Mechanical Shaft Stop in a Rotating Machine

None.

Not applicable.

Not applicable.

Oilfield and energy recovery equipment is called upon to serve under a wide variety of operating conditions and often in harsh environments. Electric submersible pump (ESP) assemblies may be expected to operate in downhole conditions of high heat and in the presence of reservoir fluids that exhibit a wide range of gas-to-liquid ratios that change dramatically over time. ESPs may be applied to lift hydrocarbons from subterranean formations. ESPs may be applied to lift geothermal fluids to the surface, where thermal energy may be recovered from hot geothermal fluids. Horizontal pump systems (HPSs) may be disposed at a surface location and pump fluids from a surface location into a wellbore (e.g., an injection well) or may provide pressure boost to drive fluid flow in a pipeline.

It should be understood at the outset that although illustrative implementations of one or more embodiments are illustrated below, the disclosed systems and methods may be implemented using any number of techniques, whether currently known or not yet in existence. The disclosure should in no way be limited to the illustrative implementations, drawings, and techniques illustrated below, but may be modified within the scope of the appended claims along with their full scope of equivalents.

As used herein, orientation terms “upstream,” “downstream,” “up,” and “down” are defined relative to the direction of flow of well fluid in the well casing. “Upstream” is directed counter to the direction of flow of well fluid, towards the source of well fluid (e.g., towards perforations in well casing through which hydrocarbons flow out of a subterranean formation and into the casing). “Downstream” is directed in the direction of flow of well fluid, away from the source of well fluid. “Down” is directed counter to the direction of flow of well fluid, towards the source of well fluid. “Up” is directed in the direction of flow of well fluid, away from the source of well fluid. As used herein, the term “about” when referring to a measured value or fraction means a range of values+/−5% of the nominal value stated. Thus, “about 1 inch,” in this sense of “about,” means the range 0.95 inches to 1.05 inches, and “about 5000 PSI,” in this sense of “about,” means the range 4750 PSI to 5250 PSI. Thus, the fraction “about 8/10s” means the range 76/100s to 84/100s.

Electric submersible pump (ESP) assemblies may feature a variety of rotating components. For example, ESP assemblies may comprise centrifugal pump stages that each comprise an impeller coupled to a rotating drive shaft and a diffuser that is statically coupled to a housing of the centrifugal pump. Gas separators may have rotating components such as fluid movers and/or centrifugal pump stages. Charge pumps can have pump stages that feature rotating components. Horizontal pump assemblies (HPSs) may also feature rotating components, such as impellers coupled to a rotating drive shaft. In some cases, it is desirable that rotating components float free of the drive shaft (e.g., the rotating component is free to move axially along the drive shaft within some range of motion). In other cases, however, it is desirable that rotating components not float freely and instead the rotating components are desirably axially fixed to the drive shaft so they turn with the drive shaft and do not move axially with reference to the drive shaft. In this case, the rotating components may be said to be in compression. For example, a centrifugal pump may comprise a plurality of impellers that are located by spacer sleeves on the drive shaft (e.g., the spacer sleeves may pass through a central bore of diffusers and may be coupled to the drive shaft) and stopped at one or both ends by a mechanical shaft stop. In some embodiments, the mechanical shaft stop may be axially fixed on the drive shaft by a retainer ring disposed in an outside groove of the drive shaft and in a retaining groove of an interior groove of the mechanical shaft stop. This arrangement may have disadvantages. For example, the outside groove cut in the outer surface of the drive shaft forms a point of weakness (e.g., drive shaft strength is functionally related to a diameter of the drive shaft, and a groove in the outside surface of the drive shaft reduces the diameter at that point, reducing the strength of the drive shaft at that point, thereby defining a point of weakness). A common failure mode of rotating equipment is drive shaft failure. Additionally, installation of such a retainer ring to secure a mechanical shaft stop during assembly of an item of rotating equipment can be difficult and time consuming, due to the dimensional constraints of the equipment.

The present disclosure teaches a new mechanical shaft stop assembly that avoids weakening a drive shaft by obviating the need to provide a groove in the drive shaft to receive a retaining ring and that promotes ease of rotating machine assembly. A mechanical shaft stop may comprise a compression stop defining an interior bore that slides over a drive shaft, a flexible collet that slides over the drive shaft and is received and stopped at one axial end by the compression stop, and a compression nut that slides over the drive shaft and that engages with the flexible collet, compressing the flexible collet onto an outside surface of the drive shaft to create a secure friction hold on the drive shaft, effectively affixing the mechanical shaft stop axially on the drive shaft. Two such mechanical shaft stop assemblies may be located at either end of a string of components to retain the rotating components (e.g., impellers and spacer sleeves) in compression. The disclosed mechanical shaft stop has application in pump rotating machines, in gas separator rotating machines, in charge pump rotating machines, in HPSs, and in other rotating machines.

