RELATED APPLICATIONS

[0001] This application claims priority to and the benefit of a US Provisional Patent Application having Serial No. 61/865,312, filed 13 August 2013, which is incorporated by reference herein.

BACKGROUND

[0002] An electric submersible pump (ESP) can include a stack of impeller and diffuser stages where the impellers are operatively coupled to a shaft driven by an electric motor. Various forces exist during operation as fluid is propelled from lower stages to upper stages of the ESP stack. Various technologies, techniques, etc. described herein may help to balance forces between two or more stages.

SUMMARY

[0003] An electric submersible pump can include a shaft; an electric motor configured to rotatably drive the shaft; a housing that includes an inner surface disposed at an inner diameter; impellers operatively coupled to the shaft; and a stack of diffusers where each diffuser includes an outer surface disposed at an outer diameter, where a clearance is defined by the inner diameter of the housing and the outer diameter of the diffusers and where a portion of the clearance is sealed to form a fluid passage that extends axially between two diffusers in the stack of diffusers. A method can include providing a clearance between diffusers and a housing of an electric submersible pump; providing a hole in an upper one of the diffusers that extends to a diffuser blade region; providing a hole in a lower one of the diffusers that extends to an impeller region; operating the electric submersible pump; and balancing pressure between the diffuser blade region and the impeller region via fluid communication in a fluid passage that includes the holes and the clearance. A diffuser can include a fluid inlet end; a fluid outlet end; an outer surface extending from the fluid inlet end to the fluid outlet end; a longitudinal axis extending from the fluid inlet end to the fluid outlet end; an axial shaft bore; a ring co-axial to the axial shaft bore where an outer surface of the ring defines in part a ring region; vanes disposed between the fluid inlet end and the fluid outlet end and about the axial shaft bore where each of the vanes includes a leading edge and a trailing edge and where adjacent vanes define throats between respective leading edges and trailing edges; a first set of openings disposed axially between the leading edges and the trailing edges of the vanes where the first set of openings extend from the outer surface to the throats; and a second set of openings disposed axially between the first set of openings and the fluid outlet end where the second set of openings extend from the outer surface to the ring region. Various other apparatuses, systems, methods, etc., are also disclosed.

[0004] 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 the claimed subject matter.

BRIEF DESCRIPTION OF THE DRAWINGS

[0005] Features and advantages of the described implementations can be more readily understood by reference to the following description taken in conjunction with the accompanying drawings.

[0006] Fig. 1 i llustrates examples of equipment in geologic environments;

[0007] Fig. 2 i llustrates an example of an electric submersible pump system;

[0008] Fig. 3 i llustrates examples of equipment;

[0009] Fig. 4 i llustrates an example of a pump with a fluid circuit;

[0010] Fig. 5 i llustrates an example of a portion of a pump;

[0011] Fig. 6 i llustrates an example of a portion of a pump;

[0012] Fig. 7 i llustrates an example of a portion of a pump;

[0013] Fig. 8 i llustrates examples of portions of a pump;

[0014] Fig. 9 i llustrates an example of a diffuser;

[0015] Fig. 10 illustrates an example of a method; and

[0016] Fig. 1 1 illustrates example components of a system and a networked system.

DETAILED DESCRIPTION

[0017] The following description includes the best mode presently

contemplated for practicing the described implementations. This description is not to be taken in a limiting sense, but rather is made merely for the purpose of describing the general principles of the implementations. The scope of the described

implementations should be ascertained with reference to the issued claims.

[0018] Fig. 1 shows examples of geologic environments 120 and 140. In Fig. 1 , the geologic environment 120 may be a sedimentary basin that includes layers (e.g., stratification) that include a reservoir 121 and that may be, for example, intersected by a fault 123 (e.g., or faults). As an example, the geologic environment 120 may be outfitted with any of a variety of sensors, detectors, actuators, etc. For example, equipment 122 may include communication circuitry to receive and to transmit information with respect to one or more networks 125. Such information may include information associated with downhole equipment 124, which may be equipment to acquire information, to assist with resource recovery, etc. Other equipment 126 may be located remote from a well site and include sensing, detecting, emitting or other circuitry. Such equipment may include storage and communication circuitry to store and to communicate data, instructions, etc. As an example, one or more satellites may be provided for purposes of communications, data acquisition, etc. For example, Fig. 1 shows a satellite in communication with the network 125 that may be configured for communications, noting that the satellite may additionally or alternatively include circuitry for imagery (e.g., spatial, spectral, temporal, radiometric, etc.).

[0019] Fig. 1 also shows the geologic environment 120 as optionally including equipment 127 and 128 associated with a well that includes a substantially horizontal portion that may intersect with one or more fractures 129. For example, consider a well in a shale formation that may include natural fractures, artificial fractures (e.g., hydraulic fractures) or a combination of natural and artificial fractures. As an example, a well may be drilled for a reservoir that is laterally extensive. In such an example, lateral variations in properties, stresses, etc. may exist where an

assessment of such variations may assist with planning, operations, etc. to develop the reservoir (e.g., via fracturing, injecting, extracting, etc.). As an example, the equipment 127 and/or 128 may include components, a system, systems, etc. for fracturing, seismic sensing, analysis of seismic data, assessment of one or more fractures, etc.

