TECHNICAL FIELD

The present invention relates to improvements to the design of actuator mechanisms to lift liquids from a deep well or wellbore by means of a reciprocating prime mover. This mechanism may also be referred to as a "Pumpjack" mechanism or prime movers and other such terms which may be described herein.

A linear reciprocating "rod pump" unit at the base of the well (which may be several thousand metres deep) is generally coupled to this drive mechanism at the surface by means of a rod string. The topmost section of the rod string - the section that emerges from the well through a pressure seal (stuffing box) - necessarily has a higher surface finish and is known as the polished (or polish) rod. For clarity, the term "rod string" can mean the rod sections connected together within the wellbore or it can also be taken to include the (uppermost section) inclusive of the polished rod. The polished rod is coupled to the reciprocating mechanism (prime mover) that relates the invention described herein.

It will also be understood that the "rod string" that connects any prime mover (drive mechanism or actuator) at the top of the well with the linear rod pump itself at the base of the well has a deadload mass of several tonnes, which must also be supported. To increase the overall efficiency of the mechanism, the deadload has to be

counterbalanced. BACKGROUND ART

It has long been known to construct such artificial lift mechanisms in the form of an oscillating horizontal beam having a hammer-shaped end, over which is cable (or bridle) from which the pumping string is suspended. The opposite end of the beam is generally driven up and down by a either a combination of a (internal combustion engine) or a rotary electric motor connected to a gearbox mechanism which ultimately converts the rotary motion torque of the gearbox to linear motion (raising and lowering) through a oscillating horizontal beam. This prime moving system which may have hundreds of moving parts is known as a conventional beam pumpjack. A North American system which is commonly known as a Roto-Flex, uses a common variable frequency drive (VFD) drive with rotary electric motor and gearbox at the base, driving a reversible belt mechanism from which the rod string is suspended on one side and a weight counterbalance on the other in which the belt is raised and lowered by the rotation and contra-rotation of a pulley mechanism. However, the Roto-flex machine is extremely large [40 to 60 feet high], and not considered energy efficient (approx 40%), expensive to move and poorly designed environmentally due to an open chain oil bath system and considered to be troublesome for these reasons.

A second example is a Chinese Harbin design, which uses an unsophisticated linear motor with an electric traveling armature and a central magnetic stator rod and mechanical type counterweights. However, this machine will, by its design demand high maintenance and is crude by North American standards.

A third example is another Chinese design, which uses a large common rotary motor and gearbox at the top of a tall tower. The back and forth rotary motor motion is converted to linear motion using cables and pulleys which, by their nature, are unreliable in the long term. With the presently used gearbox attached to the motor, the weight of the drive mechanism can be a significant problem and it encourages the tower to sway. This motor design is known to burn out and fail often making it unreliable in its present configuration.

Nevertheless, the oscillating horizontal beam or "conventional beam pumpjack" has remained the most popular device for raising and lowering a rod string that is attached to a bottomhole rod pump within a well. Variations of these reciprocating conventional pumpjacks have been in use since the eighteenth century for pumping water from tin mines. The world's first steam engine was designed to drive such a pump. Other prime movers which satisfy some of these inherent drawbacks already exist, but suffer from their own problems. In recent years a variety of alternative systems have been devised, some using directly- applied hydraulic power to raise and lower the polished rod, but these systems have many draw backs including being extremely inefficient using high amounts of power and environmentally unfriendly when high pressure hydraulic oil hoses break and oil is sprayed into and thus contaminating the local environment. They also have a poor operating history in extreme heat and / or cold weather conditions.

Although some recent mechanisms have used a gas spring (in the form of a basic pneumatic cylinder as a "prop" beneath the loaded end of the beam) it is much more common for the counterbalance to be in the form of eccentric weights, attached to the shaft of the gearbox rotary crank mechanism that drives the oscillating beam. Such a counterbalance technique adds significantly to both the inertia and the static bearing load.

For lifting fluids from a wellbore in the oil and gas industry, the linear pump stroke length has traditionally been about two or three metres, and the pumping frequency has been around seven strokes a minute although it may vary up or down depending on a specific set of circumstances. It will be understood that the traditional choices have been determined many factors such as the amount of fluid be pumped per stroke, the specific gravity of the fluid, as well as by the large mechanical masses involved and by the asymmetric action of the prime mover, which places high stress on the parts and causes significant wear on the bearings of the unit as a whole. Traditional machines have many moving parts and are required to operate for 24 hours a day, 365 days a year for several years, thus requiring regular inspection, lubrication and maintenance. It will be further understood that pumping mechanisms in the past have been designed with regard to their mechanical function alone - that is to say, the process of their design has been entirely focused on providing a reliable method of raising and lowering a long pumping string within the well tubing through which the liquid is itself raised on each upstroke of the pump. By default of the design of one such common mechanism (in which rotary motion is converted to linear motion several times a minute), no significant technology exists to measuring the means of sensing the efficacy of the pumping operation or of reacting to special conditions that may strongly affect the loads on the pumping apparatus.

For example, the mechanisms of the prior art do not generally incorporate within themselves the ability to sense and/or to react appropriately to conditions such as, a dry well, a broken rod string or a stuck valve or even "gas lock" conditions. Such conditions could only be discovered or diagnosed as a result of routine inspection and maintenance - and before that discovery the untreated condition will not only have stopped the pumping process but may have been the cause of considerable damage to the downhole tubing, rod string, rod pump or any combination of each.

