Bottom intake electric submersible pump protector gas rejection device

Abstract

A gas rejection device 18A for an electric submersible pump (ESP) protector has a first fluid chamber 182 having a pressure equalization port 182A proximate a top thereof in fluid communication with a

Description

[0001] This disclosure relates to the field of electric submersible pumps (ESPs). More specifically, the disclosure relates to protectors for ESPs wherein a pump inlet and outlet are disposed below an electric motor used to operate the pump in the ESP.

[0002] Motor fluid within an electrical submersible pump (ESP) is at atmospheric pressure prior to the ESP being inserted (“run”) into a subsurface well. Because well pressure often substantially exceeds atmospheric pressure, the fluid pressure within the ESP should be equalized to well pressure. Pressure equalization reduces pressure differential across the ESP housing and seals, particularly rotating shaft seals. A hazard of differential pressure in an ESP is that well fluid could breach such seals and leak into the electric motor portion of the ESP. This is of special concern with regard to the motor, where the well fluids, which are often electrically conductive and may have solid particles therein could create electrical short circuits and / or mechanically damage the motor. A device known as a protector (also referred to as a “seal chamber section”) communicates well fluid pressure to the motor fluid pressure while substantially separating the well fluid and the motor fluid from each other, thereby minimizing pressure differential and prolonging seal life. To perform such function, the protector contains a pressure compensation device to act as a barrier to well fluid entering the drive train part of the ESP (i.e., components proximate to and including the motor) while still transmitting the pressure from the well fluid to the drive train, including the motor. A protector may have, for example, a tortuous fluid path that slows down the migration of well fluid through the protector to reduce the chance of well fluid entering the drivetrain through any leakage in the pressure compensation device (e.g., a flexible reservoir, metal bellows, compensator piston or similar device) or mechanical seal.

[0003] For ESPs deployed in wells using cable, slickline or the like, in many instances the motor is located in the uppermost part of the ESP, the protector that equalizes well pressure to the motor fluid pressure is mounted below the motor, and the pump is at the bottom of the ESP. The protector pressure inlet in such arrangement is typically at the bottom of the protector, functionally presents to well fluid an inverted cup and thereby acts as a gas trap. Trapped gas migrating through the protector can lead to mechanical seals operating dry, which can result in seals overheating and failing prematurely. Gas migration further through the ESP system can lead to other issues related to the composition of the gas. Elastomers, bearings, metal parts, motor oil and electrical connections may all be degraded if the gas has a susceptible composition.

[0004] Accordingly, there is need for a device to prevent gas from entering the protector and have the ability to reject any accumulated gas within the protector in an ESP. SUMMARY

[0005] One aspect of the present disclosure is a gas rejection device usable with an electric submersible pump (ESP) system. A gas rejection device according to this aspect includes a pressure equalization port proximate a top thereof in fluid communication with an exterior of the ESP. A second fluid chamber is disposed above the first fluid chamber. The first and second fluid chambers are arranged to be disposed between a pump of an ESP system and the ESP protector. The second fluid chamber is arranged to be placed in fluid communication with an oil reservoir in the protector. The device comprises a fluid passage between an upper end of the at least a second fluid chamber and the exterior of the ESP, wherein gas accumulated in the upper end vents to the exterior of the ESP.

[0006] Some implementations further comprise a first bulkhead separating the first fluid chamber from the pump, a second bulkhead separating the first fluid chamber from the second fluid chamber and a third bulkhead separating the second fluid chamber from the protector.

[0007] In some implementations, the fluid passage comprises a relief valve located proximate the third bulkhead.

[0008] In some implementations, the fluid passage comprises a transfer tube extending from proximate a top of the second fluid chamber into the first fluid chamber.

[0009] Some implementations further comprise an outward relief valve positioned in a fluid flow path from the transfer tube into the first fluid chamber.

[0010] Some implementations further comprise a hanging tube extending from the third bulkhead into the second fluid chamber to a predetermined distance below the top of the second fluid chamber and in fluid communication with the oil reservoir.

[0011] Some implementations further comprise a gas shroud disposed in the first fluid chamber between the pressure equalization port and an interior of the first fluid chamber, the gas shroud comprising a relief valve at a bottom thereof in fluid communication with the interior of the first fluid chamber, whereby fluid entering the gas shroud is directed downwardly and decreases in velocity so as to separate entrained gas.

