Downhole Motor Pressure Equalization and Rotor Retrieval
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Solution Overview
Problem
Downhole artificial lift systems often fail due to hostile environments, leading to costly workover procedures and lost production, as electrical components are exposed to harsh conditions and integrated with rotating parts, increasing the risk of failure.
Innovation Solution
An electric motor design featuring a pressure-compensated housing with an incompressible fluid and a seal that equalizes pressure between the fluid inside and outside, isolating electrical components from the well fluid, allowing for a retrievable rotor-impeller and a stator that remains in the well, enhancing reliability and reducing maintenance needs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If electrical components are integrated with rotating parts in downhole artificial lift systems, then the system can function as a complete motor unit, but the reliability decreases due to exposure to hostile environments and increased risk of failure
Solution Approach 1:
The motor is divided into two separable parts: a stator that remains in the well and a rotor-impeller assembly that can be retrieved. This segmentation allows the electrical stator to be protected from harsh downhole conditions while maintaining motor functionality, thereby improving reliability without requiring complete system replacement upon rotor failure.
Solution Approach 2:
The rotor-impeller is extracted from the housing as a separate retrievable component. This extraction enables the rotor to be removed for maintenance or replacement without affecting the stator, which remains protected in the housing. This resolves the contradiction by allowing the electrical components to be isolated from the harsh environment while maintaining complete motor functionality.
2Reliability
If the housing is sealed to protect electrical components from well fluid, then reliability improves, but pressure equalization between internal and external fluids becomes difficult
Solution Approach 1:
A flexible membrane seal acts as an intermediary between the internal incompressible fluid and the external well fluid. This seal allows pressure equalization while maintaining the protective barrier that prevents well fluid ingress. The membrane transmits pressure changes from the external environment to the internal fluid, resolving the contradiction between sealing for protection and allowing pressure equalization.
3Reliability
If workover procedures are performed to maintain artificial lift systems, then equipment reliability can be restored, but production is lost during the procedure
Solution Approach 1:
The rotor-impeller is designed to be extracted and retrieved from the well independently of the stator. This allows the rotor to be removed for maintenance or replacement without requiring a full workover procedure that would shut in the well. The stator remains protected in the housing, and only the rotor needs to be accessed, thereby maintaining production while restoring equipment reliability.
4Ease of repair
If the entire motor is retrieved for maintenance, then complete inspection and repair can be performed, but production is lost and retrieval costs increase
Solution Approach 1:
The motor is segmented into a stationary stator and a retrievable rotor-impeller assembly. This segmentation enables selective maintenance where only the rotor needs to be retrieved for inspection and repair, while the stator remains in the well. This reduces the time and cost associated with complete motor retrieval while still allowing thorough inspection and repair of the rotating components.
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
This design improves the reliability of downhole artificial lift systems by reducing the frequency of workover procedures, lowering maintenance costs, and increasing production by separating electrical components from rotating parts, thus reducing pressure on the motor's housing and allowing for more efficient fluid lift.
Implementation Method 1
The seal is movable by the well fluid to apply a pressure on the incompressible fluid to equalize pressure between the incompressible fluid and the well fluid
Implementation Method 2
The electric stator can include an electromagnetic coil for driving rotation of the electric rotor-impeller
Data Source
AI summary
An electric motor is configured to be positioned in a well. The motor includes a housing flooded with an incompressible fluid, a seal, a stator in the housing, and a rotor-impeller. The housing is configured to affix to a tubing of the well. The housing defines an inner bore having an inner bore wall continuous with an inner wall of the tubing for flow of well fluid. The housing defines a port that can be in fluid communication with the well. The seal seals the port against ingress of fluid. The seal is movable by the well fluid to apply a pressure on the incompressible fluid to equalize pressure between the incompressible fluid and the well fluid. The rotor-impeller is configured to be positioned within the inner bore of the housing. The rotor-impeller is configured to be retrievable from the well while the stator remains in the well.