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Title:
ELECTRIC SUBMERSIBLE PUMP WITH COMPRESSION TUBE
Document Type and Number:
WIPO Patent Application WO/2009/139660
Kind Code:
A1
Abstract:
This invention relates to an electric submersible pump (ESP) of the type typically used in the oil industry to provide artificial lift in wells that do not have enough pressure to produce to the surface. An electric submersible pump for use in a well, comprising: a motor section; a pump section; and a rotatable shaft extending through the motor and pump sections; wherein the motor and pump sections each comprise a plurality of functional components and sleeves mounted on the shaft so as to form a substantially continuous tube around the shaft; and wherein fittings are provided at the top and bottom of the shaft so as to hold the components and sleeves forming the tube in compression.

Inventors:
ORBAN JACQUES (RU)
DAVIS JOHN (RU)
GOTLIB MIKHAIL VLADILENOVICH (US)
TURGENEV KIRILL ANATOLIEVICH (RU)
Application Number:
PCT/RU2008/000304
Publication Date:
November 19, 2009
Filing Date:
May 16, 2008
Export Citation:
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Assignee:
ORBAN JACQUES (RU)
DAVIS JOHN (RU)
GOTLIB MIKHAIL VLADILENOVICH (US)
TURGENEV KIRILL ANATOLIEVICH (RU)
SCHLUMBERGER CA LTD (CA)
SCHLUMBERGER SERVICES PETROL (FR)
SCHLUMBERGER HOLDINGS (GB)
SCHLUMBERGER TECHNOLOGY BV (NL)
PRAD RES & DEV NV (NL)
International Classes:
F04D13/10; F04D7/06; F04D29/04
Foreign References:
GB717035A1954-10-20
GB652840A1951-05-02
RU2294458C12007-02-27
RU2250392C22005-04-20
RU2018716C11994-08-30
Attorney, Agent or Firm:
PROKOFIEVA, Zhanna Sergeevna (per. Ogorodnaya Sloboda 5, Moscow 0, RU)
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Claims:

Claims

1. An electric submersible pump for use in a well, comprising: a motor section; a pump section; and

- a rotatable shaft extending through the motor and pump sections; wherein the motor and pump sections each comprise a plurality of functional components and sleeves mounted on the shaft so as to form a substantially continuous tube around the shaft; and wherein fittings are provided at the top and bottom of the shaft so as to hold the components and sleeves forming the tube in compression .

2. A pump as claimed in claim 1 , further comprising a protector section disposed between the motor section and the pump section, the shaft extending through the protector section and components and sleeves in the protector section forming part of the compression tube.

3. A pump as claimed in claim 1 or 2, wherein the sections of the ESP comprise fluid filled housings, the compression tube acting to separate the outer surface of the shaft from flowing contact with fluid in the housings.

4. A pump as claimed in claim 1 , 2 or 3, wherein the shaft is of single-piece construction between the fittings.

5. A pump as claimed in any preceding claim, wherein bearings are provided in the various sections, bearing sleeves, forming part of the compression tube, being provided around the shaft where is passes through the bearings.

6. A pump as claimed in any preceding claim, wherein the motor section comprises a stator and a rotor, the rotor being mounted on the shaft and forming part of the compression tube.

7. A pump as claimed in any preceding claim, wherein the pump section comprises a series of diffusers and impellers, the impellers being mounted on the shaft and forming part of the compression tube.

8. A pump as claimed in claim 7 where the axial load form the impellers is transmitted onto the thrust bearing via the formed compression tube.

9. A pump of any of the preceding claims, comprising a shaft of constant section between the motor and the pump.

10. A pump as claimed in any preceding claim, comprising one or more seals around the shaft to limit fluid communication between the sections, the compression tube extending through the seals.

Description:

Electric Submersible Pump With Compression Tube

Technical field

This invention relates to an electric submersible pump (ESP) of the type typically used in the oil industry to provide artificial lift in wells that do not have enough pressure to produce to the surface. In particular, the invention relates to the mounting of pump components on the pump shaft. Background art

Figure 1 shows a known type of ESP. Such devices are well-known in the oil industry and are located downhole in oil wells and operated to pump oil to the surface. The ESP shown in Figure 1 comprises a section 10 with optional electronics for either system monitoring and control or a commutation system, one or more motor sections 12 (two are shown here), each of which contains a stator and a rotor mounted on a drive shaft; a protector section 14 including a pump intake 16, and a series of pump sections 18 (four are shown here, although the number of sections can be selected according to the amount of lift and volume the pump must deliver). In each of the sections, various components are mounted on a rotary shaft and the shafts in adjacent sections are connected in order that torque can be passed from the motor section(s) 12 to the pump section(s) 18. Such a construction can comprise six or more shafts made from steel, lnconel and Monel alloys.

There are a number of problems with such an arrangement that can affect the reliability of the EPS, including the difficulty in balancing the various rotating shafts for operation at speeds of up to 3000rpm, the inherent weaknesses created by the linkages between the shafts, and the extra length that each connection adds to the overall ESP length. An ESP of the type shown in Figure 1 can easily approach 50m in length and so require complex assembly on site.

In ESPs of the type shown in Figure 1 , parts of the various shafts are exposed to fluids in the various section housings. When the shaft rotates, these fluid flow across the surface of the shaft and so can cause corrosion and/or erosion, especially in the pump section where well fluids containing acidic and/or particulate materials are encountered. In the previously proposed pump designs, the problems of corrosion and/or erosion are addressed by using high-corrosion

resistant and high-strength steel for the shafts. However, such materials are expensive. Also, the shaft is exposed to high torque between each section where there is a joint or connection, leading to potential failures.

