WO2007003597A1

WO2007003597A1 - Mehod and apparatus for actuating oilfield equipment

Info

Publication number: WO2007003597A1
Application number: PCT/EP2006/063737
Authority: WO
Inventors: William Birch; Johannis Josephus Den Boer
Original assignee: Shell Internationale Research Maatschappij B.V.; Shell Canada Limited
Priority date: 2005-07-01
Filing date: 2006-06-30
Publication date: 2007-01-11

Abstract

A method is disclosed for actuating oilfield equipment by means of at least one electrically actuated fluidic pump (70, 71) with an oscillating piston which is slideably connected to a rotating sleeve or rod (76) by a sinusoidal groove and pin assembly (73 , 75) such that the piston is oscillated in response to rotat.ion of the sleeve or rod, which fluidic pump provides a flux of fluid to a Wheatstone bridge fluidic cont.rol circuit, which directs the fluid flux to a piece of fluid actuated oilfield equipment, such as a downhole valve, which circuit comprises one or more valves (A-D) that are each actuated by an electromagnetic device comprising a magnetisable armature, which is arranged in a gap between a first and second magnet Ìissembly and which is sequentially demagnetized during selected intervals of time by an electromagnetic coil through which a sequence of electrical pulses are transmitted such that in response to an initial electric pulse the demagnetized armature is induced by spring force to move through the gap from the first to the second magnet assembly and such that in response to a subsequent electrical pulse the demagnetized armature is induced by spring force to move back through the gap from the second to the first magnet assembly.

Description

METHOD AND APPARATUS FOR ACTUATING OILFIELD EQUIPMENT

BACKGROUND OF THE INVENTION

The invention relates to a method anc apparatus for actuating oilfield equipment.

Oilfield equipment, such as hydraulically or pneumatically controlled steering assemblies for drill bits and safety or control valves for use in well drilling assemblies, oil and/or gas production wells and/or on- or offshore oil and/or gas tramsportation conduits, may be actuated by electric, pneumatic and/or hydraulic motors that generally have a leirge power consumption and require thick hydraulic, pneumatic and/or electric power supply cables.

Therefore, if for example a downhole and/or subsea control valve or other device in an oil and/or gas production well or in an oilfield tubular is actuated by a hydraulic, electric, and/or electro-hydraulic actuator then electrical and/or hydraulic control conduits of several kilometers length and a significant thickness are to be installed, which requires complex and costly installation procedures and use of expensive seals at locations where the conduit passes for example a wellhead and/or a downhole or subsea packer assembly.

US patent 5,535,828 discloses an electrical downhole gas-lift valve with a significant power consumption, which requires installation of a large dz.ameter power supply cable in the annulus between the crude oil production tubing and the well casing. It is an object of the present invention to provide a method and apparatus for actuating oilfield equipment by- means of a compact, efficient and robust actuator assembly which consumes a minimal amount of energy so that it may be operated by a low power energy supply system, such as trickle charged batteries, small diameter electrical cables and/or wireless electrical or acoustical power transmission systems. SUMMARY OF THE INVENTION In accordance with the invention there is provided a method of actuating oilfield equipment by means of at least one electrically actuated fluidic pump comprising an oscillating piston which is slideably connected to a rotating sleeve or rod by a sinusoidal groove and pin assembly such that the piston is oscillated in response to rotation of the sleeve or rod by mean.! of an electric motor, which fluidic pump provides a flux of fluid to a fluidic control circuit, which directs the fluid flux to a piece of fluid actuated oilfield equipment, which circuit comprises a valve that is actuated by an electromagnetic device comprising a magnetisable armature, which is arranged in a gap between a first and second magnet assembly and which is sequentially demagnetized during selected intervals of time by an electromagnetic coil through which a seςpience of electrical pulses are transmitted such that in response to an initial electric pulse the demagnetized armature is induced by spring force to move through the gap from the first to the second magnet assembly and such that in response to a subsequent electrical pulse the demagnetized armature is induced by spring force to move back through the gap from the second to the first magnet assembly. Preferably the rod or sleeve is a sleeve, which is arranged co-axially around a section of ε downhole production tubing and is supported by a bearing assembly which is mounted on the production tubing and the electric motor is provided by providing the sleeve or rod with a plurality of magnets which induce the sleeve to rotate in response to generation of a rotating magnetic field by means of a series of induction coils arranged adjacent to the magnets. It is furthermore preferred that the pump pumps fluid from a first section (I) into a second section (II) of the fluidic control circuit, which circuit further comprises third section (III) and a fourt.h section (IV) which are alternatingly connected to either the first section (I) or the second section (II) by a set of four connecting sections, which are each equipped with a valve (A, B, C and D) , that are arranged in a Wheatstone bridge configuration, such that fluid is pumped from a third section (III) to a fourth section IV) of the control circuit if valves (A) and (D) are: kept open, whilst valves (B) and (C) are kept closed, whereas fluid is pumped from the fourth section (IV) to the third section (III) of the control circuit if valves (B) and (C) are kept open, whilst valves (A) and (D) are kept closed.