[0012] Some implementations further comprise a lowermost fluid chamber disposed between the first fluid chamber and the pump, the lowermost fluid chamber comprising a gas venting port proximate a top thereof in fluid communication with an exterior of the ESP.

[0013] In some implementations, a bulkhead separating the lowermost fluid chamber from the first fluid chamber comprises a pedestal extending a predetermined distance into the lowermost fluid chamber and a seal disposed on the pedestal, a pump drive shaft extending through a shaft seal.

[0014] Some implementations further comprise a pedestal extending from a at least one of: a first bulkhead separating the first fluid chamber from the ESP, a second bulkhead separating the first fluid chamber from the second fluid chamber and a third bulkhead separating the second fluid chamber from the protector; the pedestal extending a predetermined distance into the respective fluid chamber below the respective bulkheads, the pedestal comprising a rotary shaft seal thereon, a pump drive shaft extending through the seal.

[0015] In some implementations, the fluid passage comprises at least two transfer tubes extending between a location proximate a top of the second fluid chamber and a location within the first fluid chamber, one of the at least two transfer tubes comprising a relief valve at a bottom end opened in a first direction, a second of the at least two transfer tubes comprising a relief valve at a bottom end thereof opened in a direction opposed to the first direction.

[0016] Some implementations, further comprise a standing tube in fluid communication with an exterior fluid chamber in the protector surrounding the oil reservoir, the standing tube extending into the second fluid chamber to a location below a top of the second fluid chamber.

[0017] In some implementations, the oil reservoir is flexible to enable fluid pressure equalization between an interior and an exterior thereof.

[0018] In some implementations, the flexible reservoir comprises at least one of an elastomer bag or bladder metallic bellows or a piston.

[0019] Some implementations further comprise a water rejection chamber disposed above the second fluid chamber, the water rejection chamber comprising a standing tube extending from a bottom of the water rejection chamber to a location proximate the bottom of the second fluid chamber.

[0020] An electric submersible pump (ESP) system according to another aspect of the present disclosure includes a motor, a protector disposed below the motor, a pump disposed below the protector and rotationally coupled to the motor and gas rejection device according to any implementation according to the previous aspect disposed between the protector and the pump.

[0021] In some implementations, the motor comprises an electric motor.

[0022] In some implementations, wherein the motor is immersed in dielectric fluid, the dielectric fluid in pressure communication with an exterior of the ESP system through the protector and the gas rejection device.

[0023] Other aspects and possible advantages will be apparent from the description and claims that follow. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] FIG. 1 shows an example implementation of an electric submersible pump (ESP) system having a protector with a gas rejection device according to the present disclosure.

[0025] FIGS. 2 and 3 show cross sections of example implementations of a gas rejection device according to the present disclosure.

[0026] FIG. 4 shows cross-sectional view of another example implementation of a gas rejection device according to the present disclosure. DETAILED DESCRIPTION

[0027] FIG. 1 shows an example implementation of an electric submersible pump (ESP) system 10 that may be conveyed into a well (not shown) using a conveyance such as, for example and without limitation, jointed tubing, wireline, slickline or coiled tubing. The ESP system 10 may include an upper or “top” sub 12 that is configured to make connection to an end of one of the foregoing conveyance devices for movement of the ESP system 10 into and out of the well (not shown). A lower end of the ESP system 10 may include a “muleshoe” sub 28. The muleshoe sub 28 may be added below a pump 26, e.g., a rotary pump such as a progressive cavity pump or centrifugal pump, to provide protection to the ESP system 10 while running it into the well during deployment, and to provide, e.g., a mounting location for a pump (ESP) intake memory gauge. In addition, the muleshoe sub 28 may provide a suitable location for inner bore sealing as part of a well barrier control mechanism (not shown). Both a single shot sealing option, and a pressure responsive valve with multiple stable positions may be considered as suitable example options for well sealing below the muleshoe sub 28. For purposes of this disclosure, the terms “up” and “above” are intended to mean in a direction toward the outlet or surface end of a wellbore, while “down” and “below” are intended to mean in the opposite direction. Corresponding terms used herein may include “upper end”, up-hole”, “down-hole” and “lower end” with reference to various modules or sections that make up the ESP system 10. It is to be understood that such reference is only for convenience in describing the various components of the ESP system 10 and is not intended to limit the arrangement of components of any other ESP or ESP system within the scope of the present disclosure.

