Rotary Steerable Steering Assembly Mandrel Dynamics
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing rotary steerable systems for directional drilling face challenges such as internal cyclic bending stresses, limited turn rates, vibration issues, and complexity in field serviceability, particularly when operating in 'point the bit' mode, which can lead to shaft fatigue and increased costs.
Innovation Solution
A steering assembly with a mandrel and housing configuration that includes a deflector device for side force application and a tool face assembly for directional control, featuring a pivot stabilizer and actuating systems to minimize bending and enhance directional control, allowing for both 'push the bit' and 'point the bit' modes with adjustable turn rates and independent directional control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional rotary steerable system operates in 'point the bit' mode with a non-rotating housing and deflection mechanism, then directional control is achieved, but internal cyclic bending stresses cause shaft fatigue and reduced reliability
Solution Approach 1:
The patent makes the housing rotatable along with the mandrel, transforming the system from a static non-rotating configuration to a dynamic rotating configuration. This eliminates cyclic bending stresses on the shaft while maintaining directional control capability through active adjustment mechanisms that can change the deflection angle during rotation.
Solution Approach 2:
The patent replaces the mechanical deflection mechanism that caused bending stresses with a bearing-supported rotatable housing system. The mandrel rotates on bearings within the housing, substituting the bending-based deflection method with a rotation-based steering method that eliminates cyclic stress on the shaft.
2Force
If the housing is made non-rotating or slowly rotating with pads pushing against the wellbore, then side force is applied to change orientation, but friction and wear increase device complexity and reduce ease of operation
Solution Approach 1:
The patent removes the pad-based side force generation mechanism entirely. Instead of using pads to push against the wellbore formation, the system generates steering force through the rotation of the mandrel and housing assembly, extracting the complex pad actuation mechanism from the design.
Solution Approach 2:
The patent employs hydraulic actuators to control the deflection angle of the mandrel relative to the housing. This hydraulic control system replaces complex mechanical pad actuation mechanisms with a more simplified and reliable fluid-powered adjustment system.
3Force
If a fixed body-mounted stabilizer with an internal deflection device is used, then the shaft is pushed away from the center providing side force, but the system becomes less adaptable to different drilling conditions
Solution Approach 1:
The patent makes the stabilizer position and deflection angle dynamically adjustable during drilling operations. The mandrel can be actively repositioned relative to the housing using hydraulic actuators, allowing the system to adapt to varying drilling conditions and switch between different steering modes as needed.
Solution Approach 2:
The rotatable housing with mandrel configuration provides universal steering capability that can function in multiple modes. The system can operate with the mandrel coaxial to the housing axis or at an angled position, providing both centralized and deflected drilling capabilities within a single unified design.
4Measurement precision
If bending mechanisms are used to tilt the drill bit in point the bit mode, then directional steering is achieved, but the shaft may break or deform after certain time increasing loss of time
Solution Approach 1:
The patent transitions from a static bent shaft configuration to a dynamic rotating system where the mandrel can be repositioned during rotation. This dynamic approach eliminates continuous cyclic bending of a fixed shaft, thereby extending service life while maintaining steering precision through active angle adjustment.
Solution Approach 2:
The patent substitutes the bending-based steering mechanism with a bearing-supported rotational system. The mandrel rotates on bearings within the housing, replacing the bending mechanism with a rotation mechanism that eliminates cyclic stress accumulation and extends shaft durability.
Data Source
AI summary
A steering assembly includes a housing having a longitudinal axis, a mandrel having a front connecting extremity and a rear connecting extremity, the mandrel passing through the housing and arranged in a first position coaxially to the longitudinal axis of the housing, a deflector device configured to exert a side force on the mandrel to offset the front connecting extremity of the mandrel from the longitudinal axis, and a tool face assembly configured to rotate the front connecting extremity of the mandrel in a desired direction.