WO2016053588A1

WO2016053588A1 - Low angle electric submersible pump with gravity sealing

Info

Publication number: WO2016053588A1
Application number: PCT/US2015/049283
Authority: WO
Inventors: Arthur Watson; Grant Thomas HARRIS; Diego Narvaez; Alejandro CAMACHO CARDENAS
Original assignee: Schlumberger Canada Limited; Services Petroliers Schlumberger; Schlumberger Holdings Limited; Schlumberger Technology B.V.; Prad Research And Development Limited; Schlumberger Technology Corporation
Priority date: 2014-09-30
Filing date: 2015-09-10
Publication date: 2016-04-07

Abstract

An electric submersible pump having a protector section with a gravity sealing chamber having a hanging orifice and a standing orifice positioned in a vertical separation orientation whereby the orifices are located on opposite sides of a center axis and the orifices are vertically separated from one another when the center axis is offset from vertical.

Description

LOW ANGLE ELECTRIC SUBMERSIBLE PUMP WITH GRAVITY SEALING

RELATED APPLICATION

[0001] This application claims priority to and the benefit of a U.S. Provisional Patent Application having Serial No. 62/057,718, filed 30 September 2014, which is incorporated by reference herein.

BACKGROUND

[0002] This section provides background information to facilitate a better understanding of the various aspects of the disclosure. It should be understood that the statements in this section of this document are to be read in this light, and not as admissions of prior art.

[0003] A variety of production fluids are pumped from subterranean environments. Different types of submersible pumping systems may be disposed in production fluid deposits at subterranean locations to pump the desired fluids to the surface of the earth.

[0004] For example, in producing petroleum and other useful fluids from production wells, it is generally known to provide a submersible pumping system for raising the fluids collected in a well. Production fluids, e.g. petroleum, enter a wellbore drilled adjacent a production formation. Fluids contained in the formation collect in the wellbore and are raised by the submersible pumping system to a collection point at or above the surface of the earth.

[0005] A typical submersible pumping system comprises several components, such as a submersible electric motor that supplies energy to a submersible pump. The system further may comprise a variety of additional components, such as a connector used to connect the submersible pumping system to a deployment system. Conventional deployment systems include production tubing, cable and coiled tubing. Additionally, power is supplied to the submersible electric motor via a power cable that runs through or along the deployment system. [0006] Often, the subterranean environment (specifically the well fluid) and fluids that are injected from the surface into the wellbore (such as acid treatments) contain corrosive compounds. These corrosive agents can be detrimental to components of the submersible pumping system, particularly to internal electric motor components, such as copper windings and bronze bearings. Moreover, irrespective of whether or not the fluid is corrosive, if the fluid enters the motor and mixes with the motor oil, the fluid can degrade the dielectric properties of the motor oil and the insulating materials of the motor components. Accordingly, it is highly desirable to keep these external fluids out of the internal motor fluid and components of the motor.

[0007] Submersible electric motors are difficult to protect from corrosive agents and external fluids because of their design requirements that allow use in the subterranean environment. A typical submersible motor is internally filled with a fluid, such as a dielectric oil, that facilitates cooling and lubrication of the motor during operation. As the motor operates, however, heat is generated, which, in turn, heats the internal motor fluid causing expansion of the oil. Conversely, the motor cools and the motor fluid contracts when the submersible pumping system is not being used.

[0008] In many applications, submersible electric motors are subject to considerable temperature variations due to the subterranean environment, injected fluids, and other internal and external factors. These temperature variations may cause undesirable fluid expansion and contraction and damage to the motor components. For example, the high temperatures common to subterranean environments may cause the motor fluid to expand excessively and cause leakage and other mechanical damage to the motor components. These high temperatures also may destroy or weaken the seals, insulating materials, and other components of the submersible pumping system. Similarly, undesirable fluid expansion and motor damage can also result from the injection of high-temperature fluids, such as steam, into the submersible pumping system.

[0009] Accordingly, this type of submersible motor benefits from a motor fluid expansion system able to accommodate the expanding and contracting motor fluid. The internal pressure of the motor must be allowed to equalize or at least substantially equalize with the surrounding pressure found within the wellbore. As a result, it becomes difficult to prevent the ingress of external fluids into the motor fluid and internal motor components.

[0010] Numerous types of motor protectors have been designed and used in isolating submersible motors while permitting expansion and contraction of the internal motor fluid. Varieties of elastomeric bladders alone or in combination with labyrinth sections have been used as a barrier between the well fluid (i.e., environmental liquid) and the motor fluid (i.e., protectant liquid). For example, expandable elastomeric bags or bladders have been used in series to prevent mixing of wellbore fluid with motor fluid while permitting expansion and contraction of the motor fluid.

[0011] The conventional labyrinth type protector uses the difference in specific gravity of the well fluid, a liquid, and the motor fluid, a liquid, to separate the fluids. For example, a typical labyrinth may embody a chamber having a first passageway to the motor fluid and a second passageway to an undesirable fluid, such as fluids in the wellbore. The first and second passageways are generally oriented on opposite sides of the chamber to maintain fluid separation in a vertical orientation. Accordingly, conventional labyrinth type protectors are generally less effective, or totally useless, in orientations deviated from the vertical orientation.

