The present invention relates to downhole pumping systems. More particularly, the present invention relates to a method of operating an underground reservoir, to a high performance pumping system for such an underground reservoir, and to a pumping system arranged to be mounted in a casing.

Oil, condensate or dense phase hydrocarbon reservoirs are often operated by natural water drive, or are developed with water injection which provides a water drive. Of course, whilst recovery factors of 30% to 60% can be achieved, the water flooding can mean that the remaining 70% to 40% of hydrocarbon is very difficult to recover. High gas oil ratio reservoirs typically are maintained at a moderately high reservoir pressure during their main operating life. This can cause the gas to be dissolved in the oil and thereby render both gas and oil non- recoverable. However, it is known that if it were possible to depressurise the reservoir, recovery factors could be improved.

It is an object of the present invention to provide a method of operating an underground reservoir which enables the recovery factor thereof to be increased. According to a first aspect of the present invention there is provided a method of operating an underground reservoir which is, at least partially, water driven, the method comprising the steps of providing in at least one well or borehole to the reservoir a high performance pumping system, said pumping system comprising two or more prime movers arranged to be operable simultaneously, and operating said prime movers simultaneously to remove water from the reservoir at a rate or pressure which is sufficient to effectively reduce the pressure of the reservoir.

The provision and use of a high performance pumping

system enables water to be removed from the reservoir at a rate or pressure which is sufficient to depressurise the reservoir. This enables the recovery factor of the reservoir to be increased. The underground reservoir may be an oil, condensate or dense phase hydrocarbon reservoir, and, preferably, is provided with production wells for producing the hydrocarbon.

The water drive for the reservoir may be natural, or it may be developed by water injection. The water drive may be the only drive of the reservoir or may be provided in conjunction with other drives. Generally the drive of a reservoir is determined by the natural structure thereof.

The prime movers of the pumping system are operated at a rate to depressurise the reservoir and this will generally enable the release of gas. If required, production wells for gas may be provided.

In a further embodiment, the prime movers may be operated at a rate to effectively dewater the reservoir. In this instance, previously unrecoverable minerals may be additionally released.

The present invention also extends to a high performance pumping system arranged to operate an underground reservoir by the method defined above. In an embodiment, the high performance pumping system comprises two or more prime movers mounted in a borehole or well extending to said reservoir, the prime movers being operable simultaneously to remove water from the reservoir at the rate or pressure required. In an embodiment, said high performance pumping system is arranged to remove water at a rate approaching 30,000 barrels a day, or greater. In one embodiment, said pumping system is arranged to have power of the order of lOOOkW.

In a preferred embodiment, at least one further prime mover is mounted in said borehole or well. Said further prime mover is arranged to be operated with one or more of

said first prime movers if there is a failure, that is, said further prime mover introduces redundancy into said pumping system.

According to an aspect of the present invention there is provided a high performance pumping system arranged for pumping fluids from an underground reservoir, said pumping system comprising a borehole or well,, and two or more prime movers mounted in said borehole or well, wherein said prime movers are operable simultaneously and arranged to remove fluids from said underground reservoir through said borehole or well at a high rate or pressure.

In an embodiment, said high performance pumping system is arranged to remove fluids at a rate approaching 30,000 barrels a day, or greater. In one embodiment, said pumping system is arranged to have power of the order of lOOOk . In a preferred embodiment, said pumping system is arranged such that water is removed from said underground reservoir through said borehole or well.

In a preferred arrangement, at least one further prime mover is mounted in said borehole or well. Said further prime mover is arranged to be operated with one or more of said first prime movers if there is a prime mover failure, that is, said further prime mover introduces redundancy into said pumping system. The prime movers may power any suitable artificial lifting means for removing the water from the reservoir. For example, the prime movers may power gas lifting means. Additionally and/or alternatively the prime movers may power pumping means, for example, hydraulic pumping means, or one or more pumps.