The disadvantages of some of these present existing designs which use VFD technology include the fact that the motor is often used along with (or in conjunction with) a gearbox acting as a torque converter which makes it heavy and difficult to service along with the fact the fact that the existing machines of this type are not used

with electronic controls and operate inefficiently, with high starting and reversing surges, and further, that it is not possible to correctly derive real time well operating parameters from them. VFD drives, when connected to prime movers in oil and gas artificial lift situations, can achieve the following in a limited method when closely compared to a servo drive system:

i) detect pump-off and reduce speed to maintain a constant flow;

ii) vary the power during the pump cycle limiting power during the heavy load

portion (going up) of the stroke and going back up to full power during the light load of the stroke;

iii) during the light loads of the stroke (down) the speed can be increased; and iv) soft start the motor to prevent power spike which increases power cost and decreases the life of the motor;

The result of the above can increase production and reduce electrical power use depending on the well. Production increases of 15% and power reductions of 40% are common.

Recently, the use of a planar wireless (brushless 3 phase DC servomotor) in the form of both cylindrical linear and rotary actuators to replace the traditionally known artificial lift structures for lifting subterranean liquids from a wellbore has been considered. The goal was to use this wireless brushless 3 phase brushless DC servomotor to be the prime mover with which to activate a bottomhole linear submersible reciprocating rod pump apparatus [better known as a "rod pump"] using only one moving part, a gas spring in combination with a sophisticated electronic control system to sense and react to all information as it relates to the entirety of the physics of lifting fluids from a wellbore in the most efficient and cost effective method that known technology allows for same.

Incorporated by reference, are co-pending patent applications PCT/CA2007/001714 and PCT/CA2009/00194 which establish the general form of a planar wireless (having no wire windings of any kind) electrical device that is able both to be driven hard to efficiently fulfill the mechanical task of lifting fluids from a wellbore and to deduce and react to in real time, as it relates to the streams of information obtained within the entirety of system inclusive of the entirety of rod string and fluid within the wellbore and down to the "rod pump" at the base of the well.

Although a great leap forward in artificial lift technology, it has become clear that the exact designs described in PCT/CA2009/000194 may not be entirely suitable in certain situations. Accordingly, having the earlier designs as a foundation, other improvements evolved. DESCRIPTION OF THE INVENTION

The present invention relates to the design of cylindrical linear and rotary electric motors which it is intended for use an actuating lift device or commonly known in the industry also as "prime movers" for artificial lift applications in the oil and gas industry. Wireless electrical machines of a related kind have been described in GB 0421593.5, GB 0424605.4, GB 0503496.2 GB 0515313.5, GB 521577.7, GB 0617989.9, GB 0713408.3, GB 0723349.7, and PCT/GB2007/003482 inter alia.

Wireless electrical machines in and of themselves are physically distinguishable from those of conventional construction because the electrical conductors are not placed in slots in the backing iron that are orthogonal to the air gap but instead lie in the air gap and occupy almost the whole surface area of that gap. The electric current flows in patterned conducting paths that are incised into layers of insulated laminations made from conducting material. The laminations are stacked in phases and the phases are nested and bonded one within the other in the magnetic field region. They are arranged to overlap one another outside that region, being bonded together to form a self- supporting structure without a dielectric substrate. Further objectives are to ensure that the backing iron is always equidistant from the central axis, that the air gap distance is minimized and that the magnetostatic forces are radially balanced.

In the permanent-magnet cylindrical linear and rotary machines of this invention, the iron pole pieces are in the form of rings having a tapered thickness. The magnetic material is axially magnetized and is produced in the form of pre-magnetized segments that key onto the flat surfaces of two opposing ring pole pieces, so that the flux emerges radially (and at increased density) from the outer periphery of each pole piece. It is thus possible to make a large-diameter, high-thrust or high torque cylindrical machine without using any individual magnet having a dimension greater than about 15 cm.

As it relates to this invention, the permanent magnets (of themselves) may, in some circumstances, be programmed in a very unique way that uses special magnetic identities to control all magnetic structure interactions. Magnetic fields and forces are programmed by encoding a spatial pattern of "south" and "north" polarities onto the surfaces. The surfaces respond to each other according to the specific manner in which the aggregate magnetic fields are preprogrammed to respond to each other. By imparting a pattern of magnetic elements, individual field emission structures (maxels) into any magnetic material and by varying the polarities, amplitude, size shape and orientation of the dipole, magnetic structures can be created that exhibit customized field shapes and behaviors. The magnetic fields can be aligned to any tolerance required by the wireless motor.

The wireless electrical part of the cylindrical actuator of this invention consists in an assembly of patterned laminations of a conducting material (such as aluminium or copper) that is wrapped around a central dielectric cylinder in which the magnetic armature is constrained to move.

It will be understood that, because each lamination has a large area and replaces many individual coils and their interconnections by a single component, the use of the wireless technology increases the reliability of the actuator and prevents the cost of the electrical stator from being strongly dependent upon the length of the stator (and the stroke of the machine).

