Patent Description:
Electrical submersible pumps (ESP) are commonly used in hydrocarbon producing wells. An ESP includes a pump driven by an electrical motor. The pump is often a centrifugal pump having impellers rotated by a shaft assembly extending from the motor.

The rotating impellers cause a normal temperature increase during operation. If liquid well fluid ceases to flow into the pump stages while the impellers are still rotating, the pump stages may experience a rapid temperature increase. That can happen because of a mistakenly closed valve or a large gas bubble entering the pump. If the pump is operating at a much higher speed than conventional, or for a long period of time, the temperature can elevate high enough to cause serious damage, such as diffuser spin, unseated bushing inserts, and in extreme cases, fusing of the impellers to the diffusers.

It is known to employ temperature sensors at the discharge adapters of pumps to monitor the temperature of the well fluid as it discharges from the pump. Also, temperature sensors are commonly used to measure the temperature of the motor lubricant in the motor.

<CIT> describes devices and methods for detecting operational parameters associated with a gas separator used in an electric submersible pump in a wellbore. A fiber optic sensing arrangement is used to detect the operational parameter and includes a fiber optic signal processor and an optic fiber that is associated with the gas separator to provide a signal indicative of the parameter to the signal processor.

From <CIT> a seal section for use in a wellbore electrical submersible pump including an optic fiber detection arrangement is known, wherein at least one optic fiber sensor is used to detect an operational parameter associated with the seal section. The operational parameters can include temperature, vibration and pressure.

<CIT> describes a gas compression separator assembly, having a series of compressors and separation chambers for entraining or dissolving the free gas component of the production fluid and separating free gas for downhole disposal to avoid gas lock in downhole ESPs.

According to the invention, an electrical submersible pump (ESP) for pumping well fluid from a well according to claim <NUM> is provided, such an ESP has a tubular pump housing with a longitudinal axis and a housing bore that is coaxial with the axis. A plurality of centrifugal pump stages are in the housing bore, each of the stages having an impeller and a diffuser. A rotatable shaft, mounted on the axis within the housing, rotates the impellers. The housing has a non-rotatable bearing mounted in the housing, the bearing has a passage through which the shaft extends. A sensor hole extends through the housing and into the bearing. The sensor hole has a bearing sensor hole portion extending within the bearing and a temperature sensor located within the sensor hole. The housing comprises a cylindrical body and a base having a base bore in which the bearing is mounted. The base has a neck of a smaller outer diameter than an upper portion of the base defining a downward facing shoulder. The sensor hole has a base sensor hole portion extending upward and inward from the downward facing shoulder toward the longitudinal axis and being aligned with the bearing sensor hole portion. The ESP further comprises a sensor line connected with the sensor and extending from the base for transmitting a signal from the sensor, and a conical section in the base bore extending downward and inward from a cylindrical section in the base bore. The bearing is mounted in the cylindrical section of the base bore, and the conical section extends downward from the bearing. A lower end of the bearing sensor hole portion is spaced from an upper end of the base sensor hole portion by a gap.

In the embodiment shown, the bearing has a hub through which the shaft passage extends. An outer wall coaxially extends around the hub and is spaced radially outward therefrom. A plurality of support arms extends from the hub to the outer wall. The sensor hole extends from one end of the bearing into one of the support arms.

The sensor hole may have a closed end spaced radially outward from the shaft passage in the bearing. In the example shown, the sensor hole is inclined relative to the axis at an acute angle less than <NUM> degrees. The bearing is located in a bottom portion of the pump in the embodiment shown.

The ESP further comprises a motor and a seal section for sealing around a motor shaft, the seal section being between the motor and the pump. The base is secured to a lower end of the body, the base having a connector for connecting the seal section to the pump.

The ESP may also have a sensing unit located at one end of the ESP. The sensor line leads from the temperature sensor to the sensing unit. The ESP may comprise a motor and a motor gauge unit mounted to a lower end of the motor. The sensor line extends from the temperature sensor in the bearing to the motor gauge unit in one embodiment.

In the embodiment shown, the base has a connector flange with bolt holes for connecting the pump to a lower module of the ESP, the connector flange being joined to the upper portion of the base by the neck and the ESP further comprises a fitting that secures the sensor line to the base sensor hole portion at the shoulder.

While the invention will be described in connection with the preferred embodiments, it will be understood that it is not intended to limit the invention to that embodiment. On the contrary, it is intended to cover all alternatives, modifications, and equivalents, only when they effectively fall within the scope of the claims.

