US20130199775A1

US20130199775A1 - Monitoring Flow Past Submersible Well Pump Motor with Sail Switch

Info

Publication number: US20130199775A1
Application number: US13/368,809
Authority: US
Inventors: Lawrence H. Burleigh
Original assignee: Baker Hughes Inc
Current assignee: Baker Hughes Holdings LLC
Priority date: 2012-02-08
Filing date: 2012-02-08
Publication date: 2013-08-08

Abstract

An electric submersible well pumping system (ESP) has a sail switch to measure fluid speed within the wellbore in the areas surrounding the motor to thereby determine fluid speed adjacent the motor. A controller controls the operation of the motor based on the inputs of the sail switch to thereby avoid overheating the motor to preserve motor longevity. The sail switch has a paddle that switches from a first toggle position to a second toggle position in response to a selected fluid speed.

Description

FIELD OF THE INVENTION

The present disclosure relates to downhole pumping systems submersible in well bore fluids. More specifically, the present disclosure concerns fluid speed measurement and submersible motor control for a downhole pumping system.

BACKGROUND OF THE INVENTION

Submersible pumping systems are often used in hydrocarbon producing wells for pumping fluids from within the well bore to the surface. These fluids are generally liquids and include produced liquid hydrocarbon as well as water. One type of system used in this application employs an electrical submersible pump (ESP). ESP's are typically disposed at the end of a length of production tubing and have an electrically powered motor. Often, electrical power is supplied to the pump motor via an electrical power cable from the surface that is strapped alongside the tubing or liner.
A motor lead is secured to the lower end of the power cable, the motor lead terminating in a connector that plugs into a receptacle of the motor. This connector is typically known as a pothead connector.
Often the power cable will be run alongside communication lines that transmit and receive data between the surface and the ESP assembly. An alternate communication method involves using the power carrying lines in the power cable to serve the dual purpose of carrying power and communication signals between the surface and the ESP assembly. Either communication setup may be used to control the operation of the motor in the ESP assembly.
Typically, the pumping unit is disposed within the well bore just above where perforations are made into a hydrocarbon producing zone. This placement allows the produced fluids to flow past the outer surface of the pumping motor and provides a cooling effect to the motor.
Heat is transferred between the fluid in the well bore and the motor. Fluid in motion over the motor or motor housing serves to disperse heat from the motor more efficiently. Overheating of the motor may be a problem when fluid flow slows down or temporarily ceases. Repeated exposure to elevated motor temperatures caused by reduced fluid flow can shorten motor longevity.

SUMMARY

The pumping system of this invention has features to measure the fluid speed of production fluids adjacent the motor assembly in an electric submersible pumping (ESP) system. A flow assurance section is included as part of an electric submersible pumping system. The flow assurance section includes a sail switch or set of sail switches that toggle at certain detected fluid speeds such as 1 ft/s or 0.5 ft/s. The fluid speed at which the flow assurance section switches power to the motor being interchangeable to best suit a given downhole environment. The toggling of the sail switches causes the power to the motor to switch on and off thereby preventing the motor from overheating. Power to the motor can be controlled by a control circuit located adjacent the pumping system or at the surface and may utilize the toggling state of the sail switches in making control decisions. The flow assurance section can be attached beneath the motor, above the pump section, or in other locations in close proximity to the ESP system. The signal from the flow assurance section can be sent to the surface as a communication on the power lines that extend to the ESP system motor or on communication lines that extend to the surface alongside or separate from the power lines.
The toggled state of the flow assurance sail switches can indicate to a surface user the fluid speed state adjacent a motor installed downhole. For example, green, yellow, and red status indicator lights or a similar representation in software can be used at the surface to alert operations personnel of the current fluid speeds adjacent the motor. This real-time indicator of downhole fluid speeds helps operations personnel to take action before a motor can overheat and fail. Additionally, the toggled state of the sail switches may be used to directly or indirectly control power to the motor. If a sail switch for a given fluid speed is toggled off, meaning the fluid flow adjacent the sail switch has a speed below that switches fluid speed, then the motor in the ESP system may be controlled based on the toggle state of that switch. Monitoring trends in fluid speed state will additionally help in determining the effect it has on motor longevity.

