The present invention relates to pump motor cooling apparatus and associated method and, particularly, though not exclusively, to a retrofittable cooling sleeve apparatus and fitting method for enhancing cooling of a downhole electrical submersible pump (ESP) motor, or a progressive cavity pump (PCP) motor.

Electrical submersible pumps (ESPs) and progressive cavity pumps (PCPs) are used for a variety of applications on surface and underground in subterranean wells, most commonly in hydrocarbon extraction (oilwell) or geothermal systems (water heating system). Subterranean wells are drilled from the surface into a formation often several thousand feet deep and typically lined with a metal casing to prevent the collapse of the formation.

In hydrocarbon wells, perforations are created through the metal casing to facilitate access to the surrounding formation and thus retrieve formation fluids, such as oil. If the pressure within the well is insufficient to allow the formation fluid to naturally flow to the surface, then an artificial lift method may be required, such as a downhole electrical submersible pump (ESP), or a progressive cavity pump (PCP). In geothermal wells, superheated water from the formation needs to be pumped to the surface.

ESP's may be set deep in a well, often 10,000 feet below the surface, in typically hot and hostile environments. By their very nature, electric motors generate heat and become very hot. Confined downhole conditions can greatly exacerbate temperatures and contribute to overheating. Existing ESP systems rely, in part, on the flow of surrounding produced fluids across the exterior surface of its motor to promote heat transfer and cooling. However, downhole geometries and changing fluid viscosities and conditions may contribute to unpredictable or insufficient cooling effects. By way of example, the annular flow path between a casing bore and the outer diameter of the motor may be such that the velocity of a produced fluid over the motor casing is insufficient to provide an adequate cooling effect.

The aforementioned issues are known to contribute to premature failures of ESP motors. Since the motors constitute the lowermost components of an ESP system - a system which itself can be situated several hundred or thousand metres below the surface, any failure of the motor necessitates the entire ESP system to be "pulled” to the surface for replacement or repair. This type of essential maintenance or remedial process - known as workover - is disruptive and very expensive and to be avoided where possible.

A known method for promoting cooling of an ESP motor employs a 'motor shroud' or tube that annularly surround the motor and extends upwards above the fluid intake point of the ESP pump. This arrangement forces fluid through a smaller annular gap defined by the inner surface of the motor shroud and the outer surface of the motor casing.

Depending upon the setting position of the downhole pump with respect to the inlet perforations from the formation to the well casing bore, the fluid will first be directed downward through the outer annular gap, then upward through the inner annular gap, defined by the inner surface of the motor shroud and the outer surface of the motor casing. If the pump is positioned above the perforations, the fluid will go directly to the inner annular gap.

By reducing the size of the annular gap proximate the outer surface of the motor casing, such arrangements serve to increase the local production fluid velocity and hence increase the cooling effect. However, motor shrouds of this type can be prohibitively expensive both in terms of material cost and surface installation time and associated expense. Their use is also restricted to certain casing geometries which are sufficiently large to accommodate the required additional annular tube.

In recognition of the important of extending the operational lifetime of ESP motors, the inventor of the present invention has developed a solution which overcomes, or at least ameliorates, one or more of the shortcomings associated with known systems of the type described above.

According to a first aspect of the present invention there is provided a cooling sleeve for mounting on a motor housing of a downhole pump system; the cooling sleeve comprising: (i) an annular body provided with outwardly projecting cooling fins extending axially along the sleeve; and

(ii) a slit extending axially between opposing ends of the annular body; wherein the outwardly projecting cooling fins are defined by circumferentially spaced apart axial folds.

It will be appreciated that by providing the cooling sleeve in the form of a standalone annular body allows it to be retrofitted to the motor housings of pre-existing ESP or PCP pump systems commonly used in artificial lift applications.

Optionally the annular body comprises a connector, the connector comprising one of a male connector or a female connector, at a distal end of the annular body.

Optionally, each outwardly projecting cooling fin extends axially along the full length of the annular body between its opposite distal ends.

Optionally, each axial fold defines a pair of cooling fin side walls which are divergent.

Alternatively, each axial fold defines a pair of cooling fin side walls which are convergent.