[0028] The top sub 12 may be followed successively in one longitudinal direction by a “star point sub” 13 and a motor 14, which in the present example may be an electric motor. The star point sub 13 may include one or more sensors and control devices related to operation of the ESP system 10 and the motor 14. The star point sub 13 may also be used to make electrical connection between a cable (not shown) and the motor 14. The motor 14 may be coupled at its lower end and its rotary output to an enclosed flexible shaft, a magnetic gear or any other rotational motion transmission 16. In the present example, the rotational motion transmission 16 accepts rotational input from the motor 14 at high rotational speed and low torque, and transmits such rotation to a pump 26, which may be a rotary pump such as a centrifugal pump or a positive displacement pump such as a progressive cavity pump. A protector 18, also known as a seal section, may be disposed in the ESP system 10 longitudinally between the motor 14 and the pump 26, and may be configured to exclude well fluid at existing well pressure and temperature from entering the motor 14. The protector 18 may also axially decouple the rotational motion transmission 16 and the motor 14 from axial and lateral loading generated by the pump 26. Not shown in FIG. 1 for clarity, the ESP system 10 may comprise a flow shroud that diverts well fluid flow from the pump outlet so that it can travel in an annular space outside the ESP system 10 and be sealingly diverted into a jointed tubing or coiled tubing and thence flow upwardly in the well (not shown).

[0029] The present example of ESP system 10 may be of modular design, and for deployment enable first lowering the pump 26, including the muleshoe sub 28 and an optional flex sub 27 (e.g., in implementations wherein the pump 26 is a progressive cavity pump) to enable relative axial deflection between the upper components, terminating at a field coupling sub 22 coupled to the upper end of a pump discharge sub 20, and thence coupled to a lower end of the protector 18 and the components described above. The pump 26, the flex sub 27, the pump discharge sub 20 and the field coupling sub 22 may be inserted into the well first, to be followed by the foregoing described components beginning with the field coupling sub 22. The entire ESP system 10 may also be lowered into the well as an assembled unit. The pump 26, the flex sub 27, the protector 18, the rotary motion transmission 16, the motor 14 and the star point sub 13 may each be enclosed in a respective pressure resistant housing, and such housings may be coupled by threads, locking rings or any other device known in the art for joining housings or housing segments of well tools together end to end.

[0030] As will be appreciated by those skilled in the art, a part of the ESP system 10 in which the motor 14 is disposed may be filled initially with dielectric fluid such as oil. The protector 18 may serve to exclude well fluid, which will be present both inside and outside the section of the ESP system 10 comprising the pump 26, from passing through the protector 18 and thus from entering the motor section and components above the motor section. The ESP system 10 may comprise a gas rejection device 18A disposed between a lower end of the protector 18 and the pump 26. Description to follow relates to example structures for the gas rejection device 18A that can reduce the amount of gas enabled to enter the protector 18 and migrate to the components above it.

[0031] An example implementation of the gas rejection device 18A is shown in cross-sectional view in FIG. 2. The orientation of the gas rejection device 18A when assembled within an ESP system is indicated by an arrow labeled UP-HOLE, meaning the gravitationally upward direction. Functionally, the gas rejection device 18A provides a fluid pressure equalization port 182A proximate a lower longitudinal end of the gas rejection device 18A that ultimately communicates well fluid pressure to the protector 18, while providing one or more gravity traps, explained below, for gas that may enter the gas rejection device 18A. Such gravity trap(s) may comprise vent(s) and / or vent valve(s) that enable releasing trapped gas into the well (not shown) under certain conditions, such as reduced fluid pressure in the well (not shown). In some implementations, hydraulic connection between adjacent, vertically separated gravity traps may be made through one or more hanging or standing tubes. Fluid movement through such hanging or standing tubes constrains movement of gas between adjacent gravity traps such that the gas accumulated in the gravity traps may be vented to the well from time to time. In the present example implementation, and in other example implementations to be explained further below, gravity separation of gas from liquids, or separation of liquids of one density such as motor dielectric fluid from liquids of another density such as well water may be obtained using vertically spaced apart fluid chambers separated by bulkheads, and using various vertical tubes extending from a bulkhead either upward into a fluid chamber above the bulkhead, or extending downward into a fluid chamber below the bulkhead. Tubes extending upward are described herein as “standing” tubes. Tubes extending downward from a bulkhead are described herein as “hanging” tubes. Tubes extending in both directions through a bulkhead may be described as “transfer” tubes. Transfer tubes may comprise a hanging tube and a standing tube in communication through the bulkhead or may comprise a single tube passing through the bulkhead into the fluid chamber above and below the bulkhead.