Turning now toa well site environmentshowing a completion string disposed in a wellbore, according to one or more aspects of the disclosure, is described. The well site environmentcomprises a wellborethat is at least partially cased with casing. As depicted in, the wellboreis substantially vertical, but the electric submersible pump (ESP) assemblydescribed herein also may be used in a wellborethat has a deviated or horizontal portion. The well site environmentmay be at an on-shore location or at an off-shore location. The ESP assemblyin an embodiment comprises an optional sensor package, an electric motor, a motor headthat couples the electric motorto a seal unit, a fluid intakehaving inlet ports, and a centrifugal pump assembly. The centrifugal pump assemblycomprises a plurality of centrifugal pump stages. The centrifugal pump assemblycomprises a novel mechanical shaft stop as disclosed further below.

In an embodiment, the electric motormay be replaced by a hydraulic turbine, a pneumatic turbine, a hydraulic motor, or an air motor, and in this case the assemblymay be referred to as a submersible pump assembly. In an embodiment, the ESP assemblymay further comprise a gas separator assembly (e.g., seeandbelow) that may be located between the fluid intakeand the centrifugal pump assembly. In an embodiment, the fluid intakemay be integrated into a downhole end of the optional gas separator. In an embodiment, the fluid intakemay be integrated into a downhole end of the centrifugal pump assembly. In an embodiment, the fluid intakemay be a separate component that is bolted at its downhole end to an uphole end of the seal unitand bolted at its uphole end to a downhole end of the centrifugal pump assemblyor to a downhole end of a gas separator assembly.

The centrifugal pump assemblymay couple to a production tubingvia a connector. An electric cablemay attach to the electric motorand extend to the surfaceto connect to an electric power source. In an embodiment, where the electric motoris replaced by a hydraulic turbine or a hydraulic motor, the electric cablemay be replaced by a hydraulic power supply line. In an embodiment, where the electric motoris replaced by a pneumatic turbine or an air motor, the electric cablemay be replaced by a pneumatic power supply line. The casingand/or wellboremay have perforationsthat allow well fluidto pass from the subterranean formation through the perforationsand into the wellbore. In some contexts, well fluidmay be referred to as reservoir fluid.

It will be appreciated that in a different embodiment, the configuration of the ESP assemblymay be different. For example, in a bottom-intake design, the fluid intakemay be located at the downhole end of the ESP assembly, the centrifugal pump assemblymay be located uphole of the fluid intake, the motormay be located uphole of the centrifugal pump assembly, and the seal sectionmay be located uphole of the motor. For example, in a through-tubing-conveyed completion, the order of placement of components of the ESP assemblymay be altered in various ways, for example with the fluid intake located at the downhole end of the ESP assembly, the centrifugal pump assemblylocated uphole of the fluid intake, the seal sectionlocated uphole of the centrifugal pump assembly, and the motorlocated uphole of the seal section. It is understood that the novel mechanical shaft stop disclosed herein can be used to advantage in any of these alternative configurations of the ESP assembly.

The well fluidmay flow uphole in the wellboretowards the ESP assembly, in the inlet ports, and into the fluid intake. The well fluidmay comprise a liquid phase fluid. The well fluidmay comprise a gas phase fluid mixed with a liquid phase fluid. The well fluidmay comprise only a gas phase fluid (e.g., simply gas). Over time, the gas-to-liquid ratio of the well fluidmay change dramatically. For example, in the circumstance of a horizontal or deviated wellbore, gas may build up in high points in the roof of the wellbore and after accumulating sufficiently may “burp” out of these high points and flow downstream to the ESP assemblyas what is commonly referred to as a gas slug. Thus, immediately before a gas slug arrives at the ESP assembly, the gas-to-liquid ratio of the well fluidmay be very low (e.g., the well fluidat the ESP assemblyis mostly liquid phase fluid); when the gas slug arrives at the ESP assembly, the gas-to-liquid ratio is very high (e.g., the well fluidat the ESP assemblyis entirely or almost entirely gas phase fluid); and after the gas slug has passed the ESP assembly, the gas-to-liquid ratio may again be very low (e.g., the well fluidat the ESP assemblyis mostly liquid phase fluid).