It is also preferred that the sleeve comprises a sinusoidal groove and pump comprises a piston which is connected to a pin which is slideably arranged within the groove such that the piston is oscillated up and down within a cavity in response to the notation of the sleeve and which cavity is alternatingly connected to the first section (I) and the second section (II) of the control circuit by means of a pair of one way valves (Vl, V2) such that if the piston moves in. one direction through the cavity fluid is sucked into the cavity from the first section (I) via the first one-way valve and if the piston moves in an opposite direction through the cavity fluid is discharged from the cavity into the second section (II) of the control circuit.

These and other features, advantages and embodiments of the method and apparatus according to the invention are further described in the accompanying claims, abstract and the following detailed description of preferred embodiments in which reference is made to the accompanying drawings .

BRIEF DESCRIPTION OF THE DRAWINGS

FIG.l is a schematic sectional and three-dimensional view of an oilfield assembly comprising a hydraulically actuated valve which is actuated by a hydraulic pump and two pairs of valves that are arranged in a Wheatstone bridge configuration;

FIG.2 is a schematic sectional and three-dimensional view of the oilfield assembly of FIG.l wherein the two pairs of valves are actuated by two apparatuses according to the invention; and

FIG.3 is a schematic three-dimensional view of a preferred embodiment of an oilfield assembly which is actuated by an electrically actuated fluidic pump according to the invention. DETAILED DESCRIPTION OF EMBODIMENTS OF TEE INVENTION

FIG.l shows an electromagnetic device 1 according to the invention. The electromagnetic device 1 actuates a reciprocating pump 2. The pump 2 forms part of a fluidic control circuit 3 that is connected to a large volume piston and cylinder assembly 4 which opens or closes: a valve 15 of an oilfield assembly, such as an oil and/or gas production well, a well drilling assembly, a crude oil and/or natural gas transportation conduit or a X-mass tree at a wellhead. The pump 2 comprises a plunger 5A which is formed by the upper end of a rod 5 which is connected to a magnetisable armature 6 and which pump comprises a pair of one way valves Vl andV2 such that in response to a downward movement of the plunger the first one way valve Vl is opened and the second one way valve is closed, and the pump 2 sucks fluid from a first section I of the fluidic control circuit, whereas in response to an upward movement of the plunger 5A the first valve Vl is closed and the second valve V2 is opened and fluid the pump discharges fluid into a second section II of the fluidic control circuit 3.

Accordingly, in response to a reciprocating movement of the plunger 5A the pump 2 pumps fluid from a first section (I) into a second section (II) of the fluidic control circuit, which circuit further ccmprises third section (III) and a fourth section (IV) which are alternatingly connected to either the first section (I) or the second section (II) by a set of fcur connecting sections, which are each equipped with a valve (A, B, C and D) , that are arranged in Wheatstone bridge configuration, such that fluid is pumped from a third section (III) into the lower part of piston and cylinder assembly 4 and discharged from the upper part of the piston and cylinder assembly 4 into a fourth section (IV) of the control circuit if valves (A) and (D) are kept open, whilst valves (B) and (C) are kept closed, whereas fluid is pumped from the fourth section (IV) via the piston and cylinder assembly 4 into the third section (III) of the control circuit if valves (B) and (C) are kept open, whilst valves (A) and (D) are kept closed.

The magnetisable armature 6 is arranged in a gap 7 between an upper and lower U-shaped magnet assembly 8A and 8B.

Each U-shaped magnet assembly 8A and 8B comprises a permanent magnet 9A, 9B which is connected at one end thereof to an I-shaped magnetisable element 1OA, 1OB and which is at another end thereof to an L-shaped magnetisable element HA, HB.