[0032] The gas rejection device 18A may comprise a plurality of fluid chambers 181, 182, 183,184 disposed one axially adjacent to another, and all of them axially disposed between the pump 26 and the protector 18. The fluid chambers 181, 182, 183, 184 may comprise individual segments or axially separated compartments of a hollow cylinder or similar structure. Each of the fluid chambers 181, 182, 183, 184 can define an enclosed volume and can resist fluid pressure in a well (not shown) by reason of the structure of the hollow cylinder, e.g., choice of material and wall thickness thereof. The individual fluid chambers, a lowermost chamber 181, a first intermediate chamber 182, a second intermediate chamber 183, and a third intermediate chamber 184 may be separated from each other hydraulically by respective bulkheads or connectors, e.g., first 181F, second 182F, third 183F, fourth 184F, and fifth 18F bulkheads, at each longitudinal end of a respective one of the fluid chambers. The bulkheads or connectors 181F, 182F, 183F, 184F, 18F may comprise one or more additional features to be explained further below. The particular structure for the bulkheads or connectors 18IF, 182F, 183F, 184F, 18F is a matter of discretion for the designer, provided that the bulkheads or connectors 18IF, 182F, 183F, 184F, 18F hydraulically isolate the fluid chambers 181, 182, 183, 184 from each other and from the external environment except as provided by the various features in the bulkheads to be described below.

[0033] The lowermost fluid chamber 181 may be coupled proximate to or directly to the upper end of the pump 26. Note that in FIG. 2, the field coupling sub (22 in FIG. 1) and the flex sub (27 in FIG. 1) may be omitted. A pump drive shaft 26C (which may extend from the rotational motion transmission (16 in FIG. 1 to the pump 26) may engage a seal such as a laminar seal 26B between itself and the first bulkhead 18 IF. A seal 18 IB may be disposed on a pedestal 182B that extends axially downward into the lowermost fluid chamber 181 from the second bulkhead 182F. In this way, the seal 181B may be substantially isolated from any gas that may accumulate at the top of the lowermost fluid chamber 181. Such isolation may reduce the amount of gas that traverses the seal 181B, thereby reducing gas accumulation in the first intermediate fluid chamber 182.

[0034] Pump discharge ports 26A provide an outlet for fluid from the pump 26, which discharged fluid flows up the well tubular (not shown) in which the ESP system (10 in FIG. 1) is disposed. A thrust bearing 26D for the pump 26 may be disposed in the lowermost fluid chamber 181. Some gas may enter the lowermost fluid chamber 181, e.g., through the shaft seal 26B. Such gas may be freely vented through a discharge port 181A in the second bulkhead 182F. Because the lowermost bulkhead 181F is disposed at the lower end of the lowermost fluid chamber 181, gas that may move into the lowermost fluid chamber 181 may freely vent into the fluid stream moving past the exterior of the ESP system (10 in FIG. 1), including the described fluid chambers 181, 182, 183, 184 through the discharge port 181 A.

[0035] The pressure equalization port 182A for the protector 18 may be disposed in or proximate to the third bulkhead 183F at or near the upper end of the first intermediate fluid chamber 182. To be described below are the various fluid interconnections among the pressure equalization port 182A, the fluid chambers 181, 182, 183, 184 and the protector 18. Through various fluid communication paths to be described in more detail, well fluid pressure present at the pressure equalization port 182A is substantially communicated to the protector 18 such that the fluid pressures are equalized between the protector 18 and the well (not shown), i.e., the external environment outside the ESP system (10 in FIG. 1).