SUMMARY

[0012] This summary is provided to introduce a selection of concepts that are further described below in the detailed description. 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 claimed subject matter.

[0013] In accordance to one or more embodiments a submersible system includes a submersible motor containing a motor liquid and a motor protector in fluid communication with the motor and an exterior environment, the motor protector having a center axis and an outer housing defining a chamber between a first end body and a base end body for gravity separation of the motor liquid from an environmental liquid. The motor protector including a hanging orifice providing fluid communication through the first end body to permit flow of a first liquid into the chamber and a motor standing orifice providing fluid communication between the chamber and the motor through the base end body, wherein the hanging orifice and the motor standing orifice are positioned in a vertical separation orientation whereby the orifices are located on opposite sides of the center axis and the orifices are vertically separated from one another when the center axis is offset from vertical.

BRIEF DESCRIPTION OF THE DRAWINGS

[0014] The disclosure is best understood from the following detailed description when read with the accompanying figures. It is emphasized that, in accordance with standard practice in the industry, various features are not drawn to scale. In fact, the dimensions of various features may be arbitrarily increased or reduced for clarity of discussion.

[0015] Figure 1 illustrates a wellbore in which an electric submersible pump (ESP) according to one or more aspects of the disclosure is deployed.

[0016] Figure 2 illustrates an ESP with a gravity sealing motor protector according to one or more aspects of the disclosure.

[0017] Figure 3 illustrates an orifice oriented motor protector according to one or more aspects of the disclosure.

[0018] Figures 4 to 11 illustrate example of connections of a motor protector according to one or more aspects of the disclosure.

[0019] Figures 12 and 13 illustrate example of orienting an ESP with a gravity sealing motor protector in a low angle position according to one or more aspects of the disclosure.

[0020] Figures 14 to 17 illustrate examples of ESP and gravity sealing motor protectors according to one or more aspects of the disclosure.

DETAILED DESCRIPTION

[0021] It is to be understood that the following disclosure provides many different embodiments, or examples, for implementing different features of various embodiments. Specific examples of components and arrangements are described below to simplify the disclosure. These are, of course, merely examples and are not intended to be limiting. In addition, the disclosure may repeat reference numerals and/or letters in the various examples. This repetition is for the purpose of simplicity and clarity and does not in itself dictate a relationship between the various embodiments and/or configurations discussed.

[0022] As used herein, the terms connect, connection, connected, in connection with, and connecting may be used to mean in direct connection with or in connection with via one or more elements. Similarly, the terms couple, coupling, coupled, coupled together, and coupled with may be used to mean directly coupled together or coupled together via one or more elements. Terms such as up, down, top and bottom and other like terms indicating relative positions to a given point or element are may be utilized to more clearly describe some elements. Commonly, these terms relate to a reference point such as the surface from which drilling operations are initiated.

[0023] Electric submersible pumps (ESPs) may be installed in a flow conduit (e.g. casing, pod, caisson, or capsule) at a wide range of angles, varying from vertical with the discharge at the upper end, to horizontal, to vertical with the discharge at the lower end. In applications that are less than approximately 30° from vertical, gravity separation of well fluid from motor oil is often utilized to retain the motor oil and to prevent well fluid entry into the motor. Gravity separation is historically done with labyrinth seal sections and gravity or barrier fluid chambers.

[0024] Labyrinth seal sections (aka protector, seal section module, compensator) chambers work on reverse gravity separation. They feature a hanging tube and a standing tube within an elongated housing. During thermal expansion of the motor oil, the denser well fluid (generally water based) in the lower end of the labyrinth is expelled upward toward the wellbore through the hanging tube. During thermal contraction, the less dense motor oil flows downward toward the motor through the standing tube.

[0025] Gravity or barrier fluid chambers feature an elongated housing without the hanging and standing tubes. The gravity chamber contains a dense barrier fluid such as fluorinated oil that prevents the less dense well fluid from entering the motor. Below the gravity chamber, there is a labyrinth to prevent the barrier fluid from migrating downward into the motor filled with lighter oil.

[0026] Both of these types of chambers depend on vertical separation of the standing and hanging orifices to establish a vertical range of interface between the separated fluids, this interface moving up and down with the thermal cycling of the motor oil. In a labyrinth chamber, the orifices comprise the open ends of the tubes, while in a gravity chamber the orifices comprise the communication passages or conduits through the bodies at the upper and lower ends of the chambers.