The invention further extends to a pumping system for mounting in a casing, the pumping system comprising at least two pumps arranged substantially in line, each said pump having an inlet and an outlet, and the outlet of each said pump being arranged to discharge into conduit means, wherein said conduit means extends substantially parallel

to the line of said pumps, and wherein said conduit means has a capacity arranged to be sufficient to carry the output of each of said pumps when discharging simultaneously. In a preferred embodiment, the circumferential extent of said conduit means is arranged to provide the necessary capacity. For example, in one embodiment, said conduit means comprise a plurality of conduits arranged side by side ^~ to provide the circumferential extent. In this case, each said pump is preferably arranged to discharge into a respective one of said conduits. For example, two pumps and two conduits therefor may be provided.

Additionally, and/or alternatively, said conduit means comprises a conduit having an extended circumferential extent into which said pumps are arranged to discharge. Preferably, said conduit has a generally curved cross- section, for example, in the shape of a crescent.

The curved conduit may have a circumferential extent which is less than, or equal to, half the circumference of the casing into which the pumping system is to be arranged. Preferably, said pumping system further comprises anti-recirculation means associated with the outlet of each said pump.

In an embodiment, said anti-recirculation means comprises a one way valve coupled to the outlet of each said pump.

In a preferred embodiment, measuring means are associated with the outlet of each said pump. For example, a housing for said measuring means may be coupled to each said pump outlet. Preferably, said housing is arranged substantially in line with the respective pump.

The measuring means associated with the outlet of each said pump may be arranged to measure parameters of said pump, and/or of a medium pumped thereby, for example, to measure flow, pressure, temperature and/or vibration. Additionally and/or alternatively, the measuring means

associated with the outlet of each=*said pump may be arranged to measure parameters of the environment of the pump, for example, of a well.

Preferably, at least one isolation wireline plug is provided in said conduit means below the level at which the outlet of one of the pumps is coupled thereto. In this manner, access to the conduit means below said isolation wireline plug is prevented. For example, said isolation wireline plug may be positioned below the level at which the lowest of the pumps is coupled to said conduit means.

According to a further aspect of the present invention there is provided a pumping system for mounting in a casing, the pumping system comprising at least two pumps arranged substantially in line, each said pump having an inlet and an outlet, and the outlet of each said pump being arranged to discharge into conduit means,, and wherein anti- recirculation means are associated with the flow path of each said pump.

Preferably, the anti-recirculation means are associated with the outlet of each said pump.

In an embodiment, said anti-recirculation means comprises a one way valve coupled to the outlet of each said pump.

In a preferred embodiment, measuring means are associated with the outlet of each said pump. For example, a housing for said measuring means may be coupled to each said pump outlet. .* referably, said housing is arranged substantially in line with the respective pump.

The measuring means associated with the outlet of each said pump may be arranged to measure parameters of said pump, and/or of a medium pumped thereby, for example, to measure flow, pressure, temperature and/or vibration. Additionally and/or alternatively, the measuring means associated with the outlet of each said pump may be arranged to measure parameters of the environment of the pump, for example, of a well.

In an embodiment, said conduit means comprises a single conduit extending substantially parallel to the line of the pumps, the outlet of each pump being coupled to said single conduit. Preferably, at least one isolation wireline plug is provided in said single conduit below the level at which the outlet of one of the pumps is coupled thereto. In this manner, access to the single conduit below said isolation wireline plug is prevented. For example, said isolation wireline plug may be positioned below the level at which the lowest_of the pumps is coupled to said single conduit.

In an embodiment, said conduit means has a capacity arranged to be sufficient to carry the output of each of said pumps when discharging simultaneously. In a preferred embodiment, the circumferential extent of said conduit means is arranged to provide the necessary capacity. For example, in one embodiment, said conduit means comprise a plurality of conduits arranged side by side to provide the circumferential extent. In this case, each said pump is preferably arranged to discharge into a respective one of said conduits. For example, two pumps and two conduits therefor may be provided.