The magnets 9A and 9B are oriented such that the ends of the upper L-shaped magnetisable element HA and the lower I-shaped magnetisable element 1OB form a pair of North poles N and that the ends of the lower L-shaped magnetisable element HA and of the upper I-shaped magnetisable element 1OA form a pair of South Poles adjacent to the gap 7.

In FIG.l the magnetisable armature 6 is located at the bottom of the gap 7, such that the armature is pulled down against the poles of the lower U-shaped magnet assembly 1OB, such that the magnet 9B, the lower I-shaped magnetisable element 1OB, the magnetisable armature 6 and the lower L-shaped magnetisable element HB form a closed magnetic circuit of which the magnetic field lines run in a loop .

The rod 5 is supported within the housing 12 between an upper and a lower spring 13A and 13B, such that in the position shown the springs 13A and 13B exert an upward spring force on the rod 5 and magnetisable armature 6, which spring force is lower than the magnetic force exerted by the lower U-shaped magnet assembly 1OB to the magnetisable armature 6. The magnetisable armature 6 is surrounded by an electrical coil 14, which is, as shown in FIG.2, coiled about an axis, which is substantially parallel to a longitudinal direction of the magnetisable armature 6. If a short electrical pulse is transmitted through the coil 14 then a magnetic field is created which counteracts the magnetic field exerted to the magnetisable armature 6 by the lower U-shaped magnet assembly 1OB. As a result the magnetisable armature 6 is demagnetised and pushed up through the gap 7 by the lower spring 13B.

The electrical pulse is so short that before the upper end of the gap 7 no magnetic field is exerted to the magnetisable armature 6 by the coil 14. The armature 6 is then magnetised by, and thereby pulled against, the upper U-shaped magnet assembly 1OA, thereby compressing the upper spring 13A.

If subsequently a short electrical pulse is transmitted through the coil 14 the armature 6 is demagnetized again and pushed by the upper spring 13A down through the gap 7, whereupon after termination of the electrical pulse the armature is again magnetized by, and pulled down again against the lower U-shaped magnet assembly 1OB. FIG.2 shows in more detail how the coil 14 is coiled around an axis which is substantially parallel to a longitudinal axis of the magnetisable armature 6 and which axis is oriented substantially transversal to the direction of movement of the armature 6 through the gap 7.

FIG.2 also shows that the valves A, B, C and D of FIG.1 may be connected to a pair of elect.romagnetic devices 20 and 30 according to the invent.ion. The construction and operation of the electromagnetic devices 20 and 30 are similar to those of: the electromagnetic device 2.

Each electromagnetic device 20, 30 comprises a magnetisable armature 26, 36 that is surrounded by a coil 24, 34 and that is movably arranged within a gap 27, 37 between a pair of U-shaped magnet assemblies 21A, 21B and 31A, 31B.

The magnetisable armatures 26, 36 are connected to rods 25, 35 that are moved up and down within housings 22, 32 of the devices 20, 30.

The upper and lower ends 25 A, B and 35 A, B of the rods 25, 35 form valve bodies that are arranged in valve housings 40, 41, 42 and 43, that are secured to the upper and lower sides of the housings 32 and 33 of the electromagnetic devices 20, 30.

The magnetisable armature 26 and rod 25 of the electromagnetic device 20 shown at the left side of FIG.2 are in the lower position thereof, whereas the magnetisable armature 36 and rod 35 of the electromagnetic device shown at the right side of FIG.2 are in the upper position thereof. Therefore the lower end 25B of the rod 25 and the upper end 35A of the rod 35 are pushed against valve seats 51 and 53 within the valve housings 41 and 53, thereby closing the valves B and C.

The upper end 25A of the rod 25 and the lower end of the rod 35 are lifted from the valve seats 50 and 52, thereby opening valves A and D, and permitting fluid to flow from an inlet port 55, 57 to an outlet port 56, 58 of these valves A and D.

Accordingly, in the position shown in FIG.2 fluid, such as hydraulic oil, air or another gas or liquid is pumped via the outlet valve V2 of the pump 2 into the second section II of the fluidic circuit and then via the open valve D into the third section III of the fluidic circuit into the bottom section of the hydraulic or pneumatic piston and cylinder assembly 4, thereby pushing the piston up through the cylinder and the associated oilfield valve 15 to be opened. Fluid discharged from the upper part of the piston and cylinder assembly 4 is fed into the fourth section IV, and then via the open valve A into the first section I, of the fluidic control circuit and is then sucked up via the one way valve Vl into the pump 2.