[0027] When either system is installed at an angle deviating from vertical, the vertical separation of the orifices is diminished. The diminishing effect can be increased by the fact that the rotational angle (around the axis of the ESP) of the orifices in relation to each other is dependent on the rotational angle of the bodies above and below the chamber. And, the rotational angle of the bodies is generally random since the parts are screwed together. Furthermore, the rotational angle of the ESP in relation to the axis of the flow conduit is random because the tubing string on which it is deployed comprises many threaded joints of tubing, which in aggregate are torsionally non-stiff. In ESPs deployed on coil tubing or on cables, the orientation is similarly uncontrollable. Therefore, at an angle near horizontal, the desired relative altitude of the orifices can actually be reversed because the orifice that should be higher is rotated to the lower side of the ESP, while the orifice that should be lower is rotated to the upper side of the ESP. These effects practically limit the application of either type of conventional gravity chambers to approximately 30 degrees from vertical (60 degrees from horizontal), though this is not an absolute limit. [0028] This disclosure generally relates to devices and methods for utilizing gravity separation at angles much closer to horizontal. The present disclosure includes: advantageous orientation of the orifices in relation to each other; advantageous orientation of an ESP system or component in relation to the fluid conduit or to the earth; labyrinth and gravity chambers designed to be effective at low angles, being defined as greater than about 60 degrees from vertical (less than about 30 degrees of horizontal); use of dense barrier fluids in combination with other fluid sealing methods; and reduction of the effective conduit diameter through a labyrinth or a gravity separation, or gravity seal, chamber to limit axial penetration in event of seal element failure.

[0029] Referring generally to Figure 1 , a well system 20 is illustrated as deployed in a wellbore 22 according to an embodiment of the disclosure. The wellbore 22 is illustrated as extending downwardly to a subterranean formation 24, e.g., a hydrocarbon reservoir, from a wellhead 26 positioned at a surface location 28. The well system 20 can be utilized in a variety of wells having generally vertical or deviated wellbores. In Figure 1 wellbore 22 is illustrated as extending vertically and substantially parallel to the direction of gravity. As illustrated, wellbore 22 is defined by a surrounding wellbore wall 30 that may be an open wellbore wall, a casing, or a combination of cased and open sections. In the example illustrated, wellbore wall 30 is defined by a casing 32 having perforations 34 that allow communication between wellbore 22 and the surrounding formation 24. For example, a production fluid, e.g. a hydrocarbon based fluid, can flow from formation 24, through perforations 34, and into wellbore 22.

[0030] The well system 20 may comprise a variety of well systems used to perform many types of well related operations. In general, the well system 20 comprises at least one submersible, electrically powered component 36 that receives power via an electric power cable 38. Power cable 38 is mechanically and electrically connected to submersible component 36 by a connector system 40. Connector system 40 is sealed with respect to submersible component 36 and power cable 38 to protect both component 36 and cable 38 from the high pressure, high temperature, and harsh wellbore environment 42. The harsh wellbore environment 42 is typically at an elevated temperature and under substantial pressure. Additionally, a variety of harsh gases, liquids and other substances found in wellbore environment 42 can have deleterious effects on submersible component 36 and/or power cable 38 if the seal is not maintained.

[0031] In the embodiment illustrated in Figure 1, submersible component 36 comprises an electric motor that is part of an overall electric submersible pump (ESP) system 44; however submersible component 36 can comprise a variety of other powered components in other systems. In the example illustrated, electric submersible pumping system 44 comprises a submersible pump 46 that draws well fluid into a pump intake 48 when powered by submersible electric motor 36. Additionally, a motor protector 50 can be deployed between submersible motor 36 and submersible pump 46. Protector 50 may have one or more chambers. In this embodiment, a pumping system connector 52 can be used to couple pumping system 44 to a conveyance 54. By way of example, conveyance 54 may comprise tubing, such as production tubing or coiled tubing. For example, pump 46 may pump the wellbore fluid to surface 28 through the production tubing. In other applications, conveyance 54 may be a cable -type conveyance or another suitable conveyance. Power cable 38 may be routed downhole along an interior or an exterior of the conveyance 54.

[0032] Figure 2 illustrates an ESP 44 disposed in a non-vertical orientation as illustrated by the angle of rotation 58 of the center axis 56 of ESP 44 relative to the vertical axis 60. In accordance to some embodiments, a low angle is one in which the ESP is installed such that its central axis 56 is greater than about 60 degrees from vertical or, said another way, less than about 30 degrees from horizontal. In Figure 2, ESP 44 is in a low angle with the angle of rotation 58 greater than about 60 degrees of vertical. It will be understood by those skilled in the art with benefit of this disclosure that the use of ESP 44 is not limited to wellbores or to petroleum installations.

[0033] With reference to Figures 2 and 3, the illustrated protector 50 includes an outer housing 62 connected at a first end 63 to a first end body 64 and connected at a second end 65 to a base end body 66 such that an internal chamber 68 is formed. Often housing 62 is connected to the first and second bodies 64, 66 by threading. With reference in particular to Figures 2 and 16 a motor shaft 70 extends through the gravity seal chamber(s) between motor 36 and pump 46 and is illustrated disposed through a shaft tube 71. Shaft tube 71 can minimize the agitation and mixing of the fluids in chamber 68 by the rotation of the shaft. A shaft seal 73 may minimize contamination of the protective motor fluid in the motor 36. For purposes of brevity and clarity in describing aspects of ESP 44, the motor shaft is not illustrated in each of the Figures. For example, Figures 3, 12-15 and 17 do not illustrate the motor shaft, although by reference the motor shaft may extend along the central axis 56.

