Variable-Bore Drill Rod Structure for Faster Core Tripping
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Solution Overview
Problem
Conventional drill rods used in deep well drilling are heavy, leading to fatigue in components and equipment, and the slow tripping rate of core sample tubes due to drag and hydraulic pressure issues, which increases drilling time and cost.
Innovation Solution
A threaded drill string component with a hollow elongate body featuring a box end, pin end, and a cylindrical mid-body portion with variable inner diameter and male projections, designed to reduce weight while maintaining stiffness and load capacity, and preventing mid-body twisting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If conventional drill rods with constant internal diameter are used, then structural simplicity and manufacturing ease are maintained, but weight is excessive and tripping speed is reduced due to drag and hydraulic pressure
Solution Approach 1:
The drill rod applies local quality by varying the internal diameter at different sections. The intermediate section has a reduced internal diameter compared to the first and second sections, creating localized weight reduction in the middle portion while maintaining larger diameters at the ends for connection purposes. This non-uniform structure optimizes both weight and tripping performance.
Solution Approach 2:
The drill rod is segmented into three distinct sections with different internal diameters. The first section (with external threading), second section (intermediate portion), and third section (with internal threading) are differentiated by their internal diameter characteristics, allowing each segment to serve its specific function while contributing to overall weight reduction and improved tripping rate.
2Weight of moving object
If drill rod weight is reduced, then fatigue loads on components and equipment are decreased, but stiffness and support against bending and twisting may be compromised
Solution Approach 1:
The varying internal diameter structure applies local quality by concentrating weight reduction in the intermediate section while maintaining adequate material thickness and structural integrity at the end sections that require higher strength for threading and connection. This localized approach reduces overall weight while preserving necessary stiffness and load capacity.
3Weight of moving object
If the internal diameter is reduced in the intermediate section, then weight is reduced and tripping speed is improved, but manufacturing complexity increases
Solution Approach 1:
The manufacturing process is segmented into distinct stages corresponding to the three sections of the drill rod. Each section can be manufactured with its specific internal diameter characteristic, and the sections are then joined together through threading. This segmentation of the manufacturing process makes the complex varying-diameter structure more manageable and producible.
Data Source
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AI summary
Threaded drill string component having a hollow elongate body with a box end portion, an opposing pin end portion and a cylindrical mid-body portion that extends longitudinally between the respective box and pin end portions and has a variable wall diameter. The mid-body inner wail of the mid-body portion has at least one projecting portion or upset that is spaced from both the box and pin end portions and extends inwardly toward a central longitudinal axis of the hollow body and a plurality of troughs defined in the mid-body inner wall of the mid-body portion.