Drill Pipe Shoulder Geometry for Buckling and Fatigue Resistance
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Solution Overview
Problem
Conventional API 5-inch drill pipes suffer from poor hydraulic efficiencies and mechanical performance due to issues like buckling, box swell, pin collapse, and premature fatigue failure, leading to misalignment and permanent damage of threads.
Innovation Solution
The development of a drill pipe with improved rotary shoulder connections featuring angled and/or curved primary and secondary shoulders, optimized tool joint dimensions, and enhanced thread forms to enhance hydraulic efficiency, buckling strength, and mechanical performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If standard double-shoulder connections are used, then thread connection is achieved, but box swell causes material yielding and connection deformation
Solution Approach 1:
The patent modifies the geometric parameters of the connection shoulders by introducing a curved profile with specific radius of curvature (R1) and axial height (H1), changing the stress distribution characteristics to prevent box swell and material yielding under axial compressive loads
Solution Approach 2:
The patent applies a curved shoulder profile instead of a straight shoulder, using a specified radius of curvature to distribute stresses more evenly across the connection interface, eliminating the box swell phenomenon caused by concentrated stresses in standard connections
2Strength
If standard single-shoulder connections are used, then thread connection is achieved, but pin collapse causes connection deformation
Solution Approach 1:
The patent modifies the pin shoulder geometric parameters including the radius of curvature (R2) and axial height (H2), optimizing the stress distribution to prevent pin collapse under high axial compressive loads and alternating stresses
Solution Approach 2:
The patent implements a curved pin shoulder profile with specified radius of curvature to distribute compressive stresses evenly, preventing the pin collapse that occurs in standard straight-shoulder connections under high axial loads
3Adaptability or versatility
If conventional API 5-inch drill pipe is used, then standardization is maintained, but poor hydraulic efficiency and buckling occur
Solution Approach 1:
The patent optimizes the tool joint dimensions and thread form locally while maintaining the standard 5-inch drill pipe body dimensions, improving hydraulic efficiency at the connection interface without compromising overall standardization and compatibility
4Ease of manufacture
If standard connections are used, then manufacturing simplicity is maintained, but premature fatigue failure occurs
Solution Approach 1:
The patent optimizes the geometric parameters of the shoulders and threads to reduce stress concentration factors, extending fatigue life under alternating axial, torsional, and bending loads while maintaining manufacturability through standard machining processes
Data Source
AI summary
A drill pipe comprises a drill pipe body having a drill pipe body outer diameter and a drill pipe body inner diameter, wherein the drill pipe body outer diameter is from about 5.1-inches to about 5.4-inches and the drill pipe body inner diameter is from about 4.4-inches to about 4.6-inches; and a tool joint comprising a rotary shoulder box connection; wherein the drill pipe has an optimization ratio and wherein the optimization ratio is at least about 0.68 for a production hole from about 7⅞-inches to about 12¼-inches. Methods of using the drill pipe are also disclosed.