[0034] In Figures 2 and 3, a fluid interface 72 is illustrated in chamber 68 between motor liquid 74 in this example and a more dense fluid 76, e.g. exterior or environmental liquid. As will be understood by those skilled in the art, the motor fluid may be motor oil or a barrier fluid. The orientation illustrated is Figure 2 is not applicable to a motor fluid or barrier fluid that is denser than the well fluid. For example, in a wellbore application such as illustrated in Figure 1, the more dense fluid may be well fluid, e.g., petroleum and water mixture. In Figure 2 and 3, a motor standing orifice 78 is in communication with the motor 36 and protector chamber 68, through base end body 66, and a hanging orifice 80 is in communication with the protector chamber 68 and the exterior 18 of the protector chamber 68 through first end body 64. In Figures 2 and 3, protector 50 is a labyrinth chamber and the motor standing orifice 78 is formed by a conduit in the form of a standing tube 82 and the hanging orifice 80 is formed by a conduit in the form of a hanging tube 84. A vertical separation 86 between the motor standing orifice 78 and the hanging orifice 80 is obtained when the center axis 56 is tilted away from vertical by arranging the orifices in what may be referred to herein as a vertical separation orientation. It will be recognized by those skilled in the art with benefit of this disclosure, that the standing and hanging orifices may be formed through the end bodies without including a hanging and standing tubes, for example in a gravity chamber arrangement.

[0035] According to one aspect, the present disclosure involves orienting orifices 78, 80 in the vertical separation orientation when the ESP 44 is deployed for use. The angle of rotation 58 of the orifices and the bodies in relation to vertical may be controlled to optimize their potential for vertical separation 86 when installed at a low angle. Generally, the orifices leading upward and downward would be oriented on opposite sides of the center axis 56 with the motor standing orifice 78 leading upward at the twelve o'clock position and the hanging orifice 80 leading downward at the six o'clock position, though in combination with other aspects it may be desirable to orient them differently. The orifices are oriented by assembling joints between bodies, housings and associated parts at a controlled angle of rotation. Orienting the orifices may be done by a number of techniques, including, but not limited to: timing or shimming the threads so that the bodies 64, 66 and the orifices end up in the desired orientation when the thread is tightened to the proper torque; joining the bodies and housing in the desired orientation by metal melting, which may include welding the base metals and the housing or a melted filler metal of similar or different composition; joining the bodies and housing in the desired orientation by means of separate elements, which may include threaded fasteners, interference fit fasteners, keys, lugs, threaded ring, swaged ring or thermal fit ring; joining the parts, e.g., the bodies and housing, by means of deforming one or both parts to create an interference or interlock, which may include swaging a diameter, dimpling, bending of integral features, thermal fit; providing multiple orifices in a body, such that after assembly of the body into the ESP assembly, the orifice(s) in unfavorable orientation may be plugged, leaving open only orifice(s) in favorable orientation; and forming the orifices in the protector body after assembly of the protector into the ESP assembly.

[0036] Examples of connections between the housings 62, 162 and the end bodies 64, 66, 164, and 264 (Figures 2-3 and 12-17) to achieve a desired orientation of the orifices are illustrated in Figures 4 to 11 with reference to section "X" of Figure 3. In the process known as timing threads, the starting point of the threads relative to the faces that bear against each other on the two components being joined may be formed such that when the threads are correctly torqued, the two components are at the desired angular orientation with respect to each other. In Figure 4 an orienting connector 92 is utilized as a timing element 88, e.g., shim, to achieve the desired orientation of the orifices. Timing element 88 is disposed between an end of the housing 62 and an end body, e.g. first end body 64. For example, with reference also to Figure 3, the base end body 66 is connected to the housing 62 by threading. The housing 62 is then threaded to first end body 64 at threads 90 until the orifices 78, 80 are located in the desired or proximate to the desired orientation with regard to vertical. Shim device 88 may then be positioned and threading completed to secure the housing 62 and the body 64 together. Alternatively, after a trial assembly of the threaded joint to determine the required thickness of shims, the joint may be disassembled to permit installation of a circular shim, after which the threaded joint is reassembled.

[0037] In Figure 5 the orienting connector 92 is in the form of a bond 94, for example melted metal or an adhesive, between the housing and the base. In the Figure 5 example, the bond 94 is a weld. Figures 6 through 8 illustrate orienting connectors 92 in the form of fasteners. In Figure 6 the connector 92 is a threaded fastener 96 interconnecting housing 62 to an end body, for example end 63 of housing 62 to first end body 64. Figure 7 illustrates the orienting connector 92 in the form of an interference fit type of connector such as a pressed pin 98. Figure 8 illustrates the orienting connector 92 in the form of anti-rotation connection. For example, a threaded ring 100 may interconnect the housing 62 (e.g., sleeve) with the end body 64 through an intervening lug 102 or key 104.