Alternatively, each axial fold defines a pair of cooling fin side walls which are mutually parallel.

It will be appreciated that, in some embodiments, a mixture of divergent and/or convergent and/or parallel axial folds may be provided on any one cooling sleeve body.

According to a second aspect of the present invention there is provided a cooling sleeve for mounting on a motor housing of a downhole pump system; the cooling sleeve comprising an annular body, and the annular body being provided with: outwardly projecting cooling fins; a slit extending axially between opposing distal ends of the annular body; and a connector, the connector comprising one of a male connector or a female connector, at a distal end of the annular body.

In the second aspect it will be appreciated that by providing at least part of the cooling sleeve in the form of an annular body allows it to be retrofitted to the motor housings of pre-existing ESP or PCP pump systems commonly used in artificial lift applications.

Optionally, each outwardly projecting cooling fin extends helically around the annular body.

Optionally the annular body is manufactured by casting, preferably investment casting.

Optionally the outwardly projecting cooling fins of the second aspect of extend axially along the annular body, preferably along the full length of the annular cooling sleeve body between its opposite distal ends; and the outwardly projecting cooling fins are defined by circumferentially spaced apart axial folds.

Optionally, each outwardly projecting cooling fin extends axially along the full length of the annular body between its opposite distal ends.

Optionally, each axial fold defines a pair of cooling fin side walls which are divergent.

Alternatively, each axial fold defines a pair of cooling fin side walls which are convergent.

Alternatively, each axial fold defines a pair of cooling fin side walls which are mutually parallel.

The following optional features may be found in the first and/or the second aspects of the present invention. Optionally, the annular body comprises one or more of: carbon steel, stainless steel, aluminium, and or aluminium coated steel; but other suitable heat conductors are not excluded.

Optionally, the slit defines a pair of opposed boundary edges which are mechanically fastenable to one another by one or more fasteners.

Optionally, the opposed boundary edges each extend axially and are located between two adjacent axial folds.

Optionally, the opposed boundary edges are each provided with a lip for engagement with a fastener.

Optionally, the opposed boundary edges are each folded back on themselves to define said Up-

Optionally, the respective lips are defined by oppositely facing U-shaped concavities extending along a major part of the overall length of each boundary edge.

Optionally, the respective lips are interrupted by at least one pair of aligned non-folded regions constituting a minor part of the overall length of each boundary edge.

Optionally, the, or each, fastener is a two-part clamp partially positionable within a non- folded region and provided with inwardly facing protrusions which are respectively locatable with the lips proximate each non-folded region.

Optionally, the respective parts of the two-part clamp are capable of being tightened toward one another to force their inwardly facing protrusions into the U-shaped concavity of each lip and hence mechanically fasten the opposed boundary edges of the slit.

Alternatively, the opposed boundary edges are each folded back on themselves along only a part of their length to define oppositely facing lip pairs for engagement with a fastener. It will be appreciated that the folded back regions may be strengthened by spot-welding proximate their fold lines.

Optionally, one or more oppositely facing lip pairs are mutually aligned along each boundary edge.

Optionally, the respective lip pairs are defined by oppositely facing U-shaped concavities.

Optionally, the boundary edges of the respective lips of each lip pair converge in an axial direction towards the slit.

Optionally, the axially convergent boundary edges are each provided with crenelations.

Optionally, a correspondingly axially convergent fastener is mechanically engageable with each lip pair.

Optionally, the axially convergent fastener is substantially U-shaped with in-turned distal edges for locating within the oppositely facing U-shaped concavities of each lip pair.

Optionally, the in-turned distal edges of each axially convergent fastener are provided with deformable lugs which are engageable between the crenelations on each lip in an interdigital manner.

Optionally the cooling sleeve comprises at least two annular bodies; the connector of the first annular body and the connector of the second annular body being arranged to interfit to prevent axial rotation of the first annular body and the second annular body relative to each other when mounted on the motor housing.

Optionally the cooling sleeve further comprises a fastening collar for fastening the annular body to a motor housing of a downhole pump system, the fastening collar having a connector arranged to interfit with the connector of the first annular body to prevent axial rotation of the first annular body and the fastening collar relative to each other when mounted on the motor housing.