If the valve 15 is to be closed then the electromagnetic devices 20 and 30 are actuated simultaneously by transmitting a short electrical pulse through the coils 24 and 34 such that the armatures 26 and 36 are demagnetized and pushed by springs 29 and 39 up and down through the housings 22, 32, thereby switching the valve positions such that valves B and C are open an valves A and D are closed. In that position the pump 2 pumps fluid via the second section II, the valve B and the fourth section IV of the fluidic control circuit into the upper part of the piston and cylinder assembly and sucks fluid via the first section I, the valve C, and the third section III of the fluidic control circuit from the bottom part of the fluid ic piston and cylinder assembly 4.

The electrical pulses supplied to the coils 14,24 and 34 to actuate the pump and to switch the position of the valves A, B, C and D may have a low power, such that the electrical energy may be supplied by a small diameter electrical cable, or via an optical cable to which a low power electrical power generator is coupled, or via batteries or rechargeable batteries that may be trickle charged by a low power electrical cable or by a small turbine or other power generator powered by the flux of oil and/or gas through the valve 15, or by a small electrical current transmitted via the wall of the production tubing, or by a piezoelectric element that generates electricity in response to acoustic pulses transmitted via the wall of the production tubing. The volume of fluid discharge by the pump 2 in response to a single stroke of the plunger 5A may be several milliliters, whereas the volume of the piston and cylinder assembly 4 may be several liters, so that the pump 2 may have to make hundreds, thousands or then thousands strokes to move the piston fully up or down through the cylinder and to fully open or close the valve 15.

Accordingly the pump 2 and Wheatstone bridge configuration of valves A₇ B, C and D actuated by electromagnetic devices 1,20 and 30 according to the invention is a relatively slow, but efficient and compact valve actuator assembly. The electromagnetic devices 1, 20 and 30 and associated pump 2 and valves A-D may be only a centimeter thick and a few centimeters tall, so that they have the size of a matchbox and can be easily mounted in the wall of a sleeve that is retrievably inserted into a production tubing of a oil and/or gas production well, which sleeve is mounted adjacent to the valve 15 and which sleeve may also a pack of rechargeable batteries for actuating the electromagnetic devices according to the invention. The electrical pulses required for powering the coils 14, 24 ar.d 34 may be supplied by small diameter electrical cables by rechargeable batteries, which may be coupled to an electrical control assembly which may be controlled by a wireless acoustic or electromagnetic signal transmission system the rechargeable batteries.

The electromagnetic devices 1, 20 and 30 may be controlled by electrical pulse transmitters that form part of an electronic control circuit that is also embedded in the sleeve that houses the devices 1, 20 and 30 and optionally the rechargeable batteries.

The power consumption by the electromagnetic devices 1,20 and 30 may be less than 10 Watt and the fluid displacement volume of the pump 2 may be several cubic millimeters .

In an alternative embodiment of the invention a fluidic control circuit comprises two pumps 2A and 2B (not shown) similar to the pump 2 shown in FIG.l and 2 of which the one way valves Vl and V2 are arranged in opposite directions, such that if the first pump 2A is actuated and the second pump 2B is inactive fluid is pumped from a first section I into a seccnd section II of the fluidic control circuit, whereas if the second pump 2B is actuated and the first pump 2A is inactive fluid is pumped from the second section II into the first section I of the fluidic control circuit. In such case leakage of fluid via the inactive pump 2P. or 2B can be prevented by a valve similar to the valve 20 shown in FIG. 1 and 2 or by preventing that at leε.st one of the one way valves Vl and/or V2 of the inactive pump 2A or 2B opens, e.g. by use of a ferromagnetic ba] 1 and a valve seat which is magnetized if the pump 2A or 2B is inactive, such that the ball is pressed cigainst the magnetized valve seat by magnetic forces.

FIG.3 shows a preferred embodiment according to the invention, wherein two pumps 70 and 71 comprise pistons that are connected to a pair of pins 73 εmd 74 that are arranged in a sinusoidally shaped groove 75 that is machined in the outer surface of a sleeve 76 that is rotatably arranged around a production tubing 77 within an oil and/or gas production well (not shown) and that is rotated relative to the tubing 77 by a series of electrical coils 78, which generate a rotating magnetic field.