Additionally, and/or alternatively, said conduit means comprises a conduit having an extended circumferential extent into which said pumps are arranged to discharge. Preferably, said conduit has a generally curved cross- section, for example, in the shape of a crescent.

The curved conduit may have a circumferential extent which is less than, or equal to, half the circumference of the casing into which the pumping system is to be arranged. The invention also extends to a submersible pumping system comprising a generally cylindrical pump assembly including a pump, and a fluid conduit extending generally parallel to.said pump assembly, wherein said fluid conduit has a generally curved cross-section, is arranged adjacent to said pump assembly, and is supported on said adjacent

pump assembly.

In an embodiment, one or more collars are provided and are arranged to clamp said fluid conduit with respect to said adjacent assembly. For example, the or each said collar may be generally curved in cross-section and may be arranged to be fastened to said conduit such that said conduit and said collar together surround or enclose said adjacent pump assembly.

Preferably, said fluid control has a generally crescent shaped cross-section.

In a preferred embodiment, the pumping system comprises at least two pump assemblies arranged substantially in line, each said pump assembly having an inlet and an outlet, and the outlet of each said pump assembly being arranged to discharge into a said fluid conduit extending generally parallel to the pump assembly. In this respect, each pump assembly may be arranged to discharge into the fluid conduit arranged adjacent thereto, and/or into a fluid conduit arranged adjacent to a succeeding pump assembly.

Preferably, anti-recirculation means are associated with the flow path of each said pump assembly.

Preferably, the anti-recirculation means are associated with the outlet of each said pump assembly. In an embodiment, said anti-recirculation means comprises a one way valve coupled to the outlet of each said pump.

In a preferred embodiment, measuring means are associated with the outlet of each said pump assembly. For example, a housing for said measuring means may be coupled to each said pump assembly outlet. Preferably, said housing is arranged substantially in line with the respective pump assembly and substantially parallel to the adjacent fluid conduit. The measuring means associated with the outlet of each said pump assembly may be arranged to measure parameters of

said pump assembly, and/or of a medium pumped thereby, for example, to measure flow, pressure, temperature and/or vibration. Additionally and/or alternatively, the measuring means associated with the outlet of each said pump assembly may be arranged to measure parameters of the environment of the pump, for example, of a well.

Preferably, said fluid conduit may have a circumferential extent which is less than, or equal to, half the circumference of the pump assembly around which it is arranged to extend.

Preferably, the pumping system comprises two or more pump assemblies arranged in line, and a respective fluid conduit is supported adjacent each said pump assembly, wherein connection means are provided for connecting said fluid conduits together in line.

In an embodiment, the end of a fluid, conduit is connected to the end of a further conduit by connection means comprising a joint having two or more bores extending therethrough and a number of tubular members arranged to be received in bores of said joint and in said conduit.

Preferably, one or more collars are arranged to be fastened to said joint to define means for encircling the pump assembly and holding the fluid conduit thereon.

In the pumping systems defined above, the pumps are preferably individually operable and individually controlled. Accordingly, the pumps may be used alternatively and/or simultaneously.

It may be required to provide two or more pumps which are to be controlled to operate simultaneously, and to provide additional pumps, to provide redundancy. The additional pumps may then be operated in the event of failure of one or more of said first pumps.

The pumps of the pumping systems defined above may comprise any suitable means for lifting fluid and may be powered by any suitable prime mover. For example, the pumps may comprise hydraulic pumping means.

In a preferred embodiment, each said pump is an electrical submersible pump. Preferably, each said electrical submersible pump is provided in a pump assembly incorporating an electric motor therefor. The pumps and/or the pump assemblies are arranged substantially in line, and generally the line extends substantially vertically. The pumps .or pump assemblies may be arranged to pump generally upwardly or to pump generally downwardly. According to a still further aspect of the present invention there is provided a bypass fluid conduit for coupling to a submersible pump assembly, said bypass fluid conduit comprising a hollow conduit having a generally curved cross-section, coupling means having a generally curved cross-section, and fastening means for fastening the coupling means and conduit together to encircle and clamp a pump assembly.

