Torque-Less Threaded Connection for Directional Drilling
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Solution Overview
Problem
Conventional threaded connections in directional drilling operations are prone to premature failure due to severe torque and longitudinal stresses, leading to costly excavation and repair operations when tools become stuck in boreholes.
Innovation Solution
A torque-less coupling design featuring a multi-lead thread form and non-threaded, slightly tapered surfaces with a torque collar to prevent torque transmission through the threaded portions, ensuring easy assembly and disassembly, and distributing loads to prevent stress concentrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional threaded connections are used to connect drill tools to drill string, then the connection can transmit torque and longitudinal stresses, but the connection is prone to premature failure due to severe torque and longitudinal stresses
Solution Approach 1:
The connection is divided into two functional segments: a torque-transmitting interface (perpendicular bearing surfaces between box and pin) and a torque-free threaded connection section. This segmentation allows the threaded portion to avoid torque loads while still providing secure mechanical connection, eliminating the stress concentration that causes premature failure in conventional single-function threaded connections.
Solution Approach 2:
The perpendicular bearing surfaces act as an intermediary mechanism that transfers torque loads away from the threaded connection. Instead of the threads directly transmitting torque, the bearing surfaces serve as a mediator that handles torque transmission, allowing the threaded portion to function solely for mechanical coupling without stress concentration.
2Ease of operation
If conventional threaded connections are used, then the connection can be assembled and disassembled, but the assembly and disassembly process is time-consuming and requires high torque
Solution Approach 1:
By separating the torque transmission function (handled by perpendicular bearing surfaces) from the connection function (handled by threads), the design enables quick make-up and break-out operations. The threaded portion only needs to engage for mechanical coupling without the added complexity of torque transmission, significantly reducing assembly and disassembly time.
Solution Approach 2:
The multi-lead thread form changes the geometric parameters of the thread, providing faster engagement and disengagement compared to conventional single-lead threads. This parameter change reduces the number of revolutions needed for make-up and break-out, directly reducing operation time.
3Power
If threaded connections are subjected to severe torque loadings, then the connection can transmit power, but the useful service lifetime of the connection is reduced
Solution Approach 1:
The connection design segments the load paths: torque loads are transmitted through the perpendicular bearing surfaces between box and pin, while the threaded connection handles only axial and lateral loads. This segmentation protects the threaded portion from torque-induced stress concentrations, extending service lifetime while maintaining full power transmission capability through the bearing surfaces.
4Productivity
If the threaded connection is designed for easy assembly, then the connection can be quickly connected and disconnected, but the connection may lack sufficient strength to handle severe torque loads
Solution Approach 1:
The design segments functions so that assembly speed is optimized by the simplified threaded engagement (without torque transmission requirements), while connection strength is maintained by the separate perpendicular bearing surfaces that handle torque loads. This segmentation allows independent optimization of both assembly speed and strength.
Solution Approach 2:
The perpendicular bearing surfaces serve as an intermediary that provides the strength needed for torque transmission without requiring the threaded connection to be over-designed for torque handling. This intermediary mechanism enables fast assembly while maintaining sufficient strength through a different load path.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution extends the useful service lifetime of the threaded connection by enhancing strength and durability, reducing the risk of tool sticking and associated costly repairs, while allowing quick connection and disconnection without transmitting torque through the threaded sections.
Implementation Method 1
A threaded tapered section extends between the first and second circumferential surfaces, the threaded tapered section including threads thereon. The threads on the threaded tapered section make up a multi-lead thread form.
Implementation Method 2
A threaded tapered section extends between the first and second circumferential surfaces, the threaded tapered section including threads thereon. At least one of the non-threaded, first and second circumferential surfaces are slightly tapered.
Implementation Method 3
The up-hole end portion is configured to interface with the drill string as part of a torque-less coupling. In one preferred form of the disclosure, the first and second non-threaded, circumferential surfaces are both slightly tapered surfaces.
Data Source
Figure 1
Figure 2
Figure 2A
AI summary
A torque-less threaded connection is shown for connecting a drill tool to a drill string for use in horizontal directional drilling operations. An up-hole end portion has a female, box end opening with a non-threaded, slightly tapered first circumferential surface having a first median inner diameter; a non-threaded, slightly tapered second circumferential surface having a second inner diameter that is larger than the first diameter. A threaded tapered section extends between the first and second circumferential surfaces. The threaded tapered section has threads thereon which make up a multi-lead thread form. The downhole end portion of the coupling has mating external pin surfaces for engaging the internal surfaces of the up-hole end portion. A torque collar slides over portions of the up-hole and downhole end portions and prevents relative rotation between the downhole and up-hole portions and prevents toque from being transmitted to the threaded portions of the connection.