Stop Collar Assembly Tapered Slip Design for Oilfield Casing
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Solution Overview
Problem
Conventional stop collars face challenges in securely attaching to oilfield casing tubulars due to industry-accepted variations in tubular dimensions, leading to issues with axial load-bearing capacity, slippage, and compatibility with close-tolerance casing schemes, which affects their ability to withstand high axial loads without loosening.
Innovation Solution
The stop collar assembly features a collar with tapered surfaces and slips that interact to provide a secure grip on the tubular, allowing for reliable attachment and axial load transmission, while accommodating diameter variations through adjustable taper angles and slip configurations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional stop collars are used to attach to oilfield casing tubulars, then they can provide basic axial load-bearing capacity, but they fail to maintain secure attachment due to industry-accepted variations in tubular dimensions, leading to slippage and loosening under high axial loads
Solution Approach 1:
The stop collar incorporates adjustable taper angles and slip configurations that can be modified to accommodate different tubular outer diameters within the acceptable range. By changing the geometric parameters of the taper surfaces and slip positions, the stop collar maintains secure attachment across varying tubular dimensions while preserving axial load-bearing capacity.
Solution Approach 2:
The stop collar design allows for dynamic adjustment of the slip position along the taper surface. This dynamic configuration enables the slip to self-adjust to the actual tubular outer diameter, ensuring continuous secure attachment without slippage even when dimensions vary within the industry-accepted range.
2Ease of manufacture
If stop collars are designed with fixed dimensions to match nominal tubular sizes, then manufacturing is simplified, but they cannot accommodate actual tubular diameter variations, resulting in poor attachment reliability
Solution Approach 1:
Rather than manufacturing multiple fixed-dimension stop collars for different tubular sizes, the invention uses a single design with adjustable parameters. The taper angle and slip position can be modified during installation or adjustment to match the actual tubular outer diameter, maintaining both manufacturing simplicity and attachment reliability.
3Strength
If stop collars are designed to withstand high axial loads of 50,000 lbs or greater, then load-bearing capacity is improved, but the attachment mechanism becomes more complex and difficult to secure consistently
Solution Approach 1:
The invention extracts the complexity from the attachment mechanism by using a simplified slip-on-taper design without requiring multiple fasteners, threads, or complex locking mechanisms. The entire attachment and load-bearing function is achieved through the geometric interaction of the slip and taper surfaces, reducing device complexity while maintaining high axial load capacity of 50,000 lbs or greater.
4Manufacturing precision
If stop collars are mounted on casing strings to restrict axial movement of centralizers, then centralizer positioning is improved, but the stop collars themselves may slip on the tubular under load, compromising the positioning
Solution Approach 1:
The dynamic adjustment capability of the slip position on the taper surface allows the stop collar to maintain optimal grip stability under varying axial loads. This ensures that the centralizer positioning remains accurate and that the stop collar does not slip, preserving both positioning precision and grip stability simultaneously.
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 solution ensures a consistently secure and reliable attachment to tubulars, capable of withstanding high axial loads without slippage, and is designed to navigate restricted diameter locations effectively, addressing the limitations of conventional stop collars.
Implementation Method 1
The first slip taper is configured to contact the collar first taper. When the collar first taper is in contact with the first slip taper, a distance from the central radial axis to the start of the first slope is less than a distance from the central radial axis to the first slip bottom end
Implementation Method 2
A stop collar mounted above a centralizer on the casing string restricts upward movement of the centralizer while lowering the casing string into the wellbore. Likewise, a stop collar mounted below a centralizer on the casing string restricts downward movement of the centralizer while lifting the casing string in the wellbore
Data Source
AI summary
A stop collar assembly includes a collar having inner and outer surfaces. The inner surface includes a taper. The outer surface includes a slope such that an outer diameter at a start of the slope is greater than an outer diameter at an end of the slope. The stop collar assembly further includes a slip having a bottom end and a taper adjoining the bottom end. The slip taper is configured to contact the collar taper. When the collar taper is in contact with the slip taper, a distance from a central radial axis of the collar to the start of the slope is less than a distance from the central radial axis to the slip bottom end, and the distance from the central radial axis to the slip bottom end is less than a distance from the central radial axis to the end of the slope.