It is an object of this invention to try to provide an ESP construction that minimises some or all of the problems discussed above. Disclosure of the invention

A first aspect of this invention provides an electric submersible pump for use in a well, comprising: a motor section; a pump section; and

- a rotatable shaft extending through the motor and pump sections; wherein the motor and pump sections each comprise a plurality of functional components and sleeves mounted on the shaft so as to form a substantially continuous tube around the shaft; and wherein fittings are provided at the top and bottom of the shaft so as to hold the components and sleeves forming the tube in compression.

By providing an end-to-end compression tube around the shaft, the effects of corrosion and/or erosion can be reduced and connections to the shaft in regions of high torque avoided.

A protector section can be disposed between the motor section and the pump section, the shaft extending through the protector section and components and sleeves in the protector section forming part of the compression tube. The sections of the ESP typically comprise fluid filled housings, the compression tube acting to separate the outer surface of the shaft from flowing contact with fluid in the housings.

The shaft can be of single-piece construction between the fittings. Bearings may be provided in the various sections, bearing sleeves, forming part of the compression tube, being provided around the shaft where is passes through the bearings.

The motor section typically comprises a stator and a rotor, the rotor being mounted on the shaft and forming part of the compression tube; and the pump section

typically comprises a series of diffusers and impellers, the impellers being mounted on the shaft and forming part of the compression tube.

One or more seals may be provided around the shaft to limit fluid communication between the sections, the compression tube extending through the seals.

Other aspects of the invention will be apparent from the following description.

Brief description of the drawings

Figure 1 shows a prior art ESP;

Figure 2 shows an ESP according to an embodiment of the invention; and

Figures 3 and 4 show detailed views of the embodiment of Figure 2.

Mode(s) for carrying out the invention

Figure 2 shows an embodiment of an ESP according to the invention. This ESP comprises a single motor section 20, a protector section with a crossover and a pump inlet 22 and a single pump section 24. The overall length of the ESP is typically less than 12m.

Figures 3 and 4 show detailed sections of the ESP of Figure 2. Parts that merely comprise repeating structure have been omitted for clarity.

Figure 3 shows the motor section 20 and part of the protector section 22. The motor section 20 comprises a housing 30 with an end closure 32 into which the shaft 34 is fitted with appropriate seals and bearings. The first part of the motor section comprises a chamber 36 for either electronics system or commutator for controlling operation of the motor. This chamber 36 is separated from the motor unit by the bulkhead 37. The bottom end of the motor unit 38 comprises a locking ring 40 to located the stator 38 in the housing 30. The shaft 34 may extend downwards through the lock ring 40. The shaft includes a snap ring 42 which fits around the shaft 34 and provides a reaction fitting for rotary components located above. So, the motor itself comprises stator components 44 fixed to the housing

30, and rotor components 46 mounted on the shaft 34.

Radial bearings 50 can be provided at locations along the motor section. The bearing 50 is fixed to the housing 30 and a bearing sleeve 52 is provided around the shaft 34 where it passes though the bearing 50.

At the top of the motor section, the stator is terminated by another lock ring 54.

The shaft 34 extends upwards and enter the crossover unit 56 of the protector

section 22. Sleeves 48 are mounted on the shaft 34 above the rotor 46 so as to extend to the runner of the trust bearing system 58.

In the protector section 22 above the thrust bearing runner, the shaft 34 is provided with a series of sleeves 59 which surround the shaft as is passes through the various seals, bearings and filters located in the protector section 22. Figure 4 shows part of the protector section 22 and the pump section 24. At the top of the protector section, the shaft 34 again passes through seals and bulheads 60 before entering the pump section 24. The sleeves 59 surround the shaft 34 here also.

The pump section comprises a pump housing 62 to which is fixed a series of pump stage diffusers 64. A series of impellers 66 are mounted on the shaft 34, one for each diffuser 64, the shaft being fitted with sleeves 68 where it passes through the diffusers 64. As with the motor section, radial bearings 70 can be provided at locations along the pump section. The bearing 70 is fixed to the housing 62 and a bearing sleeve 72 is provided around the shaft 34 where it passes though the bearing 70. In some design, a tubular spacer is installed between two successive impellers to insure proper spacing on the shaft. The spacers are similar to the sleeves 59 of previous figure (but of different length).

The top of the shaft 34 is threaded and a compression nut 74 attached thereto. The end of the housing 62 is closed by a closure fitting 76. Tightening the nut 74 causes it to bear against the uppermost sleeve 68 and in turn compress all of the other sleeves and components fitted around the shaft until a continuous tube in compression is formed, the snap ring carrying the compression thus created. The effect of this is that the shaft is enclosed in a continuous sleeve that protects it from contact with flowing or circulating fluid. While fluid may penetrate between the parts of the compression tube and contact the shaft, it will not flow and so the contact will merely corrode until it is covered and no further degradation will occur. The hydraulic axial load generated at each impeller during pumping may be transmitted onto the runner of the thrust bearing by the formed continuous tube formed the impellers, various spacers and rotary sleeves of radial bearings. Further benefits are obtained by moving the compression fittings outside the high torque sections of the shaft. The snap ring and compression nut are at the top and

bottom respectively whereas the high torque regions are found between these points. The compression tube also acts to support the shaft physically so improving the overall strength of the construction.

The shaft described in the embodiment above is a single piece element. This is particularly preferred as it avoid the need for joints which can disrupt the compression tube and introduce potential weaknesses.

Also, thanks to the axial compression onto the sleeves 59, impellers 66 and rotor element (46), rotary sleeves of the bearings and various other rotary spacers, the bending rigidity of the shaft is increased.

Other changes within the scope of the invention will be apparent.