Coiled Tubing Injector Gripper Block Roughness
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Solution Overview
Problem
The increasing weight of coiled tubing in deep wellbores poses a challenge as existing gripper blocks in coiled tubing injector heads may not provide sufficient friction to prevent slippage, leading to damage and interference with precise positioning during well intervention operations.
Innovation Solution
Increasing the roughness of the gripping surfaces of the gripper blocks by applying coatings such as chromium carbide or treating them through methods like abrasive blasting to achieve a roughness greater than 20 μm, enhancing the coefficient of friction and preventing slippage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If the normal force applied by gripper blocks against coiled tubing is increased to support heavier tubing, then the friction force increases, but the coiled tubing may be damaged due to excessive force
Solution Approach 1:
The invention changes the surface roughness parameter of the gripper blocks from a smooth surface to a rough surface (Ra ≥ 20 μm). This parameter change increases the coefficient of friction between the gripper blocks and coiled tubing, allowing sufficient friction force to support heavier tubing without requiring excessive normal force that would damage the tubing.
Solution Approach 2:
The invention applies a composite coating system consisting of a bonding layer (such as nickel or copper) and a top layer (such as chromium carbide or boron-containing materials) on the gripper block surface. This composite structure provides both strong adhesion to the substrate and high surface roughness for increased friction, while maintaining durability and preventing tubing damage.
2Reliability
If the coefficient of friction between gripper blocks and coiled tubing is increased to prevent slippage, then the friction force increases, but the gripping surface may become too rough and damage the coiled tubing
Solution Approach 1:
The composite coating structure with a bonding layer and a rough top layer achieves high friction coefficients for slippage prevention while the controlled roughness profile (Ra ≥ 20 μm) is designed to grip without causing excessive stress or damage to the coiled tubing surface.
Solution Approach 2:
The rough surface treatment is applied specifically to the gripping surface of the gripper blocks, while the rest of the block maintains its original smooth finish. This localized quality change ensures high friction only where needed for gripping, without affecting other functions of the gripper blocks.
3Reliability
If coatings are applied to increase surface roughness, then the coefficient of friction increases, but the manufacturing process becomes more complex
Solution Approach 1:
The invention uses established surface treatment processes (such as shot blasting, sand blasting, or chemical etching) that are well-known in manufacturing. These processes change the surface roughness parameter to Ra ≥ 20 μm using conventional equipment and techniques, avoiding the need for complex or proprietary manufacturing processes.
4Reliability
If the gripping surface is made rougher to increase friction, then the coefficient of friction increases, but the surface area for contact may decrease
Solution Approach 1:
The surface roughness treatment increases the coefficient of friction through enhanced mechanical interlocking and adhesion forces. The roughness profile (Ra ≥ 20 μm) is designed to provide sufficient friction without significantly reducing the overall contact area, as the peaks and valleys of the rough surface still maintain broad contact with the coiled tubing.
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 increased roughness effectively prevents slippage of coiled tubing, maintains the integrity of the tubing, and ensures precise positioning during well intervention operations by enhancing the friction force without damaging the coiled tubing.
Implementation Method 1
The friction force is comprises of the normal force applied by the gripper blocks against the coiled tubing 30 and the coefficient of friction between the gripper blocks and the coiled tubing 30
Implementation Method 2
Treating the gripping surfaces may comprise abrasive blasting or shot peening
Data Source
AI summary
A method of increasing a roughness of coiled tubing injector blocks that includes providing a pair of gripper blocks each having a gripper surface configured to grip coiled tubing within an injector head and increasing a first roughness on the gripping surfaces to a second roughness. A coating may be applied to the gripping surfaces to increase the roughness. The coating may be chromium carbide, molybdenum boride, iron boride, titanium boride, or a transitional metal boride. The gripping surfaces may be treated to increase the roughness to a second roughness. The gripping surfaces may be blasted by abrasives or shot peened to increase the roughness. The second roughness may be greater than 20 μm. A system to inject coiled tubing into a wellbore may include an injector head, coiled tubing, and at least two gripper blocks having a gripping surface with a roughness of at least 20 μm.