Flexible Collar for Rotary Steerable System Dogleg Severity
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Solution Overview
Problem
Rotary steerable systems (RSS) face challenges in achieving desired steering radii and dogleg severity during directional drilling, as existing systems lack flexibility and precision in controlling the drill bit's direction, especially when dealing with tight radii and complex wellbore trajectories.
Innovation Solution
Incorporating a flexible collar with strategically selected geometric and material properties into the RSS, allowing for adjustable bending stiffness and torsional flexibility, which can be positioned at the up-hole end or between the steering and control sections, to enhance dogleg severity capabilities and improve turning radius control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a traditional rigid collar is used in the RSS, then structural strength and stability are maintained, but the ability to achieve tight steering radii and high dogleg severity is limited
Solution Approach 1:
The patent applies this principle by replacing the traditional rigid collar with a flexible collar that can bend and deform. The flexible collar is designed with specific geometric properties (cross-sectional shape, wall thickness, material properties) that allow it to flex under lateral forces from the drill bit, enabling tight steering radii while maintaining sufficient structural strength to withstand drilling loads.
Solution Approach 2:
The patent applies this principle by strategically selecting and optimizing geometric parameters of the flexible collar including cross-sectional dimensions, wall thickness, material properties, and length. These parameter changes allow the collar to achieve the desired balance between flexibility for tight steering and strength for structural integrity under various drilling conditions.
2Productivity
If the collar bending stiffness is increased to maintain stability, then wellbore oscillations are reduced, but the dogleg severity capability and turning radius control are degraded
Solution Approach 1:
The flexible collar acts as a flexible shell that can bend controllably to achieve tight steering radii while maintaining stability. The collar's flexibility allows it to conform to the desired wellbore trajectory without excessive rigidity that would cause oscillations, thereby balancing directional control precision with drilling efficiency.
Solution Approach 2:
The patent applies this principle by selecting materials with specific properties that combine flexibility and strength. The flexible collar may use composite material structures or materials with optimized mechanical properties to achieve the right balance between bending stiffness for stability and flexibility for tight turning control, improving both drilling efficiency and ease of operation.
3Manufacturing precision
If the flexible collar is positioned closer to the drill bit to improve steering response, then turning radius control is enhanced, but the structural loads and bending stresses on the collar increase
Solution Approach 1:
The patent applies this principle by strategically selecting the collar's geometric parameters (length, cross-sectional dimensions, wall thickness) and material properties to optimize the balance between steering response and stress management. By adjusting these parameters, the collar can be positioned closer to the bit for improved precision while maintaining acceptable stress levels through optimized structural design.
Solution Approach 2:
The flexible collar design allows it to absorb and distribute bending stresses through controlled deformation. The collar's flexible shell structure can accommodate higher bending stresses near the drill bit by flexing appropriately, thereby enabling improved turning radius precision without exceeding structural stress limits through intelligent design of the flexible element.
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 flexible collar enables increased dogleg severity tolerance, reduced bending and torsional stiffness, and improved directional control, allowing for more precise and efficient drilling through complex wellbore paths by matching the drill bit's side cutting efficiency with the collar's flexibility, thereby enhancing drilling stability and reducing undesirable features like wellbore oscillations.
Implementation Method 1
The flexible collar may be constructed of a material selected to be dissimilar with respect to a material selected for the steering section... allowing for adjustable bending stiffness and torsional flexibility
Implementation Method 2
allowing for adjustable bending stiffness and torsional flexibility... reduced bending and torsional stiffness
Data Source
Figure 1
Figure 2~3A
Figure 3B~4
AI summary
A Rotary Steerable System (RSS) includes a flexible collar coupled therein or thereto that permits the stiffness of the RSS to be controlled and permits a desired turning radius to be achieved without sacrificing stability characteristics of the RSS. The flexible collar may be positioned between a steering section and the controller of the RSS. The parameters affecting the geometry, position and stiffness characteristics of the flexible collar and the RSS may be selected strategically to match the requirements of the particular wellbore being drilled. By selecting these parameters strategically, improvements may be achieved related to tool length, bending stiffness, bending stress, torsional stiffness, shear stress due to torsion and increased dogleg severity tolerance.