Under normal operating conditions (e.g., well fluidis flowing out of the perforations, the ESP assemblyis energized by electric power, the electric motoris turning, and a gas slug is not present at the ESP assembly), the well fluidenters the inlet portsof the fluid intake, flows into the centrifugal pump assembly, and the centrifugal pump assemblyflows the fluid through the connectorand up the production tubingto a wellheadat the surface. The centrifugal pump assemblyprovides pumping pressure or pump head to lift the well fluidto the surface. The well fluidmay comprise hydrocarbons such as crude oil and/or natural gas. The well fluidmay comprise water. In a geothermal application, the well fluidmay comprise hot water. An orientation of the wellboreand the ESP assemblyis illustrated inby an x-axis, a y-axis, and a z-axis.

Turning now to, a cross-section view of a plurality of centrifugal pump stagesis described. The pump stagesare enclosed within a housing(e.g., a tubular housing). Each pump stagecomprises an impellerand a diffuser. The pump stagesillustrated inare illustrated having a mixed flow pump configuration. The direction of fluid flow through the pump stageshas a significant component of radial flow (e.g., a mixed flow of radial and axial flow direction). As well fluidenters an inletof the impeller, it flows both up and radially outwards due to an outwards swelling inside surface of a shroud structure of the impellerand due to deflection by an outer surface of a hub structure of the impellerthat swells outwards at an uphole end of the hub structure. As the well fluidflows from an outletof the impellerand flows into an inletof the diffuser, it flows both uphole and radially inwards due to an inwards curved outer surface of a hub structure at an uphole end of the diffuserand due to deflection by an inner surface of a shroud structure of the diffuserthat swells inwards at an outlet at an uphole end of the shroud structure. In other embodiments, however, the pump stagesmay have a radial flow pump configuration rather than a mixed flow pump configuration.

A drive shaftof the seal sectionmay be coupled to a drive shaft of the electric motorand receive rotational power from the drive shaft of the electric motor. An uphole end of the drive shaftof the seal sectionmay be coupled via a coupling shellto a downhole end of a drive shaftof the centrifugal pump assembly. The impellersare coupled to the drive shaftof the centrifugal pump assembly (e.g., via a key inserted into keyways defined in the drive shaft and in the inside of the impeller), and the diffusersare retained by the housing.

In an embodiment, the impellersof the centrifugal pump assemblyare mechanically stopped on the drive shaftby a first mechanical stop assemblydisposed near a downhole end and by a second mechanical stop assemblydisposed near an uphole end of the centrifugal pump assembly. The mechanical shaft stop assemblies,are described further hereinafter.

Turning now to, some details of internals of the centrifugal pump assemblyare described. The downhole end of the internals is on the right side ofand the uphole end of the internals is on the left side of. Flow of fluidthrough the internals is from right to left (from downhole to uphole). The internals are assembled on the drive shafthaving a centerline. In an embodiment, a first mechanical shaft stopcomprises a first compression stopand a first compression nut. A colletis disposed between the first compression stop, and the first compression nutas described more fully below with reference to,,,,, and. When the first mechanical shaft stopis assembled as illustrated in, the first compression nuturges the colletleftwards into radial compression, causing the colletto establish a friction fit of the first mechanical shaft stopon the drive shaft.

A first sleeveis coupled to the drive shaft, and a right side of the first sleeveis in contact with or abuts a left side of the first compression stop. The first sleeveis free to rotate with the drive shaft. A first impellercomprising a plurality of vanesis coupled to the drive shaft, and a right side of the first impelleris in contact with or abuts the left side of the first sleeve. A second sleeveis coupled to the drive shaft, and a right side of the second sleeveis in contact with or abuts a left side of the first impeller. A first diffuserhaving vanesis disposed over the second sleeve. The first diffuseris statically held in place by the housingof the centrifugal pump assembly, and the second sleeveis free to rotate with the drive shaftwithin a bore defined within the first diffuser. A second impelleris coupled to the drive shaft, and a right side of the second impelleris in contact with or abuts the left side of the second sleeve. A third sleeveis coupled to the drive shaft, and a right side of the third sleeveis in contact with or abuts a left side of the second impeller. A second diffuseris statically held in place by the housingof the centrifugal pump assembly, and the third sleeveis free to rotate with the drive shaftwithin a bore defined within the second diffuser.

A third impelleris coupled to the drive shaft. It is understood that a plurality of centrifugal pump stages (each stage comprising an impeller, a sleeve, and a diffuser located over the sleeve, and a leftmost sleeve in contact with or abuts a right side of the third impeller) may be disposed between the second diffuserand the third impeller. A fourth sleeveis coupled to the drive shaft, and a right side of the fourth sleeveis in contact with or abuts a left side of the third impeller. A third diffuseris statically held in place by the housingof the centrifugal pump assembly, and the fourth sleeveis free to rotate with the drive shaftwithin a bore defined within the third diffuser. The impellers,,may be said to be configured to do work as the drive shaftrotates, for example performing work on the fluid. The sleeves,,,may be referred to in some contexts as spacer sleeves.

