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Enhanced cooling for downhole motors

Enhanced cooling for downhole motors description/claims

1. Field of Invention

The present disclosure relates to downhole pumping systems submersible in well bore fluids. More specifically, the present disclosure concerns an improved method of cooling pump motors used to drive the submersible pumping systems. Yet more specifically, the present disclosure involves enhancing the surface area of the pump motor for increasing the heat transfer between the pump motor and the well bore fluid flowing across the surface of the pump motor.

2. Description of Prior Art

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 may be supplied to the pump motor via an electrical cable. Typically, the pumping unit is disposed within the well bore above where perforations are made into a hydrocarbon producing zone. This placement thereby allows the produced fluids to flow past the outer surface of the pumping motor and provide a cooling effect.

With reference now to FIG. 1, an example of a submersible ESP disposed in a well bore is provided in a partial cross sectional view. In this embodiment, a downhole pumping system 12 is shown within a cased well bore 10 suspended within the well bore 10 on production tubing 34. The downhole pumping system 12 comprises a pump section 14, a seal section 18, and a motor 24. The seal section 18 forms an upper portion of the motor 24 and is used for equalizing lubricant pressure in the motor 24 with the wellbore hydrostatic pressure. Energizing the motor 24 then drives a shaft (not shown) coupled between the motor 24 and the pump section 14. Impellers are coaxially disposed on the shaft and rotate with the shaft within respective diffusers formed into the pump body 16. As is known, the centrifugal action of the impellers produces a localized reduction in pressure in the diffuser thereby inducing fluid flow into the diffuser. In this embodiment, a series of inlets 30 are provided on the pump housing wherein formation fluid can be drawn into the inlets and into the pump section 14. The source of the formation fluid, which is shown by the arrows, are perforations 26 formed through the casing 10 of the well bore and into a surrounding hydrocarbon producing formation 28. Thus the fluid flows from the formation 28, past the motor 24 on its way to the inlets 30. The flowing fluid contacts the housing of the motor 24 and draws heat from the motor 24.

In spite of the heat transfer between the fluid and the motor 24, over a period of time the motor 24 may become overheated. This is especially a problem when the fluid has a high viscosity, a low specific heat, and a low thermal conductivity. This is typical of highly viscous crude oils. The motor 24 may be forced to operate at an elevated temperature, past its normal operating temperature, in order to reject the internally generated heat. This temperature upset condition can reduce motor life and results in a reduction in operational times of the pumping system.

The present disclosure includes a downhole submersible pumping system comprising, a pump, a pump motor coupled to the pump, and a heat transfer member disposed on the pump motor outer surface. The pumping system is configured for being disposed within a well bore. The pumping system may further comprise a fluid intake, wherein the fluid intake is configured to receive downhole fluid and is disposed adjacent the pump motor. The downhole fluid received by the intake may create a flowpath flowing across the heat transfer member that absorbs thermal energy from the heat transfer member. In one embodiment, the entire outer surface of the heat transfer member is fully contactable by wellbore fluid. The heat transfer member may have a substantially rectangular cross section, a “T” shaped cross section, or it may be elongated and disposed substantially parallel to the pumping system axis. Optionally, the heat transfer member may be disposed at an angle to the pumping system axis. The system may further comprise a multiplicity of elongated heat transfer members disposed substantially parallel to the pumping system axis.

The present disclosure may include another embodiment of a wellbore pumping system submersible in a downhole fluid, where the system comprises a housing, a pumping device disposed in the housing, an intake in fluid communication with the housing, wherein the intake provides fluid communication with the outside of the housing and the pumping device inlet, a motor disposed in the housing mechanically coupling to the pumping device and a heat conducting fin disposed on the housing adjacent to the motor, wherein the fin freely extends away from the housing wherein its entire outer surface is in contact with the downhole fluid. The wellbore pumping system may have a pump discharge that communicates with production tubing.

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

FIG. 1 shows a prior art downhole submersible system in a partial cross sectional view.

FIG. 2 shows a side view of a pumping system in accordance with the present disclosure disposed within a cased well bore.

FIG. 3 provides a schematic cross sectional view of a portion of the pumping system having a heat transfer member extending therefrom.

FIG. 4 shows a side view of a portion of the pumping system of the present disclosure illustrating fluid flow over a heat transfer member.

FIG. 5 is a cross sectional view of an embodiment of a heat transfer member.

FIG. 6 is a cross sectional view of an alternative embodiment of a heat transfer member.

FIG. 7 is an overhead view of an alternative view of a heat transfer member.

FIG. 8 is a side view of an embodiment of a pumping system having laterally disposed fins.

• Provisional Patent
• Utility Patent

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