Asymmetric Shaped Inserts for Earth-Boring Bit Stability
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Solution Overview
Problem
Conventional earth-boring tools with PDC cutting elements face instability and damage in hard subterranean formations due to limited weight-on-bit and torque-on-bit, leading to reduced drilling efficiency and increased mechanical specific energy.
Innovation Solution
The use of an earth-boring tool with asymmetrically distributed second shaped inserts, which provide greater exposure relative to first shaped inserts, enhances imbalance forces and stability by selectively positioning these inserts on specific blades to counteract natural imbalance forces, thereby improving drilling efficiency and reducing damage to cutting elements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If weight-on-bit and torque-on-bit are increased to improve drilling efficiency, then rate-of-penetration increases, but the PDC cutting elements become prone to damage and the bit becomes unstable
Solution Approach 1:
The patent applies asymmetry by creating an imbalance force through non-uniform distribution of cutting elements and shaped inserts on the bit blades. Specifically, different blades have different numbers and positions of shaped inserts, generating a net imbalance force that stabilizes the bit during rotation without requiring excessive weight-on-bit or torque-on-bit, thus preventing PDC cutting element damage while maintaining high rate-of-penetration
Solution Approach 2:
The shaped inserts act as counterweights that generate an imbalance force to counteract the natural whirl tendency of the bit. By strategically positioning inserts with greater exposure on specific blades, the patent creates a stabilizing force that opposes the harmful precessional motion, effectively reducing bit vibration and instability without compromising cutting performance
2Productivity
If rotation speed is increased to achieve higher rate-of-penetration in hard formations, then drilling efficiency improves, but dynamic dysfunctions and damage to cutting elements increase
Solution Approach 1:
The patent uses asymmetric distribution of shaped inserts to generate a stabilizing imbalance force that counteracts dynamic dysfunctions at high rotation speeds. The non-uniform placement creates a net force that opposes the harmful vibrations and precessional motions that typically occur at elevated RPMs, allowing the bit to maintain stability and cutting element integrity while achieving high rate-of-penetration in hard formations
3Ease of manufacture
If conventional bit designs are used, then manufacturing is simple, but the bits exhibit notable vibration and instability in harder formations
Solution Approach 1:
The patent introduces asymmetry through the non-uniform distribution of shaped inserts on different blades, which generates a stabilizing imbalance force. This design choice may increase manufacturing complexity slightly compared to conventional uniform designs, but it effectively reduces bit vibration and instability in harder formations, providing superior performance that justifies the additional manufacturing consideration
Solution Approach 2:
The patent applies local quality by varying the number, position, and exposure of shaped inserts on different blades according to their specific functions and locations. Each blade receives a customized configuration of inserts that optimizes its contribution to overall bit stability and cutting performance, creating a tailored approach that addresses local requirements rather than using a uniform design throughout
Data Source
AI summary
An earth-boring tool includes a body, blades extending longitudinally and generally radially from the body, and primary cutting elements located on each blade. The earth-boring tool may include a group of at least two adjacent blades comprising the primary cutting elements and one or more first shaped inserts located rotationally behind the primary cutting elements, and one or more additional blades comprising the primary cutting elements and one or more second shaped inserts located rotationally behind the primary cutting elements, the second shaped inserts exhibiting a greater exposure relative to the first shaped inserts. Distribution of the second shaped inserts relative to the longitudinal axis may be asymmetric with respect to the longitudinal axis of the body. Methods include drilling a subterranean formation including engaging a formation with the primary cutting elements, the first shaped inserts, and the second shaped inserts of the earth-boring tool.