BIEGSAMES BOHRSTRANGTEIL UND VERFAHREN ZUM BOHREN EINES GENEIGTEN LOCHS.

摘要

The invention relates to an improved flexible drill string member having at least one spiral groove (24) formed in its outside surface (30) and incorporating a combination of engineering considerations and criteria such that the invention member will have an extraordinarily high performance capacity in directional drilling with downhole motor driven bits. The said spiral groove (24) defining lands on said main body portion between the flights thereof and the depth of said spiral groove being at least 40% of the wall thickness of said body measured from the outside diameter (30) of said land to the inside diameter of said member.