Each pump 70 and 71 is connected to a set of four valves

A, B, C and D which are arranged in a pair of valve housings 79 and 80 that are mounted at diametrically opposite locations on the production tubing 77. Each set of four valves A-D is arranged in a Wheatstone Bridge configuration, which is similar to the ccnfigurations described with reference to FIG.l and FIG .2. Each valve assembly A-D is connected to a large hydraulic piston 4 or other large hydraulically actuated device, such as a valve, and the hydraulic pumps 70,71 and valve assemblies A-D provide efficient and compact hydraulic drives for hydraulic equipment in a well, which drives can be installed in an annular space surrounding a production tubing 77 within an oil and/or gas production well. It will be understood that the sinusoidal groove 75 and pin 73,74 assembly may be built in severεl other ways than shown in FIG.3. For example the rotciting sleeve 76 may have a sinusoidal upper surface onto which the pins

73,74 are pressed by spring action. Alternatively the rotating sleeve 76 may be equipped with pins that fit into a groove of a surrounding static ring, which is moved up and down in response to rotation of the sleeve relative to the surrounding ring. In such case the pistons of the pumps 70,71 may be connect.ed to the oscillating ring and the pump cylinders to the tubing 77 so that the pumps 70,71 are actuated to pump fluid in response to rotation of the sleeve 76.

A principal advantage of the assembly shown in FIG.3 is that it provides a compact and robust assembly of pumps 70,71 and associated valves A, B, C and D, which consume a small amount of electrical power and can be built in an annular space surrounding a production tubing 77 in an oil and/or gas production well and which can be used to actuate a large hydraulic pump 4 in opposite ways, such that a non intrusive robust and energy efficient hydraulic power and control assembly is provided that can be built into any existing or new oil and/or gas production well

It will further be understood that the method and apparatus according to the invention solve the longstanding problem of actuating oilfield equipment by means of a compact, efficient and robust actuator assembly which consumes a minimal amount of electrical energy so that it may be operated by trickle charged batteries, small diameter electrical cables and/or wireless electrical or acoustical power transmission systems .

Claims

C L A I M S

1. A method of actuating oilfield equipment by means of at least one electrically actuated fluidic pump comprising an oscillating piston which iε slideably connected to a rotating sleeve or rod by a sinusoidal groove and pin assembly such that the piston is oscillated in response to rotation of the sleeve or rod by an electric motor, which fluidic pump provides a flux of fluid to a fluidic control circuit, which directs the fluid flux to a piece of fluid actuated oilfield equipment, which circuit comprises at leaist one valve that is actuated by an electromagnetic de:vice comprising a magnetisable armature, which is arranged in a gap between a first and second magnet assembly and which is sequentially demagnetized during selected intervals of time by an electromagnetic coil through which a sequence of electrical pulses are transmitted such that in response to an initial electric pulse the; demagnetized armature is induced by spring force to move through the gap from the first to the second magnet assembly and such that in response to a subsequent electrical pulse the demagnetized armature is induced by spring force to move back through the gap from the second to the first magnet assembly.

2. The method of claim 1, wherein the rod or sleeve is a sleeve, which is arranged co-axially around a section of a downhole production tubing and is supported by a bearing assembly which is mounted on the production tubing and wherein the electric motor is provided by providing the sleeve or rod with a plurality of magnets which induce the sleeve to rotate in response to generation of a rotating magnetic field by means of a series of induction coils arranged adjacent to the magnets .

3. The method of claim 1, wherein the pump pumps fluid from a first section (I) into a second section (II) of the fluidic control circuit, which circuit further comprises third section (III) and a fourth section (IV) which are alternatingly connected to either the first section (I) or the second section (II) by a set of four connecting sections, which are each equipped with a valve (A, B, C and D) , that are arranged in Wheatstone bridge configuration, such that fluid is pumped from a third section (III) to a fourth section I IV) of the control circuit if valves (A) and (D) are kept open, whilst valves (B) and (C) are kept closed, whereas fluid is pumped from the fourth section (IV) to the third section (III) of the control circuit if valves (B) and (C) are kept open, whilst valves (A) and (D) are kept closed.