Preferably, said coupling means comprise one or more collars. The or each said collar is arranged to be fastened to said conduit, for example, to connection means arranged to hold successive lengths of said conduit together in line.

In an embodiment, the end of a fluid conduit is connected to the end of a further conduit by connection means comprising a joint having two or more bores extending therethrough and a number of tubular members arranged to be received in bores of said joint and in said conduit.

Preferably, one or more collars are arranged to be fastened to each said joint. In an embodiment, said fluid conduit has a circumferential extent which is less than, or equal to, half the circumference of the pump assembly around which it is arranged to extend. Preferably, said fluid conduit is generally crescent shaped in cross-section. Embodiments of the present invention will hereinafter be described, by way of example only, with reference to the

accompanying drawings, in which:

Figure 1 shows a side elevation view of a pumping system in accordance with the present invention which incorporates two pumps, Figure 2 shows a cross-section through a pumping system as in Figure 1 when mounted in a casing,

Figure 3 shows a cross-section similar to that of Figure 2 but illustrating the provision of two conduits, Figure 4 shows a cross-section similar to that of Figure 2 but illustrating the provision of a crescent shaped conduit,

Figure 5 shows a side elevation view of a pumping system similar to that of Figure 1 but having a bottom discharge, Figure 6 shows a side elevation view of a pumping system similar to that of Figure 5,

Figure 7 shows the support of a crescent shaped conduit by a pump assembly,

Figure 8 shows a perspective view of a joint and clamping collar of the crescent shaped conduit shown in Figure 7,

Figures 9A and 9B show a plan view and side elevation of the joint and clamping collar of Figure 8, and

Figure 10 shows an end elevation of an exploded view of the connection of two sections of crescent shaped conduit by the joint of Figures 8 and 9.

Oil, condensate or dense phase hydrocarbon reservoirs are often operated by natural water drive, or are developed with water injection, to provide reservoir pressure support and water flood sweep. However, between 40% to 70% of the hydrocarbon can be very difficult to recover. High gas oil ratio reservoirs, for example, are maintained typically at a moderately high reservoir pressure during the main operating life. Recently, it has been identified that in such high gas oil reservoirs, the gas dissolved in the normally non-recoverable oil can be accessed by

depressurising the reservoir. However, this has not been possible in practice, because the pumps available for downhole do not have the necessary performance. It will be appreciated that it is not a simple matter to increase the capacity of a pump, especially when it is necessary to contain the pump within a borehole or well.

Figure 1 shows a side elevation of a pumping system which includes two pumps which are operable in tandem and are capable of providing a high performance, for example by developing a power of the order of lOOOkW. The pumping system of Figure 1 can be used downhole in any reservoir for lifting fluids at a higher rate or pressure than has been available previously.

A pumping system of the invention, for example, as shown in Figure 1, may be mounted in a well or borehole. The pumps thereof are operable simultaneously to pump fluids from a reservoir at a high rate or pressure. In particular, a pumping system of the invention, for example as in Figure 1, may be used to withdraw water from a reservoir or adjacent formation at a high rate or pressure to effect depressurising of the reservoir. In this manner the recovery factor of the reservoir can be enhanced.

The pumping system shown in Figure 1 incorporates two pump assemblies 1 arranged to operate in tandem. Each pump assembly 1 is arranged to discharge fluid into a respective bypass conduit 2. The conduits 2 are arranged to discharge fluid flowing therein into a production tubing indicated at 3. It will be appreciated that the pumping system shown in Figure 1 will be mounted within a casing, but the casing is not shown in Figure 1. A support block 13 is provided for supporting the bottom pump assembly 1. Of course, a similar support block may be provided for the lower pump assembly 1 if required, or necessary.

