Ground-Down Tubular Centralizer Assembly for Wellbore Restrictions
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Solution Overview
Problem
Bow-spring centralizers face damage and reduced effectiveness when passing through tight restrictions in wellbores due to limited clearance, and the tolerance in oilfield tubulars' outer diameters complicates precise clearance determination.
Innovation Solution
A centralizer assembly with a tubular featuring a ground-down region of consistent wall thickness and a raised region, where a centralizer is positioned and retained axially, allowing for flexible rib expansion and protection from damage during passage through restrictions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If bow-spring centralizers are used to maintain concentricity in wellbores with restrictions, then the centralizer can pass through restrictions by collapsing radially, but the flexible ribs may be damaged and the ability to provide standoff is reduced
Solution Approach 1:
The tubular is divided into distinct regions: a ground-down region with reduced outer diameter and constant wall thickness, and raised regions with larger outer diameter. This segmentation allows the centralizer to be positioned specifically in the ground-down region, providing a controlled environment for rib expansion that prevents damage while maintaining adaptability.
Solution Approach 2:
The ground-down region creates a localized area with specific geometric properties (reduced outer diameter, constant wall thickness) that is optimized for centralizer placement. This local modification provides the necessary clearance for the centralizer ribs to expand without damage, while the rest of the tubular maintains its original strength and dimensions.
2Reliability
If a ground-down region is created in the tubular to accommodate the centralizer, then the centralizer is protected from damage, but the manufacturing complexity increases
Solution Approach 1:
The ground-down region is created by modifying the outer diameter parameter of the tubular in a specific axial region. This parameter change is achieved through controlled material removal (grinding or machining) to create a region with constant, reduced outer diameter and constant wall thickness, which simplifies the geometry compared to tapered transitions.
3Strength
If the wall thickness in the ground-down region is kept constant, then the structural integrity is maintained, but the outer diameter must be reduced
Solution Approach 1:
The constant wall thickness in the ground-down region is achieved by locally modifying only the outer surface of the tubular while preserving the inner surface. This creates a region where the wall thickness remains constant at its original value, but the outer diameter is reduced, providing the necessary clearance for the centralizer without compromising structural integrity.
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 centralizer assembly maintains effective annular clearance and standoff while preventing damage by allowing flexible rib expansion and axial retention, ensuring reliable operation across varying wellbore sizes and tolerances.
Implementation Method 1
The ribs are expanded outward, and may be resilient, such that the bow-springs centralizers are capable of centralizing the tubular in the wellbore across a range of wellbore sizes
Data Source
AI summary
A centralizer assembly includes a tubular comprising a ground-down region and a raised region. A wall thickness of the tubular in the ground-down region is less than a wall thickness of the tubular in the raised region, and the wall thickness of the tubular in the ground-down region is substantially constant as proceeding around the tubular in the ground-down region. The centralizer assembly also includes a centralizer disposed at least partially in the ground-down region.