[0038] The housing 62 may be interconnected with an orienting connector 92 formed by a deformed portion of one or both of the housing and the end body. For example, in Figure 9 a swaged joint is formed between bend 106 in the housing 62 and a cooperative bend 108 in the end body 64. In Figure 10 the bends 106 and 108 are cooperative dimples. In Figure 11 a downward bend 106 in the end 63 of the housing 62 is positioned in a hole 110 formed in the outer surface of first end body 64.

[0039] According to another aspect, the present disclosure involves orienting an ESP 44 system or a component, i.e., the protector 50, in the ESP system in relation to the fluid conduit or earth. The angle of the orifices in relation to the flow conduit, and hence their elevation relative to the earth, may be controlled to optimize vertical separation between the orifices when installed at a low angle by installation of the ESP system or component at a predetermined angle of rotation 58. This may be accomplished by a number of techniques, including, but not limited to: installing the ESP system or component at a predetermined angle of rotation in a receiving structure such as a skid, frame, base, manifold or caisson; installing the ESP system or component in a capsule at a predetermined angle of rotation, and installing the capsule at a predetermined angle of rotation in a receiving structure such as a skid, frame, base, manifold or caisson; installing the ESP system or component in a flow conduit and orient the ESP by rotating the production tubing using feedback of the angle with respect to the earth or the conduit from an instrument, for example a gravity sensitive device or gyroscope, attached to the ESP; installing the ESP system or component in a flow conduit and orienting it by means of engagement of an orienting feature on the ESP with an orienting feature pre -installed in the conduit, examples of orienting features including a mule shoe, seating shoe, guide, pin, lug, keyway, or other profile; and mounting the orifices and other relevant components on a weighted and/or buoyed element within the seal section that it is free to rotate relative to the axis under the influence of gravity. The rotating element may be mounted on a low friction bearing to ensure response to gravity. The orifices in the rotating element may communicate to the non-rotating elements by a flexible tube or by a rotating sealing element. This mechanism only needs to function until the ESP is installed, so eventual sticking of the rotating mechanism due to scale and corrosion is not an issue.

[0040] Figure 12 illustrates an ESP 44 oriented at desired angle of rotation 58 relative to vertical 60 on a receiving structure 112, such as a skid, frame, base, or manifold. Receiving structure 112 may be positioned approximate the surface 28 of the earth, subterranean or subsea. For example, in Figure 12 receiving structure 1 12 and ESP 44 are deployed in a caisson type application, wherein ESP 44 is disposed at least partially below the surface 28, for example a seabed surface. Receiving structure 112 and ESP 44 disposed in a chamber 114 (e.g., caisson), which may be for example a cased dummy well, or other caisson (e.g., cement and/or metal lined chamber). Production fluid 10, for example a formation fluid from an adjacent production wellbore, may be produced into borehole 114 through inflow conduit 12. ESP 44 energizes the production fluid 10 and pumps it through the discharge 14.

[0041] Figure 13 illustrates another example of an ESP 44 oriented at a predetermined angle of rotation for use. ESP 44 is positioned in a capsule 116 having an inflow conduit 12 for receiving a production fluid 10 to be energized by the ESP and discharged through a discharge conduit 14 of the ESP 44. In one example, receiving structure 112 may be located on a surface 28 such as a seabed, the inflow conduit 12 connected for example to a subsea wellbore whereby ESP 44 is utilized as a booster pump for producing fluid 10 to the surface of the water. [0042] According to another aspect, the present disclosure involves gravity separation of fluids in an ESP 44 installed at a low angle 58 (i.e., an angle of less than about 30 degrees from horizontal or more than about 60 degrees from vertical 60). In this aspect, the least permissible angle of operation with respect to the earth is minimized by combination with other aspects of the disclosure to an angle of greater than about 60 degrees from vertical and greater than about 0 degrees from horizontal. With reference in particular to Figure 14, gravity separation may include either alone or in combination: a motor 36 and seal section 50 containing a barrier fluid 75 denser than the well fluid 76, for example a barrier fluid comprising fluorinated oil such as PFPE oil because of its high specific gravity of approximately 1.8, dielectric properties, lubricating properties, inertness and thermal stability; seal section 50 having features oriented in relation to each other to optimize vertical separation 86; a protector chamber oriented in relation to the wellbore to optimize vertical separation.

[0043] With reference for example to Figure 15 gravity separation may include any of the following either alone or in combination: a motor 36 and protector 50 containing a barrier fluid 75, such as a fluorinated oil (e.g., PFPE oil) used due to its high specific gravity of for example of approximately 1.8, dielectric properties, lubricating properties, inertness and thermal stability; a labyrinth chamber 68 of a protector 50 (e.g., seal section) separating denser barrier fluid 75 from lighter motor oil 74; a gravity chamber 268 of a protector 50 containing a barrier fluid 75; protector chambers with features oriented in relation to each other to optimize vertical separation 86 according to other aspects of this disclosure; a protector chamber oriented in relation to the wellbore to optimize vertical separation according to other aspects of this disclosure; and combining labyrinth chambers or gravity chambers in parallel to increase vertical separation.