In the embodiment of Figure 1, each pump assembly 1 is substantially the same and comprises an electric submersible pump. Thus, each said pump assembly 1

comprises, in the embodiment illustrated, an electric motor 4, a protector system 5, a fluid intake 6, one or more pumps 7, and a discharge head 8. Electric cables (not shown) extend within the casing to each electric motor 4 and are arranged to supply current and control signals thereto. Actuation of the electric motor 4 is arranged to drive the pump or pumps 7 such that fluid is pumped from its intake 6 to the outlet of the discharge head 8. In this respect, appropriate intakes for the fluid will be provided in the casing. The protector 5 seals the electric motor 4 from the fluid being pumped. The fluid discharged from the pump or pumps 7 by way of the discharge head 8 is passed by way of a Y piece 9 into the respective conduit 2. In this respect, such submersible pump assemblies 1, and their connection to bypass conduits by way of Y pieces are well known and will not be further described. In this respect, it will be appreciated that any suitable pumps and/or motors therefore may be provided in each pump assembly 1. Particularly, each pump assembly 1 may include more than one motor, as 4, and one or more pump components 7.

A pumping system somewhat similar to that shown in Figure 1 in which two pump assemblies 1 are mounted in line in a casing has already been proposed. However, in the known pumping system, one of the pump assemblies 1 is kept isolated from the production tubing 3 whilst the other pump assembly 1 is operated. If a fault occurs as the operational pump assembly 1 is being utilised, and/or the operational pump assembly fails in some manner, that pump assembly is shut down and isolated and the second pump assembly is made available for use. This redundancy provision is most important, given the high costs involved if it is necessary to shut down a production facility in order to change a faulty pump. However, the known dual system which has been proposed in order to incorporate redundancy cannot alternatively be used to provide two

pumps operating in tandem. Thus, if two in line pump assemblies are operated simultaneously, the fluid pumped by one pump assembly will generally be recirculated through the second pump assembly. Furthermore, the bypass conduits generally provided will not have sufficient capacity to carry the increased output from a number of pump assemblies operating simultaneously.

In the embodiment shown in Figure 1, an anti- recirculation means 10 is provided in each pump assembly 1. In the embodiment illustrated, the anti-recirculation means 10 is coupled to the outlet of the discharge head 8 by way of a housing 11. Preferably, the anti-recirculation means 10 is a one way valve arranged to prevent the flow of fluid from the bypass conduit 2 towards the pump or pumps 7. Whilst it is particularly convenient for the valve 10 to be connected to the Y piece 9, it is, of course, possible to house the valve within the Y piece 9 or to provide it at any other required location. Additional anti-recirculation means may also be provided at other locations if required or necessary. ^~

The housing 11 connected at the outlet of the discharge head 8 of each pump assembly 1 houses measuring means for measuring a number of parameters of the pump assembly and/or of the surrounding environment. The parameters to be measured may be, for example, flow rates, prevailing pressures, prevailing temperatures, and vibration. For example, if a measurement is taken of the pressure difference between the intake and the discharge of the pump or pumps 7, an indication of pump performance can be determined. Such a pressure difference can be measured by way of pressure gauges installed in the housing 11.

As well as the one way valves 10, the pumping system shown in Figure 1 is provided with additional isolation means for selectively isolating the pump assemblies 1. In this respect, each Y piece 9 is shaped to provide means to locate a wireline plug 12, or an isolation sleeve.

Depending upon the circumstances, each said wireline plug 12 may be arranged to prevent all flow in an adjacent part of the bypass conduit 2, or may be arranged to allow flow in one direction only. Thus, in the embodiment shown in Figure 1, the wireline plugs 12 may be arranged to prevent downward or reverse flow in the conduit 2, whilst allowing flow upwardly therethrough.

