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Title:
PRE-SHAPED COMPOSITE DIAPHRAGM FOR ELECTRIC SUBMERSIBLE PUMP PROTECTOR
Document Type and Number:
WIPO Patent Application WO/2015/200020
Kind Code:
A1
Abstract:
Pre-shaped composite diaphragms for electric submersible pump (ESP) protectors are provided. In an implementation, a motor protector for an ESP has a diaphragm for containing the expansion and contraction of ESP motor oil. The diaphragm can be pre-shaped with longitudinal lobes resulting in a multi-lobed cross-sectional profile for enabling the diaphragm to inflate and deflate into a low-stress shapes to resist and avoid collapse failure and to increase lifespan. One or more fabric layers may reinforce the collapse-resistant low-stress shape of the diaphragm, and also prevent cracks from forming circumferentially around openings.

Inventors:
BALAKIN SERGEY VLADISLAVOVICH (RU)
Application Number:
PCT/US2015/035747
Publication Date:
December 30, 2015
Filing Date:
June 15, 2015
Export Citation:
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Assignee:
SCHLUMBERGER CA LTD (CA)
SCHLUMBERGER SERVICES PETROL (FR)
SCHLUMBERGER HOLDINGS
SCHLUMBERGER TECHNOLOGY BV (NL)
PRAD RES & DEV LTD
SCHLUMBERGER TECHNOLOGY CORP (US)
International Classes:
F04D13/08; B32B27/12; F04D29/00
Foreign References:
US6268672B12001-07-31
US20050142005A12005-06-30
US20050087343A12005-04-28
US20140147307A12014-05-29
US3878867A1975-04-22
Attorney, Agent or Firm:
STONEBROOK, Michael et al. (IP Administration Center of ExcellenceRoom 472, Houston Texas, US)
Download PDF:
Claims:
CLAIMS

1 . An apparatus, comprising:

a diaphragm for containing a motor oil of an electric submersible pump (ESP), the diaphragm allowing a thermal expansion and contraction of the motor oil;

an expandable wall of the diaphragm forming a hollow member having at least one open end; and

the expandable wall of the diaphragm having a multi-lobed cross- section for at least part of a length of the hollow member.

2. The apparatus of claim 1 , wherein the expandable wall of the diaphragm forms a hollow tubular member having opposing open ends.

3. The apparatus of claim 1 , wherein the diaphragm is pre- shaped to have the multi-lobed cross-section.

4. The apparatus of claim 3, wherein the expandable wall of the diaphragm having a multi-lobed cross-section is pre-shaped with a number of lobes predicted by a buckling shell theory applied to a geometry of the diaphragm.

5. The apparatus of claim 3, wherein the expandable wall of the diaphragm has three lobes disposed 120 degrees apart around a cross- sectional circumference of the diaphragm.

6. The apparatus of claim 1 , wherein the diaphragm comprises a polymer material reinforced with a layer of a fabric material bonded to the diaphragm.

7. The apparatus of claim 6, wherein the diaphragm is reinforced with a separate layer of the fabric material bonded on each side of the polymer material.

8. The apparatus of claim 6, wherein the diaphragm comprises two layers of the polymer material bonded to one layer of the fabric material between the two layers of the polymer material.

9. The apparatus of claim 6, wherein the diaphragm comprises two layers of the polymer material bonded to two layers of the fabric material, wherein every other layer comprises the fabric material.

10. The apparatus of claim 6, wherein the diaphragm comprises a polymer material selected from the group consisting of a rubber, a nitrile rubber, NHBR, a highly saturated nitrile (HSN) polymer, a fluoroelastomer, an elastomer, an isoprene, a polyisoprene, a latex, an elastane, an elastic, a neoprene, a plastic, an elastomeric plastic, and a stretchable plastic film.

11 . The apparatus of claim 6, wherein the fabric material comprises a material selected from the group consisting of a poly- paraphenylene terephthalamide, an aramid synthetic fiber, a para-aramid synthetic fiber, a meta-aramid fiber, a fluorocarbon, a polyphenylene sulfide, a carbon fiber, a spun fiber with a high tensile strength-to-weight ratio, a polyamide, and a nylon.