The electrical laminations may be laid upon and bonded to a thin carbon fibre sleeve (or another compatible type product) upon a precision cylindrical mandrel. The backing iron may or may not be a complete cylinder into which the electrical assembly must be fitted and bonded but instead will most likely be constructed from a number of straight pieces of iron that are orientated parallel to the machine axis and packed together around the conducting laminations to form a cylindrical shell. The fabricated shell is bonded to the outer surface of the laminations and at a later stage the complete assembly is fitted within the outermost casing of the actuator (which may be made from any convenient material) and resin is introduced under vacuum between the packed iron and the casing to complete the structure and to provide a thermal conducting medium.

Thus the final assembly no longer suffers a tight constraint on the positioning of the electrical assembly in relation to the backing iron, since the backing iron is now part of the electrical assembly itself and is in good thermal contact with the electrical conductors.

It is one object of this invention to provide an economical means of constructing a cylindrical electrical machine in which the limitations on the diameter and mass of the magnetic armature are overcome so that large thrusts may be produced for artificial lift purposes if required.

It is a further object of this invention to provide an economical means of building and mass producing a cylindrical electrical machine for the oil and gas industry which when applied as an artificial lift actuator or prime moving lift device, the cost and complexity of the device does not increase rapidly.

It is a further object of this invention to provide an economical means to design an electrical machine to produce more thrust in the case of linear application and more torque as would be in the case of a rotary application and to stay operationally cool. This invention allows for much higher power outputs (high speeds at high thrusts and torques) as an example. Another object of the present invention is to provide an improved artificial lift arrangement where the arrangements incorporate planar wireless motor technology.

A further object of one embodiment of the present invention is to provide an artificial lift device, comprising in combination:

a planar wireless motor having a lift device; and a cylindrical stator.

The advantages associated with the use of planar wireless motor have been briefly enumerated.

Another object of one embodiment of the present invention is to provide an artificial lift device comprising: a planar wireless motor having a housing, a cylindrical stator and cylindrical armature, said armature being movable within said housing and in sealing relation with said stator to form a pneumatic piston absent a thrust tube.

Yet another object of one embodiment of the present invention is to provide an artificial lift device for pumping liquid from a well, said well having a well head, rod string and a rod pump, comprising: a planar wireless motor having a cylindrical armature and a stator within a housing; a passive counterbalancing means for counterbalancing the load of said rod string and liquid being lifted; and a polish rod and coupling means for coupling said counterbalancing means to said armature, said armature further coupled to a rod string polish rod and to said rod string said armature being reciprocally movable within said housing.

As a further object of one embodiment of the present invention, there is provided an artificial lift device, comprising:

a passive counterbalance; a motor, said motor comprising a high torque gearless motor and including an armature and a stator; a polish rod and a rod string; and means for connecting said armature and said counterbalance to said polish rod and rod string, said armature functioning as a drive means for said counterbalance and said polish rod, said motor comprising a rotary planar wireless motor.

A still further object of one embodiment of the present invention is to provide an artificial lift device, comprising;

a planar wireless and gearless high torque rotary motor; a walking beam pumpjack absent a gearbox having a crankshaft connected to said motor, said motor providing drive means for said lift device; and a counterweight slidably mounted to said beam of said pumpjack and slidable in response to variations in the mass of the load being lifted.

Having thus generally described the invention, reference will now be made to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is a diagrammatic cross-section of the first example of an artificial lift mechanism;

Figure 2 is a partially cut away view of Figure 1;

Figure 3 is a perspective view of the complete magnetic armatures assembly;

Figure 4 is an enlarged view of the conducting vanes (laminations);

Figure 5 is an enlarged view of the stator laminations; Figure 6 is a sectional view of the armature with a (stator) vane fitted into one of the slots of the armature;

Figure 7 is a schematic illustration of radial (cylindrical) magnet segments bonded to a pole piece assembly;

Figure 8 is a schematic illustration of a complete (radial) magnet / pole piece force unit;

Figure 9 is a perspective view of a stacked array of force units forming an (magnetic) armature;

Figure 10 is a schematic illustration of a proposed conductor (stator) lamination;

Figure 11 is a schematic illustration of a conductor lamination now in a cylindrical form;

Figure 12 is a sectional view of the cylindrical stator formed over a carbon fibre inner tube;

Figure 13 is a view similar to Figure 12 illustrating the outer backing iron strips in position;

Figure 14 is a cut away view of the generally assembled linear device;

Figure 15 is a schematic illustration of the magnet and tapered pole pieces structural relationship;

Figure 16 is a schematic illustration of the force units beginning to encircle a torque tube (not shown); Figure 17 is an axial section of the rotary armature; Figure 18 is an axial section of an assembled rotary wireless motor;

Figure 19 is an insulated lamination formed in the shape of a cylinder for a rotary motor; Figure 20 is a schematic illustration of a linear lift device according to another embodiment;

Figure 21 is a cross section of the linear lift mechanism of Figure 20; Figure 22 is a schematic illustration of the cylindrical stator without the backing iron strips assembled;

Figure 23 is a cross sectional illustration of the armature for a linear device; Figure 24 is a schematic illustration of an alternate linear embodiment; Figure 25 is a schematic illustration of an alternate linear embodiment;

Figure 26 is a schematic illustration of rotary embodiment; and

Figure 27 is a schematic illustration of yet another rotary embodiment.

