Bow-Spring Stack Centralizer for Deviated Wellbore Drag Reduction
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Solution Overview
Problem
In hydrocarbon exploration, wireline logging tools face challenges in descending deviated wells due to high friction and drag forces, which prevent accurate data acquisition and increase operational costs, as existing centralizers either collapse or induce unwanted drag, limiting their effectiveness beyond 60 degrees from vertical.
Innovation Solution
A centralizing device with a stack of bow-springs, where two or more bow-springs are combined to provide a lower spring constant and thicker overall structure, allowing for axial movement and radial force distribution to maintain centering force across varying wellbore diameters, reducing drag and ensuring tool string descent in deviated wells.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a single bow-spring is used for centering, then the structure is simple, but the centering force is insufficient in small bore diameters and drag is excessive in large bore diameters
Solution Approach 1:
The single bow-spring is divided into multiple separate bow-springs (first bow-spring, second bow-spring, etc.) arranged circumferentially around the tool string. Each bow-spring independently contacts the bore wall, allowing the system to adapt to varying bore diameters while distributing the centering force across multiple contact points, thereby reducing drag on any single spring.
Solution Approach 2:
Multiple bow-springs are combined to work together as a unified centering system. The first bow-spring, second bow-spring, and subsequent bow-springs cooperate to provide cumulative centering force that adapts to different bore sizes, achieving both sufficient centering force and reduced drag through their collective operation.
2Ease of operation
If the tool string is lowered under gravity alone, then the device is simple, but friction and drag forces prevent descent in deviated wells
Solution Approach 1:
The bow-springs generate a radial outward force that counteracts the lateral component of the tool string weight acting perpendicular to the wellbore wall. This counterforce reduces the normal force between the tool string and bore wall, thereby reducing friction and drag, enabling successful descent in deviated wells.
Solution Approach 2:
The bow-springs change the operational parameters of the tool string by introducing a radial centering force that modifies the contact mechanics between the tool string and bore wall. This parameter change reduces the effective friction coefficient and enables descent in wells where gravity alone would be insufficient.
3Strength
If bow-springs are made thicker to increase centering force, then centering capability improves, but drag increases and descent is prevented
Solution Approach 1:
Instead of using a single thick bow-spring, the centering force is distributed across multiple thinner bow-springs arranged circumferentially. Each bow-spring has reduced thickness and consequently reduced individual drag, but the collective centering force of all bow-springs combines to provide sufficient total centering capability.
Solution Approach 2:
The solution transitions from a single-point centering mechanism to a distributed circumferential arrangement. By spreading the centering function across multiple spatial locations (circumferential positions), the system achieves sufficient total centering force while minimizing drag at any single contact point.
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 device effectively centralizes the tool string across a wide range of bore diameters, reducing drag and maintaining centering force, enabling successful data acquisition in deviated wells beyond previous limitations, thus optimizing wireline logging operations and reducing operational costs.
Implementation Method 1
two or more bow-springs stacked together in a bow-spring stack, each bow-spring in the bow-spring stack extending between the first and second pivot members
Implementation Method 2
two or more bow-springs stacked together in a bow-spring stack... allowing for axial movement and radial force distribution to maintain centering force
Data Source
AI summary
A device for centering a sensor assembly in a bore has three or more bow-spring assemblies spaced circumferentially apart around a longitudinal axis of the device and pivotally attached between first and second support members. Each bow-spring assembly comprises two or more bow-springs stacked together in a bow-spring stack, with each bow-spring in the bow-spring stack extending between first and second pivot members pivotally attached to the first and second support members.