Direct-Connect Drill Pipe With Three-Stage Shoulder Sealing
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Solution Overview
Problem
Conventional drill pipes fail under extreme conditions such as high temperatures, high pressures, and large stresses due to swelling of tool joint boxes, seal failures, thread mismatches, and root fractures, particularly lacking in sealing performance and mechanical resistance.
Innovation Solution
A directly connected drill pipe design featuring a tool joint pin and box with a three-step shoulder sealing structure and spiral protrusions on the main shoulders, providing enhanced sealing and mechanical resistance through a combination of axial and radial pre-tightening forces, distributing thread stresses uniformly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional drill pipes are used under extreme conditions, then basic drilling function is maintained, but sealing performance deteriorates and mechanical resistance decreases due to swelling of tool joint boxes, seal failures, and thread mismatches
Solution Approach 1:
The tool joint structure is segmented into multiple functional components: the drill pipe body, tool joint pin with external pipe section, and tool joint box with insertion section. The annular groove divides the tool joint pin into distinct sealing zones, allowing independent optimization of each segment's sealing function under extreme conditions
Solution Approach 2:
Different regions of the tool joint are given specialized local properties: the external pipe section and insertion section have specific dimensional tolerances for sealing, the tapered pipe threads provide mechanical connection, and the annular groove creates a localized sealing chamber. This local quality differentiation ensures reliable sealing at critical locations while maintaining overall structural integrity
2Strength
If conventional drill pipes are used under extreme conditions, then basic drilling function is maintained, but mechanical resistance to torsion and bending deteriorates due to root fractures and thread failures
Solution Approach 1:
The tapered pipe threads between the tool joint pin and box are pre-formed with precise geometry before assembly. The external pipe section and insertion section are pre-configured with specific dimensional relationships, ensuring that when connected, the threads engage correctly and distribute mechanical loads uniformly, preventing root fractures and thread failures under torsion and bending
Solution Approach 2:
The tool joint structure combines different material properties and structural forms: the drill pipe body and tool joint components are made from materials suitable for extreme conditions, while the composite structure of pin and box with tapered threads creates a unified load-bearing system that resists torsion and bending through combined mechanical action
3Reliability
If the tool joint structure is simplified, then manufacturing ease is improved, but sealing performance deteriorates due to insufficient sealing surfaces
Solution Approach 1:
The sealing function is segmented across multiple surfaces: the main sealing surface between the drill pipe body and tool joint pin, the auxiliary sealing surface in the annular groove region, and the sealing interface between the tool joint box and connection elements. This segmentation allows each sealing surface to be optimized independently while maintaining manufacturability
Solution Approach 2:
Sealing surfaces are provided with local quality enhancements through precise machining of the annular groove, external pipe section, and insertion section. These localized sealing zones concentrate sealing effort where most needed, achieving reliable sealing without requiring complex structures throughout the entire tool joint
4Strength
If the tool joint structure is simplified, then manufacturing ease is improved, but mechanical resistance deteriorates due to stress concentration in threads
Solution Approach 1:
The tapered pipe threads are pre-formed with optimized geometry that distributes mechanical stresses uniformly along the thread engagement length. The external pipe section and insertion section are pre-configured with specific dimensional relationships that prevent stress concentration at critical locations, reducing the risk of root fractures and thread failures under torsion and bending loads
Data Source
AI summary
A directly connected drill pipe applicable to extreme conditions includes a tool joint pin and a tool joint box, where an external pipe section is located on an external side of a threaded section of the tool joint pin, and an annular groove is formed between the external pipe section and the threaded section of the tool joint pin. An insertion section of the tool joint box can be inserted into the annular groove in a matched manner. A main shoulder of the tool joint pin is located at an end of the external pipe section, a main auxiliary shoulder of the tool joint pin is located on a bottom surface of the annular groove, and an auxiliary shoulder of the tool joint pin is located at a small end of the tool joint pin. The tool joint box has three corresponding shoulders which form a 3-stage sealing with the tool joint pin.