[0020] As to the geologic environment 140, as shown in Fig. 1 , it includes two wells 141 and 143 (e.g., bores), which may be, for example, disposed at least partially in a layer such as a sand layer disposed between caprock and shale. As an example, the geologic environment 140 may be outfitted with equipment 145, which may be, for example, steam assisted gravity drainage (SAGD) equipment for injecting steam for enhancing extraction of a resource from a reservoir. SAGD is a technique that involves subterranean delivery of steam to enhance flow of heavy oil, bitumen, etc. SAGD can be applied for Enhanced Oil Recovery (EOR), which is also known as tertiary recovery because it changes properties of oil in situ.

[0021] As an example, a SAGD operation in the geologic environment 140 may use the well 141 for steam-injection and the well 143 for resource production. In such an example, the equipment 145 may be a downhole steam generator and the equipment 147 may be an electric submersible pump (e.g., an ESP).

[0022] As illustrated in a cross-sectional view of Fig. 1 , steam injected via the well 141 may rise in a subterranean portion of the geologic environment and transfer heat to a desirable resource such as heavy oil. In turn, as the resource is heated, its viscosity decreases, allowing it to flow more readily to the well 143 (e.g., a resource production well). In such an example, equipment 147 (e.g., an ESP) may then assist with lifting the resource in the well 143 to, for example, a surface facility (e.g., via a wellhead, etc.). As an example, where a production well includes artificial lift equipment such as an ESP, operation of such equipment may be impacted by the presence of condensed steam (e.g., water in addition to a desired resource). In such an example, an ESP may experience conditions that may depend in part on operation of other equipment (e.g., steam injection, operation of another ESP, etc.).

[0023] Conditions in a geologic environment may be transient and/or persistent. Where equipment is placed within a geologic environment, longevity of the equipment can depend on characteristics of the environment and, for example, duration of use of the equipment as well as function of the equipment. Where equipment is to endure in an environment over an extended period of time, uncertainty may arise in one or more factors that could impact integrity or expected lifetime of the equipment. As an example, where a period of time may be of the order of decades, equipment that is intended to last for such a period of time may be constructed to endure conditions imposed thereon, whether imposed by an environment or environments and/or one or more functions of the equipment itself.

[0024] Fig. 2 shows an example of an ESP system 200 that includes an ESP 210 as an example of equipment that may be placed in a geologic environment. As an example, an ESP may be expected to function in an environment over an extended period of time (e.g., optionally of the order of years). As an example, commercially available ESPs (such as the REDA™ ESPs marketed by

Schlumberger Limited, Houston, Texas) may find use in applications that call for, for example, pump rates in excess of about 4,000 barrels per day and lift of about 12,000 feet or more.

[0025] In the example of Fig. 2, the ESP system 200 includes a network 201 , a well 203 disposed in a geologic environment (e.g., with surface equipment, etc.), a power supply 205, the ESP 210, a controller 230, a motor controller 250 and a VSD unit 270. The power supply 205 may receive power from a power grid, an onsite generator (e.g., natural gas driven turbine), or other source. The power supply 205 may supply a voltage, for example, of about 4.16 kV.

[0026] As shown, the well 203 includes a wellhead that can include a choke (e.g., a choke valve). For example, the well 203 can include a choke valve to control various operations such as to reduce pressure of a fluid from high pressure in a closed wellbore to atmospheric pressure. Adjustable choke valves can include valves constructed to resist wear due to high-velocity, solids-laden fluid flowing by restricting or sealing elements. A wellhead may include one or more sensors such as a temperature sensor, a pressure sensor, a solids sensor, etc.

[0027] As to the ESP 210, it is shown as including cables 21 1 (e.g., or a cable), a pump 212, gas handling features 213, a pump intake 214, a motor 215, one or more sensors 216 (e.g., temperature, pressure, strain, current leakage, vibration, etc.) and optionally a protector 217.

[0028] As an example, an ESP may include a REDA™ Hotline high- temperature ESP motor. Such a motor may be suitable for implementation in a thermal recovery heavy oil production system, such as, for example, SAGD system or other steam-flooding system.

[0029] As an example, an ESP motor can include a three-phase squirrel cage with two-pole induction. As an example, an ESP motor may include steel stator laminations that can help focus magnetic forces on rotors, for example, to help reduce energy loss. As an example, stator windings can include copper and insulation.

[0030] In the example of Fig. 2, the well 203 may include one or more well sensors 220, for example, such as the commercially available OPTICLINE™ sensors or WELLWATCHER BRITEBLUE™ sensors marketed by Schlumberger Limited (Houston, Texas). Such sensors are fiber-optic based and can provide for real time sensing of temperature, for example, in SAGD or other operations. As shown in the example of Fig. 1 , a well can include a relatively horizontal portion. Such a portion may collect heated heavy oil responsive to steam injection. Measurements of temperature along the length of the well can provide for feedback, for example, to understand conditions downhole of an ESP. Well sensors may extend thousands of feet into a well (e.g., 4,000 feet or more) and beyond a position of an ESP.