Optionally the fastening collar comprises a second connector arranged to interfit with part of the motor housing of a downhole pump system, the interfit between the second connector and the part of the motor housing of a downhole pump system preventing axial rotation of the fastening collar and the first annular body relative to the motor housing.

Optionally the fastening collar is formed in a first and a second part; the first part comprising a ring and the second part being shaped to provide a cam wedge when one distal end of the annular body is positioned within the second part.

Optionally the cooling sleeve further comprises an annular collar, the collar having projections that project further from a central axis of the annular body than the outwardly projecting cooling fins of the annular body.

According to a third aspect of the present invention there is provided a downhole pump system comprising:

(i) a pump located within a pump housing;

(ii) a motor located within an axially extending motor housing, and operably connected to the pump;

(iii) at least one cooling sleeve according to any preceding claim attached around the exterior of the motor housing; and wherein the slit in the or each annular body facilitates attachment of the cooling sleeve to the motor housing in a retrofittable manner.

It is envisaged that the pump will be either an electrical submersible pump (ESP) or a progressive cavity pump (PCP), though other types of pump are not excluded.

Optionally, the annular body is provided with an inner surface profile matched to the exterior surface profile of the motor housing to which it is attached. Optionally, the annular body is provided with an annular inner surface profile for matching to a cylindrical surface profile of the motor housing.

Optionally, the annular inner surface profile of the annular body is adapted to substantially continuously contact the exterior surface profile of the motor housing around substantially its entire circumference.

Alternatively, the annular inner surface profile of the annular body is adapted to discontinuously contact the exterior surface profile of the motor housing around substantially its entire circumference.

It will be appreciated that the surface area engagement between the inner surface of the annular body and the exterior of the motor housing is adapted to allow a minimum predetermined degree of radial heat transfer.

Optionally, circumferential surface contact between the annular body and a motor housing is absent in circumferential positions corresponding to the locations of the cooling fins.

According to a fourth aspect of the present invention there is provided a method of fitting a cooling sleeve according to the first or second aspect to a motor housing of a downhole pump system, the method comprising the steps of:

(i) sliding the or each annular body over the motor housing; and

(ii) engaging a fastener with the opposed boundary edges of the slit to thereby move the opposed boundary edges closer together and increase the surface area contact between the annular body and motor housing.

Optionally, the cooling sleeve comprises a plurality of annular bodies which are sequentially fitted in series along the length of the motor housing.

It will be appreciated that providing the cooling sleeves in modular form provides flexibility and simplifies manufacturing, transportation, storage and fitting. Where the context allows, technical features, or combinations of technical features, are interchangeable between the first, second, third, and fourth aspects of the present invention. Further features and advantages associated with the first, second, third, and fourth aspects will become apparent from the following description.

Embodiments of the present invention will now be described by way of example only, with reference to the following diagrams, in which:

Figs la shows a first embodiment of an annular body 10 of a cooling sleeve according to the present invention (connectors not shown);

Figs lb-c show a second embodiment of an annular body 100 of a cooling sleeve according to the present invention;

Fig. 2 is a cross-sectional view through A-A in annular body 10 of Fig. la and through A-A in annular body 100 Fig. lb showing the annular body 10, 100’s engagement with the exterior surface of an ESP motor housing;

Figs 3a-c are part-sectional schematic representations of different cooling fin configurations defined by external axial folds of the annular bodies 10, 100;

Figs 4a-b are schematic representations showing the formation of cooling fin configurations using a crimping tool;

Fig. 5 shows a crenelated locking wedge formed from two oppositely facing lips forming part of the boundary edges of a slit in an annular body 10, 100 of a cooling sleeve according to the first or second embodiment;

Fig. 6 shows a fastener in the form of a buckle for engaging with the locking wedge of Fig.