12. A diaphragm for a protector section of an electric submersible pump (ESP), comprising:

an expandable polymer material forming the diaphragm; and a layer of a fabric material bonded to the polymer material to reinforce the expandable polymer material.

13. The diaphragm of claim 12, wherein the diaphragm further comprises a tubular member with opposing open ends.

14. The diaphragm of claim 12, wherein the diaphragm further comprises an arrangement of layers selected from the group consisting of a layer of the expandable polymer material reinforced with a layer of the fabric material on each side of the layer of the expandable polymer material, two layers of the expandable polymer material and one layer of the fabric material between the two layers of the expandable polymer material, two layers of the expandable polymer material bonded on each side of one layer of the fabric material, two layers of the expandable polymer material bonded to two layers of the fabric material wherein every other layer comprises the fabric material, and a layer of the expandable polymer material with fabric fibers embedded in the layer of the expandable polymer material.

15. The diaphragm of claim 12, wherein the diaphragm comprises a polymer material selected from the group consisting of a rubber, a nitrile rubber, NHBR, a highly saturated nitrile (HSN) polymer, a fluoroelastomer, an elastomer, an isoprene, a polyisoprene, a latex, an elastane, an elastic, a neoprene, a plastic, an elastomeric plastic, and a stretchable plastic film.

16. The diaphragm of claim 12, wherein the fabric material comprises a material selected from the group consisting of a poly- paraphenylene terephthalamide, an aramid synthetic fiber, a para-aramid synthetic fiber, a meta-aramid fiber, a fluorocarbon, a polyphenylene sulfide, a carbon fiber, a spun fiber with a high tensile strength-to-weight ratio, a polyamide, and a nylon.

17. The diaphragm of claim 12, wherein an expandable circumference of the diaphragm is pre-shaped to have a multi-lobed cross- section.

18. A motor protector for an electric submersible pump (ESP), comprising:

a diaphragm for containing a motor oil, the motor oil capable of expanding and contracting;

a valve to protect the diaphragm from overinflating; and a material of the diaphragm pre-shaped into a multi-lobed surface for enabling the diaphragm to inflate and deflate into a low-stress shape.

19. The motor protector of claim 18, wherein the diaphragm comprises a hollow tubular member having opposing open ends; and

the diaphragm pre-shaped with lobes disposed 120 degrees apart around a cross-sectional circumference of the diaphragm and running longitudinally along the hollow tubular member.

20. The motor protector of claim 18, further comprising a fabric layer bonded to the diaphragm to reinforce the diaphragm and the low-stress shape, the fabric layer selected from the group consisting of a poly- paraphenylene terephthalamide, an aramid synthetic fiber, a para-aramid synthetic fiber, a meta-aramid fiber, a fluorocarbon, a polyphenylene sulfide, a carbon fiber, a spun fiber with a high tensile strength-to-weight ratio, a polyamide, and a nylon.

Description:
PRE-SHAPED COMPOSITE DIAPHRAGM FOR ELECTRIC

SUBMERSIBLE PUMP PROTECTOR

BACKGROUND

[0001 ] Electric submersible pumps (ESPs) provide artificial lift of liquids from wells in the hydrocarbon and water industries. ESPs may have a pump, a motor driving the pump, and a motor protector ("protector") intervening between the two. Most ESP motors are oil-filled. The oil inside the ESP motor serves several purposes: to equalize interior motor pressure against the high environmental pressure of a deep well, to cool the motor, and sometimes to serve as dielectric between stator and rotor.

[0002] The protector is connected to the ESP motor in such a way that oil can flow back and forth between the motor and protector. The protector provides a mechanism for the thermal expansion of the oil inside the ESP motor. The protector component of an ESP may also contain thrust bearings to absorb the axial load generated by the pump being driven.

