Drilling Drive Sub Contour Profile for Cuttings Flow
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Solution Overview
Problem
Existing drive sub designs for drilling assemblies hinder the uphole flow of drilling fluid and cuttings due to a perpendicular radial wall, leading to cutting accumulation and excessive wear, and alignment issues with locking members can cause improper latching and damage during drilling operations.
Innovation Solution
A drive sub with a castellated edge featuring a contour profile that includes a radial ramp and channels to facilitate the flow of drilling fluid and cuttings, and wear-resistant members like polycrystalline diamond buttons or blades to prevent damage and improve alignment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a perpendicular radial wall is used at the downhole end of the drive sub, then the structure is simple and easy to manufacture, but it hinders the uphole flow of drilling fluid and cuttings, causing cuttings to become trapped and form abrasive bands that cause excessive wear
Solution Approach 1:
The patent applies curvature by replacing the perpendicular radial wall with a tapered surface that angles upward toward the outer circumference. This tapered contour creates a smooth transition that guides cuttings and drilling fluid upward and outward, eliminating the abrupt 90-degree corner that causes flow obstruction and cutting accumulation.
Solution Approach 2:
The patent adds a dimensional element by introducing a radial component to the flow path. The tapered surface redirects flow from a purely axial direction to include a radial outward component, allowing cuttings to escape the circumferential corner region and preventing abrasive band formation.
2Reliability
If locking members are provided to engage with slots on the drive sub, then the tool can be securely held, but misalignment between locking members and slots can prevent proper latching, requiring tool withdrawal and causing downtime
Solution Approach 1:
The patent applies preliminary action by providing alignment features such as tapered surfaces or guide surfaces on the drive sub that actively guide the locking members into proper alignment with the slots during the engagement process. This preliminary alignment action occurs before the locking members reach the final latched position, preventing misalignment issues and eliminating the need for tool withdrawal.
Solution Approach 2:
The patent introduces intermediary alignment features (such as tapered guide surfaces) that mediate between the approaching tool and the final latched position. These intermediary features gradually guide the locking members into correct alignment, acting as a transition zone that prevents direct misalignment and ensures reliable engagement.
3Reliability
If locking members project outwardly from the tool to engage with slots on the drive sub, then the tool can be securely locked, but the perpendicular radial wall creates a circumferential corner that traps cuttings against the locking members, causing excessive wear and shortening tool life
Solution Approach 1:
The patent applies curvature by replacing the perpendicular radial wall with a tapered surface that angles upward toward the outer circumference. This eliminates the sharp circumferential corner where cuttings become trapped against the locking members, thereby preventing abrasive wear and extending tool life while maintaining secure locking.
Solution Approach 2:
The patent converts the potentially harmful circumferential corner into a beneficial tapered surface. By angling the surface upward and outward, the design uses the same geometric feature to both maintain structural integrity for secure locking and to create a flow-path that actively directs cuttings away from the locking members, preventing wear.
Data Source
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AI summary
A drive sub for a drilling assembly includes a tubular body configured to receive and releasably engage a drilling tool. The body has inner and outer faces and further has a castellated edge provided on its operative downhole end, which edge defines a plurality of lugs separated from each other by intervening slots. In one aspect the drive sub has a contour profile provided at least partially along a circumference of the castellated edge, wherein the contour profile traverses the castellated edge substantially from the inner face to the outer face. In another aspect the drive sub has a channel provided in each of the lugs, wherein the channel at least partially traverses the lugs and leads from an inlet opening on the castellated edge to an outlet opening on the outer face. The contour profile and/or channel facilitate flow of drilling fluid and cuttings past the lugs during use.