5;

Fig. 7 shows the buckle of Fig. 6 in-situ fastened to the crenelated locking wedge of Fig. 5; Figs 8a-c show how the buckle and wedge interact to mechanically fasten together the opposing boundary edges of the cooling sleeve slit;

Fig. 8d is a part-sectional view through B-B of Fig. 8c;

Fig. 9 shows two aligned gaps in the oppositely facing lips forming the boundary edges of the slit in the annular body of a cooling sleeve according to a third embodiment;

Fig. 10 shows a fastener in the form a two-part clamp;

Fig. 11 shows the two-part clamp of Fig. 10 in-situ at a position corresponding with the two aligned gaps of Fig. 9;

Fig. 12 is a part-sectional view through C-C of Fig. 11;

Figs. 13a-e show five alternative fastener arrangements;

Fig. 14 depicts a first fastening collar for use with any embodiment of the present invention, partially installed on a motor;

Fig. 15 is a perspective view of an alternative fastening collar for use with any embodiment of the present invention;

Fig. 16 depicts an end view of part 90a of the collar shown in Fig. 15;

Fig. 17 is a sectional view through section through line D-D of part 90a as shown in Fig,

15, when part 90b is fully inserted within part 90a;

Fig. 18 shows a fourth embodiment of annular body according to the present invention; and Fig. 19 shows a cross section through E-E of Fig. 18.

According to the present invention there is provided a cooling sleeve for an ESP motor housing as shown in Figs. la-c. The cooling sleeve has an annular body 10, 100 which is formed from a unitary annular component such as sheet metal. While describing annular bodies 10 and 100, like numerals will be used for like features. Cooling fins 12 protrude from the exterior of the annular body 10, 100 and extend between its opposite distal ends 14a, b. The respective cooling fins 12 are distributed at regular intervals around the circumference of the annular body 10, 100 and aligned in parallel along an axial direction X thereof. It will be appreciated, however, that the spacings of the fins 12 may be varied, and may be placed at irregular intervals around the circumference of the annular body 10, 100. In particular, individual spacings can adjusted in order to provide space for and protection for control lines for sensors or chemical injection etc.. As shown in Figs la-c, the cooling fins 12 are each of equal height. As shown in Fig. la, in the first embodiment, the fins 12 of body 10 are tapered proximate the opposite distal ends 14a, b of the annular body 10. As shown in Fig. lb-c, in the second embodiment, the fins 12 of body 100 have the same height along the entire length of the annular body 100. It will be appreciated that the cooling fins may be provided with irregular heights and spacings.

In a non-limiting embodiment, the annular body 10, 100 has a length of either 0.5m; a thickness of 2.5 mm; an internal radius of 72.5 mm; and a cooling fin height of approximately 18 mm. It will be appreciated that the specific dimensions may be varied. Alternative suitable lengths include (but are not limited to) lm, 1.5m, 2m, or any other desired length. Alternative suitable thicknesses include (but are not limited to) lmm-8mm, more preferably 1.5mm-6mm, and most preferably 2 mm-3 mm. For example, the height and circumferential spacing of each cooling fin 12 can be varied to suit any particular application.

A slit 16 extends in the axial direction along the full length of the annular body 10, 100 between its opposite distal ends 14a, b. The presence of the slit 16 means that the annular body 10, 100 is not entirely tubular, but rather C-shaped. It will be appreciated that the presence of the slit 16, and the nature of the sheet metal, is such that the annular body 10, 100 exhibits a degree of resilience which permits width of the slit 16 to be enlarged and reduced to facilitate its fitting to a motor housing as described in more detail below. The slit 16 defines a pair of opposed axially extending boundary edges 18a, 18b separated by a distance of approximately 12 mm. Portions of the boundary edges 18a, 18b are folded back on themselves to define an oppositely facing locking lip pair 20 for engagement with a fastener (not shown) as described more fully below with reference to Figs 5 to 7.

As best shown in Figs lb and lc., annular body 10, 100 has a female connector, recess 21a, and a male connector, lug 21b. In the embodiment shown in Figs lb and lc, the connectors 21a and 21b are positioned diametrically opposite to the axial split 16, but it will be appreciated that other orientations are not excluded. It will be appreciated that annular bodies according to the present invention can be provided with one or more male connectors and/or one or more female connectors in any combination. Additionally, it will also be appreciated that each annular body can be positioned on a motor housing in two alternative orientations.