BRIEF DESCRIPTION OF THE DRAWINGS

Some of the features and benefits of the present invention have been stated, others will become apparent as the description proceeds when taken in conjunction with the accompanying drawings, in which:

FIG. 1 is a side elevational view of a well containing the electrical submersible pump (ESP) system having features in accordance with the present invention.

FIG. 2 is a side elevational view of a well containing the electrical submersible pump (ESP) system having features in accordance with the present invention.

FIG. 3 is a side elevational view showing a cross section of the flow assurance section of the ESP system of FIG. 2.

DETAILED DESCRIPTION OF THE DISCLOSURE

FIG. 1 and FIG. 2 illustrate a side elevational view of a cased well 10 having the electrical submersible pumping (ESP) system 12 disposed therein within casing 14. The ESP system 12 includes an electric motor 15, a seal/equalizer 17, an optional gas separator (not shown), a pump 19, and a flow assurance section 21. Production tubing 23 is coupled to the pump 19 for conveying pressurized production fluid from the ESP system 12 to the surface. The pump 19 may comprise a centrifugal pump, a progressive cavity pump, or some other form of artificial lift. The flow assurance section 21 could also be used in pumping systems having surface motors or inverted ESP's. Fluid inlets 25 can provide a passageway for receiving fluid into pump 19.
The power cable 27 extends alongside the production tubing 23, terminating in a connector 29, commonly referred to as a pothead connector, that electrically couples the power cable 27 to the electric motor 15. The power cable 27 can extend all the way from the surface to the pothead connector 29 and have an additional splice extending downward inside the electric motor 15 housing and extending through the flow assurance section 21. Often the power cable 27 will additionally include communication lines that transmit and receive data between the surface and the ESP system 12. An alternate communication method involves using the power carrying lines in the power cable 27 to serve the dual purpose of carrying power and communication signals between the surface and the ESP system 12. Either communication setup may be used to control and monitor the operation of the motor 15 housed in the ESP system 12. Additionally, in an alternate embodiment, the ESP system 12 could be supported on coiled tubing, rather than production tubing 23. The power cable 27 could be located inside or outside the coiled tubing for that embodiment.
Referring to FIG. 3, the flow assurance section 21 is shown attached beneath the motor 15. The flow assurance section 21 includes a passageway 30 through which production fluid can flow through the flow assurance section 21. The flow assurance section 21 additionally includes a sail switch 31 or set of sail switches. The production fluid flowing through passageway 30 passes over each sail switch 31 and then out of the flow assurance section 21 through outlet ports 32. Each sail switch 31 has a paddle 33 that causes the sail switch 31 to toggle at a certain minimum fluid speeds such as 1 ft/s, 0.5 ft/s, or 0.3 ft/s. For example, if fluid speed starts at 0.8 ft/s and rises to 1.2 ft/s, flow against the paddle 33 of a 1 ft/s sail switch will cause the sail switch 31 to toggle. If the fluid speed then falls back to 0.8 ft/s, the reduced flow against the sail switch paddle 33 will cause the sail switch 31 to toggle back to its original state. Transitions of the sail switch 31 between the first toggle state and the second toggle state or between the second toggle state and the first toggle state can be used by surface equipment to control the state of the motor 15. These transitions represent a fluid speed rising past the set minimum fluid speed or falling below the set minimum fluid speed. In other embodiments the sail switch 31 may include other types of sail or wind paddles, free spinning paddles, a fan and turbine having blades, or other types of flow switches.