Figure 2 shows a cross-section through a casing 14 incorporating a _pumping system and indicates the normal configuration of one or more pump assemblies 1 in the casing 14. Thus, in Figure 2, each pump assembly 1 is shown to extend along the length of the casing 14 at the side of a respective bypass conduit 2. Although it is possible for the bypass conduit 2 associated with each pump assembly 1 to be aligned with and form a common tubing with the bypass conduit 2 of an adjacent pump assembly 1, the physical capacity of the conduits 2 may restrict the effective pumping capacity of the pumping system where it is required that the pump assemblies be operated simultaneously. ^~

Figure 3 illustrates an embodiment of a pumping system mounted in a casing in a manner to improve the pumping capacity of a number of in line pump assemblies 1. In the embodiment shown in Figure 3, two bypass conduits 2\' are provided for two pump assemblies 1. These conduits 2\' are arranged side by side within the casing 14 and thus the effective circumferential extent of the two conduits is increased as compared with the conduit 2 of Figure 2. In this respect, each pump assembly 1 may be connected to a respective, individual bypass conduit 2\', or each pump assembly 1 may be connected to each conduit 2\' . The two conduits 2\' are connected to the production tubing 3 by way of an appropriate connection (not illustrated) such that each conduit 2\' discharges into the production tubing 3. The number of conduits, as 2\', within the casing 14 may be increased. The only constraint upon the number of

conduits 2\' is therefore the space within the casing 14. However, although it is relatively easy to connect bypass conduits as 2\' to production tubing 3, and to other elements, it will be appreciated from Figure 3 that the use of a number of individual conduits as 2\' is relatively inefficient in the utilisation of the space within the casing 14.

A much more efficient use of the space within the casing 14 is shown in the embodiment of Figure 4 in which an elongate conduit 2\' \' having a crescent shaped cross section is provided to receive the fluid discharged from each pump assembly 1 of a pumping system comprising a plurality of such pump assemblies. At each of its ends, the crescent shaped conduit 2\' \' can be connected to production tubing, as 3, by connector means (not shown).

The structure and support of a crescent shaped conduit 2* \' is described further below.

It will be appreciated that the pump assemblies 1 of Figure 1 can be arranged in a casing 14 together with appropriate bypass conduits 2, 2\', 2\'\' as shown in Figures 2 to 4. Operation of the pump assemblies 1 by way of their electric motors 4 will cause fluid to be discharged into the appropriate conduits 2, 2\' , 2\' \' , and hence to be discharged into the production tubing 3. In this respect, use of several pump assemblies 1 simultaneously enables the performance of the pumping system to be increased as compared to the use of a single submersible pump assembly as is conventional. It will be appreciated that as bypass conduits, as 2\', 2\'\', no longer provide a restriction on pump capacity, more than two pump assemblies 1 may be utilised and operated simultaneously in a single casing. It will also be appreciated that such a high performance pumping system may be used in any downhole location to pump any required fluid. It is also, of course, possible to provide redundancy within a pumping system of the invention. In this case, at

least two pump assemblies 1 would be provided to be operated together to give the high pumping performance, and one or more backup pumps (not shown) would additionally be provided. The back up pumps initially would be isolated from the operational pump assemblies. Of course, if one of the operational pump assemblies failed, that assembly, in its turn, would be isolated, and one of the backup pumps utilised.

In the embodiment shown in Figure 1, the pumping system is arranged vertically, and it will be appreciated that the pump assemblies 1 are arranged to pump fluid upwardly. Furthermore, the pump assemblies 1 are effectively in parallel, and discharge fluid into a single conduit 2, 2\'\' or are in tandem and discharge fluid into more than one conduit 2\'. It would, of course, be possible to arrange the pump assemblies serially if required. In this case, each pump assembly would be arranged to discharge fluid to the next pump whereby fluid is pumped serially through all of the pump assemblies of the pumping system.

In the embodiment of Figure 1, the fluid is pumped upwardly. However, and as shown in Figure 5, fluid can be pumped downwardly and discharged from the base of the pumping system. Such an arrangement is particularly useful if the pumping system is to be used for water injection into a reservoir, or for any situation where pumping from a higher to a lower region is required.

