Abstract: An erosion resistant downhole diverter tool (210) comprises a generally cylindrical body (212) which may be configured as a slick sub or may include stabilizing blades (260). Located within the body 212 are a plurality of erosion-resistant, removable, cylindrical inserts (220). Each insert has an aperture (222) formed therein, aligned with a corresponding aperture (218) formed in the cylindrical body (212). Located within the apertures (218) in the cylindrical body (212) are pressure responsive, normally-closed valve assemblies (300), incorporating jet nozzles, which open in response to increased fluid pressure within the tool to provide fluid jets directed into the annulus surrounding the tool in a borehole or the like. The upper ends of the stabilizer blades (260) may include cutting structures to provide a back-reaming function.

Abstract: A drill pipe (10) having first and second end portions (12, 14) at opposite longitudinal ends thereof and a middle portion (16) extending between said first and second end portions; said end portions having a first outside diameter and said middle portion having a second outside diameter less than said first outside diameter; and said drill pipe having a plurality of centraliser means (22, 24, 26) spaced along the length of said middle portion. The centralisers have an outside diameter greater than the outside diameter of the middle portion and, preferably, equal to or greater than the outside diameter of the end portions. The centralisers may be formed integrally with the drill pipe and arc preferably arcuate in longitudinal cross section and formed with hard-faced spiral flutes.