The electrical submersible pump according to the present invention will now be described more fully hereinafter with reference to the accompanying drawings in which embodiments are shown. The electrical submersible pump according to the present invention may be in many different forms and should not be construed as limited to the illustrated embodiments set forth herein; rather, these embodiments are provided so that the disclosure will be thorough and complete, and will fully convey its scope to those skilled in the art. In an embodiment, usage of the term "about" includes +/- <NUM>% of the cited magnitude. In an embodiment, usage of the term "substantially" includes +/- <NUM>% of the cited magnitude.

It is to be further understood that the scope of the present disclosure is not limited to the exact details of construction, operation, exact materials, or embodiments shown and described, as modifications and equivalents will be apparent to one skilled in the art. In the drawings and specification, there have been disclosed illustrative embodiments and, although specific terms are employed, they are used in a generic and descriptive sense only and not for the purpose of limitation. Furthermore, it is also to be understood that the scope of the present invention is solely defined by the appended claims.

<FIG> illustrates a cased well <NUM> having an electrical submersible well pump (ESP) <NUM> of a type commonly used to lift hydrocarbon production fluids from wells. The terms "upward," "downward," "above," "below" and the like are used only for convenience as ESP <NUM> may be operated in other orientations, such as horizontal.

ESP <NUM> has an electrical motor <NUM> coupled by a seal section <NUM> to a centrifugal pump <NUM>. Pump <NUM> has an intake port <NUM> that may be at the lower end of pump <NUM>, in a separate module, or in an upper part of seal section <NUM> as shown. If a gas separator (not shown) is employed, intake port <NUM> would be in the gas separator.

Motor <NUM> contains a dielectric motor lubricant for lubricating the bearings within. A pressure equalizer communicates with the lubricant in motor <NUM> and with the well fluid for reducing a pressure differential between the lubricant in motor <NUM> and the exterior well fluid. In this example, the pressure equalizer is contained within seal section <NUM>. Alternately, the pressure equalizer could be located below motor <NUM>, and other portions of seal section <NUM> could be above motor <NUM>.

A string of production tubing <NUM> extending downward from a wellhead (not shown) supports ESP <NUM>. Pump <NUM> discharges well fluid into production tubing <NUM>. Alternately, ESP <NUM> could be secured to a string of coiled tubing located within a production conduit. In that event, pump <NUM> would discharge into an annulus surrounding the coiled tubing within the production conduit.

In this example, a power cable <NUM> extends downward alongside production tubing <NUM> and has a motor lead on its lower portion that connects to motor <NUM>. If the ESP is installed on coiled tubing, the power cable would be inside the coiled tubing and the motor would normally be above the pump.

In this embodiment, a motor gauge unit <NUM> secures to the bottom of motor <NUM>. Motor gauge unit <NUM> has sensors for measuring parameters of the motor lubricant, such as pressure and temperature. Signals from motor gauge unit <NUM> may be transmitted to a controller adjacent the wellhead by a separate instrument wire or by superimposing those signals on the motor windings within motor <NUM> and up power cable <NUM>.

A discharge gauge unit <NUM> may be mounted to the upper end of pump <NUM>. Discharge gauge unit <NUM> has sensors that sense the discharge pressure of the well fluid being pumped by pump <NUM>. The signals from discharge gauge unit <NUM> may be transmitted down to motor gauge unit <NUM> on a signal line (not shown) for communication with the controller at the surface along with the signals from motor gauge unit <NUM>. Alternately, the signals from discharge gauge unit <NUM> could be transmitted up a separate instrument wire to the controller at the surface.

A pump temperature sensor line <NUM> extends from the lower portion of pump <NUM> along the exteriors of seal section <NUM> and motor <NUM> to motor gauge unit <NUM>. Alternately, pump temperature sensor line <NUM> could extend upward to discharge gauge unit <NUM>. Also, temperature sensor line <NUM> could extend directly to a controller at the surface adjacent the wellhead. Sensor line <NUM> could be a wire or fiber optic line.

Referring to <FIG>, pump <NUM> has a tubular body or housing <NUM> with a longitudinal axis <NUM> and a coaxial bore <NUM>. A base <NUM>, which is a part of housing <NUM>, secures by an upper threaded section <NUM> to the threads in the cylindrical portion of housing <NUM>. Base <NUM> has features to connect pump <NUM> to a next lower module, which in this instance is seal section <NUM>. In this example, the connector comprises an external flange <NUM> with bolt holes <NUM> for receiving bolts. A neck <NUM> extends upward from flange <NUM> to upper threaded section <NUM> and has a smaller outer diameter than the outer diameters of flange <NUM> and upper threaded section <NUM>.