[0044] A dense barrier fluid 75 may be used in combination with other sealing elements/methods. At low angles, a dense barrier fluid may be combined with one or more other sealing elements/methods, such as are used in other ESP 44 seal sections, to minimize mixing of the motor oil 74 and the well fluid 76 and to provide redundancy in the event of abrogation of any of the sealing measures, by way of example, the failure or bypassing of any internal sealing elements, including shaft seals, relief valves, bags, metal bellows, and internal static seals. The combination of sealing elements and sealing methods may include any of the following, either alone or in combination with one another: a motor protector chamber may be used that provides sufficient axial length for a level, e.g., parallel to horizontal, fluid interface between the motor oil 74 and the well fluid 76, or between the barrier fluid 75 and the well fluid 76, or between the barrier fluid 75 and the motor oil 74, not to extend into the seal section far enough to damage sensitive thrust bearings or electrical conductors, even in event of abrogation of one or more internal sealing elements; a labyrinth chamber may be used in combination with a barrier fluid chamber and a motor filled with lighter motor oil, where the length of the chambers and the orientation of the orifices and other features may provide sufficient axial length and vertical separation to prevent excessive barrier fluid from being lost into any chamber, or the motor below it, in response to thermal cycling of oil; a shaft seal 73 prevents mixing of barrier fluid in one chamber with well fluid or motor oil in an adjacent chamber that might otherwise occur due to centrifugal radial separation caused by the rotating shaft, rather than the desired true -vertical separation of the fluids; a shaft tube 71 that prevents forced mixing of barrier fluid and/or motor oil with well fluid within a chamber that would otherwise occur due to agitation caused by the rotating shaft, rather than the desired separation of the fluids; a bag or bellows to isolate the barrier fluid from well fluids or from motor oil; a relief valve to permit discharge of excess barrier fluid or motor oil into the flow conduit, while preventing ingress of well fluid; and a metal or elastomer bellows or bag at the lower end of the motor that compensates for the change in motor oil volume during thermal cycling so that there is no need for fluid exchange between the motor and the seal section above the motor.

[0045] In accordance to some embodiments, the effective conduit diameter through a labyrinth or gravity separation chamber may be reduced to limit axial penetration in the event of seal element failure. At a given angle of rotation 58, the axial distance that a horizontal interface 72, 172, 272 between fluids of different density will penetrate is a function of the effective diameter of the conduit or passage. The axial distance is the effective diameter divided by the tangent of the angle from horizontal. Enlargements in the actual diameter of the central portion of the conduit will not cause penetration beyond the reductions at the ends of the conduit provided the fluid interface does not extend beyond the reduced effective diameter at the ends of the conduit, including the movement of the fluid interface in response to thermal cycling of the oil. However, an enlargement in the conduit not extending to either end increases the displacement of the conduit per unit length, which decreases the axial movement due to thermal cycling, permitting shorter protector sections.

[0046] So, the effective diameter of the conduit as it relates to axial penetration of static fluid is limited by the effective diameter at either end of the fluid interface, provided thermal cycling does not move the fluid interface to the reduced diameter at the ends of the conduit. In the case of a protector section, the reduced diameter would be the normal (to the axis) distance between the highest and the lowest opening in the bodies. To minimize the effective diameter, the relief valve may be oriented at the same elevation as the shaft seal, using techniques recited in the aspects of the present disclosure. However, it can also be advantageous for some sealing elements, for example the relief valve, to be submerged in the clean barrier fluid or motor oil to prevent clogging or attack by well fluid. Therefore, such sealing elements may alternatively be oriented lower than the shaft seal.

[0047] In accordance to some embodiments, a compensator unit (e.g., bellow), external to the ESP, located in a receiving structure such as a skid, frame, base, manifold or caisson, may be utilized. The ESP may utilize an externally located compensator containing a fluid that is lighter or heavier than the motor oil or the well fluid. Embodiments according to the present disclosure may include one or more of the following: an external compensator that hydraulically communicates with the interior of the ESP motor, at a location along its length and height relative to the earth. The external compensator compensates for motor oil volume changes without the need for communication directly with the protector section. In accordance to embodiments an external compensator may communicate with the interior of the protector so that during thermal cycles movement of the interface between fluids in the gravity seal chamber is minimized, permitting minimization of the length of the protector. An external compensator may also provide positive pressure to the motor to prevent or mitigate the communication of well fluid through any failed seal elements in the motor protector. Examples of compensators and various seal arrangements are disclosed for example in US Patent Nos. 8,807,966, 8,328,539, 7,806,670 and 7,741,744 assigned to Schlumberger Technology Corporation, the teachings of which are incorporated herein by reference.