BEST MODE FOR CARRYING OUTTHE INVENTION In Figure 1, the artificial lift device 10 is enclosed within a casing 12, which casing also carries a "top hat" (not shown) or includes a particular filter so as to protect thrust tube 14 from the external environment. The multiple electrical conducting vanes 16 are fixed to a bottom plate 18 of the casing 12 and pass through radial slots in magnetic armature 20. The vanes 16 are electrically connected in series so that the currents flowing therein are synchronous and of identical magnitude. The magnets and pole piece units 22 of the armature 20 are arranged between the radial slots, so as to create a series of strong magnetic fields orthogonal to the electric currents flowing in the conducting vanes 16, thus producing a net electromagnetic force along the axis of the machine.

The electromagnetic force is transferred to the thrust tube 14, which moves on bearings 24 are affixed to the center tube 28. When operating at a well, the polished rod of the pump mechanism passes up through the center of the electromagnetic pumpjack via a core tube 26, which is open to the atmosphere at all times. The polished rod is clamped to a bearing that rests on the top cap of the thrust tube 14, so that vertical movements of the thrust tube / armature acting in combination are transferred to the bottom hole rod pump via the rod string.

The guide bearings 24 on the center tube 28 are designed to resist a torque such as might be applied by a conventional rod rotator mechanism interposed the polished rod and the top of the thrust tube 14.

Figure 2 is the configuration when the armature 22 (comprised of magnets and pole pieces) 20 is close to the upper part of the conducting vanes 16 of the machine 10 and it illustrates in particular the thrust tube sliding seal bearing assembly 28 and the polished rod core tube 26 and a sliding center tube seal 30, which allow the open area volume within the outer casing 12 to be pressurized with dry gas. It will be understood that one of the effects of that pressurization is to exert an upwards force on the thrust tube 14. When the correct degree of gas pressure is applied, the internal compressed gas acts as a gas spring supporting the deadload of the armature, thrust tube, rod string and oil column and bottomhole rod pump. The gas itself may be nitrogen and/or dry air or a combination of.

It is a feature of this design that the mass of gas within the spring is varied continuously in accordance with the sophisticated measured current consumption of the motor, which ensures that the minimum of electrical power is consumed by the mechanism. The other benefits of the pressurized gas are that the electrical system is completely isolated from any external inflammable gases that may or may not be present in the atmosphere around the well itself.

Figure 3 illustrates the complete armature 20 in more detail. It may be considered to consist of two modules of robust construction, in each of which short stacks of magnets and pole pieces 22 are clamped between the multiple radial slots into which the multiple of stator vanes are individually inserted one for each armature slot. The stability of the conducting vanes relative to the armature slots is held to the central region of those slots by outer guide bearings 32 and inner guide bearings 34.

Figure 4 illustrates the three phase conductors 36, 38 and 40 that form the stator conducting vanes 16. Theses phase conductors are separately cut from the metal sheet, then electrically insulated and laid one upon another before being brought together as illustrated. Each phase has two end terminals that are extended from the body of the vane and are here numbered 40, 42, 44, 46, 48 and 50. It will be understood that the current enters each phase from one terminal and travels in alternating directions along the conducting lamination to the distant end. The upper lamination is reversed and laid upon the lower one, so that when the distant ends of the paired laminations are electrically connected, the current returns to the near end along the alternating path of the upper lamination in such a way as so as to reinforce the effect of the current flowing in the lower stator lamination.

Figure 5 illustrates how the laminations for the three separate phases 36, 38 and 40 are arranged to nest together in the central region and to overlap outside the magnetic field region. It also shows how the terminations 40, 42, 44, 46, 48 and 50 remain clear of one another when the phases are nested.

Figure 6 is a cross sectional view of the magnetic armature 20 and of an electrical conducting vane 16 fitted into one of the slots thereof. The vane 16 is fitted into a rigid spine 52 along its outer length. That spine 52 is fitted with a hard metal bearing strip on both edges (the bearing strip is not shown here) and the strip comes into contact with the outer bearing blocks 32 if any misalignment should occur. Similar hard metal bearing strips are fitted to the outside of the inner edge of each conducting vane 16 and these may sometimes bear against the outer and inner guide blocks 32 and 34 respectively to prevent any misalignment.

When the words "stator", "conductor" or "lamination(s)" or any combination of etc. are used through out this document, it shall be taken to be the apparatus in which electric current is carried. When the words "armature", magnetic part" or "magnet(s)" or any combination of etc, it shall be taken to mean the permanent magnet assembly or magnetic apparatus.

Figure 7 illustrates in cylindrical schematic form how the magnet segments 54 are pinned and bonded to the lower pole piece 56. Figure 8 shows how a completed cylindrical pole piece ring with upper and lower pole piece rings 58 and 56 sandwiching the magnet array ring 54 as a cross sectional is shown in Fig 7, so as to produce a complete force unit. The inwards taper of the rings (which reduce the leakage flux) is clearly visible in the Figure. Figure 9 shows how a number of force units (having components 54, 56 and 58 as previously described in Figure 8) are stacked with like poles opposing and are clamped between the two non-magnetic end pieces 60 and 62, so as to form a complete cylindrical armature array. Figure 10 shows a typical conductor lamination as first manufactured from metal sheet, having transverse conducing paths 64, connected by axial conducting paths 66 (which may be considered to be equivalent to the end windings of a conventional coil-wound electrical machine). Figure 11 shows how the conductor lamination (in this case part of the stator assembly) is wrapped into cylindrical form. The transverse conducting paths 64 lie circumferentially and the connecting conducting paths 66 are arranged to lie axially. It will be understood that the conducting lamination is actually rolled upon and bonded to the outer surface of a thin carbon fibre sleeve, the sleeve itself being fitted to precision mandrel. It will also be noted that the ends of the transverse conducting paths 64 are bent outwards so that the conducting paths 66 stand clear of the paths 64.

