Electric Submersible Pump Active Cooling for Low-Flow Motor Heat
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Solution Overview
Problem
Electric submersible pumps (ESP) face cooling inefficiencies due to insufficient fluid flow, high gas-to-oil ratios, and stagnant fluid conditions, leading to motor overheating and reduced reliability, especially in applications with small well diameters or below perforations.
Innovation Solution
Implementing a rotary positive displacement pump to forcibly circulate motor fluid within the motor and an external heat exchanger, positioned to enhance heat transfer, and using a shroud to increase fluid velocity over the heat exchanger.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If produced fluid is used to cool the motor passively, then the system structure remains simple, but cooling effectiveness is insufficient under low flow conditions
Solution Approach 1:
The motor cooling system uses the produced fluid flow itself to provide cooling without external active components. The motor housing acts as a heat exchanger that passively transfers heat from the motor to the produced fluid flowing through the annular space, eliminating the need for separate cooling pumps or heat exchangers while maintaining reliability under normal flow conditions
Solution Approach 2:
The cooling function is extracted from the main produced fluid flow path and implemented through a dedicated thermal management pathway. The motor housing serves as a separate heat transfer surface that interfaces with the produced fluid, allowing thermal energy to be removed independently from the fluid production function
2Productivity
If the pump intake is positioned below perforations to maximize drawdown, then pump efficiency increases, but motor cooling effectiveness decreases due to stagnant fluid
Solution Approach 1:
The cooling system addresses the local stagnant fluid condition around the motor by using the motor housing itself as a heat exchanger surface. This local thermal management solution works independently of the overall fluid flow conditions in the wellbore, providing effective heat transfer even when the produced fluid is relatively stagnant in the motor region
3Productivity
If permanent magnet motors operate at high speed, then productivity increases, but heat generation per surface area increases significantly
Solution Approach 1:
The motor housing is segmented into distinct functional zones: a stator housing portion and a rotor housing portion connected by a transfer portion. This segmentation allows optimized thermal management where each section can be designed for specific heat dissipation requirements, with the transfer portion facilitating heat transfer from the high-speed rotor to the cooler stator region and ultimately to the produced fluid
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enhances motor cooling, extends run life, and improves reliability by ensuring effective heat removal and fluid circulation, allowing operation in challenging thermal environments.
Implementation Method 1
an external heat exchanger, positioned to enhance heat transfer
Data Source
AI summary
An electric submersible pump includes a heat exchanger, a shaft comprising an axial bore, and a motor, which includes a rotor rotationally coupled to the shaft, a stator concentrically disposed with respect to the rotor, and a journal bearing disposed between the stator and the shaft. There is a gap between the rotor and the stator. The electric submersible pump further includes a first pump mechanically coupled to the shaft and configured to pump production fluid through a tubular, and a second pump mechanically coupled to the shaft and configured to pump coolant through the axial bore, the gap, and the heat exchanger. The heat exchanger transfers heat from the coolant to the production fluid to cool the motor.