Concave Drill Bit Cutters for Breaking Ribbon Cuttings
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Solution Overview
Problem
Conventional drill bits with flat cutting faces face challenges when drilling soft formations like shale and claystone, as they experience increased frictional heat and cutter damage due to continuous ribbon-shaped cuttings, leading to reduced drilling efficiency and potential clogging issues.
Innovation Solution
The development of a cutter with a concave surface featuring a combination of planar and curved surfaces, including a chamfer extending to the cutting edge, which reduces the back rake angle and incorporates features like cutting ridges or splines to break and evacuate cuttings effectively, thereby improving cutting efficiency and reducing frictional heat.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a flat cutting face with conventional back rake angle is used, then the cutter can maintain structural strength, but it generates continuous ribbon-shaped cuttings that cause increased frictional heat and cutter damage
Solution Approach 1:
The patent applies curvature by transitioning from a flat cutting face to a concave cutting face with reduced variable back rake angle. This curved surface geometry changes the cutting action from producing continuous ribbons to producing segmented chips, thereby improving drilling efficiency while maintaining cutter strength through the optimized concave profile
2Productivity
If a smaller back rake angle is used to improve cutting efficiency in soft formations, then penetration rate increases, but frictional heat and cutter wear increase due to continuous ribbon cuttings
Solution Approach 1:
The concave cutting face with reduced variable back rake angle creates a curved surface that changes the chip formation mechanism. This curvature allows the cutter to maintain a smaller effective back rake angle for improved penetration while the segmented chip geometry reduces continuous contact and frictional heat generation
Solution Approach 2:
The concave surface geometry segments the continuous ribbon-shaped cuttings into discrete chips. This segmentation breaks the continuous contact between cutter and formation, reducing frictional heat accumulation while maintaining the penetration benefits of a smaller back rake angle
3Device complexity
If a flat cutting face is used, then the cutter structure is simple, but continuous ribbon cuttings cause clogging and evacuation difficulties
Solution Approach 1:
The concave cutting face introduces a curved surface geometry that naturally segments cuttings during the cutting process. This curvature-based design achieves improved cuttings evacuation without significantly increasing structural complexity, as the concave profile is integrated into the cutter body
4Ease of manufacture
If conventional cutters are used in soft formations, then standard cutter design can be applied, but cutting efficiency decreases due to increased friction and heat
Solution Approach 1:
The patent applies local quality by modifying only the cutting face surface geometry (creating a concave profile with reduced variable back rake angle) while maintaining the overall cutter structure and manufacturing processes. This localized modification improves cutting efficiency in soft formations without requiring complete redesign of the cutter manufacturing approach
Data Source
AI summary
A drill bit for cutting formation comprises a bit body, a plurality of cutters, and a plurality of blades with pockets to accommodate the cutters, respectively. In an embodiment, the plurality of cutters comprise a substrate, an ultra-hard layer, a concave surface on the top of the ultra-hard layer, wherein the concave surface comprises a plurality of planar and curved surfaces.