Drill Bit Cutter Elements with Varying Backrake Angles
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Solution Overview
Problem
Existing fixed cutter drill bits experience torsional vibrations during drilling, particularly when encountering heterogeneous formations, which can negatively impact drilling performance and reduce the bit's rate of penetration and durability.
Innovation Solution
The drill bit design incorporates cutter elements with cutting face geometries defining different effective backrake angles, specifically a first cutter element with a planar cutting face and a second cutter element with a non-planar cutting face, arranged in an alternating manner to reduce torsional vibrations while maintaining suitable rate of penetration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If cutter elements with uniform cutting face geometry are used, then the drilling process is simple and consistent, but torsional vibrations occur when encountering heterogeneous formations
Solution Approach 1:
The patent applies local quality by varying the effective backrake angle of individual cutter elements based on their specific location and function. Inner cutter elements have different backrake angles compared to outer cutter elements, allowing each to be optimized for its local cutting conditions and formation type, thereby reducing vibrations while maintaining high rate of penetration
Solution Approach 2:
The cutting structure is segmented into multiple cutter elements with different geometric characteristics. By dividing the uniform cutter element design into varied segments with different effective backrake angles, the system can handle heterogeneous formations more effectively without experiencing torsional vibrations
2Reliability
If cutter elements with varying effective backrake angles are used, then torsional vibrations are reduced, but the device complexity increases
Solution Approach 1:
The patent changes geometric parameters of cutter elements, specifically the effective backrake angle, to optimize performance. By adjusting this parameter across different cutter elements rather than changing the fundamental structure, the solution reduces vibrations while limiting the increase in device complexity
Data Source
AI summary
A drill bit for drilling a borehole in an earthen formation has a central axis and a cutting direction of rotation. The bit includes a bit body configured to rotate about the axis in the cutting direction of rotation. The bit body includes a bit face. The bit also includes a blade extending radially along the bit face. In addition, the bit includes a first cutter element mounted to a cutter-supporting surface of the blade and a second cutter element mounted to the cutter-supporting surface of the blade. The first cutter element has a central axis and includes a first forward-facing cutting face including a first cutting tip distal the cutter supporting surface and a first planar surface extending radially from the first cutting tip toward the central axis of the first cutter element. The first planar surface is oriented at a first effective backrake angle measured between the cutter supporting surface and a surface vector of the first planar surface. The second cutter element has a central axis and comprises a second forward-facing cutting face including a second cutting tip distal the cutter supporting surface and a second planar surface extending radially from the second cutting tip toward the central axis of the second cutter element. The second planar surface is oriented at a second effective backrake angle measured between the cutter supporting surface and a surface vector of the second planar surface. The second effective backrake angle is greater than the first effective backrake angle.