[0003] A diaphragm or bellows inside the protector, while allowing thermal expansion and contraction of the oil, also isolates the oil from wellbore fluids, which may have access to the interior of the protector to compensate for the volumetric changes of the motor oil. The diaphragm may be an elastomeric bag or balloon. The diaphragm allows the oil surrounding the ESP motor to safely expand in response to the substantial heat generated by the ESP motor during operation and to contract during a cooling cycle. The volumetric changes of the oil can be relatively large in high-power single and tandem motors with large volumes of oil inside. These deformations can create high stress in the diaphragm material and can exceed the stretch limit of the material, which deteriorates over time in thermally aggressive or chemically aggressive well fluids.

SUMMARY

[0004] A pre-shaped composite diaphragm for ESP protectors is disclosed. In certain embodiments, a pre-shaped multi-lobed diaphragm is constructed from a composite material that may include a fabric and an elastomeric material. In certain embodiments, at least a portion of the pre- shaped multi-lobed diaphragm has a cross-section presenting two or more lobes. In an apparatus, a diaphragm for containing the motor oil of an ESP allows thermal expansion and contraction of the motor oil. An expandable wall of the diaphragm forms a hollow member having at least an open end, and the expandable wall of the diaphragm has a multi-lobed cross-section for at least part of a length of the hollow member. In an implementation, a diaphragm for a protector section of an ESP has an expandable polymer material forming the diaphragm and a layer of a fabric material reinforcing the expandable polymer material. A motor protector for an ESP may have a diaphragm for containing motor oil capable of expanding and contracting, a valve to protect the diaphragm from overinflating, and a material of the diaphragm pre-shaped into a multi-lobed surface for enabling the diaphragm to inflate and deflate into a low-stress shape.

[0005] This summary is not intended to identify key or essential features of the claimed subject matter, nor is it intended to be used as an aid in limiting the scope of the claimed subject matter.

BRIEF DESCRIPTION OF THE DRAWINGS

[0006] Certain embodiments of the disclosure will hereafter be described with reference to the accompanying drawings, wherein like reference numerals denote like elements. It should be understood, however, that the accompanying figures illustrate the various implementations described herein and are not meant to limit the scope of various technologies described herein.

[0007] Fig. 1 is a diagram of an example electric submersible pump (ESP) within a wellbore, including a motor protector containing an example diaphragm.

[0008] Fig. 2 is a diagram of an example diaphragm disposed within a motor protector section of an ESP.

[0009] Fig. 3 is a diagram of an example diaphragm with longitudinal lobes and a multi-lobed cross-sectional shape.

[0010] Fig. 4 is a diagram of longitudinal crack occurrence in a ruptured conventional diaphragm in relation to an example multi-lobed diaphragm.

[001 1 ] Fig. 5 is a diagram of three wave collapse failure in a conventional diaphragm in relation to an example multi-lobed diaphragm. [0012] Fig. 6 is a diagram of an example diaphragm material that has a composite of elastomer and fabric layer reinforcement.

[0013] Fig. 7 is a diagram of an example diaphragm material that has a composite of elastomer and multiple fabric layer reinforcement.

[0014] Fig. 8 is a diagram of an example diaphragm material that has a composite of multiple elastomer layers and a single fabric layer reinforcement.

[0015] Fig. 9 is a diagram of an example diaphragm material that has a composite of multiple elastomer layers and multiple interleaved fabric layers.

[0016] Fig. 10 is a diagram of example diaphragm material construction including composite elastomer layers and fabric layer reinforcement.

[0017] Fig. 11 is a diagram of example failure of conventional diaphragm material around open ends of the diaphragm in relation to an example diaphragm reinforced with a fabric layer.

[0018] Fig. 12 is a diagram of an example diaphragm having a multi-lobe cross-sectional shape resulting from three longitudinal lobes and also having a fabric layer reinforcement.

DETAILED DESCRIPTION

[0019] In the following description, numerous details are set forth to provide an understanding of some embodiments of the present disclosure. However, it will be understood by those of ordinary skill in the art that the system and/or methodology may be practiced without these details and that numerous variations or modifications from the described embodiments may be possible.

