API 7-1 Series Heavy Weight Drilling Pipe

Heavy Weight Drill Pipe (HWDP) is an intermediate weight drill stem component which is used in 

conjunction with the drill pipes and drill collars. In some applications, heavyweight drill pipes also 

can be used instead of the drill collars.

OAK HWDP is made of AISI 4145H modified and tempered  steel (Integral Type) or welded AISI 4145H

 joints and 1340 tubes (Welded Type). It is designed for tough drilling environment in vertical and directional

 wells. HWDP is a transition member between drill collar and drill pipe. For directional holes HWDP provides

 weight on bit and additional stiffness to prevent buckling.

Technical parameters of common HWDP specifications