A second mechanical shaft stopcomprises a second compression stopand a second compression nut. Note that in the second mechanical shaft stopthe second compression stopis disposed to the right of the second compression nut. A colletis disposed between the second compression stopand the second compression nut, and the second compression nuturges the colletrightwards into radial compression, causing the colletto establish a friction fit of the second mechanical shaft stopon the drive shaft. In an embodiment, the drive shaft, the mechanical shaft stops,, the sleeves,,,, and the impellers,,rotate in a clockwise direction when looking downhole upon these components from an uphole location. In another embodiment, however, the drive shaft, the mechanical shaft stops,, the sleeves,,,, and the impellers,,may rotate in a counterclockwise direction when looking downhole upon these components from an uphole location (in which case the slant angles of the vanes,may be flipped about an axis perpendicular to the centerline).

The two mechanical shaft stops,maintain a compression on the sleeves,,,and the impellers,,such that the impellers,,are not allowed to float axially along the drive shaft. Any thrust developed by interaction between rotating impellers,,and the fluidis transferred to the drive shaft. In some contexts, the compression nuts,may be referred to as compressor flanges. In an embodiment, only the first mechanical shaft stopis employed because the thrust developed on the impellers,,is directed only to the right (downhole) and thus there is no need to secure the stack of sleeves,,,and impellers,,against axial motion to the left (uphole). Alternatively, in an embodiment, only the second mechanical shaft stopis employed because the thrust developed on the impellers,,is directed only to the left (uphole) and thus there is no need to secure the stack of sleeves,,,and impellers,,against axial motion to the right (downhole)

In an embodiment, one or more bearings may be placed on the drive shaftbetween the first mechanical shaft stopand the second mechanical shaft stop, for example abutted against a sleeve on one side and abutted against an impeller on the other side. In an embodiment, this one or more bearing may take the form of a spider bearing having vanes extending from a central bearing that radially supports the drive shaftto the housingof the centrifugal pump assembly. The spider bearing may comprise two vanes, three vanes, four vanes, five vanes, six vanes, seven vanes, eight vanes, or some greater number of vanes less than one hundred vanes. The vanes may be extended in a direction parallel to the centerlineand be thin in a direction perpendicular to the centerline, whereby the vanes may interfere less with the smooth flow of fluidthrough the impellers,,and diffusers,,. In another embodiment, however, a hub of an impeller,,may extend at least partly into an associated diffuser,,, and the impeller,,and drive shaftmay be radially stabilized by engagement of that hub with the associated diffuser,,. In another embodiment, a bore of the diffusers,,may provide radial support for the drive shaft. In another embodiment, a different structure for radially supporting the drive shaftmay be employed.

It will be appreciated that the mechanical shaft stops,and the internals (e.g., impellers,,, diffusers,,, and sleeves,,,) can be located in other rotating machines in the ESP assembly. For example, the mechanical stops,and internals described above can be assembled on a drive shaft disposed within a gas separator assembly (seeandbelow). For example, the mechanical stops,and internals can be assembled on a drive shaft in a charge pump assembly disposed upstream of a gas separator assembly in the ESP assembly. In each of these instances, one or both of the mechanical shaft stops,can be employed to maintain the impellers of the given assembly in compression and prevent the impellers from floating axially and to transfer thrust from the impellers to the drive shaft.

Turning now to, further details of the mechanical shaft stop,are described. The collethas an interior borethat is slightly greater in diameter than the outside diameter of the drive shaft. In an embodiment, the interior bore has a diameter of about 0.020 inches greater than the outside diameter (OD) of the drive shaft, of about 0.015 inches greater than the OD of the drive shaft, of about 0.010 inches greater than the OD of the drive shaft, of about 0.008 inches greater than the OD of the drive shaft, of about 0.007 inches greater than the OD of the drive shaft, of about 0.006 inches greater than the OD of the drive shaft, of about 0.005 inches greater than the OD of the drive shaft, of about 0.004 inches greater than the OD of the drive shaft, of about 0.003 inches greater than the OD of the drive shaft, of about 0.002 inches greater than the OD of the drive shaft, of about 0.001 inches greater than the OD of the drive shaft, of about 0.0008 inches greater than the OD of the drive shaft, of about 0.0007 inches greater than the OD of the drive shaft, of about 0.0006 inches greater than the OD of the drive shaft, or about 0.0005 inches greater than the OD of the drive shaft, or about 0.0004 inches greater than the OD of the drive shaft. In a preferred embodiment, the interior bore has a diameter of between 0.001 inches greater than the OD of the drive shaftand 0.007 inches greater than the OD of the drive shaft. In an embodiment, the clearance between an inside diameter (ID) of the interior boreis desirably sufficiently greater than the OD of the drive shaftthat the colletin a relaxed state can be readily slid onto or over the drive shaftwhile at the same time the ID of the interior boreis small enough (narrow enough) that the colletis not excessively deformed or stressed when urged into engagement with the drive shaftby the compression nut.