[0020] This disclosure describes example pre-shaped and composite diaphragms for electric submersible pump (ESP) protectors. Example diaphragms described herein are used in protector sections of ESPs that intervene between high-powered ESP motors and the pumps driven by the ESP motors. An example diaphragm can allow the dielectric oil in the interior of an ESP motor to safely expand and contract in response to the substantial heat generated by the ESP motor.

[0021 ] In an implementation, an example diaphragm is constructed with a multi-lobed cross-sectional shape instead of a conventional cylindrical shape with a circular cross-section. For example, a three-lobe design reduces stress because the diaphragm is manufactured in the shape that the diaphragm collapses to naturally under a theoretical model for the buckling of shells. A three-waved cross-sectional profile of the example diaphragm aims to emulate the shape of an intact collapsed diaphragm that is in a safe, low-stress shape. Destructive forces may cause a conventional diaphragm to fail by imposing structural stresses during expansion and contraction. But the example diaphragm described herein is already pre-shaped into a low-stress form that counters the usual course of collapse and failure. The example pre-shaped diaphragm not only anticipates the structural stresses imposed by destructive forces, but in an implementation, can reinforce the low-stress safe shape of the diaphragm with one or more layers of fabric composite.

[0022] In an implementation, an example diaphragm is composed of a polymer vessel, such as a rubber or elastomeric bag or balloon, reinforced with one or two layers of fabric composite to increase reliability of the example diaphragm. The fabric reinforcement may be a high tensile strength-to-weight- ratio material, such as KEVLAR (poly-paraphenylene terephthalamide - DuPont, Wilmington, Delaware), making the fiber reinforcement five times stronger than steel. The fabric reinforcing material may also be other materials enumerated further below. The composite construction increases the strength of the diaphragm significantly, while allowing the example diaphragm to remain compliant.

[0023] Certain embodiments of the example diaphragm may separately include the multi-lobed shape feature_or the fabric reinforcement feature, while certain embodiments may include both the multi-lobed shape feature and the fabric reinforcement feature.

Example Systems

[0024] In the following example systems, it will be assumed that the diaphragms or elastomeric bags described herein are used with a protector for an oil-filled electric motor of the type used with ESPs for artificial lift in wells. However, the described example diaphragms may also be used with other types of downhole or surface motors, gearboxes, pumps, turbines, or machines that benefit from employing a diaphragm or bellows.

[0025] Fig. 1 shows an example system 100, including a wellbore environment 102 with an ESP 104 installed. The wellbore 102 may be drilled into a geological formation 106 and then lined with casing 108. The casing 108 is then perforated to form channels 110 to allow fluid to flow into the casing 108. The example electric submersible pump, ESP 104, is then deployed into the wellbore 102. A deployment system 112 may consist of tubing or coiled tubing 114 connected to the pump section 116 by a connector or coupler section 118. An electrical power cable 120 may be connected to a motor 122 of the ESP 104 by an electrical connector 124, such as a pothead connector.

[0026] The example ESP 104 may have a variety of configurations depending on the application. The ESP 104 may comprise the motor 122, a motor protector 126 including an example diaphragm to be described below, a pump intake 128, and the submersible pump section 116. The example ESP 104 is deployed into the wellbore 102 to extract fluids from within the wellbore 102 and to pump the fluids to the surface. The well fluids are extracted by the example ESP 104 and delivered through the production tubing 114 from which the example ESP 104 may be suspended. [0027] Fig. 2 shows the example motor protector 126 of Fig. 1 , in greater detail, connected between an ESP motor 122 and a pump section 116 of the example ESP 104. The example protector 126 includes an example diaphragm 200. In an implementation, the example diaphragm 200 is a generally cylindrical elastomeric bladder, chamber, vessel, or bag, which may be clamped on each end by brackets, rings, or collars 202 & 202' against spaced brackets or shaft seals 204 & 204'. The example diaphragm 200 may have a multi-lobed shape profile to be explained further below.

[0028] In an implementation, a shaft 206 passes through the interior of the diaphragm 200 and connects the drive shaft (not shown) of the motor 122 to the rotor shaft (not shown) of the pump 116. An interior 208 of the diaphragm 200 is filled with (dielectric and/or cooling) oil that is conveyed to and from the ESP motor 122 through internal passages (not shown) in the protector 126 and the motor 122.