Referring again to FIG. 1, in some embodiments the toggling of the sail switches 31 will be indicated to surface equipment, such as a controller 33. For example, green, yellow, and red status indicator lights 35 or indication through computer software can be used to alert operations personnel of the current fluid speeds adjacent the motor 15. This real-time indicator of downhole fluid speed helps operations personnel to take action before a motor 15 can overheat and fail. Additionally, the toggled state of the sail switches 31 may be used to directly control power to the motor 15. If a sail switch 31 for a given fluid speed is toggled back to its original state, meaning the fluid flow through the flow assurance section 21 has a speed below that sail switches detection rate, then the controller 33 in the ESP system 12 can switch power off to the motor 15, thereby preventing the motor 15 from overheating. Power to the motor 15 can be controlled by or based on the toggling of individual sail switches 31. The fluid speed at which the flow assurance section 21 switches power to the motor 15 is interchangeable to best suit a given downhole environment. The toggling of the sail switches 31 causes the power to the motor 15 to switch on and off to thereby prevent the motor 15 or other components of the ESP system 12 from overheating. Additionally, when power to the motor 15 is being autonomously controlled based on sail switch state, a timed delay can be implemented before the motor power is switched. This delay can avoid turning a motor 15 off or on when a fluid speed change is only temporary. The flow assurance section 21 can be attached beneath the motor 15, above the pump 19 or in other locations in close proximity to the ESP system 12.
In the preferred embodiment, the flow assurance section 21 is attached beneath the ESP system 12 to advantageously measure fluid speed close to the annular space 37 between the casing 14 and the motor 15. For a given installation the preference may be to position the flow assurance section 21 further beneath the motor 15 using a tubular flow assurance extension 39. This allows for the measurement of fluid speed further beneath the motor 15 which may be a more accurate position to detect speed of the fluid flowing in the annular space 37 between the flow assurance section 21 and the casing 14. Power and communication lines for the sail switches 31 can be spliced off of the power cable 27 and extend downward from pothead connector 29 inside the motor housing through the tubular flow assurance extension 39, then into the flow assurance section 21. Alternatively, the splice of the for the power and communication lines that extend to the sail switches 31 can occur anywhere within the motor housing. In some embodiments only a power or only a communication line will be required by the sail switch 31. The communications regarding the toggle state of the sail switches 31 can be sent along the power cable 27, along a separate communication cable running alongside the power cable 27 or along a completely separate communication cable. The included figures show just a few of the intended configurations.
In an alternate configuration of the flow assurance section 21, the sail switch paddles 33 can be on the exterior of the flow assurance section 21 housing. In the preferred embodiment the sail switch paddles 33 are on the interior of the flow assurance section 21 housing so that the sail switch paddles 33 have the benefit of being better protected during installation. In another configuration the sail switches 31 can be positioned on the motor 15, seal/equalizer 17, or pump 19, protective railings positioned to protect the sail switches 31 in this configuration.
An embodiment can have a splice from the power cable 27 extending from the pothead connector 29 alongside the motor 15 to the flow assurance section 21. In another embodiment a splice from the power cable 27 can extend alongside the pothead connector 29, alongside the motor 15, and alongside the flow assurance extension into the flow assurance section 21. In some embodiments, the flow assurance section 21 can use power from the power cable 27 as needed.
An alternate positioning of the flow assurance section 21 is in the production tubing 23 above the pump section 19 of the ESP system 12. The flow assurance section 21 can connect to the power line 27 and any corresponding communication lines with a connector similar to the pothead connector 29 that connects the power line 27 to the motor 15. This position of the flow assurance section 21 measures the speed of fluid after it passes by motor 15, the fluid inlets 25, and the pump 19. This installation position is farther away from the motor and the speed being measured is of production fluid after passing through pump 19; however, this position may still be advantageous for certain downhole environments. An alternate embodiment of the ESP system 12 may have the flow assurance section 21 installed above the pump 19 and another flow assurance section 21 installed below the motor 15. In this type of installation surface equipment may have multiple fluid speed indicators and in some embodiments the controller may utilize the toggling states of the various sail switches 31 to control the motor 15 or perform other control functions.
