Roller Cone Drill Bit with Mixed Cutting Elements
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Solution Overview
Problem
Current drill bits for milling plugs in oil and gas wells are inefficient when dealing with both softer elastomer and composite materials, as they often rely solely on tungsten carbide inserts which are effective for harder materials but less efficient for softer materials, and may suffer from insert loss due to erosion and thermal issues.
Innovation Solution
The use of alternating rows of cemented metal carbide inserts and milled teeth on the roller cone cutter, where the inserts are placed on the heel row and milled teeth on the inner rows, optimizes milling efficiency across the plug's length without compromising durability, ensuring effective cutting of both softer and harder materials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If tungsten carbide inserts are used on all rows of the roller cone cutter, then durability is improved for harder materials, but milling efficiency deteriorates for softer elastomer and composite materials
Solution Approach 1:
The patent applies local quality by using different cutting element types in different locations on the roller cone cutter. Specifically, cemented metal carbide inserts are placed on the heel row (outermost row) to handle harder materials like metal slips and casing, while milled teeth are placed on inner rows to efficiently mill softer composite and elastomer materials. This spatial differentiation of cutting element properties optimizes performance for the specific material encountered at each radial position.
2Reliability
If tungsten carbide inserts are used on the heel row, then durability is improved for harder materials, but insert loss increases due to erosion and thermal issues
Solution Approach 1:
The patent protects the vulnerable heel row inserts by using cemented metal carbide which has superior erosion and thermal resistance compared to conventional milled teeth. This localized application of highly durable material at the outermost row where erosion and thermal effects are most severe reduces insert loss while maintaining overall bit durability.
Solution Approach 2:
The patent uses cemented metal carbide, a composite material consisting of tungsten carbide particles embedded in a metal binder matrix, for the heel row inserts. This composite structure provides both the hardness needed to cut harder materials and the toughness to resist erosion and thermal degradation, thereby reducing insert loss in the high-stress heel row location.
3Productivity
If milled teeth are used on inner rows, then milling efficiency is improved for softer materials, but durability deteriorates when encountering harder materials
Solution Approach 1:
The patent places milled teeth on inner rows where softer composite and elastomer materials are predominantly encountered, optimizing milling efficiency for these materials. The inner rows experience less erosion and thermal stress, making milled teeth suitable for these locations while maintaining overall bit reliability through the protective heel row inserts.
Data Source
AI summary
A roller cone drill bit having at least one roller cone cutter, the roller cone cutter having multiple rows of cutting elements, arranged concentrically around the axis of rotation of the roller cone. One row of cutting elements is located on the heel of the roller cone. Each of the rows of cutting elements includes both cemented tungsten carbide inserts and milled teeth as cutting elements.