[0029] A suitable polymer or elastomer material for the example diaphragm 200 may consist of a rubber, a nitrile rubber such as NHBR, a highly saturated nitrile (HSN) polymer, a fluoroelastomer such as VITON (Dupont, Wilmington, DE) or AFLAS (Asahi Glass Co, Tokyo, Japan), an isoprene, a polyisoprene, a latex, an elastane, an elastic, a neoprene, a plastic, an elastomeric plastic, or a stretchable plastic film. A suitable material for the example diaphragm 200 may also consist of a nitrile rubber, a tetrafluoroethylene-propylene copolymer, a vinylidene fluoride hexafluoropropylene copolymer, a virtually saturated acrylonitrile-butadiene copolymer, a vinylidene fluoride-perfluoromethyl-vinylethertetrafluoroethylene terpolymer, a vinylidene fluoride hexafluoro-propylene tetrafluoroethylene terpolymer, an ethylene propylene diene methylene-based polymer, and combinations thereof.

[0030] Fig. 3 shows an example implementation of the example diaphragm 200. In an implementation, the example diaphragm 200 is a hollow member that has one open end. In another implementation, the example diaphragm 200 is a hollow tubular member that has opposing open ends 302 & 304.

[0031 ] In an implementation, the expandable wall material making up the diaphragm 200 is pre-shaped to have a multi-lobed cross-section 306 for at least a part of the length of the hollow tubular member. The multi-lobed cross- sectional shape 306 of the example diaphragm 200 addresses a mode of failure often observed in conventional tubular diaphragms. In an implementation, the example diaphragm 200 has a three-wave multi-lobe cross-section 306, with three lobes 308 & 310 & 312 built into the diaphragm 200 at 120 degrees apart from each other. Each of the three lobes runs longitudinally down the axial length of the diaphragm 200. The three lobes 308 & 310 & 312 also result in three valleys or indents between each of the lobes, which also run longitudinally down the axial length of the diaphragm 200.

[0032] As shown in Fig. 4, a conventional tubular diaphragm 400 frequently fails by rupturing in a manner that produces three cracks in the cylindrical part of the diaphragm 400. The three cracks 402 & 404 & 406 occur approximately 120 degrees apart from each other around the circumference of the diaphragm 400 and run axially along the length of the diaphragm 400. The cracks 402 & 404 & 406 begin to appear and then the diaphragm 400 ruptures. After collapse, the conventional diaphragm 400 in the collapsed state often has a three-wave cross-sectional shape 500, as shown in Fig. 5. This three-wave collapse profile is also predicted theoretically using various buckling shell theories.

[0033] The example diaphragm 200 described herein can be pre-shaped with a three-wave multi-lobe cross-sectional profile 306 to emulate the at-rest low-stress shape of a conventional collapsed diaphragm 400. The example diaphragm 200 is built with a shape that anticipates the shape profile that best relieves the stresses imposed upon the example diaphragm 200 by the potentially destructive forces inside the protector 126. The multi-lobed construction makes the example diaphragm 200 resistant to catastrophic collapse.

[0034] The multi-lobe shape 306 ensures less stress on the example diaphragm 200, especially during deflation, by allowing the example diaphragm 200 to safely deflate along a safest shape profile as predicted by buckling shell theory and as observed over numerous instances. The buckling shell theory predicts at which locations strains are proportional to changes in curvature of a theoretical diaphragm during deformations. Thus, the example diaphragm 200 can be pre-shaped with curvatures that emulate the stress- relieved collapsed state, and strengthened against collapse. Although a three- wave multi-lobe cross-section 306 is a preferred shape, other wave profiles and other numbers of lobes, such as two, four, five, and so forth, may also be used in an example diaphragm 200.

[0035] Fig. 6 shows an example diaphragm material 600 in which the expandable wall material 602 of the diaphragm 200, such as rubber or elastomer, is reinforced with a separate layer of fabric material 604 or composite.