[0036] The pressure equalization port 182A may be in fluid communication with a gas shroud chamber 182E disposed within the first intermediate fluid chamber 182 and extending downwardly from the third bulkhead 183F. In this way, any gas entering the pressure equalization port 182A would have to travel downwardly, against gravity, to enter the first intermediate fluid chamber 182. Fluid entering the gas shroud chamber 182E is also reduced in velocity from the fluid entering the pressure equalization port 182A by reason of the relatively large cross sectional area of the gas shroud chamber 182E, thereby reducing entry of gas into the first intermediate chamber 182 by way of entrainment in the moving fluid.

[0037] The bottom of the gas shroud chamber 182E may comprise a valve 182G, such as a check valve with a fixed opening pressure, to retain oil after filling, during transport and running the ESP system into a well. The pressure at which the valve 182G is set to open may be nominal, such as 5 or 10 pounds per square inch (psi). A fluid communication tube, e.g.„ a standing tube 182C may pass through and extend upwardly from the third bulkhead 183F, terminating at one longitudinal end at the top of the first intermediate fluid chamber 182, and at the other longitudinal end above the bottom of the second intermediate fluid chamber 183. Gas which may accumulate in the first intermediate fluid chamber 182 will accumulate by gravity at the top of the first intermediate fluid chamber 182, and may move into the second intermediate fluid chamber 183 through the standing tube 182C. Gas is restricted from traveling downwardly further (into the first intermediate fluid chamber 182) by locating the other end of the standing tube 182C below the top of the second intermediate fluid chamber 183 such that the other longitudinal end is unlikely to be disposed in any accumulated gas. A hanging tube 182D extending downwardly from the third bulkhead 183F to an intermediate longitudinal position within the first intermediate fluid chamber 182 allows liquid, e.g., water, to drain into the first intermediate fluid chamber 182, but is located longitudinally such that its lower end is unlikely to be disposed in accumulated gas. The hanging tube 182D, however, enables free communication of fluid pressure between the first intermediate fluid chamber 182 and the second intermediate fluid chamber 183 disposed on the other side of the bulkhead 183F.

[0038] In the present example implementation, the pedestal 182B may extend from the third bulkhead 183F and sealingly through the second bulkhead 182F to reduce the number of rotary shaft seals needed to hydraulically isolate the fluid chambers from each other and from the external environment. It is equally within the scope of the present disclosure to have a separate pedestal and associated rotary shaft seal associated with each bulkhead or to have one or more pedestals extend through multiple bulkheads as in the present example implementation. The illustrated implementation in FIG. 2 is only meant to serve as an example of pedestal structure for rotary shaft seals according to the present disclosure. Such individual pedestals and corresponding rotary shaft seals are shown in an example implementation to be described further below with reference to FIG. 4.

[0039] In the event sufficient gas accumulates in the first intermediate fluid chamber 182, to a level below the bottom of the hanging tube 182D, and thereby gas does pass into the second intermediate fluid chamber 183, or gas accumulates in the second intermediate fluid chamber 183 by exsolution from liquids, such gas may be vented from time to time through a suitable vent (relief) valve 183C, e.g., in or proximate to the fourth bulkhead 184F at the upper end of the second intermediate fluid chamber 183. Such gas may be vented, e.g., by reducing fluid pressure in the well (not shown) by slowing or stopping operation of the pump 26.

[0040] The pump shaft 26C may engage a rotary shaft seal 183B disposed on a pedestal 183D extending downwardly into the second intermediate fluid chamber 183 to reduce movement of any accumulated gas across the rotary shaft seal 183B and thereby into the third intermediate fluid chamber 184.

[0041] A transfer tube, which may be referred to as a gas rejection tube 183 A, may extend through the fourth bulkhead 184F from a point near the top of the third intermediate fluid chamber 184, to a point near the bottom of the second intermediate fluid chamber 183. In this way, fluid pressure may be freely communicated between the second intermediate fluid chamber 183 and the third intermediate fluid chamber 184, while gravity resists upward transfer of gas between the second 183 and third 184 intermediate fluid chambers by reason of the location of the longitudinal ends of the gas rejection tube 183 A. The gas rejection tube 183 A also serves to transfer at least some of any accumulated gas at the top of the third intermediate fluid chamber 184 back into the second intermediate fluid chamber 183, whereby such transferred gas may be vented through the gas vent valve 183C in the third bulkhead 183F when the well pressure is reduced as explained above.

