Flexible drill collars

Citation

(2000), "Flexible drill collars", Anti-Corrosion Methods and Materials, Vol. 47 No. 1. https://doi.org/10.1108/acmm.2000.12847aad.005

Flexible drill collars

Keywords Brush Wellman, Alloys, Drilling

Flexible drill collars are one of the latest applications for Brush Wellman's copper-beryllium Alloy 25. It is thought that they benefit from many of the material's characteristics, including its low modulus of elasticity. This reportedly allows a collar to bend and return to its original shape, despite relatively high deflections. As the collars are rotating as they deflect, the surface is continually alternating between tension and compression, so Brush Alloy 25's good fatigue resistance and high strength are also important.

A problem frequently associated with drill strings is that galling at the threaded joints makes disassembly difficult or impossible, often leading to threads having to be re-cut. Brush Alloy 25 is said to exhibit exceptional galling resistance, both when copper-beryllium components are used together and when copper-beryllium components are used with components made of other materials.This avoids the problem of threads seizing and also eliminates the need to apply anti-seize compounds when joints are being made.

Brush Alloy 25 copper-beryllium flexible collars are said to be extremely resistant to corrosion and, unusually, to stress corrosion cracking as well. Yet copper-beryllium is reported to be easy to machine. This fact, coupled with the alloy's availability in a wide range of bar sizes, is thought to outweigh the slightly higher price per kilogram as the finished machined part is ultimately more cost-effective.

Details available from: Brush Wellman Limited. Tel: + 44 (0) 118 930 3733; Fax: + 44 (0) 118 930 3635. USA: Tel: + 1 281 358 6960; Fax: + 1 281 359 9247; e-mail: Diane-Ryan@brushwellman.com