The sail switches in the flow assurance section 21 toggle at certain detected fluid speeds such as 1 ft/s, 0.5 ft/s, or 0.3 ft/s. The fluid speed being detected would typically represent reduced fluid speeds for a given downhole installation. Potential causes of reduced fluid speed past the motor 15 may include: gas ingestion in the pump, gas locking in the pump, sand erosion in the pump, changes in well productivity, a closed surface valve that controls flow off of the production tubing, unexpected well performance, a hole in the production tubing, deposition or build up from scale on the pump or tubing, sand, asphaltenes, or other reasons. Reduced fluid speed for any of these reasons and others not mentioned could cause the motor 15 to overheat. The use of sail switches in a flow assurance section 21 to alert operations personnel or to autonomously switch power off to the motor 15 can avoid damage that would be caused if the motor 15 were to overheat.
The flow assurance section 21 can alert operations personnel and also act autonomously to increased fluid speeds detected by the sail switches 31. For example, if a sail switch 31 in the flow assurance section 21 initially caused power to be switched off to the motor 15, it could likewise cause power to be switched back on to the motor 15 when the fluid speed increases and the sail switch 31 is again toggled. Likewise, any alerts that have been made to surface equipment or to operations personnel can be turned off when fluid speed increases. Surface equipment and operations personnel can also be notified of faster fluid speeds, as detected by the sail switches 31, that have a positive effect on the cooling of the motor 15.
In the preferred installation having multiple sail switches 31 positioned in the flow assurance section 21, each sail, switch will detect a certain fluid speed. For example, one sail switch can detect 1 ft/s while another detects 0.5 ft/s. Each switch can alert surface equipment or operations personnel as to its toggled state. In some embodiments multiple sail switches 31 of the same detection rate may be used for redundancy. For example, if one of the sail switches is damaged during installation, the second sail switch could then be used.
Alternatively, one sail switch 31 could have two or more positions and offer two or more output signals to infer two or more differing fluid speed states. These outputs could be used similarly to the methods described above to alert surface equipment and operations personnel and autonomously switch power off and on to the motor 15. For example, movement of sail switch paddle 33 to a first position may represent a fluid speed above one fluid speed, such as 0.5 ft/s, and movement of sail switch paddle 33 to a second position may represent a fluid speed above another fluid speed, such as 1 ft/s.
If an ESP is installed in perforations or with perforations above and below the ESP there can be uncertainty regarding fluid speed past the motor. This invention is capable of assuring that minimum fluid speeds are achieved and that the motor may safely operate.
There are other uses of the flow assurance section 21. These uses include: tracking when a well is producing or not, tracking well fluid speeds over time, preventing the overheating of other downhole equipment that may be susceptible to heat when fluid speeds are low. More specific examples include: tracking a motors heat exposure and corresponding insulation life, tracking fluid speed to cool the thrust bearing in the seal section, or tracking fluid speed past a rod driven PCP where the PCP elastomers could melt. With other forms of lift there may still exist further benefits of installing a flow assurance section 21. For example, tracking the production rate of a well or tracking when a well is producing or not producing over a period of time. Another benefit may exist when the flow assurance section 21 is installed in a PCP or rod pump installation. In this type of installation, for example, if the pump operates with no fluid movement, line pressure can build and result in bursting of equipment either in the well or on the surface. Having a flow assurance section 21 can provide the benefit of alerting to this condition before it becomes more serious.
In view of the foregoing, electric submersible pumping systems that are capable of operating in downhole environments are provided as embodiments of the present invention. For example, motor longevity may be improved by using an ESP system with an integrated flow assurance mechanism as illustrated in the above described embodiments.