Figure 12 illustrates a part of the completed cylindrical stator of the example machine. Two other sets of patterned conducting laminations 68, 70 comprise the second and third phases of the electrical system and they are nested with the first lamination 64. The connecting paths (or "end windings") 72, 74 of the phases 68, 70 are arranged to lie parallel to the connecting paths 66. The three phases are carefully insulated one from another and the ends of the phases are brought out to connecting terminals 76. The drawing shows the thin carbon fibre sleeve 78 onto which the laminations are formed and bonded. One of the end pieces of the stator assembly 80 is also shown here.

Figure 13 illustrates the assembly of Figure 12 at a later stage, with the backing iron strips 82 packed upon and bonded to the outer surface of the conducting laminations (though insulated therefrom). It should be noted that the backing iron strips 82 are omitted from the region of the axial connecting paths of the laminations and that the strips that are close to the connectors in the region 84 are shorter than the others. It will be understood that there is a corresponding gap in the iron 82 diagonally opposite to that shown, so as to maintain a magnetostatic balance across the axis of the machine.

Figure 14 illustrates how a magnetic armature assembly 86 is mounted to the output thrust tube 88 and is free to move within the sleeve 78 that forms the inner surface of the cylindrical stator assembly. The stator is fitted within and bonded to the outer casing 90, which may be made of any suitable material, such as glass fibre, aluminium or steel. The left hand side of the drawing shows a section through the transverse conducting paths 64, 68, 70 surrounded by the backing iron strips 82, whilst the right hand side of the drawing shows how the axial elements 66, 72, 74 fit within a space in the backing iron and connect with the terminations 76. Advantages attributable to these examples include: i. By the use of ring-shaped, tapered pole pieces fitted with pre-magnetized

segments, the diameter of the armature and the mass of magnetic material can be increased, so as to enhance the continuously-rated thrust of a linear actuator; ii. The mass of the electrical part such a machine may be reduced by the

replacement of wire windings (of any kind) by laminar conductors, also commonly known as stators or (stator laminations); iii. The manufacturing cost may be greatly reduced by eliminating the work of

winding and assembling a large number of coils and of bonding them into the mechanical structure; iv. The manufacturing quality and the operational reliability of the machine may be increased by the corresponding reduction in complexity; v. Because the rate of heat flow from a flat surface is greater than that from a wire bundle, the machine can be driven harder than a conventional coil-wound machine; vi. If aluminium conductors are used, they may be insulated by an anodizing process or other process, which is simple and provides a robust insulating coating that will withstand high temperature operation if necessary; vii. The construction of the backing iron, from a number of individual strips lying axially, prevents eddy current losses that would otherwise tend to flow circumferentially in a solid cylindrical casing; viii. The construction of the backing iron, from a number of individual strips lying axially and bonded to the stator conductors precisely defines the air gap distance; ix. It is possible for the electrical system to be manufactured and transported in sections, so that a very large motor may be assembled on site without undue difficulty; x. The thrust tube of such a machine may be sealed to act as part of a sophisticated gas spring subsystem that supports a deadload whilst the electromagnetic system provides the dynamic forces; xi. Such a sealed machine may also function as a fluid pump or as a mechanism by which fluid energy may be efficiently converted to electrical energy, the wireless motor being driven in reverse; and xii. The technology is fully scaleable and may be applied to electrical machines

having a wide range of sizes and power outputs. Figure 15 illustrates in diagrammatic form how the magnets 92 are fitted between tapered pole pieces 94, so as to concentrate the flux and redirect it radially outwards via the conducting laminations. It will be understood that the outer surfaces 96 of the magnet and polepieces (here shown flat) can be curved to conform to the bounding cylinder of the armature.

Figure 16 shows how the force units of Figure 15 may be abutted to encircle a torque tube (not shown). It will be understood that the taper angle of the pole piece is matched to the number of force units around the torque tube. Again, the outer facet edges 96 of the polepieces 94 and magnets 92 can also be curved to match the bounding cylinder of the armature.

Figure 17 shows an axial section of the armature, indicating how the magnets 92 are abutted along the length of each pole piece 94. Every force unit experiences a strong magnetostatic force radially outwards across the air gap and it is necessary for the complete assembly to be restrained by a bounding cylinder 98, which may, for example, be made of a non-ferrous metal or from one or more wound layers of a strong fibre. The force units are keyed into slots in torque tube 100, which rotates around the central axis 102. Figure 18 shows an axial section of the complete motor including the conducting laminations 104 and the backing iron 106. The whole assembly is fitted within a motor casing 108, which carries bearings 110 supporting the torque tube 100. It will be understood that the proportions of the motor here shown are for diagrammatical convenience only and that the machine may be constructed according to the same invention, but having an axial length much smaller than its outer diameter.