[0048] Figure 14 illustrates an ESP 44 according to one or more embodiments. In Figure 14, the chamber 68 of the protector 50 is a gravity chamber. A standing conduit 82 is formed through the base end body 66 between the chamber 68 and motor 36. In this example, the motor 36 includes a barrier fluid 75 which is denser (higher specific gravity) than the well fluid 76. The hanging conduit 84 is formed through the first end body 64 to communicate environmental liquid, e.g., well fluid 76, between chamber 68 and exterior 18. The vertical separation 86 is illustrated between the motor standing orifice 78 and the hanging orifice 80 of the hanging conduit. Figure 14 illustrates two fluid interfaces indicating the movement of the fluid interface due to thermal cycling. The interface 172 is the elevation of the fluid interface when the motor fluid, barrier fluid 75 in this example, is cold and the fluid interface 272 is the hot fluid interface.

[0049] Figure 15 illustrates an ESP 44 having a protector 50 with two seal chambers 68, 268 and Figure 16 is an expanded illustration of the protector 50 of Figure 15 illustrating the motor shaft 70 and seal elements such as shaft tube 71 and shaft seals 73.

[0050] The lower elevation chamber 68, adjacent the motor 36, is a labyrinth chamber and the second or upper elevation chamber 268 is a gravity chamber in this example. In this example, the motor 36 is filled with motor oil 74 and the labyrinth chamber 68 and the gravity chamber 268 contain a barrier fluid 75 which has a higher specific gravity than the motor oil 74 and the well fluid 76. Figure 15 illustrates the change in the fluid interface elevation due to thermal cycling between the cold fluid interface 172 and the hot fluid interface 272. With reference to Figs 15 and 16, labyrinth chamber 68 includes the standing tube conduit 82 in communication through end body 66 between the motor 36 and the motor standing orifice 78 in chamber 68. The hanging tube conduit 84 through end body 64 provides fluid communication between the upper gravity chamber 268 and the lower labyrinth chamber 68. Upper gravity chamber 268 comprises a standing orifice 278 located at the opposite end of hanging tube conduit 84 from the hanging orifice 80 disposed in the lower chamber 68. Barrier fluid 75 is communicated between chamber 68 and chamber 268 through hanging tube conduit 84 in response to thermal cycling. An exterior fluid, for example well fluid 76, is communicated from exterior 18 to the ESP 44 through the hanging conduit 284 formed through the first or top end body 264. ESP 44 is assembled and positioned in use such that the orifices in each of the separation chambers 68, 268 are positioned in a vertical separation orientation to achieve a desired vertical separation 86. It will be recognized by those skilled in the art with reference to Figures 15 and 16 that housing 62 may be interconnected with end bodies 64, 66 in a manner to position of orifices 78 and 80 relative to one another to achieve the desired vertical separation orientation and housing 262 may be interconnected with end bodies 64 and 264 to achieve the desired vertical separation orientation of orifices 278 and 280, whereby orifices 278 and 280 are positioned on opposite sides of the center axis and vertically separated when the center axis is offset from the vertical axis.

[0051] Figure 17 illustrates an embodiment of an ESP 44 having protector 50 including two separation chambers 68, 168 in parallel. In this example the chambers are labyrinth chambers. A first chamber 68 adjacent to motor 36 is formed by housing 62 and end bodies 66 and 164 and the second chamber 168 is formed by housing 162 and end bodies 64 and 164. Standing tube conduit 82 extends from the motor 36 through bodies 66 and 164 to the motor standing orifice 78 located in the second chamber 168. Standing tube conduit 82 communicates motor fluid, in this example motor oil 74 between the motor 36 to the second chamber 168. The hanging tube conduit 84 extends through bodies 64 and 164 and across second chamber 168 to the hanging orifice 80 located in the first chamber 68. Hanging tube conduit 82 communicates fluid, in this example well fluid 76, from the exterior 18 to first chamber 68. The parallel chamber arrangement achieves a significant vertical separation 86 between the motor standing orifice 78 and the hanging orifice 80. In this example, the cold fluid interface 172 is located in the second chamber 168 and the hot fluid interface is located in the first chamber 68. The arrangement of common tubes 82 and 84 in the first and second chambers is schematic. It should be understood by those skilled in the art that they may comprise multiple tubes assembled to achieve the same schematic. [0052] The foregoing outlines features of several embodiments so that those skilled in the art may better understand the aspects of the disclosure. Those skilled in the art should appreciate that they may readily use the disclosure as a basis for designing or modifying other processes and structures for carrying out the same purposes and/or achieving the same advantages of the embodiments introduced herein. Those skilled in the art should also realize that such equivalent constructions do not depart from the spirit and scope of the disclosure, and that they may make various changes, substitutions and alterations herein without departing from the spirit and scope of the disclosure. The scope of the invention should be determined only by the language of the claims that follow. The term "comprising" within the claims is intended to mean "including at least" such that the recited listing of elements in a claim are an open group. The terms "a," "an" and other singular terms are intended to include the plural forms thereof unless specifically excluded.