When the cooling sleeve comprises multiple annular bodies 10, 100, it is clear that if two or more annular bodies 10, 100 are positioned on a motor housing they will all lie on axis X. Insertion of lug 21b of one annular body 10, 100 into recess 21a of another annular body 10, 100 prevents the first and second annular bodies 10, 100 from rotating around axis X. Prevention of rotation of the annular bodies relative to each other provides the advantage that the concave spaces lying between adjacent cooling fins 12 may also provide protection for control lines for sensors or chemical injection etc. even when each cooling sleeve is made up of multiple component annular bodies. An advantage of providing cooling sleeves made of multiple smaller component annular bodies is that smaller components are easier to transport, but in particular they are far easier to safely, quickly, and accurately retrofit onto downhole motors. Any downtime for downhole motor pumps is extremely expensive, so providing a retrofittable cooling system that can be installed quickly, accurately, and safely is extremely useful.

Fig. 2 is a sectional view through line A-A of Fig. la and Fig. lb showing the annular body 10, 100 surrounding the housing of an ESP motor 22. As is described more fully below, the internal cylindrical surface profile of the annular body 10, 100 contacts the exterior housing of the ESP motor 22 to promote radial heat dissipation towards the cooling fins 12.

Various cooling fin 12 configurations are shown in Figs 3a-c. The cooling fins 12 are formed as radially extending contiguous folds protruding away from intervening arcuate sheet metal segments 24 of the annular body 10, 100. Each cooling fin 12 comprises a first transition fold 13a directed away from the arcuate segments 24; an apex fold 13b directed back towards the arcuate segments 24; and a second transition fold 13c. Cooling fin side walls 26 extend between the respective transition folds 13a, 13c and the apex fold 13b, respectively.

A closed fin configuration is shown in Fig. 3a whereby the first and second transition folds 13a, 13c are immediately adjacent one another such that the side walls 26 of each cooling fin 12 slightly diverge towards the apex fold 13b. A V-shaped fin configuration is shown in Fig. 3b whereby the first and second transition folds 13a, 13c are spaced apart from one another and the side walls 26 of each cooling fin 12 converge towards the apex fold 13b. A U-shaped fin configuration is shown in Fig. 3b whereby the first and second transition folds 13a, 13c are spaced apart from one another and the side walls 26 of each cooling fin 12 extend in a mutually parallel manner towards a larger the apex fold 13b. Figs. 4a and 4b illustrate how a V-shaped fin configuration of the type shown in Fig. 3b can be formed into a closed fin configuration of the type shown in Fig. 3a by means of a crimping action (shown by arrows) which progressively reduces the radius of curvature of the apex fold 13b and moves the transitions folds 13a, 13c closer together. It will be appreciated that each of the fin configurations described above will provide differing heat dissipation characteristics; and different volumetric shapes between adjacent cooling fins 12.

Aligned portions of each boundary edge 18a, 18b are folded back on themselves, as shown in the embodiment of Figs. 5 to 8, to define oppositely facing locking lip pairs 20, having a typical length of 160 mm, for engagement with a fastener of the type shown in Fig. 6. The locking lip pairs 20 are defined by oppositely facing U-shaped concavities 28, the circumferential depths of which gradually diminish in the axial direction. The distal edges 30 of the locking lip pairs 20 converge towards the slit 16 from one end to the other at an acute angle of, for example, 2 degrees. Six pairs of notches 32 are formed along the converging distal edges 30 to provide a locking lip pair 20 in the form of a crenelated wedge.

A fastener 40 of the type shown in Fig. 6 is provided to fasten together the locking lip pairs 20 as shown in Fig. 7. The fastener 40 is generally trapezoidal in shape to match the general wedge shape of the locking lip pairs 20. The longitudinal edges of the fastener 40 are folded downwards, to form a shallow U-shaped channel, and then folded inwardly towards one another to define two inwardly turned converging distal edges 42. A series of four pairs of aligned deformable lugs 44 are distributed along the length of the respective in-turned converging distal edges 42. A series of five apertures 46 are distributed along the length of the upper surface of the fastener 40.