Figure 19 illustrates how the same type of lamination as shown in Figure 11 may be formed into a cylinder for use in a rotary motor. The alternating transverse conducting paths 112 are parallel to the axis of the machine, whilst the connecting paths 114 are circumferential at the ends of the motor and clear of the backing iron. For large rotary machines it may be an advantage for the formed laminations to be divided into a plurality of sectors around the circumference of the complete machine, so that each sector may be independently (but synchronously) powered at a lower voltage.

The key advantages associated with these structures include: i. By the use of tapered pole pieces fitted with pre-magnetized segments and

arranged in a ring of any chosen diameter, the mass of magnetic material can be increased as required, so as to improve the continuously-rated torque of a rotary motor; ii. The mass of the electrical part such a machine is reduced by the replacement of copper wire by laminar aluminium conductors; iii. The manufacturing cost may be greatly reduced by eliminating the work of

winding and assembling a large number of coils and of bonding them into the mechanical structure; iv. The manufacturing quality and the operational reliability of the machine are increased by the corresponding reduction in complexity; v. Because the rate of heat flow from the flat surfaces of the conducting

laminations is greater than that from a wire bundle, the machine can be driven harder than a conventional coil-wound machine; vi. If aluminium conductors are used, they may be insulated by an anodizing

process, which is simple and provides a robust insulating coating that will withstand high temperature operation if necessary; vii. The construction of the backing iron, by winding iron wire or thin steel strip to achieve the required thickness, prevents eddy current losses that would otherwise be induced in a solid cylindrical casing; and viii. The technology is fully scaleable and may be applied to electrical machines

having a wide range of sizes and power outputs.

In light of the previous advancements in the artificial lift arrangements, further embodiments are schematically illustrated in Figures 20 through 27.

Referring to Figure 20, a polished rod 120 is provided which passes through a rod rotator 130 and thrust bearing 126 set in a rod plate 128. It then passes down through the artificial lift structure 124 through the center tube seals 139 on the top surface of the center tube 135 and through dust wiper seals 156 in the base plate 158 and then into a well 180 via a stuffing box seal 122. The rod rotator 130 permits small rotations of the rod 120 with each stroke so that the rod string 121 wears evenly over time right down to the base of the wellbore where the rod pump 123 is situated. The base of the thrust tube 132, having an internal volume of gas 150 is connected to an armature 138 having stacked armature rings. The internal volume of the center tube 137 is at atmospheric pressure.

The armature 138 is comprised of a mechanical type structure and arrays of magnet pole pieces, which are caused to move with respect to stator laminations 142 provided on the inside of a backing iron assembly 144 when current is passed through the stator laminations 142. The backing iron 144 is nested to the external outer casing 143. The thrust tube 132 enters the outer main 143 body of the structure 124 via a guide bearing and seals 146 in a removable top plate 148. A gas spring effect is achieved by the presence of dry nitrogen or air 150 in a pressurized chamber which applies required additional counterbalancing force to that generated by the electrical and magnetic components of the structure. The armature 138 also has open passages 131 in the mechanical structure to allow free movement of gas within the device 124.

Figure 21 is a three dimensional cross section of an example lift mechanism is schematically illustrated in Figure 20.

Figure 22 is a schematic example of the cylindrical stator lamination arrangement 142.

Figure 23 is a cross-sectional example of the armature ring arrangement 138. Returning to Figure 21 the base of the thrust tube 132 is not sealed and gas flows from within the thrust tube 132 to and from the central volume 150. The guide rods 152 fixedly secured within the device are received by openings 154 in the armature 138. Thus, the armature 138 is maintained concentrically with the stator (not shown) and also prevented from rotation so as to resist any reactive torques.

A significant disadvantage of previous designs (in certain operational situations) is that during active artificial lift operations the height of the machine is always more than twice the stroke. This embodiment is an excellent design for machines with a stroke not exceeding 5 metres (200 inches). A machine with a five metre stroke will stand about 12 metres (39 feet) high. It will be understood that the flexing of the anti-rotation guide rods will then be significant and that the complete structure will need to be braced against strong winds. A rotary machine functions better for longstroke machines or an actuator machine, an example of which is described later in Figure 26. Another embodiment of the artificial lift structure using a internally contained piston with no extending thrust tube is schematically illustrated in Figure 24. This design almost halves the height of the machine and may completely enclose the working mechanism within the main body of the device 167 as referred to in Figure 24. In this embodiment, the motor is also a planar wireless (3 phase brushless DC servomotor) linear machine of the type described herein previously.

Referring to this embodiment 167, the artificial lift mechanism includes a base gas seal 156 in a base plate 158 and also has a gas seal 161 on the bottom outside of the armature 138 which creates a gas tight seal within the lower pressurized area 150 of the device. The device 167 is positioned over the stuffing box 122 and top of the oil well 180. The polish rod 120 connects to the rod string 121 in the top layer of the well and the rod string connects to the rod pump 123 at the base of the well. Referring to embodiment 167, an internal base plate 127 is provided to which a backing iron (strips) 144 and associated electrical conductors 142 are fixed. The outer casing is referenced by numeral 143. An upper free air space 166 is provided from which and into which atmospheric air from the outside can move via an air breathing vent 168. Foreign matter is prevented from entering the air space 166 by a protective grid/screen 170. The armature 138 is comprised of a mechanical structure and an array of magnets and pole piece rings. The polished rod 120 is coupled to the rod rotator 130 and armature 138 via a combination guide bearing and gas seal 174 which is inset into the bottom armature thrust plate 160. The anti-rotation guide rods 152 are shown as per Fig 21 also carry pressure seals (not shown).

