet assemblies may be mounted on the drive rod assembly.
In some embodiments the reciprocating action positive displacement pump may comprise a valve body having a passively actuated intake valve and a passively actuated discharge valve.
In some embodiments the intake valve and/or the discharge valve may comprise at least one of a disk valve, a poppet valve and a ball valve.
In some embodiments the intake valve may comprise a valve member having a stem disposed in a bore in a pushrod, wherein the pushrod is coupled to the linear motion output of the magnetically operated rotary to linear motion converter. The bore and the stem may be configured to cause immediate opening of the intake valve and damped closing thereof. Such immediate opening of the intake valve may seek to minimize any flow restriction encountered by inlet flow as quickly as possible. This may assist to quickly minimize any pressure drop of inlet flow due to any flow restriction, thus assisting to minimize cavitation within the inlet flow.
In some embodiments the stem of the valve member may be slidably mounted within the bore of the pushrod between an extended position and a retracted position. When the stem is in its extended position a low restriction to flow to and/or from the bore in the pushrod may be created, whereas when the stem is in its retracted position an increased restriction to flow to and/or from the bore in the pushrod may be created. Such a variation of flow restriction may be achieved by a profile provided along the axial length of the stem. In such an arrangement relative movement between the stem and the bore of the pushrod when the stem is in or near its retracted position will be subject to a greater degree of fluid damping than when the stem is in or near its extended position.
When the intake valve is in a closed position the stem may be in or near its retracted position. Movement of the pushrod to open the intake valve may thus cause a rapid lifting of the valve member due to the increased fluid damping between he valve stem and bore of the pushrod.
When the intake valve is in an open position the stem may be in or near its extended position. Movement of the pushrod to close the intake valve may thus cause the valve member to close against a seat while allowing the pushrod to continue movement, with such movement being damped by interaction of the stem and the bore of the pushrod. Such continued movement of the pushrod may function to provide a pumping force to fluid previously drawn in via the intake valve during the preceding stroke of the pushrod.
Another aspect or embodiment of the present disclosure relates to a method for pumping a fluid from a wellbore region. The method comprises operating a reciprocating positive displacement pump within a wellbore and establishing fluid communication between a fluid intake of the pump and the wellbore region, and fluid communication between a fluid discharge of the pump and a well conduit. The operating comprises rotating an input of a magnetic rotary to linear to motion converter and transferring an output of the rotary to linear motion converter to an input of the reciprocating positive displacement pump. The rotating the input of the magnetic rotary to linear motion converter comprises operating rotary drive.
The method may comprise pumping the fluid along the wellbore conduit to another wellbore region and/or to surface.
The method may comprise providing a rotary drive source form an electric motor, such as a permanent magnet electric motor.
The method may be performed using a pump or pump system according to any other aspect.
An aspect or embodiment of the present disclosure may relate to a pump. The pump may comprise a reciprocating rod and an intake valve for providing fluid communication with a fluid source. The intake valve comprises a valve member having a stem disposed in a bore of the reciprocating rod. The bore and stem are configured to cause immediate opening of the intake valve and damped closing thereof.
The pump may comprise a discharge valve for providing fluid communication with a fluid target.
Another aspect or embodiment of the present disclosure may relate to a downhole system, comprising a downhole linearly operated apparatus and a magnetically operated rotary to linear motion converter having a rotary motion coupled to a downhole rotary drive source. A linear motion output of the converter is coupled to a linear motion input of the downhole linearly operated apparatus.
The downhole linearly operated apparatus may comprise a pump, such as a reciprocating action positive displacement pump.
Another aspect or embodiment of the present disclosure relates to a downhole drive system, comprising a rotary electric motor having a rotary motion output. A magnetically operated rotary to linear motion converter has a rotary motion input coupled to the rotary motion output of the electric motor, and a linear reciprocating motion output.
Features defined in relation to one aspect set out above may be provided in combination with any other aspect.