In use, the annular body 10, 100 is installed onto a motor housing by sliding it axially from one end thereof. The C-shaped cross-sectional profile of the cooling sleeve, and its inherent resilience, provides a virtual hinge opposite the slit 16 to assist the installation process. Once in position, the fastener 40 is presented with its widest (divergent) end proximate the narrowest (convergent) end of a locking lip pair 20 as shown in Fig. 8a. The inwardly turned converging distal edges 42 of the fastener 40 are introduced in an axial sliding manner beneath the oppositely facing U-shaped concavities 28 of the locking lip pair 20. As the fastener 40 is progressively slid over the locking lip pair 20 (see Fig. 8b) its inwardly turned converging distal edges 42 abut against the U-shaped concavities 28 of the locking lip pair. In doing so, the inwardly turned converging distal edges 42 impart a compressive force tending to move the respective lips of the locking lip pairs 20 towards one another and hence reduce the width of the slit 16. Once a desired degree of compression is achieved the lugs 44 distributed along the length of the respective in-turned converging distal edges 42 are deformed inwardly (see circled parts of Fig. 8c) to engage within corresponding notches 32 provided along the respective converging distal edges 30 of the locking lip pair 20. The fastener 40 is thereby interdigitally secured in position on the locking lip pair 20 as shown in Fig. 8d. In practice, a plurality of locking lip pairs 20 and associated fasteners 40 are distributed along the length of the slit 16 of the annular body 10, 100. In an alternative embodiment shown in Figs. 9 to 12, the respective boundary edges 18a, 18b are folded back on themselves to define lips 20 extending axially along the major part of their lengths between the opposing distal ends of the cooling sleeve 10, 100. The lips 20 are defined by oppositely facing U-shaped concavities 28. As shown in Fig. 9, the respective lips 20 are interrupted or spaced apart along their lengths to define non-folded regions 21 which are aligned across the longitudinal axis of the slit 16. The non-folded regions 21 are relatively short in length and cumulatively represent a minor part of the overall length of each boundary edge 18a, 18b.

A fastener 60 of the type shown in Fig. 10 is provided to fasten together the respective boundary edges 18a, 18b as shown in Fig. 11. The fastener 60 is a two-part clamp having two elongate wings 62, 64 each provided with oppositely threaded central apertures 66, 68. Each elongate wing 62, 64 is provided with an inwardly extending protrusion 65 extending along the major part of its lowermost peripheral edge. A bolt 70 extends laterally between the respective elongate wings 62, 64 and is provided with oppositely threaded ends 72 for cooperation with the correspondingly oppositely threaded central apertures 66, 68. A hex nut 74 is located within a central (non-threaded) portion of the bolt 70 between its oppositely threaded ends 72. A deformable tab washer 76 is mounted on the bolt 70 proximate the hex nut 74.

In use, the annular body 10, 100 is installed onto a motor housing by sliding it axially from one end thereof. The C-shaped cross-sectional profile of the cooling sleeve, and its inherent resilience, provides a virtual hinge opposite the slit 16 to assist the installation process. Once in position, the fastener 60 is provided in an initially loosened state such that its elongate wings 62, 64 are sufficiently spaced apart from one another by the bolt 70. The fastener 60 is then positioned so as to extend between two aligned non-folded regions 21 of the boundary edges 18a, 18b. Each elongate wing 62, 64 is adapted to be longer than each non-folded region 21 such that the opposing distal ends thereof partially overlap with the surrounding lips 20. The respective inwardly extending protrusions 65 of each elongate wing 62, 64 are aligned with the outwardly facing U-shaped concavities 28 of the lips 20. Once this alignment is achieved, the hex nut 74 is rotated to thereby draw together the elongate wing 62, 64 by virtue of their oppositely threaded connections with the bolt 70. In doing so, the inwardly extending protrusions 65 locate within the corresponding U-shaped concavities 28 at either side of the non-folded region 21.

Continued rotation of the hex bolt 74 imparts a compressive force tending to move the respective lips 20 towards one another and hence reduce the width of the slit 16. Once a desired degree of compression is achieved the tab washer 76 is deformed to overlie the uppermost and lowermost extents of the hex nut 74 as best shown in Fig. 12.