[0042] The fifth bulkhead 18F at the top end of the third intermediate fluid chamber 184 may also bound the lower axial end of the protector 18. The protector 18 may comprise, for example and without limitation one or more elastomer bags, bladders or otherwise shaped flexible reservoirs 18B holding dielectric fluid (e.g., motor oil) for the motor (13 in FIG. 1). The flexible reservoir 18B may be hydraulically connected through a hanging tube 184B having a pressure relief vent valve 184E at an end disposed below the top of the third intermediate fluid chamber 184, but above the bottom thereof, such that neither gas nor water is likely to enter the flexible reservoir 18B by reason of thermal and pressure expansion and contraction of the fluid in the flexible reservoir 18B. Correspondingly, an end of a hanging tube 184A extending from the fifth bulkhead 18F may be disposed in the third intermediate fluid chamber 184 between the top and the bottom thereof. Such hanging tube 184A may provide fluid pressure equalization about the exterior of the flexible reservoir 18B.

[0043] While the present example implementation shows an elastomer bag used as the flexible reservoir 18B, other structures may be used to obtain the same result, for example and without limitation, metal bellows or a compensation piston enabled to move in a cylinder, with one side of such piston exposed to external pressure and the other side exposed to internal pressure of the flexible reservoir 18B.

[0044] The pump shaft 26C may engage a rotary shaft seal 184D disposed on a pedestal 184G extending from the fifth bulkhead 18F into the third intermediate fluid chamber 184, as with the other pedestals, to locate the rotary shaft seal 184D below the level of any accumulated gas in upper part of the third intermediate fluid chamber 184. The protector 18 may comprise, or the fifth bulkhead 18F may comprise, the pedestal with associated rotary shaft seal 184D through which the pump drive shaft 26C may pass. As with other pedestal / seal structures, having the rotary shaft seal 184D disposed below the top of the third intermediate fluid chamber 184 may restrict gas from entering the protector 18 through the rotary shaft seal 184D.

[0045] Another example implementation of a gas rejection device is shown in FIG. 3. The implementation shown in FIG. 3 may comprise all the structure of the example implementation shown in FIG. 2, and may further comprise a sixth bulkhead 186F, which may define a fourth intermediate fluid chamber 186. In the present example implementation, the fourth intermediate fluid chamber 186 may be disposed longitudinally between the second intermediate fluid chamber 183 and the third intermediate fluid chamber 184. The sixth bulkhead 186F may comprise a first transfer or gas rejection tube 186C therethrough, similar in structure and in placement of its longitudinal ends within the relevant fluid chambers (third 183 and fourth 184 intermediate fluid chambers) as the gas rejection tube (183A in FIG. 2) of the previously described implementation. In the present example implementation, a second transfer gas rejection tube 186A may be disposed through the fourth bulkhead 184F and have one longitudinal end disposed proximate the top of the fourth intermediate fluid chamber 186 and the other longitudinal end disposed proximate the bottom of the second intermediate fluid chamber 183. The additional fluid chamber and gas rejection tube may further reduce upward migration of gas, and facilitate downward movement of any gas that may migrate into the third 184 and fourth 186 intermediate fluid chambers.

[0046] Another example implementation of a protector having a gas rejection device 18A is shown in cross section view in FIG. 4. As with other example implementations of the gas rejection device described herein, like reference numerals are used to show like components among the various implementations. In the present example implementation, each bulkhead 182F, 183F, 184F and 18F comprises a corresponding pedestal 181G, 182H, 183D and 184C that extends into the respective fluid chamber below 181, 182, 183 and 184, respectively to a position below the top thereof so that a corresponding rotary shaft seal 181B, 182G, 183B and 184D is less likely to be disposed in accumulated gas during operation of the ESP system (10 in FIG. 1).

[0047] In the present example implementation, the hanging tube shown at 184A in FIG. 2 may be substituted by a simple vent port 284A to equalize fluid pressure between the third intermediate chamber 184 and the exterior of the flexible reservoir 18B. Hanging tube 184B and pressure relief vent valve 184E may be as shown in and explained with reference to FIG. 2. The lowermost fluid chamber 181 and gas vent 181A may be substantially as explained with reference to FIG. 2.