To provide adequate dead volume to allow the gas spring to be "soft" in its action, but to allow the machine to be virtually self-contained, the armature 138 and sealing components 161 are supported (or cushioned) by a pressure chamber 150 on the underside of the armature which is able to act as a piston via a lower chamber with adequate gas flow passages are connected to an external air/nitrogen type storage tank 171. This external storage tank 171 provides all the necessary volume and pressure required by the sophisticated gas spring control system. The result of allowing the gas spring to balance the root mean square value of the current while going up and down is that the peak thrust demand from the motor is minimized. This embodiment therefore provides an artificial lift mechanism in which the armature is dynamically sealed to the inner polished lining tube of the stator 142 so as to form a pneumatic piston seal. The stator 142 is that is wrapped around the central dielectric cylinder in which the magnetic armature is constrained to move.

In this case, the gas spring system is more complex and expensive than a simple counterweight. The means of using a gas spring when applied to long-stroke machines requires an adequate sized pressure vessel 171 for the dead volume. With the exception of the technique of this second embodiment, the types of linear artificial lift device using a sophisticated gas spring typically require the machine to be more than twice the height of the stroke.

In all of the mentioned embodiments, the planar wireless servomotor may be operated in a position control loop that defines the trajectory of the motion, so that the current drawn at every instant can be used as a measure of the forces required. The current measurements can be used to calculate the key parameters of the artificial lifting operation and related process and electronically react and electronically adjust the prime mover actuator accordingly. The current measurements can also detect pipeline flow problems, low fluid levels and slow or stop the pumping as required and restarting the pumping when the problem conditions are gone. Other automatic optimizations can be added to increase flow or reduce power consumption. Down hole friction can also be measured and any changes can be displayed on a control panel or transmitted to a central control office for review. Other parameters such as fluid level and flow rate will also be available for review.

A further embodiment of an artificial lift structure using a mechanical counterbalance with a planar wireless linear motor is schematically illustrated in Figure 25. In Figure 25, no pressurized gas of any kind is required with in the main body 143 of the structure 191, but rather an external mechanical counterbalance 190 is used. The lower polished rod 120 is coupled through rod rotator 130 and a guide bearing seal assembly 174 set within the armature thrust plate 160 and passes through the dust seal 156 which enters the wellhead, 180 through a stuffing box 122 and into the well 180. The backing iron component(s) 144 and associated electrical conductor 142 is affixed and thus supported by an internal lower structural base plate 127 which is attached to the outer body.

The armature structure 138 which is also comprised of magnets and pole piece rings has venting tubes 139 to permit free air flow. An upper polished rod 184 enters via a bearing and dust seal 186 in the top of the device 191. The polished rod 184 which is suspended from a counterbalance belt 188 and pulley wheels 189 and also

counterbalance weights 190. The mass weight of the counterbalance thus supports the deadload mass of the belt 188 and the polish rod 184, the armature 138, and the lower polished rod 120 and the rod string 121 and the well fluid 125 and the rod pump 123. The armature 138 has sliding bearings 163 on the bottom outer edge which are slideably moved along the stator surface 142. Within the outer casing 143 is contained internal air 150 is at atmospheric pressure.

As will be appreciated, this is a motor having similarities to the previous embodiments, but in which the outer pressurized housing is removed and both sides of the piston are at a common pressure because the hollow piston is open at both ends. The lower piston plate is connected to the rod string and the upper piston plate is connected to a counterweight via a belt passing over a pulley (not shown). It will be understood that, in the alternative, the planar wireless linear motor may be mounted so that the counterweight forms part and/or an extension of, the armature and the pulley/roller and the belt system is connected to the bridle of the rod-string. In this case the counterweight may be smaller and the rod-rotator is affixed to the bridle so that no anti-rotation bearings need to be provided for the motor. In this embodiment, the armature does not act as a type of piston as in Figure; 24, but an open cylinder that freely travels within the confines of the stator tube, the bottom side of the armature being connected to the rod string and the top side of the armature being affixed a counterbalance weight and having a pulley or roller so mounted that a belt between the rod string and the counterweight passes there over, the motor being placed on either side of the pulley/roller as appropriate.

This embodiment therefore provides an artificial lift mechanism arranged such that the mass of the rod string and oil column is counterbalanced by a pulley and cable (or a roller and belt) that reverses the direction of travel of an appropriately-sized

counterweight so as to reduce the force required from an electric linear motor. The electrical machine is a planar wireless servomotor.

The servomotor may be operated in a position control loop that defines the trajectory of the motion, so that the current drawn at every instant can be used as a measure of the forces then required to lift the entirety of the rod string and rod pump assembly. The current measurements can be used to calculate the key parameters of the well and of the pumping system and adjust the pumping accordingly. The current measurements can also detect pipeline flow problems, low fluid levels and slow or stop the pumping as required and restarting the pumping when the problem conditions are gone. Other automatic optimizations can be added to increase flow or reduce power consumption. It should be noted that in all linear embodiments, the pumping waveform can be in any convenient form such as sections having any mathematics (e.g. a triangular waveform having different slopes and pseudo-sinusoidal end reversals). The chosen waveform is loaded into the motor controller, which measures the position of the armature by using a transducer and it provides such drive current as is necessary for the lift device to follow the waveform exactly as specified. It will be understood that in relation to all above mentioned linear embodiments, that in the alternative, the planar wireless stator of itself may also be designed with an overall length that is slightly longer than the length of stroke for the artificial lift mechanism. Embodiments of the dynamic (moving) secondary part could consist of either permanent magnet arrays, or an arrangement of short circuited wireless conductors forming an induction motor, or could consist of a moving wireless stator connected to a separate power supply forming what is known as a synchronous motor.