The fasteners 40, 60 of the embodiments described above both serve to compress the annular body 10, 100 against the exterior of a motor housing (e.g. ESP or PCP motor housings) to secure them against unwanted relative movement; and to maximise surface contact and hence heat dissipation.

It will be appreciated that present invention provides numerous advantages vis-a-vis existing cooling systems. Primarily, the addition of the cooling fins increases the surface area around the motor which is in direct contact with the passing fluid, thereby creating greater heat dissipation. In addition to providing a conduction path for heat dissipation away from a motor housing, the presence of radially extending cooling fins 12, may reduce the volume of the surrounding downhole annular flow path for production fluids, e.g. by 10-20%. Consequently, the fluid velocity adjacent the cooling fins 12 is increased which promotes more efficient heat transfer from the cooling fins to the production fluids. Another advantageous feature of the radially extending cooling fins 12 arises due to their ability to assist with centralising of an ESP or PCP within a well bore. If a motor housing is intentionally offset within a well bore, fins 12 may be provides with varying heights and/or varying spacing in order to maintain the desired positioning of an ESP or PCP within the well bore Furthermore, the concave spaces lying between adjacent cooling fins 12 may also provide protection for control lines for sensors or chemical injection etc.

A significant advantage associated with the present invention is that the annular body 10, 100 is a standalone component which may be retrofitted to pre-existing ESP or PCP motor housings. Accordingly, there is no need to make expensive or bespoke modifications to existing motor housings. Instead, an annular body 10, 100 according to the present invention can be quickly and inexpensively secured to an ESP or PCP motor housing in a workshop or at a well site using simple hydraulic tools to apply and secure fasteners 40, 60. Providing cooling sleeves as a series of modular component annular bodies 10, 100 allows relatively lightweight components, typically 0.5m or lm but longer lengths can of course be provided such as 1.5m or 2m. The modular nature of annular bodies 10, 100 allows them to be installed in series to longer motor housings, which are typically 8m in length. Applicant has found that shorter components are easier to install, particularly in downhole environments.

Although particular embodiments of the invention have been disclosed herein in detail, this has been done by way of example and for the purposes of illustration only. The aforementioned embodiments are not intended to be limiting with respect to the scope of the appended claims. It is contemplated by the inventors that various substitutions, alterations, and modifications may be made to the invention without departing from the scope of the invention as defined by the claims. In particular, although the connectors are not shown in the figures relating to annular body 10, it will be appreciated that any of the features depicted and/or described in relation to annular body 10 may be included in annular body 100, and vice versa. Particularly, annular body has at least one connector. Annular body 100 may be provided with any of the features described in relation to annular body 10, including but not limited to the nature of the axial split, the nature and/or formation of the axial fins, the boundary edges, the fastener arrangements, etc..

Examples of such modifications include alternative fastener arrangements such as those illustrated in Figs, 13a. For example, the fastener shown in Fig. 13a is a simplified version of the two-part clamp of Fig. 10. The simplified fastener employs a traditional hex nut, hex bolt and deformable washer to imparts the compressive force to the boundary edges 18a, 18b of the annular body 10, 100.

Fig. 13b depicts a mechanical hinge arrangement located diametrically opposite the slit 16. This would allow two near half-cylindrical parts of the cooling sleeve to be pivoted away from one another to simplify the process of installing the annular body 10, 100 onto a motor housing. For example, such a mechanical hinge would facilitate a clam-shell opening motion and thus enable an alternative to the axial mounting process described above.

Fig. 13c shows an alternative structure and manufacturing method for the cooling fins 12. Here, those sections can be extruded then interlocked and, optionally, spot welded to secure the extrusions and form the complete cooling sleeve.

Fig. 13d shows a deformable washer which is compressed in order to apply compressive force to the boundary edges 18a, 18b of the cooling sleeve 10, 100.

Fig. 13e shows the result of welding boundary edges 18a, 18b to each other.

