Patent Application
20160123123
Not Applicable.
Not applicable.
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.
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
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
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 34a, 34b 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
The various magnetic poles illustrated in
When in the configuration shown in
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
A schematic perspective view of the R2L motion converter of
In a similar manner to that described in relation to
While the embodiment illustrated in
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
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
Having explained various embodiments of the R2L motion converter, an example ESP according to the present disclosure will now be explained with reference to
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
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
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.
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.