It is to be understood that both the foregoing summarized description and the following detailed description are only intended as examples of various aspects and embodiments according to the present disclosure. The accompanying drawings are included to provide a further understanding of the embodiments and are incorporated in and constitute a part of the present disclosure.
An example electrical submersible pump (ESP) system, generally identified by reference numeral 2, according to some embodiments is shown schematically in FIG. 1. A winch 11 or similar spooling device may include thereon a coiled tubing, armored electrical cable or similar structure shown at 10 to be unwound and extended into a well (not shown). The coiled tubing or cable 10 may include one or more insulated electrical conductors therein (not shown separately) to provide electrical power to operate an electric motor 14. The electric motor 14 may be coupled to an end of the coiled tubing or cable 10 by an adapter sub 16. The adapter sub 16 may include any internal structures required to route the one or more insulated electrical conductors (not shown) to the electric motor 14 and may include passageways (not shown separately) to provide a fluid path to the interior of coiled tubing or a well production tubing, as explained in the Background section herein, so that discharge from a pump 18 may be conducted therethrough to the surface. It will be appreciated by those skilled in the art that if coiled tubing is used, the adapter sub 16 may conduct fluid discharge from the pump 18 to the interior of the coiled tubing.
The electric motor 14 may be any type known in the art used with ESPs, including, for example and without limitation, three phase, frequency speed controlled motors. The electric motor 14 may be disposed so that its rotational output is generally parallel to the longitudinal direction of the end of the well tubing (e.g., coiled tubing 10 in FIG. 1). A magnetically operated rotary to linear (“R2L”) motion converter 12 may be rotationally coupled to a rotary output of the electric motor 14. A linear motion output of the R2L motion converter 12 may be coupled to a reciprocating positive displacement pump 18. The positive displacement pump 18 may include a valve body 19 at one end thereof and may include valves as will be explained further below with reference to FIGS. 7, 8 and 9.
FIG. 2 is a schematic illustration of the pump system 2 of FIG. 1, shown deployed in a drilled wellbore 3. As noted above, the system 2 may be deployed on coiled tubing 10 and may include a motor 14 coupled to a pump 18 via a R2L motion converter 12. The motor 14 may include a rotary motion output 4 which is coupled to a rotary motion input 5 of the R2L motion converter 12. The R2L motion converter 12 may include a linear motion output 6 which is coupled to a linear input 7 of the pump 18. Accordingly, rotation of the motor 14 may provide linear reciprocating motion of the pump 18. The pump 18 may be positioned in the wellbore 3 so that a pump inlet, which may be provided by the valve body 19 is in fluid communication with a wellbore region 8. A pump outlet or discharge (not illustrated) may be in fluid communication with the coiled tubing 10. Accordingly, operation of the pump 18 may drive fluid from the wellbore region 8 towards surface via the coiled tubing 10.
FIG. 3A is a schematic illustration of an embodiment of a R2L motion converter 12. The motion converter 12 may comprise first and second outer magnet assemblies 22, 24 which are longitudinally separated along an axis 26 of the R2L motion converter 12. Each outer magnet assembly 22, 24 may comprise north and south magnetic poles 28 a, 28 b, 30 a, 30 b. The opposing poles 28 a, 28 b, 30 a, 30 b may be diametrically arranged about the axis 26, and in the present embodiment illustrated in FIG. 3A the north and south poles 28 a, 28 b of one outer magnet assembly 22 are arranged 180 degrees out-of-phase with the north and south poles 30 a, 30 b of the other outer magnet assembly 24.
The motion converter 12 may further comprise an inner magnet assembly 32 which is axially interposed between the first and second outer magnet assemblies 22, 24. The inner magnet assembly 32 may comprise north and south magnetic poles 34 a, 34 b diametrically arranged about the axis 26.
In the present illustrated embodiment the first and second outer magnet assemblies 22, 24 are intended to be coupled to the rotary motion input 5 (see FIG. 2) of the R2L motion converter 12, while the inner magnet assembly 32 is intended to be coupled to the linear motion output 6 (see FIG. 2) of the R2L motion converter 12. As such, rotation of the outer magnet assemblies 22, 24 is intended to induce reciprocating motion of the inner magnet assembly 32. However, in other embodiments the reverse position may be provided, with the outer magnet assemblies coupled to the linear motion output 6 and the inner magnet assembly coupled to the rotary motion input 5.
