An electrical submersible well pump assembly has shaft couplings. One of the couplings has a lower hub that rotates in unison with the motor shaft and an upper hub that rotates in unison with the pump shaft. A helical spring clutch engages both hubs when the motor shaft is being driven by the motor. Ceasing driving rotation of the motor shaft causes the spring clutch to disengage from the upper hub, enabling the pump shaft to rotate the upper hub without rotating the lower hub.

A downhole-type device includes an electric machine. The electric machine includes an electrical rotor configured to couple with a device to drive or be driven by the electric machine. An electrical stator surrounds the electric rotor. The electric stator includes a seal configured to isolate stator windings from an outside, downhole environment. An inner surface of the seal and an outer surface of the electric rotor define an annulus exposed to the outside environment. A bearing couples the electric rotor to the electric stator. A lubrication system is fluidically coupled to the downhole-type device. The lubrication system includes a topside pressure pump and a downhole-type distribution manifold configured to be used within a wellbore. The distribution manifold is fluidically connected to the topside pressure pump and the bearing to receive a flow of lubricant from the topside pressure pump.

A downhole-type device includes an electric machine. The electric machine includes an electrical rotor configured to couple with a device to drive or be driven by the electric machine. An electrical stator surrounds the electric rotor. The electric stator includes a seal configured to isolate stator windings from an outside, downhole environment. An inner surface of the seal and an outer surface of the electric rotor define an annulus exposed to the outside environment. A bearing couples the electric rotor to the electric stator. A lubrication system is fluidically coupled to the downhole-type device. The lubrication system includes a topside pressure pump and a downhole-type distribution manifold configured to be used within a wellbore. The distribution manifold is fluidically connected to the topside pressure pump and the bearing to receive a flow of lubricant from the topside pressure pump.

A well pump includes a plurality of diffusers, wherein each diffuser comprises a first threaded coupling on one longitudinal end and a second threaded coupling on an opposed longitudinal end. An impeller is disposed in each diffuser. The plurality of diffusers are coupled end to end to form a pump housing, in which the first threaded coupling on one diffuser is threadedly engaged to the second threaded coupling on adjacent diffuser.

Downhole pumps may include, at the inlet, a component that reduces the amount of water taken up by the pump. For example, a downhole assembly may include a tool string that includes a fluid pump, a fluid intake subassembly, a motor, and a downhole control system each coupled such that a fluid flowing into the fluid intake assembly is conveyed to the fluid pump; one or more inlets defined in the fluid intake subassembly; a flow line fluidly coupled to at least one of the one or more inlets and containing a filter component that contains a filter media at least partially coated with a relative permeability modifier (RPM), wherein the fluid flowing through the flow line contacts the RPM.

An electric submersible pump includes a pump, an electric motor that is coupled to the pump by a rotatable shaft, a seal section that is positioned between the pump and the electric motor. The seal section contains an additive and a motor oil for the electric motor. The additive includes one or more superabsorbent polymers or imidate salts to contact the motor oil and to react with a wellbore fluid from a wellbore to prevent premature failure of the electric submersible pump from the wellbore fluid contamination of the motor oil.

An electric submersible pump includes a pump, an electric motor that is coupled to the pump by a rotatable shaft, a seal section that is positioned between the pump and the electric motor. The seal section contains an additive and a motor oil for the electric motor. The additive includes one or more superabsorbent polymers or imidate salts to contact the motor oil and to react with a wellbore fluid from a wellbore to prevent premature failure of the electric submersible pump from the wellbore fluid contamination of the motor oil.

An electrical submersible pumping system includes thrust bearings and radial bearings fabricated from a micro-grained polycrystalline diamond compact (“USPCD”) material that is ultra-strong; and where the USPCD is produced using a catalyst free process. In examples, all components of the bearings are formed from the ultra-strong USPCD material. Pads are in the bearings that have a contact surface, and the pads selectively tilt about a tilt member in response to variations in an opposing contact surface. The tilt members are attached to or otherwise associated with the pads, and are in contact with a resilient member that improves tilting response of the pads. The resilient members are encased in jackets that cover surfaces of the resilient members not in contact with the tilt members. The jackets are set in channels formed in structure of the bearings.

Systems and methods for producing fluids from a subterranean well include an electrical submersible pump assembly with a motor-pump unit. The motor-pump unit has a motor housing and a stator is located within the motor housing. The stator has a stator body with an interior cavity. A rotor assembly is located within the interior cavity of the stator. The rotor assembly includes a rotor shaft extending along the central axis of the stator, a rotor member, and an intermediate rotor bearing assembly. The rotor member and the intermediate rotor bearing assembly circumscribe the rotor shaft. An impeller is mounted on the rotor shaft and located within the interior cavity of the stator. A liner with a polygonal cross section is located along an interior surface of the interior cavity. The liner is secured to the motor housing and seals the stator body from a wellbore fluid.

Systems and methods for producing fluids from a subterranean well include an electrical submersible pump assembly with a motor-pump unit. The motor-pump unit has a motor housing and a stator is located within the motor housing. The stator has a stator body with an interior cavity. A rotor assembly is located within the interior cavity of the stator. The rotor assembly includes a rotor shaft extending along the central axis of the stator, a rotor member, and an intermediate rotor bearing assembly. The rotor member and the intermediate rotor bearing assembly circumscribe the rotor shaft. An impeller is mounted on the rotor shaft and located within the interior cavity of the stator. A liner with a polygonal cross section is located along an interior surface of the interior cavity. The liner is secured to the motor housing and seals the stator body from a wellbore fluid.