[0048] In the present example implementation, the third intermediate fluid chamber 184 may serve principally as a water rejection chamber, wherein a hanging tube 283A may extend from the third bulkhead 184F (at the bottom of the third intermediate fluid chamber 184) to a location proximate the bottom of the second intermediate chamber 183 or to some intermediate level therein to avoid transfer of both gas and water. In this way, any water that is communicated, e.g., by entrainment and gravity separation, into the third intermediate fluid chamber 184 may drain into the second intermediate fluid chamber 183 by gravity.

[0049] In the present example implementation, the gas shroud 182E, relief valve 182G, hanging tube 182D and standing tube 182C and (transfer) gas rejection tube 183 A shown in FIG. 2 may be substituted in FIG 4 by a first gas transfer tube 283B and second gas transfer tube 284 extending between a location proximate the top of the second intermediate fluid chamber 183 and approximately the middle of the first intermediate fluid chamber 182. Continuing in FIG 4, the first gas transfer tube 283B may comprise a relief valve 283B1 at its lower end, whereby during times of reduced fluid pressure in the well (e.g., during pump slowdown or shut off), gas accumulated near the top of the second intermediate fluid chamber 183 may move through the first gas transfer tube into the first intermediate fluid chamber 182. Such gas may move by gravity to the top of the first intermediate fluid chamber 182 to be vented into the well (not shown) through the pressure equalization port 182A in or proximate the second bulkhead 183F. The second gas transfer tube may comprise a relief valve 284B1 at its lower end having opposed direction to the relief valve 283B1 on the first gas transfer tube. In this way, as gas accumulates in the second intermediate fluid chamber 183 during ESP system operation, excess gas may be vented to the first intermediate fluid chamber 182 through the relief valve 283B1. Such excess gas venting may reduce the possibility of the rotary shaft seal 182G being disposed in gas.

[0050] In the various example implementations described herein, gas which accumulates in the first intermediate fluid chamber, shown at 182 in each of FIGS. 2, 3 and 4, eventually accumulating in the second intermediate fluid chamber, shown at 183 in each of FIGS. 2, 3 and 4, is ultimately rejected (vented) to the exterior of the ESP system (10 in FIG. 1) through a fluid passage. The fluid passage hydraulically connects the top end of the second intermediate fluid chamber 183 to the exterior of the ESP system (10 in FIG. 1) and may comprise an outward vent valve. The fluid passage may be direct, e.g., through the vent valve 183C in FIGS. 2 and 3, wherein the gas moves directly from the second intermediate fluid chamber 183 to the exterior. The fluid passage may be indirect, such as through the one or more transfer tubes such as at 283B in FIG. 4 interconnecting the second intermediate fluid chamber 183 to the first intermediate fluid chamber 182. Such gas rejection may take place through a relief valve, e.g., at 183C in FIGS. 2 and 3, and at283Bl in FIG. 4. As explained above, when pressure outside the ESP system (10 in FIG. 1) is reduced, such as when the pump is slowed or stopped, accumulated gas may expand and thereby vent through any of the foregoing fluid passages.

[0051] A gas rejection device according to the present disclosure, when used in connection with an ESP system having a motor and protector above the pump may reduce accumulation of gas in the protector, and consequent the negative effects of gas therein, such as running seals dry.

[0052] In light of the principles and example implementations described and illustrated herein, it will be recognized that the example implementations can be modified in arrangement and detail without departing from such principles. The foregoing discussion has focused on specific implementations, but other configurations are also contemplated. In particular, even though expressions such as in “an implementation," or the like are used herein, these phrases are meant to generally reference implementation possibilities, and are not intended to limit the disclosure to particular implementation configurations. As used herein, these terms may reference the same or different implementations that are combinable into other implementations. As a rule, any implementation referenced herein is freely combinable with any one or more of the other implementations referenced herein, and any number of features of different implementations are combinable with one another, unless indicated otherwise. Although only a few examples have been described in detail above, those skilled in the art will readily appreciate that many modifications are possible within the scope of the described examples. Accordingly, all such modifications are intended to be included within the scope of this disclosure as defined in the following claims.