The various magnetic poles illustrated in FIG. 3A generate magnetic fields, at least a portion of which extend in the direction along the axis 26. As will be described in more detail below, upon rotation of the outer magnet assemblies 22, 24, these magnetic fields may cooperate to generate linear reciprocating motion of the inner magnet assembly 32 (and thus of the rotary motion output 6 of the R2L motion converter 12).
When in the configuration shown in FIG. 3A, the inner magnet assembly 32 is attracted towards the second outer magnet assembly 24 by virtue of the poles 34 a, 34 b of the inner magnet assembly 32 being circumferentially aligned with the opposing poles 30 b, 30 a of the second outer magnet assembly 24. Additionally, as the poles 28 a, 28 b of the first outer magnet assembly 22 are 180 degrees out-of-phase with the poles 30 a, 30 b of the second outer magnet assembly, a repelling force is also established to assist the linear movement of the inner magnet assembly 32.
As the first and second outer magnet assemblies 22, 24 rotate the orientation of the various poles change, with a 180 degree rotation illustrated in FIG. 3B. In this configuration the first outer magnet assembly 22 is orientated to attract the inner magnet assembly 32, while the second outer magnet assembly 24 is oriented to repel the inner magnet assembly 32. Continued rotation of the outer magnet assemblies 22, 24 will result in continuous reciprocation of the inner magnet assembly 32, with every 360 degree of revolution providing a single reciprocation.
A schematic perspective view of the R2L motion converter of FIG. 3A is provided in FIG. 4. This illustrates a possible form or geometry of the respective magnet assemblies 22, 24, 32. In this respect the first and second outer magnet assemblies 22, 24 may include diametrically polarized ring-shaped magnets, wherein the inner magnet 32 may include a diametrically polarized disc shaped magnet.
FIG. 5 provides a schematic illustration of a modified embodiment of a R2L motion converter 12. The motion converter 12 of this embodiment is largely similar to that illustrated in FIG. 3A and as such like features share like reference numerals. As such, the motion converter 12 may include first and second outer magnet assemblies 22, 24 axially spaced along an axis 26, with an inner magnet assembly 32 axially interposed therebetween. In the present embodiment each magnet assembly may include multiple pairs of circumferentially arranged north and south magnetic poles. Specifically, the first and second outer magnet assemblies 22, 24 may each comprise four pairs of opposing poles, with the poles of the first outer magnet assembly 22 being circumferentially out-of-phase with the poles of the second outer magnet assembly 24. Further, the inner magnet assembly 32 may comprise four pairs of poles.
In a similar manner to that described in relation to FIG. 3A, rotation of the outer magnet assemblies 22, 24 causes the inner magnet assembly to reciprocate by virtue of the varying orientation of the magnetic poles. In the present embodiment of FIG. 5, a single 360 degree rotation of the outer magnet assemblies 22, 24 will cause four reciprocations of the inner magnet assembly 32.
While the embodiment illustrated in FIG. 5 is arranged such that the outer magnet assemblies 22, 24 rotate while the inner magnet assembly 32 reciprocates, the reverse position is possible, such that rotation of the inner magnet assembly 32 may cause reciprocation of the outer magnet assemblies 22, 24.
FIG. 6 shows a schematic illustration of the functional components of a further example embodiment of the magnetically operated R2L motion converter 12. The R2L motion converter 12 may include first and second outer magnet assemblies 22, 24. Each of the outer magnet assemblies 22, 24 are effectively radially polarized to establish a laterally directed magnetic field, as shown by arrows 50. The longitudinal distance between the outer magnet assemblies 22, 24 may be selected based on desired properties of the R2L motion converter 12, for example, the stroke length of the linearly movable portion.
An inner magnet assembly 32 may be disposed longitudinally between the outer magnet assemblies 22, 24 and may be substantially coaxial therewith. The inner magnet assembly 32 may include a pair of semicircular magnets 32A, 32B each longitudinally polarized (in the direction of arrows 52) and in opposed direction to each other. The provision of the opposed longitudinally polarized magnets 32A, 32B permits the outer magnet assemblies 22, 24 to be positioned or aligned with the same magnetic orientation, which may assist to reduce the complexity of assembly.
The R2L motion converter 12 as shown in FIG. 6 may be operated either by rotating the outer magnet assemblies 22, 24 to induce reciprocating motion in the inner magnet assembly 32, or by rotating the inner magnet assembly 32 to induce corresponding reciprocating motion in the outer magnet assemblies 22, 24. For purposes of the present disclosure, any structure to which the outer magnet assemblies 22, 24 is mounted may be configured such that the longitudinal distance between the outer magnet assemblies 22, 24 is maintained substantially constant.