The colletdefines a first plurality of gapsextending from a left endof the colletaxially rightwards into an interior of the colletbut not through a right endof the collet. The colletdefines a second plurality of gapsextending from the left endof the colletaxially leftwards into an interior of the colletbut not through the left endof the collet. The gaps,enable the colletto elastically deform radially inwards in response to radial compression forces applied to the colletby the compression nut. In an embodiment, the colletmay be made of spring steel or of another elastic metal material. A righthand portion of the colletdefines a conical frustum shape, and a lefthand portion of the colletdefines a cylindrical shoulder. In some contexts, the gaps,may be referred to as kerf cuts or slits. In an embodiment, the gaps,may be between 0.020 inches wide and 0.150 inches wide. In an embodiment, the gaps,may be between 0.030 inches wide and 0.100 inches wide. In an embodiment, the gaps,may be between 0.040 inches wide and 0.080 inches wide. In an embodiment, the gaps,may be about the width of a saw blade used to cut the gaps,into the collet. In an embodiment, the colletmay have between 6 and 18 gaps,. In an embodiment, for a larger diameter collet(e.g., where the drive shaftmay be larger in diameter), the colletmay have between 16 and 24 gaps,.

The compression stopdefines a first interior bore, a second interior bore, and a shoulderwhere the first interior boremeets the second interior bore. The compression stophas a left sideand a right side. A lefthand portion of the compression nutdefines a conical frustum shaped borethat is configured to mate with the conical frustum shapeof the collet. A righthand portion of the compression nutdefines a cylindrical bore. The compression nuthas a left sideand a right side. The right sideof the compression nutdefines a plurality of receiving bores. In an embodiment, the compression stopand the compression nutare made of stainless steel, carbide steel, case hardened steel, or some other metal.

In an embodiment, a surface of the conical frustum shapeof the colletdefines male threads, and a surface of the conical frustum boreof the compression nutdefines female threads. When assembled, the left sideof the compression stopmay be placed in contact with or abutting structure (e.g., the first sleevein), the left sideof the colletmay be inserted into the second boreof the compression stopand in contact with or abutting the interior shoulderof the compression stop, the female threadsof the compression nutmay be threaded onto the male threadsof the collet, whereby the compression nutcompresses the colletand urges the interior boreof the colletto make a friction fit with an outside of the drive shaft, thereby axially fixing the mechanical shaft stop,to the drive shaft. The assembled state of the mechanical stopis illustrated in.

Turning now to, a spanner wrenchfor use in screwing the compression nutonto and off of the colletis described. The spanner wrenchcomprises a handleand a plurality of lugsthat are configured to engage with the plurality of receiving bores. By inserting the lugsinto the receiving boresand turning the handle, the compression nutmay be rotated about the centerline.

Turning now toand, an alternative embodiment of the mechanical stop,is described. Here the male threadson the surface of the conical frustum shapeof the colletare omitted (relative toand), the female threadsin the interior boreof the compression nutare omitted (relative toand), male threadsare disposed on an outside of the compression nut, and female threadsare disposed on the interior of the second boreof the compression stop. It will be appreciated that the colletcan be compressed by the compression nutby screwing the male threadsof the compression nutinto the female threadsof the compression stopusing the spanner wrenchto turn the compression nut. As the compression nutthreads into the compression stop, the interior boreof the compression nutslides leftwards over the surface of the conical frustum shapeof the collet, compressing the colletand urging the interior boreof the colletto engage with the outside of the drive shaft, securing the colletby a friction fit to the drive shaftand likewise securing the mechanical stop,as a whole. With the exception of the different location of male and female threads, the alternative embodiment of the mechanical stop,described with reference toandis substantially similar to the embodiment described with reference toand.

Turning now to, another alternative embodiment of the mechanical stopis described. In the embodiment of, the colletdoes not have male threads, and the compression nutdoes not have female threadsurging the compression nutto compress the collet. Instead, the compression stopdefines a plurality of threaded bores, the colletdefines a plurality of through holes, and the compression nutdefines a plurality of through holes. A plurality of boltshaving male threads at one end are fitted through the through holes, through the through holes, and are threaded into the female threads defined by the threaded bores. By tightening the bolts, the compression nutcan urge the colletinto compression so that it establishes a friction fit with the drive shaft.

