Modular Low-Clearance Centralizer and Method of Making Modular Low-Clearance Centralizer

Abstract

A low-clearance bow spring centralizer (10) can be made by providing a plurality of bow spring modules (54), each having an elongate rib (52) with a first integrally-formed collar segment (54) at a first end and a second integrally-formed collar segment (56) at a second end wherein the first collar segment (54) and the second collar segment (56) are joined to adjacent first and second collar segments, respectively. The bow spring modules may be interlinked by welding a seam (55) formed between abutting sides of adjacent pairs of first collar segments and / or second collar segments. The sides (54a) of the first collar segment and the sides (56a) of the second collar segment may each be perpendicular to the axis of the centralizer bore, and seams (55) therebetween may be welded to form a first centralizer collar and a second centralizer collar, coupled one to the other by the ribs (52).

Description

BACKGROUND OF THE INVENTION[0001]1. Field of the Invention[0002]This invention is directed to a low-clearance centralizer to center a tubular within a borehole, and to a low-cost method of making a modular low-clearance centralizer that can radially collapse to pass through a restriction, and that can deploy to generally center a tubular within a drilled borehole.[0003]2. Description of the Related Art[0004]Centralizers can be secured at spaced intervals along a tubular string to provide radial stand-off between the tubular and the wall of a drilled borehole in which the tubular is installed. Bow spring centralizers generally comprise a pair of aligned collars defining a bore therethrough to receive the tubular, and a plurality of angularly-spaced bow springs biased to provide stand-off. Bow spring centralizers may collapse to pass, e.g., along with the tubular, through restrictions, and to deploy to provide a generally uniform annulus between the exterior of the tubular and the wal...

AI Technical Summary

Benefits of technology

The present invention provides an efficient and inexpensive method to make a low-clearance modular bow spring centralizer to center a tubular within a drilled borehole. The method involves interlinking multiple bow spring modules together to form a centralizer with low-clearance collars. Each bow spring module has an elongate rib with an integrally formed first collar segment and a second collar segment at its ends. The method may include automating the process of forming bow spring modules by interlinking a plurality of bow spring modules together. The resulting bow spring centralizer is efficient and can be used at a lower cost than a centralizer made from a single piece of material. The bow spring modules can be stacked and handled, and the residual material stresses resulting from cold working of the material can be removed by heating the bow spring module for a period of time and then quenching it.

Problems solved by technology

Low-clearance bow spring centralizers cut from a unitary piece of tubular may be expensive to make.

These special tools can add substantially to the manufacturing cost of the centralizer.

The alternative method described is time consuming and may require post-fabrication heat treating and / or quenching to alleviate the heat-affected zones.

Conversely, a relatively low-weight tubular to be installed in a substantially vertical section of a borehole may require fewer bow springs to adequately center the tubular.

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