A shaft <NUM> rotated by motor <NUM> (<FIG>) is mounted coaxially within housing <NUM>. Shaft <NUM> has a lower splined end for coupling to a shaft in seal section <NUM> (<FIG>), the coupling being indicated by the dotted lines. Pump <NUM> is a centrifugal type, having a large number of stages, each stage comprising a diffuser <NUM> and an impeller <NUM>. Diffusers <NUM> do not rotate relative to housing <NUM>. Shaft <NUM> rotates impellers <NUM> relative to housing <NUM>.

A non-rotating bottom bearing <NUM> below diffusers <NUM> and impellers <NUM> radially stabilizes shaft <NUM>. Bottom bearing <NUM> has flow channels <NUM> to enable the upward passage of well fluid. A similar top bearing (not shown) provides radial stabilization to the upper end of shaft <NUM>. Bottom bearing <NUM> locates within an upper portion of the bore in base <NUM> in this example.

A temperature sensor <NUM>, such as a thermocouple, fiber optic or other temperature sensing device, is located within bottom bearing <NUM>. A base sensor hole <NUM> extends inward and upward through the side wall of base <NUM> and aligns with a bearing sensor hole <NUM> in bottom bearing <NUM>. Temperature sensor <NUM> locates within bearing sensor hole <NUM>, and temperature sensor line <NUM> extends through base sensor hole <NUM> to temperature sensor <NUM>. Temperature sensor <NUM> and at least portions of temperature sensor line <NUM> may have a metal sheath. A conventional swage type fitting <NUM> secures by threads to base <NUM>, clamping temperature sensor line <NUM> in base sensor hole <NUM>.

Bottom bearing <NUM> has an axial bore with a shaft passage <NUM> defined by a non-rotating bushing <NUM>, which may be of a carbide material. Bushing <NUM> comprises a journal portion of bearing <NUM>. Shaft <NUM> will typically have a shaft sleeve <NUM> that is keyed to shaft <NUM> for rotation. Shaft sleeve <NUM> is in rotational sliding engagement with bottom bearing bushing <NUM>. Bearing sensor hole <NUM> has a closed end that is radially outward from bushing <NUM>.

Referring to <FIG>, bottom bearing <NUM> has a cylindrical outer wall <NUM> that coaxially surrounds a cylindrical inner wall or hub <NUM>. A number of support arms <NUM> (three shown) extend from hub <NUM> to outer wall <NUM>. The spaces between arms <NUM> define flow channels <NUM>. Arms <NUM> may be integrally formed with hub <NUM> and outer wall <NUM>. Arms <NUM> are located in radial planes from axis <NUM> in this example, and they are evenly spaced apart at <NUM> degree angles. Each arm <NUM> may have flat sides <NUM> that are parallel with each other. An axially extending slot <NUM> in outer wall <NUM> receives an anti-rotation pin (not shown). The anti-rotation pin engages a mating slot (not shown) in the bore of base <NUM> (<FIG>) to prevent rotation of bottom bearing <NUM> relative to base <NUM>.

Each arm <NUM> has an upper end <NUM> that may be rounded and recessed below the upper end of outer wall <NUM>. Each arm <NUM> has a lower end <NUM> that may be substantially flush with the lower end of outer wall <NUM>. The upper end of hub <NUM> may be substantially flush with each arm upper end <NUM>. The lower end of hub <NUM> is substantially flush with the lower end <NUM> of each arm <NUM> in this example. Bushing <NUM> is secured in the bore of hub <NUM> by a lower shoulder in the bore of hub <NUM> and a conventional retainer ring on <NUM> engaging the bore of hub <NUM> on the upper end bushing <NUM>.

Bearing sensor hole <NUM> extends into the lower end <NUM> of one of the arms <NUM> and has a closed upper end within arm <NUM> a short distance radially outward from bushing <NUM>. Bearing sensor hole <NUM> is in a plane parallel with and between the flat sides <NUM> of arm <NUM>. Bearing sensor hole <NUM> has a smaller diameter than the thickness of arm <NUM> measured from one side <NUM> to the opposite side <NUM>. In this example, bearing sensor hole <NUM> is located in a radial plane of axis <NUM>. Bearing sensor hole <NUM> extends upward and inward at an acute angle relative to axis <NUM> that is less than <NUM> degrees and is illustrated to be about <NUM> degrees. The closed upper end of bearing sensor hole <NUM> is closer to bushing <NUM> than to the exterior of outer wall <NUM>.