[0031] In the example of Fig. 2, the controller 230 can include one or more interfaces, for example, for receipt, transmission or receipt and transmission of information with the motor controller 250, a VSD unit 270, the power supply 205 (e.g., a gas fueled turbine generator, a power company, etc.), the network 201 , equipment in the well 203, equipment in another well, etc.

[0032] As shown in Fig. 2, the controller 230 may include or provide access to one or more modules or frameworks. Further, the controller 230 may include features of an ESP motor controller and optionally supplant the ESP motor controller 250. For example, the controller 230 may include the UNICONN™ motor controller 282 marketed by Schlumberger Limited (Houston, Texas). In the example of Fig. 2, the controller 230 may access one or more of the PIPESIM™ framework 284, the ECLIPSE™ framework 286 marketed by Schlumberger Limited (Houston, Texas) and the PETREL™ framework 288 marketed by Schlumberger Limited (Houston, Texas) (e.g., and optionally the OCEAN™ framework marketed by Schlumberger Limited (Houston, Texas)).

[0033] In the example of Fig. 2, the motor controller 250 may be a

commercially available motor controller such as the UNICONN™ motor controller. The UNICONN™ motor controller can connect to a SCADA system, the

ESPWATCHER™ surveillance system, etc. The UNICONN™ motor controller can perform some control and data acquisition tasks for ESPs, surface pumps or other monitored wells. The UNICONN™ motor controller can interface with the

PHOENIX™ monitoring system, for example, to access pressure, temperature and vibration data and various protection parameters as well as to provide direct current power to downhole sensors. The UNICONN™ motor controller can interface with fixed speed drive (FSD) controllers or a VSD unit, for example, such as the VSD unit 270. [0034] For FSD controllers, the UNICONN ' ^M motor controller can monitor ESP system three-phase currents, three-phase surface voltage, supply voltage and frequency, ESP spinning frequency and leg ground, power factor and motor load.

[0035] For VSD units, the UNICONN™ motor controller can monitor VSD output current, ESP running current, VSD output voltage, supply voltage, VSD input and VSD output power, VSD output frequency, drive loading, motor load, three- phase ESP running current, three-phase VSD input or output voltage, ESP spinning frequency, and leg-ground.

[0036] In the example of Fig. 2, the ESP motor controller 250 includes various modules to handle, for example, backspin of an ESP, sanding of an ESP, flux of an ESP and gas lock of an ESP. The motor controller 250 may include any of a variety of features, additionally, alternatively, etc.

[0037] In the example of Fig. 2, the VSD unit 270 may be a low voltage drive (VSD) unit, a medium voltage drive (MVD) unit or other type of unit (e.g., a high voltage drive, which may provide a voltage in excess of about 4.16 kV). As an example, the VSD unit 270 may receive power with a voltage of about 4.16 kV and control a motor as a load with a voltage from about 0 V to about 4.16 kV. The VSD unit 270 may include commercially available control circuitry such as the

SPEEDSTAR™ MVD control circuitry marketed by Schlumberger Limited (Houston, Texas).

[0038] Fig. 3 shows cut-away views of examples of equipment such as, for example, a portion of a pump 320, a protector 370 and a motor 350 of an ESP. The pump 320, the protector 370 and the motor 350 are shown with respect to cylindrical coordinate systems (e.g., r, z, Θ). Various features of equipment may be described, defined, etc. with respect to a cylindrical coordinate system. As an example, a lower end of the pump 320 may be coupled to an upper end of the protector 370 and a lower end of the protector 370 may be coupled to an upper end of the motor 350. As shown in Fig. 3, a shaft segment of the pump 320 may be coupled via a connector to a shaft segment of the protector 370 and the shaft segment of the protector 370 may be coupled via a connector to a shaft segment of the motor 350. As an example, an ESP may be oriented in a desired direction, which may be vertical, horizontal or other angle. Orientation of an ESP with respect to gravity may be considered as a factor, for example, to determine ESP features, operation, etc. [0039] Fig. 4 shows a cut-away view of a pump 420 that includes a stack of impeller and diffuser stages where the impellers are operatively coupled to a shaft that may be driven by an electric motor (see, e.g., the electric motor 350 of Fig. 3). In such a pump, various forces exist during operation as fluid is propelled from lower stages to upper stages of a stack. As an example, a pump may be oriented vertically, horizontally or at an angle between vertical and horizontal with respect to an environment. In such an example, vertical may be aligned substantially with gravity.

[0040] In an enlarged cut-away view, a portion of the pump 420 is shown as including a housing 430, four diffusers 440-1 , 440-2, 440-3 and 440-4, three impellers 460-1 , 460-2 and 460-3, and a shaft 422 operatively coupled to the impellers 460-1 , 460-2 and 460-3 (e.g., optionally via a key or keys in a keyway or key ways).

