Concentric Rotary Downhole Motor Without Elastomeric Joints
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Solution Overview
Problem
Conventional downhole motors used in directional drilling have length limitations and temperature constraints due to the use of Moineau-type drive systems, which restrict their effectiveness in high-temperature applications and require elastomeric elements that can fail under stress, especially at the universal joints and threaded connections.
Innovation Solution
A concentric rotary drive system with a system of longitudinal lobes and gates, eliminating the need for a driveshaft with universal joints by integrating the drive system directly within the bearing assembly, allowing for a shorter motor length and operation at high temperatures without elastomeric elements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If Moineau-type drive system is used, then the downhole motor can operate in directional drilling applications, but the motor length becomes excessive (4.6-6.1 meters) and elastomeric elements are required which fail under high temperature and stress
Solution Approach 1:
The patent removes elastomeric elements entirely from the drive system, replacing them with a metal-to-metal gate and lobe mechanism. This extraction of problematic elastomeric components eliminates their failure under high temperature and stress while maintaining the directional drilling capability through the concentric rotary drive system.
Solution Approach 2:
The patent replaces the Moineau-type mechanical drive system with a concentric rotary drive system featuring longitudinal lobes and gates. This substitution eliminates the need for elastomeric elements and universal joints, resulting in a more reliable system that operates without the length limitations of conventional Moineau motors.
2Adaptability or versatility
If Moineau-type drive system with universal joints is used, then the downhole motor can accommodate angular misalignment, but fractures occur at the universal joints and threaded connections making them the weakest parts
Solution Approach 1:
The patent eliminates universal joints and threaded connections from the drive system by implementing a direct-drive concentric rotary mechanism. This extraction removes the weakest parts of the assembly that are prone to fractures, while the gate and lobe design inherently accommodates angular misalignment without requiring separate universal joint components.
Solution Approach 2:
The patent merges the functions of angular misalignment accommodation and power transmission into a single integrated concentric rotary drive system. The longitudinal lobes and gates work together as a unified mechanism that simultaneously handles misalignment and torque transmission, eliminating the need for separate universal joints and reducing fracture risk.
3Ease of manufacture
If conventional downhole motor design is used, then the motor can be manufactured with standard components, but the motor length is limited and temperature constraints apply due to elastomeric element limitations
Solution Approach 1:
The patent removes elastomeric elements from the design, eliminating their temperature constraints. The resulting metal-to-metal gate and lobe system can operate at high temperatures without degradation, while the modular concentric design maintains ease of manufacture through standardized machining processes for the rotor, stator, and bearing assembly.
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 solution enables a more compact and durable downhole motor design capable of operating effectively in high-temperature conditions, reducing the risk of fractures and maintaining performance beyond the limits of conventional Moineau-type systems, with improved steerability and efficiency in directional drilling.
Implementation Method 1
a system of longitudinal lobes and gates, with intake and exhaust ports for directing fluid to build pressure between the lobes and gates to drive the rotation of the motor
Implementation Method 2
The drilling fluid, which may be water-based or oil-based, is typically viscous to enhance its ability to carry wellbore cuttings to the surface
Data Source
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AI summary
A downhole motor includes a bearing assembly (100) having a mandrel (10) rotatable within a cylindrical housing (20), with the mandrel co-rotatably engaging the rotor (120) of a concentric rotary drive system (110) incorporating an arrangement of housing-mounted gates (130) pivotably deflectable by rotor lobes (124) as the rotor rotates in response to fluid flow through an annular space (40) between the rotor and the housing, building up pressure in longitudinal chambers (140) formed between adjacent gates and lobes and thus inducing rotation of the mandrel. Preferably, the drive system is coupled directly to the bearing assembly, without need for a connecting driveshaft, and with the housing incorporating a bent sub (210) positioned above the drive section. Alternatively, a bent sub may be positioned below the drive system in conjunction with the use of a driveshaft to connect the drive system to the bearing section, in order to position the bend as close as possible to the bit.