PCT No. PCT/GB94/01001 Sec. 371 Date Nov. 14, 1995 Sec. 102(e) Date Nov. 14, 1995 PCT Filed May 9, 1994 PCT Pub. No. WO94/27024 PCT Pub. Date Nov. 24, 1994A 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.
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