Turning now to, an alternate embodiment of the ESP assemblyis described. The well site environmentis substantially similar to that illustrated in, with the difference that the ESP assemblycomprises a gas separator assemblydefining a plurality of gas phase discharge portsdisposed at an uphole end of the gas separator assembly.

Turning now to, further details of the gas separator assemblyare described. A downhole end of the gas separator assemblyis coupled to an uphole end of the fluid intake. The gas separator assemblycomprises a housing, a crossover, and a head. The headmay allow for bolting the gas separator assemblyto a base of the centrifugal pump assembly. The housingmay be a cylindrical hollow metal pipe (e.g., a tubular housing). In an embodiment, an inside of the housingmay be machined or drilled at one or more locations to create slots or shallow holes for fixing and retaining components within the housing, for example diffusers or other components.

In an embodiment, the housingencloses a plurality of centrifugal pump stages, for example a first centrifugal pump stageA and a second centrifugal pump stageB. Each centrifugal pump stagecomprises an impellermechanically coupled to a drive shaftof the gas separator assemblyand a diffuserthat is retained and held stationary by the housing. In an embodiment, the impellermay have a keyway that mates with a keyway in the drive shaftand the keyway of the impellermay be secured to the keyway in the drive shaftby a key. In an embodiment, the impellermay be mechanically coupled to the drive shaftin a different way. When the drive shaftturns, the impellerturns. The first centrifugal pump stageA comprises a first impellerA and a first diffuserA; the second centrifugal pump stageB comprises a second impellerB and a second diffuserB. While two centrifugal pump stagesA andB are illustrated in, in another embodiment, there may be a single centrifugal pump stage, three centrifugal pump stages, four centrifugal pump stages, five centrifugal pump stages, six centrifugal pump stages, or more centrifugal pump stageslocated between the baseand the fluid reservoir. The centrifugal pump stagesmay be referred to as a first fluid mover in some contexts.

In an embodiment, the centrifugal pump stagesare similar to the internal components described above with reference to, for example the impellers,,, the diffusers,,, and the sleeves,,,. The centrifugal pump stages can be kept in compression by mechanical shaft stopsA (corresponding to first mechanical shaft stop) andB (corresponding to second mechanical shaft stop). As described above, the centrifugal pump stages of the gas separatormay be axially retained by only one of the mechanical shaft stopsA orB. In an embodiment, the centrifugal pump stagesof the gas separator assemblyare replaced by another fluid mover mechanism, for example replaced by an auger mechanically coupled to the drive shaft, one or more impeller mechanically coupled to the drive shaft(e.g., without a corresponding diffuser), and/or a paddle wheel mechanically coupled to the drive shaft. These alternative fluid movers may also be held axially fixed on the drive shaftby the mechanical shaft stopsA,B.

In an embodiment, the drive shaftis mechanically coupled to a drive shaft of the seal unit, and the drive shaft of the seal unitis mechanically coupled to a drive shaft of the electric motor. Thus, the drive shaftand the impellers(e.g., impellersA andB in) of the one or more centrifugal pump stagesare turned indirectly by the electric motorwhen it is energized by electric power via the electric cable. The drive shaftis mechanically coupled to the drive shaftof the centrifugal pump assemblyand transfers rotational power to the drive shaft of the centrifugal pump assemblyand to impellers of the centrifugal pump stages of the centrifugal pump assembly. The several different drive shaft mechanical couplings may be provided by splines cut in the mating ends of shafts and coupled by a spline coupler or hub. In another embodiment, the drive shaft mechanical couplings may be provided by other devices.

In an embodiment, the housingalso encloses a stationary auger. In one or more embodiments, the stationary augeris disposed or positioned within a sleeve. The centrifugal pump stagescommunicates or forces well fluidreceived at the one or more inlet portsthrough the stationary auger. In an embodiment, an outside edge of the stationary augerengages sealingly with an inside surfaceof the sleeve, and the flow of well fluidthrough the sleeveis hence confined to the passageway or passageways defined by the stationary auger. The sleevemay be disposed or positioned within and retained by the housing. In an embodiment, the stationary augerand the sleevemay be built or manufactured as a single component.

In an embodiment, there is no sleeveand the stationary augeris disposed within the inside of the housing. The stationary augermay be retained by the inside of the housing. In an embodiment, the stationary augerengages sealingly with an inside surface of the housing. In an embodiment, there is a space between the outside edges of the stationary augerand the inside surfaceof the sleeveor a space between the outside edges of the stationary augerand the inside surface of the housing.

