Hybrid Elastomer Metal Stator for Downhole Motor Durability
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Solution Overview
Problem
Conventional downhole drilling motors with elastomeric stators face durability issues due to thermal expansion and chemical absorption, leading to premature failure under load and temperature conditions, requiring frequent and costly stator replacements.
Innovation Solution
A hybrid stator design combining elastically deformable elastomeric material with rigid sections and a cylindrical sleeve, where the rigid sections are made from stacked disks with a helically convoluted profile, providing additional support and reducing sideload on the elastomeric sections, thereby enhancing durability and reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the stator is made entirely of elastomeric material to maintain sealing, then sealing performance is improved, but durability deteriorates due to thermal expansion and chemical absorption
Solution Approach 1:
The stator is constructed as a composite structure combining an elastomeric lining (for sealing) with a metal support structure (for durability). The elastomeric material is bonded to the metal support, creating a hybrid component that leverages the advantages of both materials: the elastomer provides conformal sealing against the rotor while the metal framework resists thermal expansion and chemical degradation.
Solution Approach 2:
Different portions of the stator have different material properties optimized for their specific functions. The elastomeric lining is concentrated in regions requiring flexible sealing contact, while the rigid metal support is distributed throughout to provide structural stability and resist harmful environmental factors. This localized material assignment resolves the contradiction between sealing needs and durability requirements.
2Reliability
If the elastomeric material is made thicker to improve sealing, then sealing performance is improved, but thermal expansion and chemical absorption increase
Solution Approach 1:
The composite construction allows the elastomeric layer to be kept thin while maintaining effective sealing, because the rigid metal support structure provides dimensional stability that prevents excessive thermal expansion and reduces chemical absorption. The metal framework acts as a constraint that limits the elastomer's expansion while still allowing it to conform to the rotor surface for sealing.
Solution Approach 2:
The elastomeric material is applied selectively in thin layers only where sealing contact is required, rather than using thick uniform walls throughout. The metal support structure assumes the load-bearing and environmental resistance functions, allowing the elastomer to remain thin and thus less susceptible to thermal and chemical degradation.
3Ease of manufacture
If conventional elastomeric stators are used to allow complex shape manufacturing, then ease of manufacture is improved, but durability deteriorates under load and temperature conditions
Solution Approach 1:
The stator is segmented into two manufacturable components: a rigid metal support structure that can be fabricated using conventional machining or forming processes, and an elastomeric lining that is separately manufactured and then bonded to the metal support. This segmentation allows each component to be optimized for its material properties and manufacturing processes, with the metal portion providing durability and the elastomer providing the complex sealing geometry.
Solution Approach 2:
The hybrid construction separates the structural function (handled by the durable metal support) from the sealing function (handled by the elastomeric lining). This allows the complex sealing geometry to be achieved through the elastomer's flexibility and bonding capability, while the metal framework provides the mechanical strength and environmental resistance needed for long service life under load and temperature conditions.
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
The hybrid stator design extends the operational life of downhole drilling motors by maintaining a tight seal and reducing fatigue, allowing the motor to continue operating under challenging conditions with reduced efficiency, thus minimizing the need for costly stator replacements.
Implementation Method 1
a first section (22) within the stator housing (26) comprising a generally tubular configuration having elastically deformable elastomeric material
Data Source
AI summary
A hybrid elastomer/metal on metal motor for a helical gear device includes a rotor and stator comprising a hydraulic motor that produces work when a working fluid is pumped therethrough. The improvement involves the stator being, for part of its length, a conventional or even wall stator, using an elastomer to form a seal against the moving rotor. The stator's remaining length comprises a profiled rigid surface that forms a seal directly with the moving rotor. This gives the motor the high efficiency of the elastomer sealing against the rotor, and simultaneously provides a backup of the stator's rigid section allowing continued motor operation at reduced efficiency, if the elastomer part failed in service. The invention also includes combinations of a regular disk stack with a rubber lining, a rigid material disk stack (or unitized element) and a circular rigid sleeve which react to rotor sideloading while permitting proper rotor orbiting.