Downhole Tool Guide Mechanism for Rotational Alignment
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Solution Overview
Problem
Current methods for changing drill bits and reamer bits in boreholes require tripping the entire drill string, which is time-consuming and prone to misalignment, leading to potential damage and inefficiencies in drilling fluid distribution, especially in broken or fractured ground conditions.
Innovation Solution
A downhole device delivery and drive transfer system that includes a sub and a tool with a guide mechanism to ensure correct rotational alignment and a fluid flow control system for efficient torque transfer and fluid management, allowing for the direct replacement of drill bits and reamer pads without pulling the drill string, and facilitating changes in drilling direction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If tripping the drill string is used to replace drill bits, then the drill bit can be replaced, but the process takes more than 24 hours and is time-consuming
Solution Approach 1:
The drill string system is segmented into modular components: a drive sub that remains in the hole, a delivery tool that travels through the string, and interchangeable drill bits. This segmentation allows the drill bit to be replaced independently without retrieving the entire drill string, reducing replacement time from over 24 hours to a fraction of that time.
Solution Approach 2:
A drive sub acts as an intermediary device installed at the downhole end of the drill string. It provides a interface for the delivery tool to engage and transfer torque, enabling drill bit replacement while the drill string remains in place. The drive sub mediates between the surface delivery system and the downhole drill bit.
2Productivity
If the Mindrill system is used to change drill bits, then tripping is avoided, but misalignment between drive dogs and drill string holes may occur causing severe damage
Solution Approach 1:
The delivery tool is preliminarily oriented using a guide mechanism (edge and portion) that establishes correct rotational alignment before the drive dogs are released. This preliminary orientation ensures that when the drive dogs engage the holes in the drive sub, they are properly aligned, preventing misalignment damage while maintaining high replacement efficiency.
Solution Approach 2:
The guide mechanism provides feedback on the rotational orientation of the delivery tool as it approaches the drive sub. The edge and portion interaction creates a mechanical feedback system that guides the tool to the correct orientation, ensuring reliable alignment between drive dogs and drill string holes before torque transfer begins.
3Temperature
If water is pumped down the string to flow through the tool to the drill bit, then cooling and cleaning are achieved, but the fluid bypasses the reamer bit pads causing excessive wear and damage
Solution Approach 1:
The fluid flow system is configured with different flow paths for different components: one path directs fluid through the drill bit for cooling and cleaning, while another path directs fluid to the reamer pads for their specific cooling and lubrication needs. This local differentiation ensures each component receives appropriate fluid treatment, preventing reamer pad wear while maintaining drill bit cooling.
Solution Approach 2:
The fluid distribution system is segmented into separate flow channels: a main flow path through the drill bit and a dedicated flow path to the reamer pads. This segmentation allows independent control of fluid distribution to different components, ensuring the reamer pads receive sufficient fluid for cooling and lubrication without compromising drill bit performance.
Data Source
Figure 1
Figure 2~4
Figure 5a~5b
AI summary
A downhole device delivery and drive transfer system 10 comprises a sub 12 which is arranged to attach to a drill string 14 and a tool 16 which is configured to enable it to travel through the drill string 14 and releasably couple to the sub 12. The sub 12 and the tool 16 are arranged so that when they are releasably coupled to each other torque imparted to the drill string is transferred by the sub 12 to the tool 16. The tool 16 is arranged to carry one or more devices for performing one or more downhole functions such as core drilling, hole reaming or wedge placement for directional drilling. The system 10 also has a guide mechanism 24 that operates between the sub 12 and the tool 16 to guide the tool 16 to a known rotational orientation relative to the sub 12 as the tool 16 travels into the sub 12. A fluid control system controls the flow of fluid through the tool through a downhole outlet and and a plurality of ports intermediate opposite ends of the tool.