While in the above exemplary embodiments a single pair of outer magnet assemblies is illustrated with an inner magnet assembly therebetween, in other embodiments multiple pairs of outer magnet assemblies may be provided, with at least one inner magnet assembly interposed between each pair. Such a modified R2L motion converter 12 is illustrated in FIG. 7, in which multiple outer magnet assemblies 60, 62, 64 (similar in form and function to assemblies 22, 24 in FIG. 6) are provided with corresponding inner magnet assemblies 66, 68 (similar in form and function to assembly 32 in FIG. 6) axially interposed therebetween. As described above, the form of the assemblies is such that the each magnet assembly may be positioned or aligned with the same magnetic orientation.
Having explained various embodiments of the R2L motion converter, an example ESP according to the present disclosure will now be explained with reference to FIG. 8. The electric motor 14 may be an induction motor of any type known in the art, e.g., comprising a rotor 14C (which may include permanent magnets or high magnetic permeability inserts therein) rotatably supported in bearings 14A and caused to rotate by passing alternating electrical current (AC) through a stator coil 14B. The stator coil 14B may be wound such that passing AC therethrough causes a rotating magnetic field to be induced, thus causing corresponding rotation of the rotor 14C. In the example embodiment shown in FIG. 8, the rotor may be rotationally coupled to the inner magnet assembly 32. The outer magnet assemblies 22, 24 may be coupled to a pushrod 18A. The pushrod 18A applies the reciprocating motion induced in the outer magnet assemblies 22, 24 to a pump 18. Various embodiments of a pump will be further explained below with reference to FIGS. 12, 13 and 14. Electrical wiring to supply AC to the stator coil 14B may be provided by suitable wiring from the adapter sub 16, as explained with reference to FIG. 1.
FIG. 9 shows another embodiment of an ESP according to the present disclosure. The embodiment shown in FIG. 9 may include an electric motor 14 as in the previously described embodiment. In the present example embodiment, the rotor 14C may be rotationally coupled to the outer magnet assemblies 22, 24, thus causing the outer magnet assemblies 22, 24 to rotate correspondingly with the rotor 14C. The pushrod 18A may be coupled to the inner magnet assembly 32. The inner magnet assembly 32, as explained with reference to FIGS. 3 to 7 will be caused to undergo reciprocating motion by rotation of the outer magnet assemblies 22, 24. The reciprocating motion applied to the pushrod 18A operates a pump 18 substantially as explained with reference to FIG. 8.
FIG. 10 shows another example embodiment similar in configuration to the example embodiment shown in FIG. 8. In FIG. 10, however, the electric motor 14 and the inner magnet assembly 32 may be enclosed in a sealed housing 40. The sealed housing 40 may be filled with a dielectric fluid such as oil and may be pressure compensated by a pressure compensator 42 of any type known in the art, including, without limitation, a piston in a cylinder exposed on one face to external fluid pressure and on the other face to the dielectric fluid, an elastomeric bladder or flexible metal bellows. By having pressure compensation, the thickness of the housing 40 may be minimized so as not to occupy an excessive amount of the diameter available for the components of the ESP. In one example the housing 40 may be made from non-magnetic metal such as stainless steel, monel or various alloys sold under the trademark INCONEL, which is a registered trademark of Huntington Alloys Corp., Huntington, W. Va. It may also be preferable to minimize the thickness of the housing 40 if so made to reduce the effects of eddy currents that may be induced in the housing 30 by reason of rotating magnetic fields in both the stator coil (14B in FIG. 8) and by the rotation of the inner magnet assembly 32.
A housing extension 40A may be provided to cover the outer magnet assemblies 22, 24. The housing extension 40A may thus reduce the possibility of wear on the outer magnet assemblies 22, 24. In such embodiments, ports 44 may be provided in the housing extension 40A so that movement of the outer magnet assemblies 22, 24 will substantially not be impeded by fluid compression within the housing extension 40A.
Another embodiment of an ESP is shown in FIG. 11. The embodiment shown in FIG. 11 may be similar in configuration to the embodiment shown in FIG. 9, wherein the rotor 14C of the electric motor 14 rotates the outer magnet assemblies 22, 24, and reciprocating motion is induced in the inner magnet assembly 32. The inner magnet assembly 32 may be coupled to the pushrod 18A so as to operate the pump 18. In the embodiment shown in FIG. 11, the electric motor 14 and the outer magnet assemblies 22, 24 may be enclosed in a sealed housing 40. The housing 40 may be made from similar materials and may be pressure compensated as explained with reference to the embodiment shown in FIG. 10.