Claims

WHAT IS CLAIMED IS:

1. A submersible system, comprising:

a submersible motor comprising a motor liquid; and

a motor protector in fluid communication with the motor and an exterior environment, the motor protector having a center axis and an outer housing defining a chamber between a first end body and a base end body for gravity separation of the motor liquid from an environmental liquid, the motor protector comprising: a hanging orifice providing fluid communication through the first end body to permit flow of a first liquid into the chamber, wherein the first liquid is one of the environmental liquid and a barrier liquid; and

a motor standing orifice providing fluid communication between the chamber and the motor through the base end body, wherein the hanging orifice and the motor standing orifice are positioned in a vertical separation orientation whereby the standing and hanging orifices are located on opposite sides of the center axis and the standing and hanging orifices are vertically separated from one another when the center axis is offset from vertical.

2. The system of claim 1, comprising an orienting connector between the outer housing and one of the first end body and the base end body to achieve the vertical separation orientation.

3. The system of claim 2, wherein the orienting connector comprises one selected from the group of a timing element in a threaded connection, a bonded connection, a threaded fastener, an interference connector, and cooperative deformations.

4. The system of claim 1 , wherein the hanging orifice is positioned vertically below the motor standing orifice when the center axis is offset from vertical.

5. The system of claim 1, wherein the hanging orifice is positioned vertically above the motor standing orifice when the center axis is offset from vertical.

6. The system of claim 1, wherein the chamber is a gravity chamber and the hanging orifice is located at the first end body and the motor standing orifice is located at the base end body.

7. The system of claim 1, wherein the chamber is a labyrinth chamber and the hanging orifice is provided by a hanging tube extending from the first end body into the chamber and the motor standing orifice is formed by a standing tube extending into the chamber.

8. The system of claim 1 , wherein the motor protector comprises:

a second chamber formed between a head end body and the first end body; and a second hanging orifice disposed in the second chamber and providing fluid

communication through the head end body to the exterior environment, wherein the second hanging orifice and the hanging orifice are located on opposite sides of the center axis from one another.

9. The system of claim 1, wherein the motor protector comprises an intermediate end body separating an upper elevation chamber from the chamber, wherein the motor standing orifice is positioned in the upper elevation chamber and the hanging orifice is positioned in the chamber.

10. A method of protecting a submersible motor, comprising:

orienting a motor protector of an electric submersible pump (ESP) in a vertical separation orientation whereby a center axis of the motor protector is tilted at an angle offset from vertical and wherein a hanging orifice and a motor standing orifice are positioned on opposite sides of the center axis and vertically separated from one another, wherein the ESP comprises:

a pump;

a submersible motor to power the pump, the motor comprising a motor liquid; the motor protector in fluid communication with the motor and an exterior

environment, the motor protector having an outer housing defining a chamber between a first end body and a base end body for gravity separation of the motor liquid from an environmental liquid; the hanging orifice providing fluid communication through the first end body to permit flow of a first liquid into the chamber, wherein the first liquid is one of the environmental liquid and a barrier liquid; and

the motor standing orifice providing fluid communication between the chamber and the motor through the base end body.

The method of claim 10, wherein the ESP is deployed in a low angle of greater than about 60 degrees from vertical.

The method of claim 10, wherein the orienting to achieve the vertical separation orientation comprises connecting the outer housing to one of the base end body and the first end body with an orienting connector, wherein the orienting connector comprises one selected from the group of a timing element in a threaded connection, a bonded connection, a threaded fastener, an interference connector, and cooperative deformations.

The method of claim 10, wherein the orienting to achieve the vertical separation orientation comprises selecting or forming the hanging and standing orifices after assembling the motor protector.

The method of claim 10, wherein the orienting comprises moving one or more of the orifices into the vertical separation orientation in response to the influence of gravity.

15. The method of claim 10, wherein the motor protector comprises:

16. The method of claim 10, wherein the motor protector comprises an intermediate end body separating an upper elevation chamber from the chamber, wherein the motor standing orifice is positioned in the upper elevation chamber and the hanging orifice is positioned in the chamber.

17. The method of claim 16, wherein the ESP is deployed in a low angle of greater than

about 60 degrees from vertical.

18. An electric submersible pump (ESP) system, the system comprising:

an ESP deployed at a low angle of greater than about 60 degrees from vertical, the ESP comprising a pump, a submersible motor to power the pump, the motor comprising a motor liquid, and a motor protector in fluid communication with the motor and an exterior environment, the motor protector having a center axis and an outer housing defining a chamber between a first end body and a base end body for gravity separation of the motor liquid from an environmental liquid, wherein the motor protector comprises:

a hanging orifice providing fluid communication through the first end body to permit flow of a first liquid into the chamber, wherein the first liquid is one of the environmental liquid and a barrier liquid; and

a motor standing orifice providing fluid communication between the chamber and the motor through the base end body, wherein the hanging orifice and the motor standing orifice are positioned in a vertical separation orientation whereby the orifices are located on opposite sides of the center axis and the orifices are vertically separated from one another when the center axis is offset from vertical.

19. The ESP system of claim 18, wherein the motor protector comprises:

20. The ESP system of claim 18, wherein the motor protector comprises an intermediate end body separating an upper elevation chamber from the chamber, wherein the motor standing orifice is positioned in the upper elevation chamber and the hanging orifice is positioned in the chamber.