Claims

What is claimed is:

1. A gas rejection device for an electric submersible pump (ESP) protector, comprising:at least a first fluid chamber having a pressure equalization port proximate a top thereof in fluid communication with an exterior of the ESP;at least a second fluid chamber disposed above the at least a first fluid chamber, the at least a first and second fluid chambers disposed between a pump of an ESP system and the ESP protector, the at least a second fluid chamber arranged to be placed in fluid communication with an oil reservoir in the protector;at least one fluid communication tube connecting the at least a first fluid chamber to the at least a second fluid chamber; anda fluid passage between an upper end of the at least a second fluid chamber and the exterior of the ESP, wherein gas accumulated in the upper end vents to the exterior of the ESP.

2. The device of claim 1 further comprising a first bulkhead separating the first fluid chamber from the pump, a second bulkhead separating the first fluid chamber from the second fluid chamber and a third bulkhead separating the second fluid chamber from the protector.

3. The device of claim 2 wherein the fluid passage comprises a relief valve located proximate the third bulkhead.

4. The device of claim 2 wherein the fluid passage comprises a transfer tube extending from proximate the upper end of the second fluid chamber into the first fluid chamber.

5. The device of claim 4 further comprising an outward relief valve positioned in a fluid flow path from the transfer tube into the first fluid chamber.

6. The device of claim 2 further comprising a hanging tube extending from the third bulkhead into the second fluid chamber to a predetermined distance below the upper end of the second fluid chamber and in fluid communication with the oil reservoir.

7. The device of claim 1 further comprising a gas shroud disposed in the first fluid chamberbetween the pressure equalization port and an interior of the first fluid chamber, the gas shroud comprising a relief valve at a bottom thereof in fluid communication with the interior of the first fluid chamber, whereby fluid entering the gas shroud is directed downwardly and decreases in velocity so as to separate entrained gas.

8. The device of claim 1 further comprising a lowermost fluid chamber disposed between the first fluid chamber and the pump, the lowermost fluid chamber comprising a gas venting port proximate a top thereof in fluid communication with an exterior of the ESP.

9. The device of claim 7 wherein a bulkhead separating the lowermost fluid chamber from the first fluid chamber comprises a pedestal extending a predetermined distance into the lowermost fluid chamber and a seal disposed on the pedestal, a pump drive shaft extending through shaft seal.

10. The device of claim 1 further comprising a pedestal extending from a at least one of: a first bulkhead separating the first fluid chamber from the ESP, a second bulkhead separating the first fluid chamber from the second fluid chamber and a third bulkhead separating the second fluid chamber from the protector; the pedestal extending a predetermined distance into the respective fluid chamber below the respective bulkheads, the pedestal comprising a rotary shaft seal thereon, a pump drive shaft extending through the shaft seal.

11. The device of claim 1 wherein the fluid passage comprises at least two transfer tubes extending between a location proximate a top of the second fluid chamber and a location within the first fluid chamber, one of the at least two transfer tubes comprising a relief valve at a bottom end opened in a first direction, a second of the at least two transfer tubes comprising a relief valve at a bottom end thereof opened in a direction opposed to the first direction.

12. The device of claim 1 further comprising a standing tube in fluid communication with an exterior fluid chamber in the protector surrounding the oil reservoir, the standing tube extending into the second fluid chamber to a location below a top of the second fluid chamber.

13. The device of claim 1 wherein the oil reservoir is flexible to enable fluid pressure equalization between an interior and an exterior thereof.

14. The device of claim 13 wherein the flexible reservoir comprises at least one of an elastomer bag or bladder metallic bellows or a piston.

15. The device of claim 1 further comprising a water rejection chamber disposed above the second fluid chamber, the water rejection chamber comprising a standing tube extending from a bottom of the water rejection chamber to a location proximate the bottom of the second fluid chamber.

16. An electric submersible pump (ESP) system, comprising: a motor;a protector disposed below the motor;a pump disposed below the protector and rotationally coupled to the motor; anda gas rejection device according to any of claims 1 through 15 disposed between the protector and the pump.

17. The ESP system of claim 16 wherein the motor comprises an electric motor.

18. The ESP system of claim 16 wherein the motor is immersed in dielectric fluid, thedielectric fluid in pressure communication with an exterior of the ESP system through the protector and the gas rejection device.s

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