FIG. 12 shows one example embodiment of a valve body 19 that may form part of the pump (18 in FIG. 1). The valve body 19 may include a housing 19C having a bore 19D through which the pushrod 18A reciprocates. The pushrod 18A may be sealingly engaged with the bore 19D, e.g., using metal seal rings, elastomer O-rings, or the pushrod 18A may effect substantially sealed volume changes with respect to the bore 19D by keeping clearances between the pushrod 18A and the bore 19D relatively small.
An intake port 19AA in the valve body 19 may have a disk or other type of passively actuated intake valve 19A disposed therein. When the pushrod 18A moves to increase the internal volume in the bore 19D, the intake valve 19A will lift to open the intake port 19AA so that well fluid may enter. A corresponding discharge valve 19B will be caused to close a discharge port 19BB in the valve body 19 so that the bore 19D will be filled with fluid from the well. When the pushrod 18A is moved in the opposite direction, the volume in the bore 19D is reduced. The intake valve 19A will close the intake port, and the discharge valve 19B will open the discharge port 19BB. Fluid displaced from the bore 19D will thus be moved under pressure into the discharge port 19BB. The discharge port 19BB may be in fluid communication with the well tubing coiled tubing (see FIG. 1), for example through the adapter sub (16 in FIG. 1) or by any other suitable fluid porting and/or connection arrangement known in the art. Both the intake valve 19A and discharge valve 19B in FIG. 12 may be disk type valves, however, other types of valves may be used, as will be further explained below, to reduce the possibility of cavitation when the pump 18 is operated at high speeds.
Because the pump is intended to operate a high speeds, it may be desirable to minimize pressure drop in the intake valve area. If the pressure in the well fluid is reduced below a certain level, the phenomenon known as cavitation will occur. In this case, gas bubbles form in the fluid, and may implode, which reduces volumetric efficiency, and in more severe cases, may cause localized surface damage to the valves and valve seats. One technique to reduce pressure drop in the intake valve area is to provide a smooth flow passage for the fluid. In one example, the inlet to the intake valve port is radiused. In this way, the flow does not have to traverse a sharp corner.
FIG. 13 shows another example of the valve body 19 in which both the intake valve 19A and the discharge valve 19B may be disposed in a common bore. The configuration shown in FIG. 13 may provide a minimum residual pump volume and thus may operate at relatively high mechanical efficiency.
FIG. 14 shows another example of the valve body in which the intake valve 19A is a poppet type valve having a tapered sealing face and the discharge valve 19B may be a ball type valve. Near the head of the intake valve 19A, the valve stem and a bore 18AA in the pushrod 18A are a relatively close fit, so that when the pushrod 18A begins to upstroke, it will also raise the intake valve 19A off its seat, allowing free flow of fluid into the valve body 19. Further up, the valve stem is relieved to allow free relative motion of the valve stem in the bore 18AA, by allowing fluid to flow past the valve stem in the relieved area.
A means may be provided to limit the opening of the intake valve 19A. This may be by a feature provided in the machining of the valve body 19, or by an additional component which contacts the opposite side of the valve head to the seating surface (not shown in the illustration).
When the intake valve reaches the limit of opening, the bore 18AA in the pushrod 18A engages with the part of the valve stem which is relieved, so that fluid can flow past the valve stem into the space in the bore 18AA above the end of the valve stem. When the pushrod starts its downstroke, the first action is to assist the closing of the intake valve 19A, and to expel the fluid from the aforementioned space. When the pushrod 18A nears the end of its downstroke, the bore 18AA engages with the un-relieved part of the intake valve stem. This achieves three things: first, the intake valve 19A is forced onto its seat; second, the motion of the pushrod 18A is damped as it reaches the end of its stroke; third, the valve stem is in effect gripped by the pushrod 18A so that the intake valve 19A will be pulled open immediately on the start of the pushrod 18A upstroke.
While the invention has been described with respect to a limited number of embodiments, those skilled in the art, having benefit of this disclosure, will appreciate that other embodiments can be devised which do not depart from the scope of the invention as disclosed herein. Accordingly, the scope of the invention should be limited only by the attached claims.