4. The method of claim 1, wherein the sleeve comprises a sinusoidal groove and pump comprises a piston which is connected to a pin which is slideably arranged within the groove such that the piston is oscillated up and down within a cavity in response to the rotation of the sleeve and which cavity is alternatingly connected to the first section (I) and the second section (II) of the control circuit by means of a pair of ono way valves (Vl, V2) such that if the piston moves in one direction through the cavity fluid is sucked into :he cavity from the first section (I) via the first one-way valve and if the piston moves in an opposite direction through the cavity fluid is discharged from the cavity into the second section (II) of the control circuit.

5. The method of claim 4, wherein the oilfield equipment is actuated by a hydraulic or pneumatic piston and cylinder assembly comprising a cylinder which has a significantly larger volume than the cavity, which cylinder is at one end connected to the third section (III) and at another end to the fourth section (IV) of the control circuit such that the piston of the assembly is induced to move in one direction through the cylinder if fluid is pumped from the third section (III) into one end of the cylinder and fluid is discharged from the other end of the cylinder into the fourth section (IV) of the control circuit , whereas the pist.on is induced to move in an opposite direction through the cylinder if fluid is pumped from the fourth section i IV) into said one end of the cylinder and fluid is discharged from the other end of the cylinder into the third section (III) of the control circuit.

6. The method of claim 5, wherein the volume of the cylinder is at least 100 times larger them the volume of the cavity.

7. The method of claim 6, wherein the volume of the cylinder is at least 10000 times larger than the volume of the cavity.

8. The method of claim 3, wherein the valves A and C and the valves B and D are arranged at opposite sides of a pair of valve control rods that are each connected to a electromagnetic valve control assembly which comprises a magnetisable armature that is arranged in a gap between a pair of magnet assemblies, wherein the: polarity of the armature is switched such that the armature is induced to move up or down in the gap between the magnet assemblies, thereby moving the valve control rods up or down such that either valves A and D are closed and valves B and C are open or that valves A and D are open and valves B and C are closed.

9. The method of claim 1, wherein the oilfield equipment is a safety and/or control valve in a crude oil and/or natural gas production conduit.

10. The method of claim 9, wherein the valve is a downhole safety and/or control valve, which is arranged in a crude oil and/or natural gas production well.

11. The method of claim 1, wherein the oilfield equipment is a downhole safety and/or control valve: or a bit steering assembly in a well drilling assembly.

12. The method of claim 4, wherein the electrical pulses are provided by low power signal transmiεision system that supplies less than 10 Watt of electrical power to the electromagnetic device.

13. The method of claim 12, wherein the low power signal transmission system is selected from an insulated electrical wire, a fiber optical cable, em acoustic telemetry system, a wireless telemetry system which transmits electrical power via the well t.ubulars, and/or a rechargeable battery which is trickle charged by one or more of the foregoing low power transmission systems and/or a primary battery.

14. The method of claim 3, wherein the armature is arranged in the gap between a pair of U-ε;haped magnet assemblies and is surrounded by an electromagnetic coil which coiled around an axis which is substantially transversal to the direction of movement, of the demagnetized armature through the gap in response to transmission of an electrical pulse thrcaigh the coil and wherein the armature is connected to a rod which is oriented substantially parallel to the direction of movement of the demagnetized armature thiough the gap in response to transmission of an electrical pulse through the coil.

15. An apparatus for actuating oilfield equipment, the apparatus comprising a fluidic control circuit connected to the oilfield equipment, which circuit is connected to an oscillating pump and comprises a valve comprising an electromagnetic device with a magnetisable armature which is arranged in a gap between a firε.t and second magnet assembly and which is adapted to be sequentially demagnetized during a selected intervals of time by an electromagnetic coil through which a sequence of short electrical pulses are transmitted such that in response to an initial electric pulse the demagnet.ized armature is induced by spring force to move through the gap from the first to the second magnet assembly and such that in response to a subsequent electrical pulse the demagnetized armature is induced by spring force to move back through the gap from the second to t.he first magnet assembly.

16. The apparatus of claim 15, wherein pump comprises a piston which is connected to a pin that :.s arranged in a sinusoidal groove within a sleeve or rod that is rotated within a wellbore by an electrical moter such that the piston is induced to make a reciprocating movement within a cavity in response to a rotation of the sleeve within the wellbore.