[0041] In the cut-away view of Fig. 4, each of the diffusers 440-1 , 440-2, 440-3 and 440-4 includes an outer surface (e.g., a cylindrical surface) defined by an outer diameter and the housing 430 includes an inner surface (e.g., a cylindrical surface) defined by an inner diameter. As shown, a clearance exists between the outer surfaces of the diffusers 440-1 , 440-2, 440-3 and 440-4 and the inner surface of the housing 430 (e.g., a radial clearance, an annular clearance, etc.). In such an example, features may be included to space diffusers with respect to a housing (e.g., via spacers, etc.). A spacer may be a feature of a diffuser, a feature of a housing, a separate component (e.g., seated in a seat of a housing, a diffuser, or both). As an example, a clearance may exist due to one or more channels being formed along an outer surface of a diffuser. For example, a diffuser may include one or more channels (e.g., with a polygonal cross-section and/or a curved cross-section) that extends at least from a hole to an end of the diffuser. As an example, a channel may be straight, curved, helical (e.g., spiral), etc. and, for example, achieved via casting, machining, etc.

[0042] In the arrangement of Fig. 4, the clearance is a fluid passage that can fluidly couple two or more stages of the pump 420. For example, as shown, a region of the diffuser 440-1 (e.g., a chamber) is fluidly coupled to a region of the impeller 460-3 (e.g., a chamber) via the clearance.

[0043] Fig. 4 also shows examples of seal elements 450-1 and 450-2 that act to form fluid seals between the diffuser 440-1 and the housing 430 and the diffuser 440-4 and the housing 430. Such seal elements may define an axial extent of the clearance that acts as a fluid passage (e.g., an axial length). As an example, seal elements 445-1 , 445-2, 465-1 and 465-2 may be provided that seal passages of the diffusers 440-2 and 440-3. As an example, a diffuser may be provided with seal elements that may optionally be used to seal the diffuser from a fluid passage such as a fluid passage formed by an annular clearance (e.g., or other clearance or clearances) between the diffuser and a housing.

[0044] As mentioned, while the fluid passage in the example of Fig. 4 may be an annular clearance, as an example, a diffuser may include one or more channels formed along an outer surface, for example, to define a clearance with respect to an inner surface of a housing (e.g., one or more radial clearances). Such a clearance may be used as a fluid passage, for example, to communicate fluid pressure from one stage to another stage of a multistage pump.

[0045] As an example, during operation, an upper stage of a pump may experience a higher fluid pressure than a lower stage of the pump. As an example, a pump can include one or more fluid passages that can fluidly couple two or more stages of a pump. For example, a fluid passage may be defined in part between a surface of a housing wall and surfaces of components of two or more stages. For example, a fluid passage may be substantially annular with an upper opening and a lower opening where, for example, a region with a higher pressure provided at the upper opening may be fluidly communicated via the fluid passage to a region with a lower pressure provided at the lower opening. In such an example, the higher pressure may act to balance the lower pressure (e.g., the higher pressure may act to increase the lower pressure).

[0046] As an example, a pump may be provided with features to use a higher pressure in an upper stage area to balance an impeller in a lower stage area by connecting these two areas via an annulus or other fluid passage or passages (e.g., a space or spaces between diffusers and a housing). As an example, a hole may be introduced in an upper stage diffuser bore that connects to an annulus (e.g., a space between a diffuser OD and a housing ID). In such an example, another hole may be introduced in a lower stage diffuser bore to fluidly couple a chamber under an impeller lower shroud and the annulus. In such an example, pressure may be transferred from the upper stage that may act upon the lower impeller shroud at the lower stage. Such pressure may exert an axially upwardly directed force that may, for example, compensate for an axially downwardly directed force.

[0047] As an example, a fluid passage may be sealed. For example, stages may be sealed from one or more other stages with respect to an annulus by one or more sealing mechanisms (e.g., O-rings, diffuser shoulders, etc.). As an example, a diffuser may include a set of holes, for example, disposed at an axial position and located at different azimuthal angles. Such a diffuser may optionally include another set of holes, for example, at a different axial position and located azimuthally at angles about a central axis of the diffuser. As an example, a set of holes may connect to an annular groove, for example, such that a seal element may be seated in the annular groove to seal the set of holes. As an example, a seal element may be configured to alter hole cross-sectional area, seal some holes, etc. As an example, a diffuser may be provided with one or more seal elements that may be removable prior to insertion of the diffusers into a housing to determine which stages of a pump may form a fluid circuit or be impacted by pressure in a fluid circuit.

[0048] As an example, axially downwardly directed forces may occur during operation of impellers in a centrifugal, mixed-flow (e.g., partially radial and partially axial) pump (e.g., as reaction forces that can act in a direction opposite to a direction of fluid flow).

[0049] As an example, various types of pumps may include a balance ring and balance holes on a top impeller shroud. Such balance mechanisms tend to operate in an intrastage manner rather than an interstage manner. As an example, an approach such as that of Fig. 4 may be implemented in conjunction with a balance ring, balance holes, etc. For example, a pump can include features that provide for intrastage pressure balancing and interstage pressure balancing.