Claims

What is claimed is:

1. A downhole pump system, comprising:

a reciprocating action positive displacement pump having a fluid intake for providing fluid communication with a wellbore region and a fluid discharge for providing fluid communication with a well conduit; and

a magnetically operated rotary to linear motion converter having a rotary motion input to be coupled to a downhole rotary drive source, and a linear reciprocating motion output coupled to a linear reciprocating motion input of the reciprocating action positive displacement pump.

2. The downhole pump system of claim 1, wherein the magnetically operated rotary to linear motion converter comprises:

a pair of axially arranged outer magnet assemblies each having at least one pair of circumferentially arranged opposed magnetic poles; and

an inner magnet assembly positioned axially intermediate the outer magnet assemblies, wherein the inner magnet assembly comprises at least one pair of circumferentially arranged opposed magnetic poles.

3. The downhole pump system of claim 2, wherein at least a portion of a magnetic field developed by each of the pair of outer magnet assemblies and the inner magnet assembly extends in an axial direction such that relative rotation between the pair of outer magnet assemblies and the inner magnet assembly causes a cyclical alignment and misalignment between the magnetic poles of the inner and outer magnet assemblies, causing one of the inner and outer magnet assemblies to linearly reciprocate.

4. The downhole pump system of claim 2, wherein the opposed poles of one outer magnet assembly are circumferentially aligned in-phase with the opposed poles of the other outer magnet assembly.

5. The downhole pump system of claim 2, wherein the opposed poles of one outer magnet assembly are circumferentially misaligned out-of-phase with the opposed poles of the other outer magnet assembly.

6. The downhole pump system of claim 2, wherein the pair of outer magnet assemblies and the inner magnet assembly each comprises a single pair of opposed magnetic poles.

7. The downhole pump system according to claim 2, wherein at least one of the pair of outer magnet assemblies comprises multiple pairs of circumferentially arranged opposed magnetic poles, and the inner magnet assembly comprises an equal number of pairs of circumferentially arranged opposed magnetic poles.

8. The downhole pump system according to claim 2, wherein at least one of the pair of outer magnet assemblies includes a radially polarized magnetic ring having two or more radially polarized, opposed polarity magnet segments.

9. The downhole pump system according to claim 2, wherein the inner magnet assembly comprises a plurality of longitudinally polarized magnet segments coupled to each other in opposed polarity.

10. The downhole pump system according to claim 2, further comprising a plurality of pairs of axially spaced outer magnet assemblies, and at least one inner magnet assembly positioned between each of the plurality of pairs of outer magnet assemblies.

11. The downhole pump system according to claim 2, wherein the rotary input of the magnetically operated rotary to linear motion converter is coupled to the pair of outer magnet assemblies, and the linear reciprocating motion output of the magnetically operated rotary to linear motion converter is coupled to the inner magnet assembly.

12. The downhole pump system according to claim 2, wherein the rotary input of the magnetically operated rotary to linear motion converter is coupled to the inner magnet assembly, and the linear reciprocating motion output of the magnetically operated rotary to linear motion converter is coupled to the pair of outer magnet assemblies.

13. The downhole pump system according to claim 1, further comprising a magnetic control arrangement for directing a magnetic field associated with the magnetically operated rotary to linear motion converter.

14. The downhole pump system according to claim 1, further comprising a downhole rotary drive source.

15. The downhole pump system according to claim 14, wherein the downhole rotary drive source comprises an electric motor.

16. The downhole pump system according to claim 14, wherein at least a portion of the downhole rotary drive source and the rotary input to the magnetically operated rotary to linear motion converter are disposed in a sealed housing at least partially filled with a dielectric fluid.

17. The downhole pump system according to claim 16, wherein an interior of the sealed housing is pressure compensated to equalize pressure therein to an external fluid pressure.

18. The downhole pump system according to claim 16, wherein the sealed housing is made from a non-magnetic metal.

19. The downhole pump system according to claim 1, wherein the reciprocating action positive displacement pump comprises a valve body having a passively actuated intake valve and a passively actuated discharge valve.

20. The downhole pump system according to claim 19, wherein at least one of the intake valve and the discharge valve comprises at least one of a disk valve, a poppet valve and a ball valve.

21. The downhole pump system according to claim 20, wherein the intake valve comprises a valve member having a stem disposed in a bore in a pushrod, wherein the pushrod is coupled to the linear motion output of the magnetically operated rotary to linear motion converter, the bore and the stem configured to cause immediate opening of the intake valve and damped closing thereof.

22. A method for pumping a fluid from a wellbore region, the method comprising:

operating a reciprocating action positive displacement pump within a wellbore and establishing fluid communication between a fluid intake of the pump and the wellbore region, and establishing fluid communication between a fluid discharge of the reciprocating action positive displacement pump and a well conduit, wherein a linear reciprocating motion input of the pump is coupled to a linear reciprocating motion output of a magnetically operated rotary to linear motion converter; and

23.

operating a rotary drive from a downhole rotary drive source coupled to a rotary motion input of the magnetically operated rotary to linear motion converter to operate the reciprocating action positive displacement pump. The method according to claim 23 further comprising directing a discharge of the reciprocating action positive displacement pump through a well conduit to a surface end of wellbore.