Referring to <FIG>, bottom bearing <NUM> fits within a counterbore <NUM> of base <NUM>, landing on an upward-facing shoulder <NUM>. Bottom bearing <NUM> may be simply dropped in place, or secured to base <NUM> in various manners, such as by a press-fit.

The upper end of base sensor hole <NUM> is separated from the lower end of bearing sensor hole <NUM> by a short distance or gap <NUM> due to a conical band <NUM> extending downward from upward facing shoulder <NUM> in the bore of base <NUM>. Swage fitting <NUM> secures to a threaded hole <NUM> in base <NUM>. Threaded hole <NUM> extends upward and inward from a downward facing shoulder <NUM> at the upper end of base neck <NUM>.

In operation, as pump <NUM> operates, it will increase in temperature to a normal operating temperature. Liquid well fluid flowing through pump <NUM> will provide cooling for the components, including bottom bearing <NUM>. In the event pump <NUM> become gas locked, or a valve for the flowing well fluid is accidentally closed, the rotating shaft <NUM> could rapidly increase the temperature of bottom bearing <NUM>, causing damage to bottom bearing <NUM>. The spinning impellers <NUM> would also rapidly increase in temperature. If unchecked, impellers <NUM> could fuse to diffusers <NUM>. This rapid increase particularly occurs when pump <NUM> is operating at a much higher speed than a conventional speed.

Temperature sensor <NUM> will sense the temperature and send a signal over sensor line <NUM> to motor gauge unit <NUM>, which in turn transmits the signal to the controller adjacent the wellhead. In case of a rapid temperature increase, the controller will quickly take remedial action, such as slowing the speed of pump <NUM> or completely shutting it down. Locating temperature sensor <NUM> in bottom bearing <NUM> places it closer to the pump intake <NUM> than the diffusers <NUM> and impellers <NUM> so that it will encounter a rise in temperature due to a loss in liquid well fluid flow before the temperature rise occurs in diffusers <NUM> and impellers <NUM>.

The present disclosure described herein, therefore, is well adapted to carry out the objects and attain the ends and advantages mentioned, as well as others inherent therein.

Claim 1:
An electrical submersible pump (ESP) (<NUM>) for pumping well fluid from a well (<NUM>), comprising:
a tubular pump housing (<NUM>) having a longitudinal axis (<NUM>) and a housing bore (<NUM>) that is coaxial with the axis (<NUM>);
a plurality of centrifugal pump stages in the housing bore, each of the stages having an impeller (<NUM>) and a diffuser (<NUM>);
a rotatable shaft (<NUM>) mounted on the axis (<NUM>) within the housing (<NUM>) for rotating the impellers (<NUM>);
a non-rotatable bearing (<NUM>) mounted in the housing (<NUM>), the bearing (<NUM>) having a shaft passage (<NUM>) through which the shaft (<NUM>) extends;
a sensor hole (<NUM>, <NUM>) extending through the housing (<NUM>) and into the bearing (<NUM>), the sensor hole (<NUM>, <NUM>) having a bearing sensor hole portion (<NUM>) extending within the bearing (<NUM>); and
a temperature sensor (<NUM>) located within the sensor hole (<NUM>, <NUM>);
the housing (<NUM>) comprising a cylindrical body and a base (<NUM>) having a base bore (<NUM>) in which the bearing (<NUM>) is mounted, the base (<NUM>) having a neck (<NUM>) of a smaller outer diameter than an upper portion of the base (<NUM>) defining a downward facing shoulder (<NUM>),
the sensor hole (<NUM>, <NUM>) having a base sensor hole portion (<NUM>) extending upward and inward from the downward facing shoulder (<NUM>) toward the longitudinal axis (<NUM>) and being aligned with the bearing sensor hole portion (<NUM>);
a sensor line (<NUM>) connected with the sensor (<NUM>) and extending from the base (<NUM>) for transmitting a signal from the sensor (<NUM>); and
a conical section (<NUM>) in the base bore extending downward and inward from a cylindrical section (<NUM>) in the base bore; wherein
the bearing (<NUM>) is mounted in the cylindrical section of the base bore, and the conical section (<NUM>) extends downward from the bearing (<NUM>); and
a lower end of the bearing sensor hole portion (<NUM>) is spaced from an upper end of the base sensor hole portion (<NUM>) by a gap (<NUM>).