[0050] Fig. 5 shows a cut-away view of an example of a portion of a pump that includes two diffusers 540-1 and 540-2 and an impeller 560 as well as a perspective view of the impeller 560. The views of Fig. 5 show the impeller 560 as including an impeller balance ring 562 and an impeller balance hole 564, noting that the impeller 560 can include a plurality of impeller balance holes. As shown in the cut-away view, the impeller balance hole 564 extends from an opening in an external surface of the impeller 560 to an opening in an internal surface of the impeller 560. The impeller balance hole 564 can allow for recirculation of a portion of fluid propelled by rotation of a plurality of impeller blades such as the blade 566, which includes a leading edge and a trailing edge. In the example of Fig. 5, the impeller balance hole 564 can recirculate fluid to a region at or proximate to the leading edge of the blade 566. For example, a portion of fluid passing the trailing edge of the blade 566 may, via a radial clearance, pass the impeller balance ring 562 and enter a chamber defined by the impeller 560 and the diffuser 540-1 . As shown in Fig. 5, the chamber is in fluid communication with the impeller balance hole 564 such that a pressure differential across the impeller balance hole 564 may result in flow of fluid from the chamber to the region at or proximate to the leading edge of the blade 566.

[0051] As shown in the example of Fig. 5, the diffuser 540-2 includes an upper hole 546 and a lower hole 548 as well as an annular groove 547 disposed axially between the upper hole 546 and the lower hole 548 that may seat a seal element 580 (e.g., an O-ring, etc.). In such an example, the seal element 580 may optionally act to center one or more diffusers in a housing (e.g., to help maintain a more uniform clearance between a diffuser and the housing); noting that adjacent diffusers may stack and axially locate each other (see, e.g., an annular shoulder joint between the diffuser 540-1 and 540-2).

[0052] As indicated in the example of Fig. 5, a pressure differential may exist (see, e.g., P _H and P|_) that may act to communicate fluid pressure, fluid flow, etc. from a region of a diffuser to a region of an impeller. For example, a chamber may be defined in part by a lower surface of the impeller 560 and an upper surface of the diffuser 540-2 where the hole 546 in the diffuser 540-2 provides for communication of fluid pressure to the chamber. Such fluid pressure may act to counter a downwardly directed axial force of the impeller 560.

[0053] Fig. 6 shows a cut-away view of an example of a portion of a pump that includes two diffusers 640-1 and 640-2 and an impeller 660. As shown, the diffuser 640-2 includes an upper hole 646 and a lower hole 648 as well as an annular shoulder 649 disposed axially between the upper hole 646 and the lower hole 648 that may seat, for example, against an inner surface of a housing. As an example, a diffuser may be provided with an annular shoulder that includes cutouts or removable portions that may serve to communicate fluid in a space between the diffuser and a housing. For example, upon assembly of stages in a housing, an annular shoulder may be configured to seal against passage of fluid or may be configured to pass fluid. Such a shoulder may act to center a diffuser and pass fluid or to center a diffuser and block fluid. A method may include configuring some diffusers to block fluid and some diffusers to pass fluid (e.g., in a diffuser/housing clearance) and then inserting the diffusers as a stack into the housing.

[0054] As indicated in the example of Fig. 6, a pressure differential may exist (see, e.g., PH and PL) that may act to communicate fluid pressure, fluid flow, etc. from a region of a diffuser to a region of an impeller. For example, a chamber may be defined in part by a lower surface of the impeller 660 and an upper surface of the diffuser 640-2 where the hole 646 in the diffuser 640-2 provides for communication of fluid pressure to the chamber. Such fluid pressure may act to counter a downwardly directed axial force of the impeller 660.

[0055] Fig. 7 shows a cut-away view of an example of a portion of a pump that includes two diffusers 740-1 and 740-2 and an impeller 760. As shown, the diffuser 740-2 includes an upper hole 746 and a lower hole 748 as well as an annular groove 747 disposed axially between the upper hole 746 and the lower hole 748 that may seat a seal element 780 (e.g., an O-ring, etc.). As an example, a shoulder may be implemented, for example, as shown in Fig. 6. As indicated, a pressure differential may exist (see, e.g., PH and PL) that may act to communicate fluid pressure, fluid flow, etc. from a region of a diffuser to a region of an impeller. For example, a chamber may be defined in part by a lower surface of the impeller 760 and an upper surface of the diffuser 740-2 where the hole 746 in the diffuser 740-2 provides for communication of fluid pressure to the chamber. Such fluid pressure may act to counter a downwardly directed axial force of the impeller 760.

[0056] In the example of Fig. 7, the impeller 760 includes an annular lip 761 that extends axially downwardly into the chamber. As shown, the annular lip 761 may include an outer surface at an outer diameter and the diffuser 740-1 may include an inner surface at an inner diameter where a clearance (e.g., a radial clearance) is formed between the outer surface of the annular lip 761 and the inner surface of the diffuser 740-1 . As an example, the clearance may act to reduce flow of fluid from the chamber to a region axially above the chamber, for example, where trailing edges of impeller blades and leading edges of diffuser blades (e.g., diffuser vanes) exist. In such an example, the annular lip 761 may reduce influence of fluid in the chamber below to the chamber above, for example, to avoid detrimental fluid dynamic effects on flow from the trailing edges of the impeller blades to the leading edges of the diffuser blades. [0057] Fig. 8 shows examples of assemblies 810, 820, 860 and 870, which may be assemblies of multiple pump stages (e.g., stacks of impellers and diffusers). The assembly 810 includes inner components 81 1 , seal elements 812-1 and 812-2 and an outer housing 813. As shown, the seal elements 812-1 and 812-2 define a space in which fluid may flow, for example, from one or more openings 814-1 to one or more openings 814-2. In such an example, fluid flow can include vorticity, for example, as imparted by an impeller operatively coupled to a rotating shaft.