[0036] In certain embodiments, the pre-shaped multi-lobed diaphragm 200 can be constructed from a fabric-rubber composite material. An example diaphragm 200 may be initially composed of rubber, for example, and then reinforced with fabric 604 that has better strength properties than elastomers. In an implementation, one or two layers of the fabric material 604 can be used by being bonded to the rubber or elastomeric diaphragm 200. The fabric 604 can be made of polymer fibers that have high or even extreme strength properties. A suitable fabric layer 604 or reinforcing fibers may be composed of KEVLAR (poly-paraphenylene terephthalamide, a para-aramid - DuPont, Wilmington, Delaware), a meta-aramid, such as NOMEX (Dupont, Wilmington, DE), a fluorocarbon, such as TEFLON (Dupont, Wilmington, DE), a polyphenylene sulfide, such as RYTON (Chevron Phillips Chemical Company LP, The Woodlands, TX), or polyamide fibers that have good chemical resistance to crude and synthetic oils, such as H 2 S, HCO 3 , HCI, and other acids at the high temperatures that are common in downhole conditions (e.g., 80-200 degrees C). Additionally, the fabric layer 604 or reinforcing fibers may be a carbon fiber, a polyamide, or a nylon, for example.

[0037] The fabric layer 604 and the composite material may be formed by a number of different methods, including, but not limited to, adhering the fabric 604 and rubber or elastomer layer 602 together, molding the fabric 604 and rubber layer 602, embedding the fabric layer 604 within the rubber or elastomer layer 602, and other conventional manufacturing techniques. For example, a first reinforcement, such as fabric strip, fiber, or a fabric layer 604 can be wound above, on top, or between raw rubber layers 602 and then the diaphragm can be vulcanized in an outer mold or heat wrap.

[0038] Fig. 7 shows an example diaphragm material 700 in which the expandable wall material 702, such as rubber or elastomer, is reinforced with a separate layer of the fabric material 704 on each side of the expandable wall material 702.

[0039] Fig. 8 shows an example diaphragm material 800 in which two layers of the expandable wall material 802, such as rubber or elastomer, are bonded on each side of a single layer of the fabric material 804.

[0040] Fig. 9 shows an example diaphragm material 900 in which two layers of the expandable wall material 902, such as rubber or elastomer, are interleaved with two layers of the fabric material 904, wherein every other layer comprises the fabric material 904.

[0041 ] Fig. 10 shows an example bonded sheet of the diaphragm material 800 of Fig. 8. Two layers of the expandable wall material 802, such as rubber or elastomer, are bonded on each side of a single layer of the fabric material 804.

[0042] Fig. 11 shows the location of another common type of crack 1102 and failure mode due to stress in a conventional diaphragm 400. In this failure mode, a crack 1102 forms circumferentially proximate to an open end 302 of the diaphragm 200. This failure mode may occur at either end or both ends 302 & 304 of the diaphragm 400. The reinforcement of the example diaphragm 200 with one or more of the fabric layers 604 can prevent this type of diaphragm failure.

[0043] Fig. 12 shows the example diaphragm 200 with a multi-lobe cross- sectional shape 306 resulting from three longitudinal lobes 308 & 310 & 312, and also with a fabric layer reinforcement 604. The shaft 206 transmitting drive power between the ESP motor 122 and the ESP pump section 116 may reside in a tube 1202, which may also provide a conduit for the motor oil, and provide support for collars 202 & 202' and shaft seals 204 & 204'. The multi- lobe and three-wave cross-sectional shape 306 and the fabric layer reinforcement 604 resist and prevent catastrophic collapse of the example diaphragm 200 along longitudinal lines 402 & 404 & 406 and prevent cracks 1102 from forming circumferentially near open ends 302 & 304 of the example diaphragm 200. Conclusion

[0044] Although a few embodiments of the disclosure have been described in detail above, those of ordinary skill in the art will readily appreciate that many modifications are possible without materially departing from the teachings of this disclosure. Accordingly, such modifications are intended to be included within the scope of this disclosure as defined in the claims.