In one or more embodiments, the stationary augercomprises one or more helixes or vanes. In one or more embodiments, the helixes or vanesmay be crescent-shaped. In one or more embodiments, the stationary augercomprises one or more helixes or vanesdisposed about a solid core, for example shaftthat encloses the drive shaft, or an open core (for example, a coreless auger or an auger flighting). The stationary augermay cause the well fluidto be separated into a liquid phaseand gas phasebased, at least in part, on rotational flow of the well fluid.

For example, the one or more helixes or vanesmay impart rotation to the well fluidas the well fluidflows through, across or about the one or more helixes or vanes. The stationary auger, then, can be referred to as a fluid mover at least because it imparts a rotating motion to the well fluidas the well fluidflows through the stationary auger. For example, fluid moverforces the well fluidat a velocity or flow rate into the sleeveand up or across the one or more helixes or vanesof stationary auger. The rotation of the well fluidinduced by the stationary augermay be based, at least in part, on the velocity or flow rate of the well fluidgenerated by the centrifugal pump stages. For example, the centrifugal pump stagesmay increase the flow rate or velocity of the well fluidto increase rotation of the well fluidthrough the stationary augerto create a more efficient and effective separation of the well fluidinto a plurality of phases, for example, a liquid phase fluidand a gas phase fluid. As the well fluidflows through the stationary auger, centrifugal forces, static friction or both, cause the heavier component of the well fluid, a liquid phase fluid, to circulate along an outer perimeter of the stationary augerwhile the lighter component of the well fluid, the gas phase fluid, is circulated along an inner perimeter of the stationary auger. In one or more embodiments, well fluidmay begin to separate while flowing through stationary auger. In one or more embodiments, the liquid phase fluidmay comprise residual gas that did not separate into the gas phase fluid. However, the embodiments discussed herein reduce this residual gas to protect the centrifugal pump assemblyfrom gas build-up or gas lock.

In an embodiment, the stationary augeris not present and instead a different kind of second fluid mover is provided. The second fluid mover may be provided by an auger mechanically coupled to the drive shaft, a paddle wheel mechanically coupled to the drive shaft, a centrifuge rotor mechanically coupled to the drive shaft, or an impeller mechanically coupled to the drive shaftthat induce rotating motion of the well fluid. In an embodiment, a third fluid mover is provided downstream of the stationary auger, for example a paddle wheel may be installed downstream of the stationary augerthat induces and/or increases rotating motion of the well fluid.

A separation chamberis provided downstream of the second fluid mover (e.g., the stationary auger) and downstream of the optional third fluid mover. An upstream end of the separation chamberis fluidically coupled to a downstream end or an outlet of the stationary augeror other second fluid mover. Alternatively, the upstream end of the separation chamberis fluidically coupled to a downstream end or an outlet of the optional third fluid mover and is fluidically coupled to the third fluid mover and, via the third fluid mover, fluidically coupled to the second fluid mover. The separation chamberis defined by an annulus formed between the inside of the housingand the outside of the drive shaft. In an embodiment, the separation chamber is less than 36 inches long and at least 4 inches long, at least 6 inches long, at least 8 inches long, at least 10 inches long, at least 12 inches long, or at least 14 inches long. In an embodiment, the separation chamber is at least 6 inches long and less than 17 inches long. The stationary auger(or other second fluid mover and/or third fluid mover) induces a rotating motion in the well fluid. As the well fluidexits the stationary auger(or other second fluid mover and/or third fluid mover) and enters the separation chamber, this rotating motion of the well fluidcontinues. The rotating motion of the well fluidwithin the separation chamberinduces gas phase fluid (which is less dense than the liquid phase fluid) to concentrate near the drive shaftand the liquid phase fluid to concentrate near the inside surface of the housing.

In one or more embodiments, the separated fluids (for example, liquid phase fluidand gas phase fluid) are directed to a crossover. For example, the crossovermay be disposed or positioned at a downstream end of the separation chamberor housing. In some contexts, the crossovermay be referred to as a gas flow path and liquid flow path separator. The crossovermay comprise a plurality of channels or define a plurality of channels, for example, a gas phase discharge(a first pathway) and a liquid phase discharge(a second pathway). A gas phase fluidof the well fluidmay be discharged through the gas phase discharge, out the gas phase discharge ports, and a liquid phase fluidof the well fluidmay be discharged through the liquid phase discharge.