[0058] As shown Fig. 8, the assembly 820 includes inner components 821 , seal elements 822-1 and 822-2 and an outer housing 823. In the assembly 820, the seal elements 822-1 and 822-2 can define a space in which fluid may flow, for example, from one or more openings 824-1 to one or more openings 824-2. In such an example, flow may be guided by one or more ridges 826-1 and 826-2 that may define flow passages, for example, consider notches, clearances, etc. As an example, a ridge may influence flow, for example, a ridge may have an influence on one or more of vorticity, velocity, pressure, etc. As an example, a ridge may be part of an internal component and/or part of a housing. As an example, an assembly may include ridges that extend radially outwardly from a diffuser and/or ridges that extend radially inwardly from a housing.

[0059] As shown in Fig. 8, the assembly 860 includes inner components 861 and seal elements 862-1 and 862-2 as well as one or more openings 864-1 and one or more openings 864-2. In the assembly 860, flow passages (e.g., channels) 866-1 , 866-2 and 866-3 are in fluid communication with the one or more openings 864-1 and the one or more openings 864-2. As an example, the assembly 860 can include an outer housing where an inner surface of the housing may cover the flow passages 866-1 , 866-2 and 866-3. For example, an inner surface of a housing may act to confine fluid substantially to the flow passages 866-1 , 866-2 and 866-3. In such an example, fluid may flow from the one or more openings 864-1 to the one or more openings 864-2 via the one or more flow passages 866-1 , 866-2 and 866-3.

[0060] As shown in Fig. 8, the assembly 870 includes inner components 871 and seal elements 872-1 and 872-2 as well as one or more openings 874-1 and one or more openings 874-2. In the assembly 870, flow passages (e.g., channels) 876-1 , 876-2 and 876-3 are in fluid communication with the one or more openings 874-1 and the one or more openings 874-2. As an example, the assembly 870 can include an outer housing where an inner surface of the housing may cover the flow passages 876-1 , 876-2 and 876-3. For example, an inner surface of a housing may act to confine fluid substantially to the flow passages 876-1 , 876-2 and 876-3. In such an example, fluid may flow from the one or more openings 874-1 to the one or more openings 874-2 via the one or more flow passages 876-1 , 876-2 and 876-3.

[0061] In the example assemblies 810, 820, 860 and 870, the seal elements 812-1 , 812-2, 822-1 , 822-2, 862-1 , 862-2, 872-1 , and 872-2 may be metallic, polymeric, metallic and polymeric, etc. As an example, a seal element may be a piston type of ring. As an example, a seal element may be an O-ring. As an example, a seal element may be integral to a diffuser. As an example, a seal element may be integral to a housing. As an example, a diffuser may include a groove that can seat a seal element or seal elements. As an example, a housing may include a groove that can seat a seal element or seal elements. As an example, a diffuser may include a groove and a housing may include a groove where one or more seal elements may be seated with respect to the groove of the diffuser and the groove of the housing.

[0062] Fig. 9 shows cross-sectional views of an example of a diffuser 940, including a cross-sectional view along a line A-A and a cross-sectional view along a line B-B. Fig. 9 also shows coordinates of a cylindrical coordinate system (r, z, Θ), which may be used to define various features of the diffuser 940.

[0063] In the example of Fig. 9, the diffuser 940 includes an axial shaft bore 941 , an upper end 942 (e.g., a fluid outlet end), a ring 943 and a lower end 944 (e.g., a fluid inlet end). The axial shaft bore 941 may be dimensioned to receive a portion of an impeller or at least a portion of an impeller spacer through which a shaft may pass. The ring 943 extends an axial distance and includes an outer surface that defines a ring region. As an example, the ring region may define part of a chamber, for example, in conjunction with a lower surface of an impeller.

[0064] Between the upper end 942 and the lower end 944, the diffuser 940 includes a set of openings 946 and a set of openings 948 as well as, for example, a groove 947 that may seat one or more seal elements. The diffuser 940 also includes a plurality of vanes 949-1 to 949-N, which may direct fluid, for example, from trailing edges of impeller blades of one impeller to leading edges of impeller blades of another impeller. [0065] In the example of Fig. 9, the diffuser 949 includes an annular groove (see, e.g., Ar) about the set of openings 946 and an annular groove (see, e.g., Ar) about the set of openings 948. In such an example, a seal element may be seated in one of the grooves to seal off a set of the openings. As an example, a diffuser may be fitted with two seal elements that seal of respective sets of openings, for example, where the diffuser may be an intermediate diffuser in a stack where flow occurs from openings of a diffuser positioned above to a openings of a diffuser positioned below.

[0066] In the example of Fig. 9, the sets of openings 946 and 948 may be along radial lines or, for example, disposed at an angle (see, e.g., enlarged views). As an example, an angle may be selected based on one or more flow characteristics (e.g., vorticity, etc.).

[0067] As an example, a pump may include a plurality of the diffusers 940 where, for example, fluid in one or more of the plurality of diffusers exits via a set of openings such as the set of openings 948 and then enters one or more of the plurality of diffusers via a set of openings such as the set of openings 946. In such an example, where the plurality of diffusers are in a stack, fluid may flow in a direction from upper diffusers to lower diffusers (e.g., from the set of openings 948 of one diffuser to the set of openings 946 of another diffuser).