In the pumping system of Figure 5, two pump assemblies 1 are provided and it will be seen that each pump assembly 1 is substantially the same as the assemblies shown in

Figure 1 except that each assembly is arranged the other way up. In this respect, components of the embodiment of Figure 5 which are the same or similar to components of the embodiment of Figure 1 have been given the same reference numerals. In the embodiment illustrated in Figure 5 a bottom set packer 17 is provided around discharge tubing

18 .

Figure 6 illustrates a pumping system which is similar to that of Figure 5, particularly in that it is arranged to pump fluid to a bottom discharge tubing 18. In Figure 6, components which are the same or similar to components of the embodiments Figures 1 and 5 have been given the same reference numerals. In this respect,. Figure 6 is provided with two packing systems, 17 and 19. The use of a pumping system as shown in Figure 6, for example, enables fluids to be pumped from selected zones down to further selected zones below the packer 17.

Figure 7 shows a perspective view of a pump assembly 1 and illustrates the support thereby of an adjacent crescent shaped conduit 20. The pump assembly 1 may be arranged to discharge into the conduit 20, or a further pump assembly (not shown in full) connected in line with the illustrated pump assembly 1 may additionally or alternatively be arranged to discharge into the conduit 20. In this respect, the pump assembly 1 has, as is typical, a generally cylindrical shape with reduced diameter upper and lower neck portions 21. These neck portions 21 are utilised for the support of the crescent shaped conduit 20. The crescent shaped conduit 20 is provided in sections, adjacent individual sections thereof being connected together by way of a joint 22. Each section of the conduit 20 is arranged to have substantially the same length as the length of a pump assembly 1, so that the joints 22 at either end of a section of the conduit 20 are aligned with respective ones of the neck portions 21. Each joint 22 is arranged to be connected to a respective collar 23 whereby a clamping means is defined which is arranged to fix the crescent shaped conduit 20 with respect to the pump assembly 1.

A perspective view of the joint 22 and the respective collar 23 is shown in Figure 8, whilst a plan view and an end elevation thereof are shown in Figures 9A and 9B.

Figure 10 shows schematically the connection of two sections of the crescent shaped conduit 20 by way of the joint 22.

The crescent shaped conduit 20 is generally hollow throughout. However, at each end it is formed to have three, generally parallel, cylindrical bores 24 therein. The joint 22 is similarly provided with three through bores 25. It will therefore be appreciated that an end of the crescent shaped conduit 20 can be engaged with the joint 22 by means of three tubes 26 each received within a respective bore 24 provided in the end of the crescent shaped conduit 20, and with each tube 26 similarly being received within a respective bore 25 in the joint 22. The bores 25 in the joint 22 may be straight through bores or may be provided with flanges (not shown) restricting the depth of insertion of the respective tubes 26 thereinto. It will thus be appreciated that two sections of the crescent shaped conduit 20 can be mounted together so that they are in fluid communication by way of a respective joint 22 and the tubes 26 associated therewith.

As is apparent from Figures 8 and 9A, the crescent shaped conduit 20 is shaped so that its inner concave surface can encircle part of the pump assembly 1. However, the joint 22 is stepped to form a radially inwardly extending flange 27 which extends into the neck portion 21 and can act as a support surface for the pump assembly 1. Furthermore, the flange 27 is provided with circumferential extensions 28 for engagement within the collar 23. As is indicated in Figures 9A and 9B, the coupling of the extensions 28 to the collar 23 is preferably by way of screws 29. In this respect, the collar 23 is provided with external grooves for receiving the heads of the screws 29. In the embodiment illustrated, the bores 24 are only provided at or near the end of each section of the crescent shaped conduit 20 such that the whole of the internal volume of the conduit 20 is generally available for fluid

flow. Of course, if preferred, the bores 24 could be arranged to extend over the full length of the crescent shaped conduit 20.

It will be appreciated that other modifications and variations may be made to the invention within the scope of the present application.