Fig. 14 shows a two part fastening collar 78a, 78b for fastening an annular body (not shown in Fig. 14) to the housing of an ESP motor 22. Fastening collar 78a, 78b is formed in two half-cylindrical parts and is affixed to housing 22 by bolting part 78a to part 78b by inserting bolt 80a, through bolthole 82a and into part 78b, and by inserting bolt 80b, through bolthole 82b and into part 78a. The fastening collar has connectors 84a, 84b, which are male connectors in the form of protrusions in the present embodiment. Connectors 84a, 84b are received in the gaps between bolts 86 of the ESP motor 22, preventing rotation of collar 78a, 78b relative to ESP motor 22. Fastening collar 78a, 78b also has projections 88. The size of projections 88 is chosen so that projections 88 project further from the central axis of the ESP motor 22 than the outwardly projecting cooling fins of the annular body (not pictured in Fig. 14). Having projections that project further from the central axis of the ESP motor 22 than the outwardly projecting cooling fins of the annular body allows the projections 88 to protect the outwardly projecting cooling fins.

An alternative fastening collar is depicted in Figs. 15-17. This alternative fastening collar 90 is also formed in two parts 90a and 90b. Part 90a is an annular ring, with a connector, recess 92, which is shaped to interfit with any of the male connectors, lugs 21b, of embodiments of the annular body 10, 100 to prevent axial rotation of the annular body 10, 100 relative to fastening collar 90a, 90b when mounted on ESP motor 22. Parts 90a and 90b interfit by part 90b being expanded when an annular component is inserted through part 90a and 90b so that outer surface 94 of part 90b is forced into close frictional contact with inner surface 96 of part 90a to provide a cam wedge. Fastening collar 90a, 90b additionally has projections 98. The size of projections 98 is chosen so that projections 98 project further from the central axis of the ESP motor 22 than the outwardly projecting cooling fins of the annular body (not pictured in Fig. 14). Having projections that project further from the central axis of the ESP motor 22 than the outwardly projecting cooling fins of the annular body allows the projections 98 to protect the outwardly projecting cooling fins.

Fastening collars 78a, 78b and fastening collar 90a, 90b also restrict movement of annular bodies in one direction along the axis of a pump motor. If fastening collars are positioned at either end of an annular body, then the annular body is constrained and cannot move along the axis of the pump motor. If a cooling sleeve that comprises multiple annular bodies is fitted to a pump motor, then fastening collar 78a, 78b and fastening collar 90a, 90b can be used to prevent axial movement of multiple annular bodies, thus keeping the connectors of the multiple annular bodies connected. It will be appreciated that the prevention of axial movement of one or more annular bodies could be achieved by using multiple fastening collars 78a, 78b, or multiple fastening collars 90a, 90b, or a combination of fastening collars 78a, 78b and fastening collars 90a, 90b, or any combination of fastening collars 78a, 78b and/or fastening collars 90a, 90b with another collar or other blocking device that can prevent axial movement of an annular body.

Figs. 18 and 19 show an alternative embodiment of cooling sleeve, in which annular body 1000 is provided with outwardly projecting cooling fins 1200 that extend helically around the annular body 1000. All of the features of annular body 1000 are identical to those in annular body 10, 100, with the exception of the fin arrangements and forming methods. Like numerals are used for like features in the embodiment of Figs. 18 and 19.

In particular, it will be appreciated that any of the features described in relation to annular body 10 and/or that are described in relation to annular body 100 may be found in in annular body 1000, or compatibly used with annular body 1000, and vice versa. Particularly, annular body 1000 may be provided with any of the features described in relation to annular body 10 or 100, including but not limited to the nature of the axial split, the boundary edges, the fastener arrangements, the compatibility with locking collars, the ability to be retrofitted to a motor in a downhole environment, formation of the cooling sleeve in multiple modular parts that can be installed independently of each other, interlocked via connectors, and the interlocking preventing rotation of each annular body relative to the other annular bodies.

Annular body 1000 is formed by investment casting, and the helical fins 1200 are integrally formed. It will be appreciated that alternatively, helical fins could be retrofitted to an annular body by welding or any other suitable method.

Finally, although the described embodiments relate to cooling of motors employed in a downhole environment, it will be appreciated that the present invention is not strictly limited to downhole applications and can also be employed within surface applications.