[0068] As an example, a diffuser can include a fluid inlet end; a fluid outlet end; an outer surface extending from the fluid inlet end to the fluid outlet end; a longitudinal axis extending from the fluid inlet end to the fluid outlet end; an axial shaft bore; a ring co-axial to the axial shaft bore where an outer surface of the ring defines in part a ring region; vanes disposed between the fluid inlet end and the fluid outlet end and about the axial shaft bore where each of the vanes includes a leading edge and a trailing edge and where adjacent vanes define throats between respective leading edges and trailing edges; a first set of openings disposed axially between the leading edges and the trailing edges of the vanes where the first set of openings extend from the outer surface to the throats; and a second set of openings disposed axially between the first set of openings and the fluid outlet end where the second set of openings extend from the outer surface to the ring region. In such an example, the diffuser may include one or more annular grooves. As an example, a diffuser may include one or more seal elements disposed at least in part in an annular groove. As an example, a diffuser can include an annular groove configured to seat a seal element. As an example, a diffuser may include a shoulder that may extend radially outwardly, for example, to contact an inner surface of a housing.

[0069] As an example, a diffuser may include a hole in a region of a diffuser vane passage and may include a hole in a region that is below an impeller shroud. As an example, a diffuser may include a plurality of holes (e.g., openings) in a first region and a plurality of holes (e.g., openings) in a second region. As an example, a hole in a diffuser may be drilled or otherwise formed at an angle. For example, consider a hole drilled in a radial direction aligned with a longitudinal axis of a diffuser, a hole drilled with a tangential angle.

[0070] As an example, a number of holes in each of an upper stage and a lower stage may be one or more and may be placed radially. As an example, holes and characteristics thereof may depend on a pump application, axial thrust value and effect on pump efficiency.

[0071] As an example, a pump may include a plurality of fluid circuits where each fluid circuit is implemented, for example, in sets of two or more stages. As an example, a fluid circuit may connect to stages one-by-one, one after two, one after three, etc. For example, sealing mechanisms may be provided to separate multiple stages.

[0072] As an example, an impeller may include an annular lip, for example, to reduce leakage that may affect volumetric efficiency. As an example, a diffuser may include a smaller bore ID, for example, to reduce a clearance with an OD of an impeller, which may be specified by a standard impeller tip OD (e.g., to reduce leakage). For example, a fluid circuit may act to balance impeller forces by increasing pressure in a region below an exducer portion of an impeller, which, in turn, may act to increase leakage between an OD of the impeller and an ID of a bore of a diffuser. To reduce risk of leakage, one or more approaches may be taken, for example, increasing impeller OD, providing an impeller with an annular lip, providing a diffuser with a smaller bore ID, etc. As an example, by reducing an OD of a diffuser to form a clearance with an ID of a housing, by decreasing the ID of the diffuser, a wall thickness at a particular portion of the diffuser may be maintained.

[0073] As an example, a fluid passage may be formed by one or more channels in an outer surface of a diffuser where such diffusers may be stacked and housed in a housing. For example, an axial passage like a keyway may be on a diffuser outer wall in order to improve fluid communication between an upper stage and a lower stage. As an example, such a passage may be cast, machined, etc. into a diffuser.

[0074] As an example, a sealing mechanism in an annulus may be formed via one or more of O-rings, diffuser shoulders with larger ODs, etc. As an example, two diffuser shoulders may seal an annulus under compression forces applied to a diffuser stack during an assembly process (e.g., using a compression nut, compression fitting, etc.) or under thermal expansion due to pump temperature increase during operation.

[0075] As an example, a pump may be a mixed flow pump. As an example, a pump may be a radial flow pump. As an example, a pump may have a floater or a compression type construction.

[0076] As an example, an electric submersible pump can include a shaft; an electric motor configured to rotatably drive the shaft; a housing that includes an inner surface disposed at an inner diameter; impellers operatively coupled to the shaft; and a stack of diffusers where each diffuser includes an outer surface disposed at an outer diameter, where a clearance is defined by the inner diameter of the housing and the outer diameter of the diffusers and where a portion of the clearance is sealed to form a fluid passage that extends axially between two diffusers in the stack of diffusers. In such an example, the two diffusers in the stack of diffusers can include at least one diffuser disposed axially therebetween.

[0077] As an example, an upper diffuser of two diffusers in a stack of diffusers can include a hole that extends radially inwardly to a diffuser blade region (e.g., a diffuser vane region) and a lower diffuser of the two diffusers can include a hole that extends radially inwardly to an impeller region. In such an example, a clearance may provide for fluid communication between the hole of the upper diffuser and the hole of the lower diffuser. As an example, in an operational state of an electric submersible pump, a diffuser blade region can have a higher fluid pressure than an impeller region, for example, where a fluid circuit may act to balance such pressures.