In one or more embodiments, any one or more of the gas phase discharge portsand the one or more liquid phase discharge portsmay be defined by a channel or pathway having an opening, for example, a teardrop shaped opening, a round opening, an elliptical opening, a triangular opening, a square opening, or another shaped opening. The crossovermay be threadingly coupled at an upstream end by threaded couplingto a downstream end of the housing. The crossovermay be threadingly coupled at a downstream end by threaded couplingto a head. Alternatively, the headmay be integrated with the headrather than threadingly coupled to the head. The headmay provide bolt holes for coupling to an upstream end of the centrifugal pump assembly. In some contexts, the crossovermay be said to be mechanically coupled at an upstream end to a downstream end of the housing. When the crossoverand the headare not integrated as a single component, the crossovermay be said to be mechanically coupled at a downstream end to an upstream end of the head. In an embodiment, two or more instances of gas separator assembliesare connected in series, such that the drive shafts of each adjacent gas separator assemblycouples to the corresponding adjacent gas separator assembly, and wherein the liquid phase dischargeof the adjacent downhole gas separator assemblyfeeds into the fluid inlet of the adjacent uphole gas separator assembly.

Turning now to, a horizontal pumping system (HPS)is described. In an embodiment, the HPScomprises a motor, a rotational coupling, a mechanical seal, and a centrifugal pump assembly. In an embodiment, a fluid inletis integrated into a first end of the centrifugal pump assemblyand a fluid outletmay be integrated into a second end of the centrifugal pump assembly. The motor, the rotational coupling, the mechanical seal, and the centrifugal pump assemblymay be mounted on a skidsuch that it can be easily transported to a location on a truck and placed on the ground at the location. The centrifugal pump assemblyis substantially similar to the centrifugal pump assemblydescribed above with reference to,,,,, and. For example, the centrifugal pump assemblycomprises a plurality of pump stageswith an impellerand a diffuserand one or more sleeves as described above, where each pump stage comprises the impellercoupled to a drive shaft of the centrifugal pump assemblyand the diffuserthat is retained by a housing (e.g., a tubular housing) of the centrifugal pump assembly. In an embodiment, the centrifugal pump assemblycomprises from one to four hundred pump stages.

The motormay be an electric motor, a hydraulic turbine, or an air turbine. When the motorturns, the drive shaft of the centrifugal pump assemblyturns, turning the impellers of the centrifugal pump assembly. The torque provided by the motoris transferred via the rotational couplingto the drive shaft of the centrifugal pump assembly.

The HPSmay be applied for use in a variety of different surface operations. The HPScan be used as a crude oil pipeline pressure and/or flow booster. The HPScan be used in a mine dewatering operation (e.g., removing water from a mine). The HPScan be used in geothermal energy applications, for example to pump geothermal water from a wellhead through a pipe to an end-use or energy conversion facility. The HPScan be used in carbon sequestration operations. The HPScan be used in salt water disposal operations, for example receiving salt water from a wellbore and pumping the salt water under pressure down into a disposal well. The HPScan be used in desalinization operations. In any of these surface pumping applications, the novel diffuser structures taught above can advantageously be applied to increase the efficiency of the centrifugal pump assembly, to increase the head and/or flow rate produced by the centrifugal pump assembly, and/or increase the service life of the centrifugal pump assembly. In some contexts, the HPS

Turning now to, a methodis described. In an embodiment, the methodcomprises a method of assembling a rotating machine. In an embodiment, the rotating machine is at least a part of a centrifugal pump assembly. In an embodiment, the rotating machine is part of a gas separator assembly. In an embodiment, the rotating machine is at least a part of a charge pump assembly. In an embodiment, the rotating machine is at least a part of an HPS. At block, the methodcomprises coupling a component to a drive shaft, wherein the component is configured to do work as the drive shaft turns. In an embodiment, the component that is configured to do work as the drive shaft turns is one or more impellers. In an embodiment, the component that is configured to work as the drive shaft turns is a rotating auger. In an embodiment, the component that is configured to do work as the drive shaft turns is a paddlewheel. At block, the methodcomprises sliding a compression stop over the drive shaft.

At block, the methodcomprises sliding a collet over the drive shaft to abut the compression stop. In an embodiment, the collet comprises spring steel. In an embodiment, the collet defines a plurality of gaps. In an embodiment, the collet defines a plurality of kerf cuts. At block, the methodcomprises sliding a compressor flange over the drive shaft.

At block, the methodcomprises compressing the collet by the compressor flange to cause the collet to form a friction fit with the drive shaft. In an embodiment, an outside surface of the collet defines a conical frustum shape where it engages with an interior of the compressor flange. At block, the methodcomprises installing the drive shaft, the component that is configured to do work as the drive shaft turns, the compression stop, the collet, and the compressor flange into a tubular housing. In an embodiment, the methodfurther comprises sliding a sleeve over the drive shaft, sliding a diffuser over the sleeve, wherein installing the drive shaft, the component that is configured to work as the drive shaft turns, the compression stop, the collet, and the compressor flange into the tubular housing further comprises installing the sleeve and the diffuser into the housing.