Claims

1. An apparatus for pumping fluid from a cased well, comprising:

an electrical submersible pump assembly (ESP) having a pump and an electrical motor positioned within casing of the cased well;

at least one sail switch mounted to the ESP, the sail switch having an external paddle that moves in response to a change in fluid speed of well fluid flowing past the motor from a first toggle position to a second toggle position;

a controller at a surface position of the well that is electrically linked to the sail switch for performing a motor control function in response to the change from the first toggle position to the second toggle position.

2. The system of claim 1, wherein said at least one sail switch comprises a plurality of sail switches, each one of the plurality of sail switches set to change toggle position in respect to a different fluid speed of the well fluid flowing past the motor.

3. The system of claim 1, further comprising a toggling status indicator at the controller that indicates whether the sail switch is in the first position or the second position.

4. The system of claim 1, wherein the sail switch is mounted below the motor.

5. The system of claim 4, further comprising an extension member that supports the sail switch a selected distance below the motor.

6. The system of claim 1, wherein an increase in the fluid speed of the well fluid above a selected minimum can cause the sail switch to move from the first toggle position to the second toggle position and a decrease in the fluid speed below the selected minimum can cause the sail switch to move from the second toggle position to the first toggle position.

7. The system of claim 1, wherein the controller shuts off the motor if the fluid speed, over a selected time interval, is inadequate to move the sail switch from the first toggle position to the second toggle position.

8. An apparatus for pumping fluid from a cased well, comprising:

a housing mounted to the ESP below the motor that allows for the ingress and egress of fluids moving in the cased well;

at least one sail switch mounted between the housing walls, the sail switch having an external paddle that moves in response to a change in fluid speed of well fluid flowing past the motor, an increase in the fluid speed of the well fluid above a selected minimum can cause the sail switch paddle to move from the first toggle position to the second toggle position and a decrease in the fluid speed below the selected minimum can cause the sail switch paddle to move from the second toggle position to the first toggle position;

a controller at a surface of the well that is electrically linked to the sail switch for performing a motor control function in response to the change from the first toggle position to the second toggle position.

9. The system of claim 8, wherein said at least one sail switch comprises a plurality of sail switches, each set to change a toggle position in respect to a different fluid speed of the well fluid flowing past the motor.

10. The system of claim 8, further comprising an extension member that supports the sail switch a selected distance below the motor.

11. The system of claim 8, wherein the controller shuts off the motor if the fluid speed over a selected time interval is inadequate to move the sail switch from the first toggle position to the second toggle position.

12. The system of claim 8, further comprising a toggling status indicator at the controller that indicates whether the sail switch is in the first position or the second position.

13. The system of claim 8, wherein the sail switch has at least three toggle positions, an increase in the fluid speed of the well fluid above a selected minimum can cause the sail switch to move from the first toggle position to the second toggle position and an increase above a second selected minimum can cause the sail switch to move from the second toggle position to the third toggle position, a decrease in the fluid speed below the second selected minimum can cause the sail switch to move from the third toggle position to the second toggle position, a decrease in the fluid speed below the selected minimum can cause the sail switch to move from the second toggle position to the first toggle position.

14. The system of claim 13, further comprising a toggling status indicator at the controller that indicates whether the sail switch is in the first position, the second position, or the third position.

15. A method for pumping well fluid for a well, comprising:

mounting at least one sail switch to an electrical submersible pumping assembly (ESP) having a pump, an electric motor, and a surface controller;

then lowering the ESP into the well;

supplying power to the motor to operate the pump;

causing the well fluid flowing past the motor to move the sail switch from a first toggle position to a second toggle position if a fluid speed of well fluid reaches a selected minimum; and

the surface controller performing a motor control function in response to the change from the first toggle position to the second toggle position.

16. A method according to claim 15, wherein the motor control function comprises providing a visible indication at the controller of the sail switches toggle position.

17. A method according to claim 15, wherein the motor control function comprises shutting down the motor.

18. A method according to claim 15, further comprising:

detecting downhole fluid speed with a plurality of sail switches, each sail switch toggling at a different selected minimum fluid speed.

19. A method according to claim 15, further comprising:

a sail switch toggling in response to a decrease in the fluid speed below the selected minimum that causes the sail switch to move from the second toggle position to the first toggle position.

20. A method according to claim 15, further comprising:

mounting at least one sail switch to an electrical submersible pumping assembly (ESP) beneath the motor.