Another embodiment of an artificial lift structure using a counterbalance with a rotary wireless motor is schematically illustrated in Figure 26.

Figure 26 illustrates a further rotary embodiment in schematic form and as also shown in partial cross-section in reference to Figures 15, 16, 17, 18, and 19. In this

embodiment, a tower 192 is provided on a base 194, and has a platform 196 at the top supporting a high torque rotary wireless and gearless motor 272 which is connected to a cable or a belt 200, one end of which extends via a roller 202 to a bridle supporting a polished rod 120 traveling through a stuffing box 122 in well 180 and connected to rod string 121 and a rod pump 123 at the base of the well. The other end of which extends via a roller 204 to a counterweight 206 which balances the force exerted on the belt line by its own weight and the weight of the counterbalanced rod string and fluid in the well 125 The motion of the rotary gearless wireless motor 272 moves in a rotation / contra- rotation. The cable (or belt) attaches to the polished rod 120, which then enters the well 180 through the stuffing box 122 and the polished rod connects to the rod string 121 and the rod pump 123 at the base of the well.

It would be possible to simplify the system still further by constructing the motor so that the outer part was itself the belt roller and the inner stator was fixed. An artificial lift mechanism is therefore provided which comprises a pulley or roller counterbalance arrangement in which the armature of the motor itself forms the drive roller of the counterbalance belt and the motor is a planar wireless rotary servomotor. Since the principal disadvantage of the pump designs requiring heavy motor and gearbox combinations is that they need to be placed on a tall tower, the gearless high torque planar wireless motor technology offers considerable advantages. The motors in historic designs are full of heavy wire windings and are difficult to service. Further, the existing machines are not used with electronic controls and operate inefficiently with high starting and reversing surges and that it is not possible to derive well parameters from them.

In this embodiment the artificial life device comprises a rotary planar wireless servomotor of the type described in published PCT application W02009/093044, which itself forms the roller drive system of a counterbalanced rod string arrangement. A detailed description of the structure and operation of this type of rotary planar wireless motor is described in W02009/093044. The rotary wireless servomotor may be operated in a position control loop that defines the trajectory of the motion, so that the current drawn at every instant can be used as a measure of the forces then required for moving the pump. The current measurements can be used to calculate the key parameters of the well and of the pumping system. It should also be noted that an existing, well-developed high-pressure gas spring counterbalance unit as suggested in our co-pending patent application

PCT/CA2007/001714 might be modified to fit into the hollow drum on the central axis of this rotary embodiment. Referring now to Figure 27, shown is yet another embodiment of this type of rotary wireless servomotor motor 308 capable of being retro-fitted to an existing conventional beam style pumpjack 300 on a base 312. It will now be possible to use the large high torque rotary wireless motor 308 to drive the crank 310 directly as it can be gearless and drive the crank mechanism efficiently at low rpm. A computer controlled electric motor adjustable counter weight 306 that slides along the top of the walking beam 320 will maintain perfect balance, by moving a counterweight along a slide 314 with a small motor 302 and screw assembly 304 along the top of the walking beam to do fine adjustments of the counterweights 306. The conventional eccentric counterbalance arrangement of weights may still be required (not shown). The hammer head 318 of the pumpjack attaches to the bridle 316 which attaches to the polished rod 120. The polished rod goes into the stuffing box 122 and into the well 180 and connects then to the rod string 121 and ultimately to the rod pump 123 at the base of the well as discussed in pervious embodiments.

The servomotor may be operated in a position control loop that defines the trajectory of the motion, so that the current drawn at every instant can be used as a measure of the forces then required to lift the entirety of the rod string and rod pump assembly. The current measurements can be used to calculate the key parameters of the well and of the pumping system and adjust the pumping accordingly. The current measurements can also detect pipeline flow problems, low fluid levels and slow or stop the pumping as required and restarting the pumping when the problem conditions are gone. Other automatic optimizations can be added to increase flow or reduce power consumption.

It will be also understood that, (as an alternate to permanent magnet arrays), the planar wireless rotary motor may also be designed as an arrangement of short circuited wireless conductors forming a rotary wireless induction motor, or could consist of a moving wireless stator connected to a separate power supply forming what is known as a planar wireless rotary synchronous motor.

Advantageously, the use of planar wireless (brushless 3 phase DC) servomotors in all the embodiments as they relate to linear and rotary artificial lift as described at least provide the following advantages:

> automatically monitor, control, optimize and report well pumping conditions;

> zero hysteresis [current flow to output thrust];

> can be operated remotely from other locations; > design can be scaled for large or small across a wide range of torques, thrusts, speeds, etc.;

> maximum power limits can be pre-set;

> automatic shutdown on unsafe conditions;

> increase efficiency - high power efficiencies through proprietary design features; and

> can be gearless and operate efficiently at low revolutions per minute (rpm).