Earth-Boring Tool Cutting Elements for Torque Control
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Solution Overview
Problem
Rotary drag bits with PDC cutting elements face issues of excessive aggressiveness, particularly in formations with varying compressive strengths, leading to stick-slip, impact damage, and torque fluctuations, which conventional depth-of-cut control features fail to adequately address, especially during rapid transitions between harder and softer rock layers.
Innovation Solution
Incorporating inefficient cutting elements with a shear-type cutting action, positioned to engage the formation simultaneously with superabrasive cutting elements, which reduces bit aggressiveness by increasing the required weight-on-bit while maintaining controlled torque, thus mitigating stick-slip and impact damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional depth-of-cut control features are used, then cutting element penetration is limited, but bit aggressiveness is not adequately reduced during rapid transitions between harder and softer rock layers
Solution Approach 1:
The patent employs inefficient cutting elements with shear-type cutting action that dynamically adjust bit aggressiveness based on formation properties. These elements engage simultaneously with superabrasive cutting elements and provide adaptive response to rapid transitions between harder and softer rock layers, maintaining stable torque and weight-on-bit requirements across varying formation compressive strengths.
Solution Approach 2:
The bit incorporates a composite cutting structure combining superabrasive cutting elements (PDC) with inefficient cutting elements having shear-type cutting action. This composite approach allows the bit to leverage the high penetration capability of PDC elements while the shear-type elements provide aggressiveness control and stability during formation transitions.
2Productivity
If aggressive cutting structures are employed to achieve high ROP, then penetration rate increases, but torque to WOB ratio becomes excessively high causing overloading
Solution Approach 1:
The bit face is segmented into different functional zones with superabrasive cutting elements positioned to provide aggressive cutting action for high ROP, while inefficient cutting elements with shear-type action are positioned to control torque. This segmentation allows simultaneous optimization of penetration rate and torque management.
Solution Approach 2:
The patent changes the cutting mechanism parameter by introducing shear-type cutting action through inefficient cutting elements. This parameter change reduces the torque to WOB ratio while maintaining acceptable penetration rates, preventing overloading conditions.
3Productivity
If weight-on-bit is increased to maintain penetration in softer formations, then ROP is maintained, but torque increases causing stick-slip and impact damage
Solution Approach 1:
Inefficient cutting elements with shear-type cutting action serve as intermediaries between the drill string and formation. These elements absorb excess torque and weight-on-bit variations, preventing stick-slip phenomena and impact damage to both the formation and drilling equipment while maintaining stable penetration.
4Productivity
If superabrasive cutting elements are used to cut harder formations, then penetration efficiency is high, but sudden torque increase occurs when transitioning to softer zones
Solution Approach 1:
Inefficient cutting elements with shear-type cutting action are positioned to engage the formation simultaneously with superabrasive cutting elements. These elements provide preliminary torque control and prevent sudden torque increases when the bit transitions from harder to softer formation zones, protecting the drilling system from damage.
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 approach significantly reduces the potential for stick-slip and impact damage by allowing increased weight-on-bit without excessive torque, providing stable and predictable drilling performance across formations with varying compressive strengths.
Implementation Method 1
Incorporating inefficient cutting elements with a shear-type cutting action, positioned to engage the formation simultaneously with superabrasive cutting elements
Data Source
AI summary
An earth-boring tool comprising a body having first cutting elements mounted to an axially leading face, the first cutting elements each having a cutting face exposed to a height above the face of the body, the cutting faces of the first cutting elements back raked and facing a direction of intended rotation of the earth-boring tool. The earth-bring tool further comprises second cutting elements mounted to the axially leading face of the body adjacent first cutting elements in a cone region of the bit face, the second cutting elements each having a cutting face exposed to a height above the face of the body and configured for a shear-type cutting action, the cutting faces of the second cutting elements back raked to about a same or greater extent than the first cutting elements and generally facing the direction of intended rotation of the earth-boring tool.