Rotary Shoulder Drill Pipe Geometry Against Buckling and Box Swell
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Solution Overview
Problem
Conventional American Petroleum Institute (API) 5-inch drill pipes suffer from poor hydraulic efficiencies and mechanical performance due to buckling, box swell, pin collapse, and premature fatigue failure.
Innovation Solution
The development of a drill pipe with a rotary shoulder connection featuring primary and secondary angled and/or curved shoulder features for threaded pipe connections, enhancing hydraulic efficiency and mechanical strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If standard tapered thread connections are used in drill pipe, then the connection can be manufactured with conventional processes, but box swell occurs due to high axial compressive loads causing material yield and permanent deformation
Solution Approach 1:
The patent changes the geometric parameters of the thread connection by introducing a rotary shoulder with specific angles (15-30 degrees) and radii (0.125-0.250 inches) to redistribute the axial compressive loads. This parameter modification allows the connection to withstand box swell forces without permanent deformation while remaining manufacturable with standard processes.
Solution Approach 2:
The patent introduces curved or rounded shoulder features with specified radii at critical stress concentration points in the box connection. These curved transitions reduce stress concentration and prevent material yield under axial compression, eliminating box swell while maintaining conventional manufacturing capabilities.
2Device complexity
If standard tapered thread connections are used in drill pipe, then the connection structure is simple, but pin collapse occurs due to high axial compressive loads causing inward deformation of the pin nose
Solution Approach 1:
The patent modifies the geometric parameters of the pin connection by adding a rotary shoulder with controlled angles and radii. This changes the load distribution path and reduces stress concentration at the pin nose, preventing collapse under axial compression while adding minimal structural complexity.
Solution Approach 2:
The patent incorporates curved shoulder features with specific radii on the pin connection to eliminate sharp corners and stress concentration points. This curvature distributes the axial compressive loads more evenly, preventing pin nose collapse while maintaining a relatively simple overall structure.
3Productivity
If conventional API 5-inch drill pipe is used, then the pipe dimensions are standardized, but poor hydraulic efficiency results due to buckling under compressive loads
Solution Approach 1:
The patent changes the dimensional parameters of the drill pipe by introducing a non-standard outer diameter (5.276 inches) that optimizes the buckling resistance. This parameter adjustment increases the critical buckling load while improving hydraulic efficiency through better annular flow characteristics, deviating from the conventional API 5-inch standard.
4Device complexity
If standard single-shoulder or double-shoulder connections are used, then the connection design is conventional, but premature fatigue failure occurs due to combined box swell and pin collapse under alternating axial, torsional, and bending loads
Solution Approach 1:
The patent modifies the geometric parameters of the shoulder connection by introducing optimized angles (15-30 degrees) and radii (0.125-0.250 inches) that reduce stress concentration factors. This parameter optimization decreases the amplitude of stress cycles under alternating loads, significantly extending fatigue life and preventing premature failure while maintaining a conventional connection design.
Solution Approach 2:
The patent introduces curved shoulder features with controlled radii to eliminate sharp transitions in the connection geometry. This curvature distributes stresses more evenly during alternating axial, torsional, and bending loads, reducing fatigue stress concentration and preventing premature failure without substantially increasing design complexity.
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 average diameter ratio and wherein the average diameter ratio is from about 1.32 to about 1.58 for a production hole from about 7⅞-inches to about 12¼-inches. Methods of using the drill pipe are also disclosed.