[0078] As an example, an impeller may include an annular lip that extends axially downwardly away from trailing edges of blades of the impeller. In such an example, a diffuser can include an inner surface that defines a radial clearance with respect to an outer surface of the annular lip of the impeller. [0079] As an example, an electric submersible pump may include a fluid pressure circuit configured to communicate fluid pressure from an upper stage to a lower stage of the electric submersible pump via at least a portion of a clearance (e.g., defined by an inner surface of a housing and outer surfaces of diffusers).

[0080] As an example, an impeller may include balance holes. As an example, an electric submersible pump may include at least one balance ring.

[0081] As an example, an electric submersible pump can include a protector disposed axially between an electric motor and a housing of pump stages.

[0082] As an example, an impeller can include blades where each of the blades extends from a leading edge to a trailing edge. As an example, an impeller may be a mixed flow impeller configured to direct fluid radially and axially.

[0083] Fig. 10 shows an example of a method 1010 that includes a provision block 1012 for providing a clearance between diffusers and a housing of an electric submersible pump; a provision block 1014 for providing a hole in an upper one of the diffusers that extends to a diffuser blade region; a provision block 1016 for providing a hole in a lower one of the diffusers that extends to an impeller region; an operation block 1018 for operating the electric submersible pump; and a balance block 1020 for balancing pressure between the diffuser blade region and the impeller region via fluid communication in a fluid passage that includes the holes and the clearance.

[0084] As an example, a method can include providing a clearance between diffusers and a housing of an electric submersible pump; providing a hole in an upper one of the diffusers that extends to a diffuser blade region; providing a hole in a lower one of the diffusers that extends to an impeller region; operating the electric submersible pump; and balancing pressure between the diffuser blade region and the impeller region via fluid communication in a fluid passage that includes the holes and the clearance. In such an example, the method may include exerting an axially directed upward force on a lower surface of an impeller disposed at least partially in the impeller region, for example, where the axially directed upward force acts to balance an axially directed downward force of the impeller.

[0085] As an example, a method may include operating an electric

submersible pump by delivering power to an electric motor to rotate a shaft where impellers of a pump are operatively coupled to the shaft. In such an example, the method may include protecting the electric motor using a protector disposed axially between the pump and the electric motor. [0086] As an example, one or more control modules (e.g., for a controller such as the controller 230, the controller 250, etc.) may be configured to control an ESP (e.g., a motor, etc.) based at least in part on information as to one or more fluid circuits in that may exist between stages of a pump. For example, one or more of backspin, sanding, flux, gas lock or other operation may be implemented in a manner that accounts for one or more fluid circuits (e.g., as provided by diffusers with fluid coupling holes). As an example, a controller may control an ESP based on one or more pressure estimations for a fluid circuit or circuits (e.g., during start up, transients, change in conditions, etc.), for example, where a fluid circuit or circuits may act to balance thrust force.

[0087] As an example, one or more methods described herein may include associated computer-readable storage media (CRM) blocks. Such blocks can include instructions suitable for execution by one or more processors (or cores) to instruct a computing device or system to perform one or more actions.

[0088] According to an embodiment, one or more computer-readable media may include computer-executable instructions to instruct a computing system to output information for controlling a process. For example, such instructions may provide for output to sensing process, an injection process, drilling process, an extraction process, an extrusion process, a pumping process, a heating process, etc.

[0089] Fig. 1 1 shows components of a computing system 1 100 and a networked system 1 1 10. The system 1 100 includes one or more processors 1 102, memory and/or storage components 1 104, one or more input and/or output devices 1 106 and a bus 1 108. According to an embodiment, instructions may be stored in one or more computer-readable media (e.g., memory/storage components 1 104). Such instructions may be read by one or more processors (e.g., the processor(s) 1 102) via a communication bus (e.g., the bus 1 108), which may be wired or wireless. The one or more processors may execute such instructions to implement (wholly or in part) one or more attributes (e.g., as part of a method). A user may view output from and interact with a process via an I/O device (e.g., the device 1 106). According to an embodiment, a computer-readable medium may be a storage component such as a physical memory storage device, for example, a chip, a chip on a package, a memory card, etc.

[0090] According to an embodiment, components may be distributed, such as in the network system 1 1 10. The network system 1 1 10 includes components 1 122- 1 , 1 122-2, 1 122-3, . . ., 1 122-N. For example, the components 1 122-1 may include the processor(s) 802 while the component(s) 1 122-3 may include memory accessible by the processor(s) 1 102. Further, the component(s) 1 102-2 may include an I/O device for display and optionally interaction with a method. The network may be or include the Internet, an intranet, a cellular network, a satellite network, etc.

Conclusion

[0091] Although only a few examples have been described in detail above, those skilled in the art will readily appreciate that many modifications are possible in the examples. Accordingly, all such modifications are intended to be included within the scope of this disclosure as defined in the following claims. In the claims, means- plus-function clauses are intended to cover the structures described herein as performing the recited function and not only structural equivalents, but also equivalent structures. Thus, although a nail and a screw may not be structural equivalents in that a nail employs a cylindrical surface to secure wooden parts together, whereas a screw employs a helical surface, in the environment of fastening wooden parts, a nail and a screw may be equivalent structures. It is the express intention of the applicant not to invoke 35 U.S.C. § 1 12, paragraph 6 for any limitations of any of the claims herein, except for those in which the claim expressly uses the words "means for" together with an associated function.